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Polymers
Volume 14
Issue 23
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Polymers, Volume 14, Issue 23 (December-1 2022) – 280 articles

Cover Story (view full-size image): Lignin is a natural polymer second only to cellulose among natural reserves, which is linked by chemical bonds such as carbon–carbon bonds and ether bonds. Degradation is one of the ways to achieve high value conversion of lignin, of which heating degradation of lignin with deep eutectic solvent (DES) is a good green degradation method. In this study, we used choline chloride as the hydrogen bond acceptor, and urea, ethylene glycol, glycerol, acetic acid, formic acid mixed acid, oxalic acid, and p-toluenesulfonic acid as the hydrogen bond donors to degrade lignin and evaluated the recovery of DES. View this paper
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10 pages, 2015 KiB  
Article
Relation of Chemical Composition and Colour of Spruce Wood
by Viera Kučerová, Richard Hrčka and Tatiana Hýrošová
Polymers 2022, 14(23), 5333; https://doi.org/10.3390/polym14235333 - 6 Dec 2022
Cited by 8 | Viewed by 1671
Abstract
The visual inspection of fresh cut spruce wood (Picea abies, L. Karst.) showed the variability of its colour. Wood visual inspection is a part of wood quality assessment, for example, prior to or after its processing. The detail spruce wood colour [...] Read more.
The visual inspection of fresh cut spruce wood (Picea abies, L. Karst.) showed the variability of its colour. Wood visual inspection is a part of wood quality assessment, for example, prior to or after its processing. The detail spruce wood colour analysis was performed using spectrophotometric data. The colour was measured by the bench-top spectrophotometer CM-5 Konica Minolta. The spectrophotometer was calibrated with a built-in white standard and on air. The whole analysis was performed in an xy chromaticity diagram supplemented with coordinate Y and CIE L*a*b* colour spaces. The ratio of the white chromophore amount to the amount of all achromatic chromophores is related to the Y coordinate. The ratio of the chromatic chromophore amount to all chromophores amount is saturation. The constructed model of the spruce wood colour is composed of four chromophores. The white chromophore belongs to holocellulose. The black chromophore belongs to lignin. The saturation is influenced by two chromophores. One of them belongs to extractives, another to lignin. The amounts of chromophores correlated with the spruce wood chemical composition. The chemical composition was measured using the procedures of Seifert, Wise, Sluiter, and ASTM. Moreover, the wood colour is affected by the moisture content. Full article
(This article belongs to the Special Issue Biodegradable and Natural Polymers)
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Figure 1
<p>Scheme of test figure production.</p> Full article ">Figure 2
<p>The coordinate L* in dependence on the distance from the pith.</p> Full article ">Figure 3
<p>The coordinates a* (<b>a</b>) and b* (<b>b</b>) show reverses characters in dependence on the distance.</p> Full article ">Figure 4
<p>The measured data of the <span class="html-italic">Y</span> spruce wood colour coordinate and its theoretical representative on different anatomical sections.</p> Full article ">Figure 5
<p>Spruce wood and its chemical compounds in chromaticity diagram.</p> Full article ">
18 pages, 3098 KiB  
Article
Molecular Dynamics and Nuclear Magnetic Resonance Studies of Supercritical CO2 Sorption in Poly(Methyl Methacrylate)
by Valentina V. Sobornova, Konstantin V. Belov, Alexey A. Dyshin, Darya L. Gurina, Ilya A. Khodov and Michael G. Kiselev
Polymers 2022, 14(23), 5332; https://doi.org/10.3390/polym14235332 - 6 Dec 2022
Cited by 6 | Viewed by 16011
Abstract
The study of supercritical carbon dioxide sorption processes is an important and urgent task in the field of “green” chemistry and for the selection of conditions for new polymer material formation. However, at the moment, the research of these processes is very limited, [...] Read more.
The study of supercritical carbon dioxide sorption processes is an important and urgent task in the field of “green” chemistry and for the selection of conditions for new polymer material formation. However, at the moment, the research of these processes is very limited, and it is necessary to select the methodology for each polymer material separately. In this paper, the principal possibility to study the powder sorption processes using 13C nuclear magnetic resonance spectroscopy, relaxation-relaxation correlation spectroscopy and molecular dynamic modeling methods will be demonstrated based on the example of polymethylmethacrylate and supercritical carbon dioxide. It was found that in the first nanoseconds and seconds during the sorption process, most of the carbon dioxide, about 75%, is sorbed into polymethylmethacrylate, while on the clock scale the remaining 25% is sorbed. The methodology presented in this paper makes it possible to select optimal conditions for technological processes associated with the production of new polymer materials based on supercritical fluids. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers)
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Graphical abstract
Full article ">Figure 1
<p>Scheme of the apparatus for producing and maintaining high-pressure for NMR measurements in carbon dioxide media, where 1 is a cylinder with carbon dioxide, 2 is a pressure gauge, 3, 6 are taper seal valves for filling (<b>upper</b>) and purging (<b>lower</b>), 4 is a manual press, 5 and 8 are electronic pressure transmitters, and 9 is a high-pressure NMR cell (see. <a href="#polymers-14-05332-f002" class="html-fig">Figure 2</a>).</p> Full article ">Figure 2
<p>(<b>a</b>) High-pressure NMR cell (cross section): 1 is a capillary inlet seal (Teflon, Chemours, Wilmington, DE, USA), 2 is an ampoule seal (MVQ Silicones GmbH, Weinheim, Germany), 3 is a compensating gasket (Caprolon—polyamide, Shik Polymers, Moscow, Russia) (<b>b</b>) High-pressure NMR cell (full view): 4 is a high-pressure tube (synthetic single crystal sapphire Al<sub>2</sub>O<sub>3</sub>), 5 is a tube holder (D16T, Metatorg, Ivanovo, Russia), 6 is a input port (D16T, Metatorg, Ivanovo, Russia), 7 is a capillary inlet high-pressure (D16T, Metatorg, Ivanovo, Russia).</p> Full article ">Figure 3
<p>Time dependence of pressure (<b>a</b>) and temperature (<b>b</b>) during simulation process for 150 ns with a time step of 2 fs. These graphs confirm the reliability of the use of the barostat and thermostat and the absence of parameters of state (temperature in K and pressure MPa) changes throughout the duration of the simulation.</p> Full article ">Figure 4
<p>The RRCOSY pulse sequence used in the experiment consisting of two 90° and three 180° radio frequency pulses, where t<sub>1</sub> is the time of the indirect encoding period, t<sub>2</sub> is the time of the detection period, t<sub>m</sub> is the mixing time, m and n are the numbers of echo times in the encoding periods.</p> Full article ">Figure 5
<p>An example of quality of approximation of the spectral contour of the <sup>13</sup>C NMR resonance signals of CO<sub>2</sub> and standard С<sub>6</sub>D<sub>6</sub> (red line) by Lorentz-like profiles (blue line) using pseudo-Voigt functions.</p> Full article ">Figure 6
<p>A graph of the change dependence in the parameter of the chemical shift of the <sup>13</sup>C CO<sub>2</sub> signal on time, approximated by a one-exponential model. Where δ<sub>0</sub> is the value of the chemical shift of the <sup>13</sup>C CO<sub>2</sub> signal at the initial time, δ<sub>t</sub> is the value of the chemical shifts of the <sup>13</sup>C CO<sub>2</sub> signal at observation time t. The blue circle on the graph indicates the correlation time of this sorption process, defined as the reciprocal of the rate constant of the sorption process (k).</p> Full article ">Figure 7
<p>(<b>a</b>) A graph of the change dependence in the signal width parameter at the half-height of the <sup>13</sup>C CO<sub>2</sub> signal on time, approximated by a two-exponential model. Where ∆FWHM = FWHM<sub>0</sub>-FWHM<sub>t</sub>, where FWHM<sub>0</sub> and FWHM<sub>t</sub> are the half-widths of the signals at half-height at the initial time and observation time t, respectively. (<b>b</b>) A graph of the change dependence in the parameter of the integral intensity of the <sup>13</sup>C CO<sub>2</sub> signal on time, approximated by a two-exponential model. Where I<sub>0</sub> and I<sub>t</sub> are the values of the integral signal intensity at the initial moment of time and the observation time t. The blue and green circles on the graphs show the values of the correlation times of the sorption and swelling processes, respectively.</p> Full article ">Figure 8
<p>Two-dimensional correlation map obtained on the basis of the developed method. The ordinate and abscissa show the values of the logarithms of the relaxation times T<sub>1</sub> and T<sub>2</sub> spin–lattice to spin–spin relaxation times, respectively, while the sites in the spectroscopic image correspond to free solvent scCO<sub>2</sub> (<b>left</b>) and impregnated into the polymer matrix (<b>right</b>).</p> Full article ">Figure 9
<p>Instant snapshots of PMMA samples in three directions. Blue represents CO<sub>2</sub> molecules. The red, orange, and yellow colors in the figure represent sections of the polymer from the center of the sample in three different planes. It can be seen from the figure that some of the CO<sub>2</sub> molecules are not uniformly distributed in the polymer volume. The simulation results were used to further estimate the proportion of CO<sub>2</sub> sorbed by the PMMA polymer matrix.</p> Full article ">Figure 10
<p>Snapshot of PMMA (gray) and the central part of the PMMA considered for calculation of absorbed CO<sub>2.</sub> This snapshot shows the volume that was used to calculate the parameters of sorption according to Equation 14 at various simulation times.</p> Full article ">
11 pages, 4716 KiB  
Article
Phase Diagrams of Polymerization-Induced Self-Assembly Are Largely Determined by Polymer Recombination
by Artem Petrov, Alexander V. Chertovich and Alexey A. Gavrilov
Polymers 2022, 14(23), 5331; https://doi.org/10.3390/polym14235331 - 6 Dec 2022
Cited by 4 | Viewed by 1734
Abstract
In the current work, atom transfer radical polymerization-induced self-assembly (ATRP PISA) phase diagrams were obtained by the means of dissipative particle dynamics simulations. A fast algorithm for determining the equilibrium morphology of block copolymer aggregates was developed. Our goal was to assess how [...] Read more.
In the current work, atom transfer radical polymerization-induced self-assembly (ATRP PISA) phase diagrams were obtained by the means of dissipative particle dynamics simulations. A fast algorithm for determining the equilibrium morphology of block copolymer aggregates was developed. Our goal was to assess how the chemical nature of ATRP affects the self-assembly of diblock copolymers in the course of PISA. We discovered that the chain growth termination via recombination played a key role in determining the ATRP PISA phase diagrams. In particular, ATRP with turned off recombination yielded a PISA phase diagram very similar to that obtained for a simple ideal living polymerization process. However, an increase in the recombination probability led to a significant change of the phase diagram: the transition between cylindrical micelles and vesicles was strongly shifted, and a dependence of the aggregate morphology on the concentration was observed. We speculate that this effect occurred due to the simultaneous action of two factors: the triblock copolymer architecture of the terminated chains and the dispersity of the solvophobic blocks. We showed that these two factors affected the phase diagram weakly if they acted separately; however, their combination, which naturally occurs during ATRP, affected the ATRP PISA phase diagram strongly. We suggest that the recombination reaction is a key factor leading to the complexity of experimental PISA phase diagrams. Full article
(This article belongs to the Collection Design and Synthesis of Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Algorithm of the ATRP simulation.</p> Full article ">Figure 2
<p>Molecular weight distributions of the modeled systems at a fixed chain composition (<math display="inline"><semantics> <mrow> <msub> <mi>N</mi> <mi>A</mi> </msub> <mo>=</mo> <mn>6</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mi>N</mi> <mi>B</mi> </msub> <mo>=</mo> <mn>34</mn> </mrow> </semantics></math>) at different polymer volume fractions <math display="inline"><semantics> <mi mathvariant="sans-serif">Φ</mi> </semantics></math> and termination probabilities <math display="inline"><semantics> <msub> <mi>p</mi> <mi>t</mi> </msub> </semantics></math> at 100% conversion; 95% of the chains in the system with <math display="inline"><semantics> <mrow> <msub> <mi>p</mi> <mi>t</mi> </msub> <mo>=</mo> <mn>0.05</mn> </mrow> </semantics></math> underwent termination. Dispersities (values of <math display="inline"><semantics> <mrow> <msub> <mi>M</mi> <mi>w</mi> </msub> <mo>/</mo> <msub> <mi>M</mi> <mi>n</mi> </msub> </mrow> </semantics></math>) are equal to <math display="inline"><semantics> <mrow> <mn>1.13</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>1.07</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mn>1.14</mn> </mrow> </semantics></math> for the black, red, and blue curves, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) Phase diagram for the systems without recombination (<math display="inline"><semantics> <mrow> <msub> <mi>p</mi> <mi>t</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math>, transition lines are dashed) and for the systems with the fraction of terminated chains via recombination equal to ≈95% (<math display="inline"><semantics> <mrow> <msub> <mi>p</mi> <mi>t</mi> </msub> <mo>=</mo> <mn>0.05</mn> </mrow> </semantics></math>, transition lines are dash-dotted). Sph+cyl and cyl regions are to the left and to the right side of the red lines, respectively. Cyl and ves regions are to the left and to the right side of the blue lines, respectively. (<b>b</b>) Transition lines between cylinders and vesicles for the systems with different fractions of terminated chains. Squares show the simulation data. Transition points for the reference systems (monodisperse diblock copolymers and ideal polymerization PISA at 10% and 20%) were obtained in ref. [<a href="#B21-polymers-14-05331" class="html-bibr">21</a>] and are shown in black. The cyl&lt;-&gt;ves transition points were tested in three independent runs for the systems with 95% of terminated chains. (<b>c</b>) Snapshots of the observed morphologies.</p> Full article ">Figure 4
<p>Schematic representation of the packing of ABA triblock copolymers inside micelles.</p> Full article ">
10 pages, 2052 KiB  
Article
Dual Responsive Dependent Background Color Based on Thermochromic 1D Photonic Crystal Multilayer Films
by Yejin Kim, Seo Hyun Kim, Henok Getachew Girma, Seungju Jeon, Bogyu Lim and Seo-Hyun Jung
Polymers 2022, 14(23), 5330; https://doi.org/10.3390/polym14235330 - 6 Dec 2022
Cited by 3 | Viewed by 2177
Abstract
In this paper, we present dual responsive one-dimensional (1D) photonic crystal (PC) multilayer films that utilize a high-humidity environment and temperature. Dual responsive 1D PC multilayer films are fabricated on precoated thermochromic film by sequential alternate layer deposition of photo-crosslinkable poly(2-vinylnaphthalene-co-benzophenone acrylate) (P(2VN-co-BPA)) [...] Read more.
In this paper, we present dual responsive one-dimensional (1D) photonic crystal (PC) multilayer films that utilize a high-humidity environment and temperature. Dual responsive 1D PC multilayer films are fabricated on precoated thermochromic film by sequential alternate layer deposition of photo-crosslinkable poly(2-vinylnaphthalene-co-benzophenone acrylate) (P(2VN-co-BPA)) as a high refractive index polymer, and poly(4-vinylpyrollidone-co-benzophenone acrylate) P(4VP-co-BPA) as a low refractive index polymer. The thermochromic film shows a vivid color transition from black to white at 28 °C. Three different colors of thermochromic 1D PC multilayer films are prepared by thickness modulation of P(4VP-co-BPA) layers, and the films on a black background exhibit visible spectrum color only in a high-humidity environment (over 90% relative humidity (RH)). For the three films placed on a hands display, three different composite colors are synthesized by the reflection of light, including yellow, magenta, and cyan, due to the changing of backgrounds from black to white with temperature. Additionally, the films show remarkable color transitions with reliable reversibility. The films can be applied as anti-counterfeiting labels and can be used for smart decoration films. To the best of our knowledge, this is the first report of dual response colorimetric films that change color in various ways depending on temperature and humidity changes, and we believe that it can be applied to various applications. Full article
(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Synthesis process of photo-crosslinkable P(2VN-co-BPA) and P(4VP-co-BPA) as high/low refractive index polymers. (<b>b</b>,<b>c</b>) Monolayer refractive index and thickness of HP and LP polymers.</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic depicting the fabrication method for a thermal and humidity responsive 1D PC multilayer via bar- and spin-coating processes. (<b>b</b>) Color parameter (L*) of thermochromic films with temperature. (<b>c</b>) Initial reflectance spectra of purple, green, and red films. (<b>d</b>) Theoretical reflectance spectra of purple, green, and red films via ellipsometry data.</p> Full article ">Figure 3
<p>(<b>a</b>) Images of three films with black background after showing color changes when exposed to 30 to 98% RH level. (<b>b</b>) Reflectance spectra of three films as RH increased from 10 to 98%.</p> Full article ">Figure 4
<p>(<b>a</b>) Schematic illustration of high-humidity and temperature responsive films. (<b>b</b>) Images of three films with a black background after showing color changes caused by human blowing. (<b>c</b>) Dynamic reflectance spectra of three films based on human blowing. (<b>d</b>) Images of three films depending on black and white backgrounds with temperature.</p> Full article ">Figure 5
<p>Changes in the maximum PSB after 10 cycles of alternating exposure of three films to human blowing.</p> Full article ">
19 pages, 3180 KiB  
Article
Characteristics and Properties of Acid- and Pepsin-Solubilized Collagens from the Tail Tendon of Skipjack Tuna (Katsuwonus pelamis)
by Sagun Chanmangkang, Sutee Wangtueai, Nantipa Pansawat, Pramvadee Tepwong, Atikorn Panya and Jirawan Maneerote
Polymers 2022, 14(23), 5329; https://doi.org/10.3390/polym14235329 - 6 Dec 2022
Cited by 3 | Viewed by 2748
Abstract
The tail tendons of skipjack tuna (Katsuwonus pelamis), a by-product from the meat-separation process in canned-tuna production, was used as an alternative source of collagen extraction. The acid-solubilized collagens using vinegar (VTC) and acetic-acid (ATC) extraction and pepsin-solubilized collagen (APTC) were [...] Read more.
The tail tendons of skipjack tuna (Katsuwonus pelamis), a by-product from the meat-separation process in canned-tuna production, was used as an alternative source of collagen extraction. The acid-solubilized collagens using vinegar (VTC) and acetic-acid (ATC) extraction and pepsin-solubilized collagen (APTC) were extracted from tuna-tail tendon. The physiochemical properties and characteristics of those collagens were investigated. The obtained yield of VTC, ATC, and APTC were 7.88 ± 0.41, 8.67 ± 0.35, and 12.04 ± 0.07%, respectively. The determination of protein-collagen solubility, the effect of pH and NaCl on collagen solubility, Fourier-transform infrared spectroscopy (FTIR) spectrum, and microstructure of the collagen-fibril surface using a scanning electron microscope (SEM) were done. The protein solubility of VTC, ATC, and APTC were 0.44 ± 0.03, 0.52 ± 0.07, and 0.67 ± 0.12 mg protein/mg collagen. The solubility of collagen decreased with increasing of NaCl content. These three collagens were good solubility at low pH with the highest solubility at pH 5. The FTIR spectrum showed absorbance of Amide A, Amide B, Amide I, Amide II, and Amide III groups as 3286–3293 cm−1, 2853–2922 cm−1, 1634–1646 cm−1, 1543–1544 cm−1, and 1236–1237 cm−1, respectively. The SEM analysis indicated a microstructure of collagen surface as folding of fibril with small pore. Full article
(This article belongs to the Special Issue Biodegradable and Natural Polymers)
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Graphical abstract
Full article ">Figure 1
<p>The effect of NaCl on protein solubility of tuna-tendon collagens (VTC: acid-solubilized collagen using vinegar extraction, ATC: acid-solubilized collagen using acetic-acid extraction, and APTC: pepsin-solubilized collagen).</p> Full article ">Figure 2
<p>The effect of pH on protein solubility of tuna-tendon collagens (VTC: acid-solubilized collagen using vinegar extraction, ATC: acid-solubilized collagen using acetic-acid extraction, and APTC: pepsin-solubilized collagen).</p> Full article ">Figure 3
<p>The FTIR spectra wavenumber of tuna-tail-tendon collagens (VTC: acid-solubilized collagen using vinegar extraction, ATC: acid-solubilized collagen using acetic-acid extraction, and APTC: pepsin-solubilized collagen).</p> Full article ">Figure 4
<p>Surface microstructure of tuna-tendon collagens as VTC (acid-solubilized collagen using vinegar extraction) ×100 (<b>A1</b>), ×300 (<b>A2</b>), ×700 (<b>A3</b>); ATC (acid-solubilized collagen using acetic acid extraction) ×100 (<b>B1</b>), ×300 (<b>B2</b>), ×700 (<b>B3</b>); APTC (pepsin-solubilized collagen) ×100 (<b>C1</b>), ×300 (<b>C2</b>), ×700 (<b>C3</b>).</p> Full article ">Figure 5
<p>Viscosity (<b>A</b>) and fractional viscosity (<b>B</b>) of tuna-tail-tendon collagen (VTC: acid-solubilized collagen using vinegar extraction, ATC: acid-solubilized collagen using acetic-acid extraction, and APTC: pepsin-solubilized collagen).</p> Full article ">Figure 6
<p>SDS–PAGE pattern of collagen from the tuna-tail tendon, Marker (1), Calf skin (2), VTC: acid-solubilized collagen using vinegar extraction (3), ATC: acid-solubilized collagen using acetic-acid extraction (4), APTC: pepsin-solubilized collagen (5).</p> Full article ">
23 pages, 5784 KiB  
Article
New Crosslinked Single-Ion Silica-PEO Hybrid Electrolytes
by Sébastien Issa, Roselyne Jeanne-Brou, Sumit Mehan, Didier Devaux, Fabrice Cousin, Didier Gigmes, Renaud Bouchet and Trang N. T. Phan
Polymers 2022, 14(23), 5328; https://doi.org/10.3390/polym14235328 - 6 Dec 2022
Cited by 4 | Viewed by 2009
Abstract
New single-ion hybrid electrolytes have been synthetized via an original and simple synthetic approach combining Michael addition, epoxidation, and sol–gel polycondensation. We designed an organic PEO network as a matrix for the lithium transport, mechanically reinforced thanks to crosslinking inorganic (SiO1.5) [...] Read more.
New single-ion hybrid electrolytes have been synthetized via an original and simple synthetic approach combining Michael addition, epoxidation, and sol–gel polycondensation. We designed an organic PEO network as a matrix for the lithium transport, mechanically reinforced thanks to crosslinking inorganic (SiO1.5) sites, while highly delocalized anions based on lithium vinyl sulfonyl(trifluoromethane sulfonyl)imide (VSTFSILi) were grafted onto the inorganic sites to produce single-ion hybrid electrolytes (HySI). The influence of the electrolyte composition in terms of the inorganic/organic ratio and the grafted VSTFSILi content on the local structural organization, the thermal, mechanical, and ionic transport properties (ionic conductivity, transference number) are studied by a variety of techniques including SAXS, DSC, rheometry, and electrochemical impedance spectroscopy. SAXS measurements at 25 °C and 60 °C reveal that HySI electrolyte films display locally a spatial phase separation with domains composed of PEO rich phase and silica/VSTFSILi clusters. The size of these clusters increases with the silica and VSTFSILi content. A maximum ionic conductivity of 2.1 × 10−5 S·cm−1 at 80 °C has been obtained with HySI having an EO/Li ratio of 20. The Li+ ion transfer number of HySI electrolytes is high, as expected for a single-ion electrolyte, and comprises between 0.80 and 0.92. Full article
(This article belongs to the Section Smart and Functional Polymers)
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<p>Synthesis route of hybrid single-ion electrolytes.</p> Full article ">Figure 2
<p>Frequency response at 75 °C and at a strain value fixed at 1% of (<b>a</b>) the storage modulus G′ and (<b>b</b>) the loss modulus G″ of the HySI electrolytes. The symbols correspond to <span class="html-italic">w</span><sub>VSTFSILi</sub> value of (green cross) 15, (red diamond) 17, (orange circle) 20, (black triangle) 25, and (blue square) 33.</p> Full article ">Figure 2 Cont.
<p>Frequency response at 75 °C and at a strain value fixed at 1% of (<b>a</b>) the storage modulus G′ and (<b>b</b>) the loss modulus G″ of the HySI electrolytes. The symbols correspond to <span class="html-italic">w</span><sub>VSTFSILi</sub> value of (green cross) 15, (red diamond) 17, (orange circle) 20, (black triangle) 25, and (blue square) 33.</p> Full article ">Figure 3
<p>Thermograms from −100 °C to 125 °C at 10 °C·min<sup>−1</sup> of the HySI electrolytes.</p> Full article ">Figure 4
<p>(<b>a</b>) Glass transition temperature (<span class="html-italic">T</span><sub>g</sub>), and (<b>b</b>) melting temperatI (<span class="html-italic">T</span><sub>m</sub>) and degree of crystallinity (χ<sub>c</sub>) as a function of <span class="html-italic">w</span><sub>VSTFSILi</sub>. The circle symbols correspond to the HySI_<span class="html-italic">w</span><sub>VSTFSILi</sub> electrolytes while the up and down triangles correspond to HySI_20_TEOS and HySI_20_TEMS, respectively. In figure (<b>b</b>), filled and open symbols correspond to <span class="html-italic">T</span><sub>m</sub> and χ<sub>c</sub>, respectively. The dash lines are eye guides.</p> Full article ">Figure 5
<p>SAXS/WAXS scattering curves recorded at (<b>a</b>) 25 °C and (<b>b</b>) 60 °C for the HySI_<span class="html-italic">w</span><sub>VSTFSILi</sub> electrolytes with <span class="html-italic">w</span><sub>VSTFSILi</sub> of (▽) 0, (✕) 15, (◇) 17, (◯) 20, (△) 25, and (☐) 33. The curves are shifted in intensity for clarity. The inset in figure a) is a magnification in the high <span class="html-italic">q</span> range. The yellow continuous lines in figure (<b>b</b>) are the fit curves from the ad hoc model (see main text).</p> Full article ">Figure 5 Cont.
<p>SAXS/WAXS scattering curves recorded at (<b>a</b>) 25 °C and (<b>b</b>) 60 °C for the HySI_<span class="html-italic">w</span><sub>VSTFSILi</sub> electrolytes with <span class="html-italic">w</span><sub>VSTFSILi</sub> of (▽) 0, (✕) 15, (◇) 17, (◯) 20, (△) 25, and (☐) 33. The curves are shifted in intensity for clarity. The inset in figure a) is a magnification in the high <span class="html-italic">q</span> range. The yellow continuous lines in figure (<b>b</b>) are the fit curves from the ad hoc model (see main text).</p> Full article ">Figure 6
<p>Schematic representation of hybrid-electrolyte network at 60 °C for HySI_0, HySI_15 and HySI_33. The gray background represents the PEO, the darker paths represent the silicic bridges and the black points the salt vinyl-TFSI crosslinked with the silica on the PEO chains.</p> Full article ">Figure 7
<p>Impedance spectrum of the (△) HySI_25 electrolyte at 60 °C in Li symmetric cell. The fit of the contribution arising from the rich PEO phase (0.86 MHz) and the Li/electrolyte interface (550 Hz) are shown as a straight and dotted line, respectively. The contribution at MF (24 kHz, black circle) is obtained by the subtraction method (see text, TFSI/SiO<sub>1.5</sub> phase contribution). The inset is a magnification in the MF range.</p> Full article ">Figure 8
<p>Ionic conductivity of the PEO-rich as a function of the inverse of the temperature for HySI_<span class="html-italic">w</span><sub>VSTFSILi</sub> electrolytes. The lines correspond to the VTF fits.</p> Full article ">Figure 9
<p>Ratio of the resistance <span class="html-italic">R</span>, multiplied by the capacitor <span class="html-italic">C</span> (fits results from EIS), of the phases TFSI/SiO<sub>1</sub>.-rich on PEO-rich at 60 °C as a function of <span class="html-italic">w</span><sub>VSTFSILi</sub>. The lines are guidelines for the eyes.</p> Full article ">Figure 10
<p>Isothermal variations at 60 °C of the (<span style="color:red">●</span>) total conductivity <span class="html-italic">σ</span><sub>t</sub> containing PEO-rich phase with TFSI-rich domains and (<span style="color:#0000FF">▲</span>) PEO-rich phase <span class="html-italic">σ</span><sub>PEO</sub>, as a function of <span class="html-italic">w</span><sub>VSTFSILi</sub>.</p> Full article ">Figure 11
<p>Cationic transference number at 80 °C as a function of <span class="html-italic">w</span><sub>VSTFSILi</sub>. The lines are guidelines for the eyes.</p> Full article ">
15 pages, 9013 KiB  
Article
Polyacrylonitrile-Polyvinyl Alcohol-Based Composite Gel-Polymer Electrolyte for All-Solid-State Lithium-Ion Batteries
by Yer-Targyn Tleukenov, Gulnur Kalimuldina, Anar Arinova, Nurbolat Issatayev, Zhumabay Bakenov and Arailym Nurpeissova
Polymers 2022, 14(23), 5327; https://doi.org/10.3390/polym14235327 - 6 Dec 2022
Cited by 6 | Viewed by 2496
Abstract
The three-dimensional (3D) structure of batteries nowadays obtains a lot of attention because it provides the electrodes a vast surface area to accommodate and employ more active material, resulting in a notable increase in areal capacity. However, the integration of polymer electrolytes to [...] Read more.
The three-dimensional (3D) structure of batteries nowadays obtains a lot of attention because it provides the electrodes a vast surface area to accommodate and employ more active material, resulting in a notable increase in areal capacity. However, the integration of polymer electrolytes to complicated three-dimensional structures without defects is appealing. This paper presents the creation of a flawless conformal coating for a distinctive 3D-structured NiO/Ni anode using a simple thermal oxidation technique and a polymer electrolyte consisting of three layers of PAN-(PAN-PVA)-PVA with the addition of Al2O3 nanoparticles as nanofillers. Such a composition with a unique combination of polymers demonstrated superior electrode performance. PAN in the polymer matrix provides mechanical stability and corrosion resistance, while PVA contributes to excellent ionic conductivity. As a result, NiO/Ni@PAN-(PAN-PVA)-PVA with 0.5 wt% Al2O3 NPs configuration demonstrated enhanced cycling stability and superior electrochemical performance, reaching 546 mAh g−1 at a 0.1 C rate. Full article
(This article belongs to the Section Polymer Applications)
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<p>XRD patterns of NiO/Ni thermally oxidized at 700 °C for 5 min compared with the standard peak for Ni-foam.</p> Full article ">Figure 2
<p>SEM images for (<b>a</b>) pristine Ni foam, (<b>b</b>) after thermal oxidation, (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>d</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.25% Al<sub>2</sub>O<sub>3</sub>, and (<b>e</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 3
<p>Cross-sectional SEM images for (<b>a</b>) NiO/Ni foam, (<b>b</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.25 % Al<sub>2</sub>O<sub>3</sub>, and (<b>d</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 4
<p>Cross-sectional SEM images and EDS analysis for (<b>a</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>b</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub>, and (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 4 Cont.
<p>Cross-sectional SEM images and EDS analysis for (<b>a</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>b</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub>, and (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 5
<p>FTIR spectra for NiO/Ni coated with PAN-(PVA-PAN)-PVA layers and Al<sub>2</sub>O<sub>3</sub> nanofillers.</p> Full article ">Figure 6
<p>CV plateaus and charge–discharge curves of (<b>a</b>,<b>e</b>) NiO/Ni foam, (<b>b</b>,<b>f</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>c</b>,<b>g</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub>, (<b>d</b>,<b>h</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub> electrodes. Cycle performance for 100 cycles of (<b>i</b>) NiO/Ni foam, (<b>j</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub> (<b>k</b>), NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub> electrodes (<b>l</b>).</p> Full article ">Figure 6 Cont.
<p>CV plateaus and charge–discharge curves of (<b>a</b>,<b>e</b>) NiO/Ni foam, (<b>b</b>,<b>f</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>c</b>,<b>g</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub>, (<b>d</b>,<b>h</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub> electrodes. Cycle performance for 100 cycles of (<b>i</b>) NiO/Ni foam, (<b>j</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with addition of 0.25 wt% Al<sub>2</sub>O<sub>3</sub> (<b>k</b>), NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub> electrodes (<b>l</b>).</p> Full article ">Figure 7
<p>Nyquist plots of cycled NiO/Ni@PAN-(PAN-PVA)-PVA, and NiO/Ni@PAN-(PAN-PVA)-PVA with the addition of 0.5 wt% Al<sub>2</sub>O<sub>3</sub> electrodes with the fitted circuit.</p> Full article ">Figure 8
<p>Post-mortem SEM images after 100 cycles of (<b>a</b>) NiO/Ni@PAN-(PAN-PVA)-PVA, (<b>b</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with 0.25 wt% Al<sub>2</sub>O<sub>3</sub> and (<b>c</b>) NiO/Ni@PAN-(PAN-PVA)-PVA with 0.5 wt% Al<sub>2</sub>O<sub>3</sub>.</p> Full article ">
19 pages, 753 KiB  
Review
Prospects of Biogenic Xanthan and Gellan in Removal of Heavy Metals from Contaminated Waters
by Katarína Balíková, Bence Farkas, Peter Matúš and Martin Urík
Polymers 2022, 14(23), 5326; https://doi.org/10.3390/polym14235326 - 6 Dec 2022
Cited by 8 | Viewed by 2115
Abstract
Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, [...] Read more.
Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, including two commercially available heteropolysaccharides—xanthan and gellan. As biodegradable and non-toxic fermentation products, xanthan and gellan have been successfully tested in various remediation techniques. Here, to highlight their prospects as green adsorbents for water decontamination, we have reviewed their biosynthesis machinery and chemical properties that are linked to their sorptive interactions, as well as their actual performance in the remediation of heavy metal contaminated waters. Their sorptive performance in native and modified forms is promising; thus, both xanthan and gellan are emerging as new green-based materials for the cost-effective and efficient remediation of heavy metal-contaminated waters. Full article
(This article belongs to the Special Issue Polymers for Wastewater and Soil Treatment)
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<p>Schematic model of xanthan polysaccharide biosynthesis machinery.</p> Full article ">Figure 2
<p>Schematic model of gellan polysaccharide biosynthesis machinery.</p> Full article ">
16 pages, 3464 KiB  
Article
Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus
by Kellen Mitchell, Lily Raymond, Joshua Wood, Ji Su, Jun Zhang and Yifei Jin
Polymers 2022, 14(23), 5325; https://doi.org/10.3390/polym14235325 - 6 Dec 2022
Viewed by 1992
Abstract
Astronauts suffer skeletal muscle atrophy in microgravity and/or zero-gravity environments. Artificial muscle-actuated exoskeletons can aid astronauts in physically strenuous situations to mitigate risk during spaceflight missions. Current artificial muscle fabrication methods are technically challenging to be performed during spaceflight. The objective of this [...] Read more.
Astronauts suffer skeletal muscle atrophy in microgravity and/or zero-gravity environments. Artificial muscle-actuated exoskeletons can aid astronauts in physically strenuous situations to mitigate risk during spaceflight missions. Current artificial muscle fabrication methods are technically challenging to be performed during spaceflight. The objective of this research is to unveil the effects of critical operating conditions on artificial muscle formation and geometry in a newly developed helical fiber extrusion method. It is found that the fiber outer diameter decreases and pitch increases when the printhead temperature increases, inlet pressure increases, or cooling fan speed decreases. Similarly, fiber thickness increases when the cooling fan speed decreases or printhead temperature increases. Extrusion conditions also affect surface morphology and mechanical properties. Particularly, extrusion conditions leading to an increased polymer temperature during extrusion can result in lower surface roughness and increased tensile strength and elastic modulus. The shape memory properties of an extruded fiber are demonstrated in this study to validate the ability of the fiber from shape memory polymer to act as an artificial muscle. The effects of the operating conditions are summarized into a phase diagram for selecting suitable parameters for fabricating helical artificial muscles with controllable geometries and excellent performance in the future. Full article
(This article belongs to the Special Issue Advanced Additive Processes and 3D Printing for Polymer Composites)
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<p>(<b>a</b>) Artificial muscle extrusion system. (<b>b</b>) Extrusion system printhead during artificial muscle extrusion. (<b>c</b>) Polylactic acid helical artificial muscle. (<b>d</b>) Potential helical artificial muscle application driven exoskeletal elbow apparatus.</p> Full article ">Figure 2
<p>Measured geometry of artificial muscles extruded at a constant cooling fan speed of 75% and inlet pressure of 12 psi. (<b>a</b>) Effects of printhead temperature on muscle diameter and representative extrusion results. (<b>b</b>) Effects of printhead temperature on fiber thickness. (<b>c</b>) Effects of printhead temperature on pitch (scale bar: 10 mm).</p> Full article ">Figure 3
<p>Measured geometry of artificial muscles extruded at a constant printhead temperature of 125 °C and inlet pressure of 12 psi. (<b>a</b>) Effects of cooling fan speed on muscle diameter and representative extrusion results. (<b>b</b>) Effects of cooling fan speed on fiber thickness. (<b>c</b>) Effects of cooling fan speed on pitch (scale bar: 10 mm).</p> Full article ">Figure 4
<p>Measured geometry of artificial muscles extruded at a constant printhead temperature of 125 °C and cooling fan speed of 75%. (<b>a</b>) Effects of inlet pressure on muscle diameter and representative extrusion results. (<b>b</b>) Effects of inlet pressure on fiber thickness. (<b>c</b>) Effects of inlet pressure speed on pitch (scale bar: 10 mm).</p> Full article ">Figure 5
<p>(<b>a</b>) Three-dimensional phase diagram of artificial muscle fabrication results at the tested extrusion conditions. (<b>b</b>) Sub-phase diagram of artificial muscle fabrication at a constant inlet pressure of 82.7 kPa. (<b>c</b>) Sub-phase diagram of artificial muscle fabrication at a constant cooling fan speed of 75%. (<b>d</b>) Sub-phase diagram of artificial muscle fabrication at a constant printhead temperature of 125 °C.</p> Full article ">Figure 6
<p>Polylactic acid viscosity as a function of shear rate and the zero-shear rate viscosity at 160 °C.</p> Full article ">Figure 7
<p>Two-dimensional phase diagram constructed from the Brinkman and Nusselt number of the extrusion process.</p> Full article ">Figure 8
<p>Mechanical and morphology properties of muscle group 2 and 6. (<b>a</b>) Stress–strain curves, max stresses, and elastic moduli of muscle group 2 and 6. (<b>b</b>) Artificial muscle surface morphology and roughness of (<b>b1</b>) muscle group 2 and (<b>b2</b>) muscle group 6.</p> Full article ">Figure 9
<p>Artificial muscle contraction stress and stress rate over time when heated to 60 °C (scale bar: 10 mm).</p> Full article ">
17 pages, 3517 KiB  
Article
Synergistic Enhancement of Flame Retardancy Behavior of Glass-Fiber Reinforced Polylactide Composites through Using Phosphorus-Based Flame Retardants and Chain Modifiers
by Ceren Yargici Kovanci, Mohammadreza Nofar and Abbas Ghanbari
Polymers 2022, 14(23), 5324; https://doi.org/10.3390/polym14235324 - 6 Dec 2022
Cited by 7 | Viewed by 2237
Abstract
Flame retardancy properties of neat PLA can be improved with different phosphorus-based flame retardants (FRs), however, developing flame retardant PLA-based engineering composites with maintained mechanical performance is still a challenge. This study proposes symbiosis approaches to enhance the flame retardancy behavior of polylactide [...] Read more.
Flame retardancy properties of neat PLA can be improved with different phosphorus-based flame retardants (FRs), however, developing flame retardant PLA-based engineering composites with maintained mechanical performance is still a challenge. This study proposes symbiosis approaches to enhance the flame retardancy behavior of polylactide (PLA) composites with 20 wt% short glass fibers (GF). This was first implemented by exploring the effects of various phosphorus-based FRs up to 5 wt% in neat PLA samples. Among the used phosphorus-based FRs, the use of only 3 wt% of diphosphoric acid-based FR (P/N), melamine coated ammonium polyphosphate (APPcoated), and APP with melamine synergist (APP/Mel) resulted in achieving the V0 value in a vertical burning test in the neat PLA samples. In addition to their superior efficiency in improving the flame retardancy of neat PLA, P/N had the least negative effect on the final mechanical performance of PLA samples. When incorporated in PLA composites with 20 wt% GF, however, even with the use of 30 wt% P/N, the V0 value could not be obtained due to the candlewick effect. To resolve this issue, the synergistic effect of P/N and aromatic polycarbodiimide (PCDI) cross-linker or Joncryl epoxy-based chain-extender (CE) on the flame retardancy characteristics of composites was examined. Due to the further chain modification, which also enhances the melt strength of PLA, the dripping of composites in the vertical burning test terminated and the V0 value could be reached when using only 1 wt% PCDI or CE. According to the scanning electron microscopic analysis, the use of noted chain modifiers further homogenized the distribution and refined the particle size of P/N within the PLA matrix. Hence this could synergistically contribute to the enhancements of the fire resistance performance of the PLA composites. Such incorporation of P/N and chain modifiers further leads to the enhancement of the mechanical performance of PLA composites and hence the resultant product can be proposed as a promising durable bioplastic engineering product where fire risk exists. Full article
(This article belongs to the Special Issue Advance in Polymer-Based Flame Retardant Materials)
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<p>MFI results of PLA and PLA composites with and without FR and chain modifiers at 190 °C and 2.16 kg.</p> Full article ">Figure 2
<p>Possible reaction between PLA and the PCDI [<a href="#B55-polymers-14-05324" class="html-bibr">55</a>].</p> Full article ">Figure 3
<p>The possible reaction between PLA and the epoxy chain extender [<a href="#B47-polymers-14-05324" class="html-bibr">47</a>].</p> Full article ">Figure 4
<p>SEM images of impact fracture surfaces: (<b>a</b>) PA-GF-25FR; (<b>b</b>) PLA-GF-24FR-1PCDI; (<b>c</b>) PLA-GF-24FR-CE (the scale bar is 1 μm).</p> Full article ">Figure 5
<p>Piperazine pyrophosphate [<a href="#B59-polymers-14-05324" class="html-bibr">59</a>].</p> Full article ">Figure 6
<p>Possible flame retardant mechanism of PLA GF composites.</p> Full article ">Figure 7
<p>Storage modulus comparison of PLA composites with (<b>a</b>) 25 wt% and (<b>b</b>) 30 wt% FR; and tan δ graphs with (<b>c</b>) 25 wt% and (<b>d</b>) 30 wt% FR.</p> Full article ">Figure 8
<p>TG curves of the neat PLA and PLA-GF composites (<b>a</b>) comparison with 25 wt% FR content (<b>b</b>) comparison with 30 wt% FR content; and DTG graphs with (<b>c</b>) 25 wt% and (<b>d</b>) 30 wt% FR.</p> Full article ">
19 pages, 6543 KiB  
Article
Enhancement of Mechanical Properties and Bonding Properties of Flake-Zinc-Powder-Modified Epoxy Resin Composites
by Xu Luo, Yu Li, Shuaijie Li and Xin Liu
Polymers 2022, 14(23), 5323; https://doi.org/10.3390/polym14235323 - 5 Dec 2022
Cited by 8 | Viewed by 1879
Abstract
As a typical brittle material, epoxy resin cannot meet its application requirements in specific fields by only considering a single toughening method. In this paper, the effects of carboxyl-terminated polybutylene adipate (CTPBA) and zinc powder on the mechanical properties, adhesion properties, thermodynamic properties [...] Read more.
As a typical brittle material, epoxy resin cannot meet its application requirements in specific fields by only considering a single toughening method. In this paper, the effects of carboxyl-terminated polybutylene adipate (CTPBA) and zinc powder on the mechanical properties, adhesion properties, thermodynamic properties and medium resistance of epoxy resin were studied. A silane coupling agent (KH-550) was used to modify zinc powder. It was found that KH-550 could significantly improve the mechanical properties and bonding properties of epoxy resin, and the modification effect of flake zinc powder (f-Zn) was significantly better than that of spherical zinc powder (s-Zn). When the addition amount of f-Zn was 5 phr, the tensile shear strength and peel strength of the composites reached a maximum value of 13.16 MPa and 0.124 kN/m, respectively, which were 15.95% and 55% higher than those without filler. The tensile strength and impact strength reached a maximum value of 43.09 MPa and 7.09 kJ/m2, respectively, which were 40.54% and 91.11% higher than those without filler. This study provides scientific support for the preparation of f-Zn-modified epoxy resin. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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<p>The schematic diagram of the preparation process of Mf-Zn/CTPBA/EP.</p> Full article ">Figure 2
<p>Infrared spectra of (<b>a</b>) s-Zn and Ms-Zn; (<b>b</b>) f-Zn and Mf-Zn.</p> Full article ">Figure 3
<p>XRD spectra of f-Zn, Mf-Zn, s-Zn and Ms-Zn.</p> Full article ">Figure 4
<p>SEM images of (<b>a</b>) f-Zn, (<b>c</b>) Mf-Zn, (<b>e</b>) s-Zn and (<b>g</b>) Ms-Zn; The dashed line points to the EDS spectra of (<b>b</b>) f-Zn, (<b>d</b>) Mf-Zn, (<b>f</b>) s-Zn, (<b>h</b>) Ms-Zn for this location.</p> Full article ">Figure 4 Cont.
<p>SEM images of (<b>a</b>) f-Zn, (<b>c</b>) Mf-Zn, (<b>e</b>) s-Zn and (<b>g</b>) Ms-Zn; The dashed line points to the EDS spectra of (<b>b</b>) f-Zn, (<b>d</b>) Mf-Zn, (<b>f</b>) s-Zn, (<b>h</b>) Ms-Zn for this location.</p> Full article ">Figure 5
<p>Contact angle of (<b>a</b>) s-Zn; (<b>b</b>) Ms-Zn; (<b>c</b>) f-Zn; (<b>d</b>) Mf-Zn.</p> Full article ">Figure 5 Cont.
<p>Contact angle of (<b>a</b>) s-Zn; (<b>b</b>) Ms-Zn; (<b>c</b>) f-Zn; (<b>d</b>) Mf-Zn.</p> Full article ">Figure 6
<p>Effect of Mf-Zn and Ms-Zn content on the tensile shear strength of the CTPBA/EP epoxy resin.</p> Full article ">Figure 7
<p>Effect of Mf-Zn and Ms-Zn content on the peel strength of the CTPBA/EP epoxy resin adhesive.</p> Full article ">Figure 8
<p>(<b>a</b>) Tensile strength and (<b>b</b>) elongation at break curve of Mf-Zn and Ms-Zn on the CTPBA/EP epoxy resin adhesives.</p> Full article ">Figure 9
<p>Impact strength curve of Mf-Zn and Ms-Zn on CTPBA/EP.</p> Full article ">Figure 10
<p>SEM images of (<b>a</b>) 0 phr; (<b>b</b>) 5 phr; (<b>c</b>) 10 phr; (<b>d</b>) 15 phr; (<b>e</b>) 20 phr and (<b>f</b>) 30 phr Mf-Zn-modified CTPBA/EP epoxy resin impact section.</p> Full article ">Figure 11
<p>EDS diagram of impact section of epoxy resin adhesive with 5 phr (<b>a</b>) Mf-Zn, (<b>b</b>) Ms-Zn content.</p> Full article ">Figure 12
<p>SEM images of (<b>a</b>) 0 phr; (<b>b</b>) 5 phr; (<b>c</b>) 10 phr; (<b>d</b>) 15 phr; (<b>e</b>) 20 phr and (<b>f</b>) 30 phr Ms-Zn-modified CTPBA/EP epoxy resin impact section.</p> Full article ">Figure 13
<p>(<b>a</b>) TG curve; (<b>b</b>) DTG curve of CTPBA/EP epoxy resin adhesives modified with different Mf-Zn content.</p> Full article ">Figure 14
<p>T-tanδ curves of CTPBA/EP epoxy resin adhesives modified with different Mf-Zn content.</p> Full article ">Figure 15
<p>(<b>a</b>) The mass change rate of Mf-Zn/CTPBA/EP immersed in different media; (<b>b</b>) Tensile shear strength of Mf-Zn/CTPBA/EP immersed in different media.</p> Full article ">
15 pages, 3292 KiB  
Article
Curing Kinetics of Bioderived Furan-Based Epoxy Resins: Study on the Effect of the Epoxy Monomer/Hardener Ratio
by Angela Marotta, Noemi Faggio and Cosimo Brondi
Polymers 2022, 14(23), 5322; https://doi.org/10.3390/polym14235322 - 5 Dec 2022
Cited by 4 | Viewed by 1904
Abstract
The potential of furan-based epoxy thermosets as a greener alternative to diglycidyl ether of Bisphenol A (DGEBA)-based resins has been demonstrated in recent literature. Therefore, a deep investigation of the curing behaviour of these systems may allow their use for industrial applications. In [...] Read more.
The potential of furan-based epoxy thermosets as a greener alternative to diglycidyl ether of Bisphenol A (DGEBA)-based resins has been demonstrated in recent literature. Therefore, a deep investigation of the curing behaviour of these systems may allow their use for industrial applications. In this work, the curing mechanism of 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) with methyl nadic anhydride (MNA) in the presence of 2-methylimidazole as a catalyst is analyzed. In particular, three systems characterized by different epoxy/anhydride molar ratios are investigated. The curing kinetics are studied through differential scanning calorimetry, both in isothermal and non-isothermal modes. The total heat of reaction of the epoxy resin as well as its activation energy are estimated by the non-isothermal measurements, while the fitting of isothermal data with Kamal’s autocatalytic model provides the kinetic parameters. The results are discussed as a function of the resin composition. The global activation energy for the curing process of BOMF/MNA resins is in the range 72–79 kJ/mol, depending on both the model used and the sample composition; higher values are experienced by the system with balanced stoichiometry. By the fitting of the isothermal analysis, it emerged that the order of reaction is not only dependent on the temperature, but also on the composition, even though the values range between 0.31 and 1.24. Full article
(This article belongs to the Special Issue Bio-Based Polymers' Application and Technology for Better Quality of Life)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Non-isothermal DSC thermograms of BOMF/MNA resins with (<b>a</b>) a stoichiometric epoxy/anhydride ratio, (<b>c</b>) epoxy excess, and (<b>e</b>) anhydride excess. Dynamic DSC analyses were conducted at five heating rates (i.e., 1 °C/min, 1.5 °C/min, 3 °C/min, 5 °C/min, and 10 °C/min) for each sample. Isothermal DSC thermograms of BOMF/MNA resins with (<b>b</b>) a stoichiometric epoxy/anhydride ratio, (<b>d</b>) epoxy excess, and (<b>f</b>) anhydride excess at five different temperatures (i.e., 90, 100, 110, 120, and 130 °C) for each sample.</p> Full article ">Figure 1 Cont.
<p>Non-isothermal DSC thermograms of BOMF/MNA resins with (<b>a</b>) a stoichiometric epoxy/anhydride ratio, (<b>c</b>) epoxy excess, and (<b>e</b>) anhydride excess. Dynamic DSC analyses were conducted at five heating rates (i.e., 1 °C/min, 1.5 °C/min, 3 °C/min, 5 °C/min, and 10 °C/min) for each sample. Isothermal DSC thermograms of BOMF/MNA resins with (<b>b</b>) a stoichiometric epoxy/anhydride ratio, (<b>d</b>) epoxy excess, and (<b>f</b>) anhydride excess at five different temperatures (i.e., 90, 100, 110, 120, and 130 °C) for each sample.</p> Full article ">Figure 2
<p>Plots of the heating rate versus 1/<span class="html-italic">T<sub>p</sub></span>. Dash lines represent the linear fit according to (<b>a</b>) Kissinger (Equation (11)) and (<b>b</b>) Ozawa (Equation (13)).</p> Full article ">Figure 3
<p>Plots of the degree of conversion (<span class="html-italic">α</span>) as a function of time and conversion rate (<span class="html-italic">dα</span>/<span class="html-italic">dt</span>) as function of conversion for epoxy/anhydride mixtures with (<b>a</b>,<b>b</b>) a stoichiometric ratio, (<b>c</b>,<b>d</b>) epoxy excess, and (<b>e,f</b>) anhydride excess, respectively. Solid lines in (<b>b</b>,<b>d</b>,<b>f</b>) represent the fitting curves of the experimental data by the Kamal model (Equation (9)).</p> Full article ">Figure 3 Cont.
<p>Plots of the degree of conversion (<span class="html-italic">α</span>) as a function of time and conversion rate (<span class="html-italic">dα</span>/<span class="html-italic">dt</span>) as function of conversion for epoxy/anhydride mixtures with (<b>a</b>,<b>b</b>) a stoichiometric ratio, (<b>c</b>,<b>d</b>) epoxy excess, and (<b>e,f</b>) anhydride excess, respectively. Solid lines in (<b>b</b>,<b>d</b>,<b>f</b>) represent the fitting curves of the experimental data by the Kamal model (Equation (9)).</p> Full article ">Figure 4
<p>Linear plots of the logarithm of the rate constants, (<b>a</b>) ln(<span class="html-italic">k</span><sub>1</sub>) and (<b>b</b>) ln(<span class="html-italic">k</span><sub>2</sub>)), obtained by fitting the isothermal data with the Kamal model (Equation (9)) as function of the inverse of the cure temperature (1/<span class="html-italic">T<sub>c</sub></span>) at different epoxy/anhydride ratios.</p> Full article ">Scheme 1
<p>Reaction steps of epoxy/anhydride cure: (<b>a</b>) initiation, (<b>b</b>) propagation, (<b>c</b>) polyetherification and (<b>d</b>) polyesterification.</p> Full article ">
37 pages, 8946 KiB  
Review
Advanced Optical Wavefront Technologies to Improve Patient Quality of Vision and Meet Clinical Requests
by Martina Vacalebre, Renato Frison, Carmelo Corsaro, Fortunato Neri, Sabrina Conoci, Elena Anastasi, Maria Cristina Curatolo and Enza Fazio
Polymers 2022, 14(23), 5321; https://doi.org/10.3390/polym14235321 - 5 Dec 2022
Cited by 8 | Viewed by 3770
Abstract
Adaptive optics (AO) is employed for the continuous measurement and correction of ocular aberrations. Human eye refractive errors (lower-order aberrations such as myopia and astigmatism) are corrected with contact lenses and excimer laser surgery. Under twilight vision conditions, when the pupil of the [...] Read more.
Adaptive optics (AO) is employed for the continuous measurement and correction of ocular aberrations. Human eye refractive errors (lower-order aberrations such as myopia and astigmatism) are corrected with contact lenses and excimer laser surgery. Under twilight vision conditions, when the pupil of the human eye dilates to 5–7 mm in diameter, higher-order aberrations affect the visual acuity. The combined use of wavefront (WF) technology and AO systems allows the pre-operative evaluation of refractive surgical procedures to compensate for the higher-order optical aberrations of the human eye, guiding the surgeon in choosing the procedure parameters. Here, we report a brief history of AO, starting from the description of the Shack–Hartmann method, which allowed the first in vivo measurement of the eye’s wave aberration, the wavefront sensing technologies (WSTs), and their principles. Then, the limitations of the ocular wavefront ascribed to the IOL polymeric materials and design, as well as future perspectives on improving patient vision quality and meeting clinical requests, are described. Full article
(This article belongs to the Section Polymer Applications)
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<p>Scheme of wavefronts and corresponding contour maps for different cases. Teal color indicates no deviations; colors towards yellow indicate positive deviations, while those towards blue indicate negative deviations. Therefore, in the case of the myopic eye (bottom-left panel) the wavefront is represented by a paraboloid with the minimum in the center and the maximum at the edge. The contrary happens in the case of the hyperopic eye (top-right panel): the paraboloid is turned upside down with the maximum in the center and the minimum at the edges. Figure adapted with permission from Wiley from Ref. [<a href="#B3-polymers-14-05321" class="html-bibr">3</a>] Naoyuki Maeda, Clinical applications of wavefront aberrometry—a review, <span class="html-italic">Clinical &amp; Experimental Ophthalmology</span>, 37: 118–129. © 2009 Royal Australian and New Zealand College of Ophthalmologists.</p> Full article ">Figure 2
<p>Zernike pyramid. As for previous figure colors towards yellow indicate positive deviations, while those towards blue indicate negative deviations. Zero deviations are indicated in teal color.</p> Full article ">Figure 3
<p>Working principle of the Shack–Hartmann sensor: the micro-lenslet array (green ellipses) creates spots (full red circles) on the sensor according to the wavefront (big solid red line) coming out of the eye. Figure reused with permission from Ref. [<a href="#B47-polymers-14-05321" class="html-bibr">47</a>] Larry N. Thibos, Principles of Hartmann-Shack Aberrometry, <span class="html-italic">Journal of Refractive Surgery</span> 16, S563-S565, 2000, copyright International Society of Refractive Surgery.</p> Full article ">Figure 4
<p>Principle of optical differentiation WF sensor. A filter with linear field transmission gradient is located at the Fourier plane of a 4f line. Figure reused from Ref. [<a href="#B28-polymers-14-05321" class="html-bibr">28</a>] under the terms of the OSA Open Access Publishing Agreement, © 2019 Optical Society of America.</p> Full article ">Figure 5
<p>(<b>a</b>) Pyramid sensor (adapted with permission from Ref. [<a href="#B58-polymers-14-05321" class="html-bibr">58</a>] I. Shatokhina, V. Hutterer, R. Ramlau, Review on methods for wavefront reconstruction from pyramid wavefront sensor data, <span class="html-italic">Journal of Astronomical Telescopes, Instruments, and Systems</span>, 6 (1), 010901 (2020). © 2020 Society of Photo-Optical Instrumentation Engineers (SPIE). (<b>b</b>–<b>d</b>) Simulated CCD images of the source at different pyramid positions and Zemax images showing the ray behavior close to the PS for different aberrations. See main text for details.</p> Full article ">Figure 6
<p>Principle of the curvature wavefront sensor. The wavefront curvature distribution can be evaluated by measuring the non-uniform illumination at two positions, before and after the pupil plane. Figure reprinted from Ref. [<a href="#B15-polymers-14-05321" class="html-bibr">15</a>] New methods and techniques for sensing the wave aberrations of human eyes, M. Lombardo and G. Lombardo, <span class="html-italic">Clinical and Experimental Optometry</span>, 2009 Taylor &amp; Francis Ltd., with permission of the publisher (Taylor &amp; Francis Ltd., Abingdon-on-Thames, UK, <a href="http://www.tandfonline.com" target="_blank">http://www.tandfonline.com</a>).</p> Full article ">Figure 7
<p>Differences between the dynamic range explored by SHWFS (<b>a</b>) and DWFS (<b>b</b>). The big squares represent the zoomed vision of the selected area. Figure reused from Ref. [<a href="#B24-polymers-14-05321" class="html-bibr">24</a>] under the terms of the OSA Open Access Publishing Agreement, © 2019 Optical Society of America.</p> Full article ">Figure 8
<p>The measured spherical equivalent power (M) versus the trial lens power for SHWFS (blue symbols) and DWFS (red symbols) for three different illuminating sources: LD (<b>a</b>), LD+LSR (<b>b</b>), and LED (<b>c</b>). Dashed vertical lines indicate the corresponding predicted dynamic range. * Power-limited. Figure reused from Ref. [<a href="#B24-polymers-14-05321" class="html-bibr">24</a>] under the terms of the OSA Open Access Publishing Agreement, © 2019 Optical Society of America.</p> Full article ">Figure 9
<p>Coordinate system of the original (W, dashed circle) and the two sheared wavefronts, W1 and W2, as when adopting the shearing interferometry. Figure reprinted from Ref. [<a href="#B15-polymers-14-05321" class="html-bibr">15</a>] New methods and techniques for sensing the wave aberrations of human eyes, M. Lombardo and G. Lombardo, <span class="html-italic">Clinical and Experimental Optometry</span>, 2009 Taylor &amp; Francis Ltd., with permission of the publisher (Taylor &amp; Francis Ltd., Abingdon-on-Thames, UK, <a href="http://www.tandfonline.com" target="_blank">http://www.tandfonline.com</a>).</p> Full article ">Figure 10
<p>Talbot Moiré principle where d represents the spacing of the grating, b the width of the slit, Δz the Talbot distance and Δs the local phase shift of the fundamental frequency component of the grating image. Figure reprinted from Ref. [<a href="#B15-polymers-14-05321" class="html-bibr">15</a>] New methods and techniques for sensing the wave aberrations of human eyes, M. Lombardo and G. Lombardo, <span class="html-italic">Clinical and Experimental Optometry</span>, 2009 Taylor &amp; Francis Ltd., with permission of the publisher (Taylor &amp; Francis Ltd., Abingdon-on-Thames, UK, <a href="http://www.tandfonline.com" target="_blank">http://www.tandfonline.com</a>).</p> Full article ">Figure 11
<p>Scheme of the wavefront analyzer based on the principles of Tscherning aberrometer. Figure reused with permission from Ref. [<a href="#B32-polymers-14-05321" class="html-bibr">32</a>], M. Mrochen et al., Principles of Tscherning Aberrometry, <span class="html-italic">Journal of Refractive Surgery</span> 16, S570-S571, 2000, copyright International Society of Refractive Surgery.</p> Full article ">Figure 12
<p>Basic setup of the laser ray tracing technique. The retinal image (A, B) is projected onto a CCD camera forming the image (A’, B’). Figure adapted with permission from Ref. [<a href="#B48-polymers-14-05321" class="html-bibr">48</a>] © The Optical Society.</p> Full article ">Figure 13
<p>Scheme of a simple optical setup for the measurement of wavefront aberrations. Figure reprinted from Ref. [<a href="#B76-polymers-14-05321" class="html-bibr">76</a>] under the terms of the Creative Commons Attribution License.</p> Full article ">Figure 14
<p>Scheme of an optical layout using an artificial cornea. Reprinted from Ref. [<a href="#B77-polymers-14-05321" class="html-bibr">77</a>] under the terms of the Creative Commons Attribution (CC BY) license by IOP Publishing Ltd., Bristol, UK.</p> Full article ">Figure 15
<p>Setup to measure the 1st (<b>left</b>) and 0th (<b>right</b>) order diffractive efficiency. The 0th order remains collimated behind the diffractive lens and is brought to focus by using an additional convergent lens of 100 mm focal length (<b>right</b>), which has a high Strehl ratio (98%). The Strehl ratio S is a suitable figure of merit, defined as the normalized peak intensity of the PSF of the lens: S = I<sub>real</sub>(0,0)/I<sub>ideal</sub>(0,0) = |∫∫e<sup>ikψ(x,y)</sup> dxdy|<sup>2</sup> where I<sub>real</sub>(0, 0) and I<sub>ideal</sub>(0, 0) denote the intensities at the center of the real point image and the ideal point spread function (PSF) without aberrations, respectively [<a href="#B19-polymers-14-05321" class="html-bibr">19</a>]. Figure reprinted from Ref. [<a href="#B82-polymers-14-05321" class="html-bibr">82</a>] under the terms of the Creative Commons Attribution License 4.0.</p> Full article ">Figure 16
<p>Complete adaptive optics IOL metrology system. Reprinted with permission from Ref. [<a href="#B83-polymers-14-05321" class="html-bibr">83</a>]. L. Zheleznyak et al. Impact of corneal aberrations on through-focus image quality of presbyopia-correcting intraocular lenses using an adaptive optics bench system, <span class="html-italic">Journal of Cataract and Refractive Surgery</span> 38 (10):1724–1733, 2012, © Wolters Kluwer Health, Inc., Philadelphia, PA, USA.</p> Full article ">Figure 17
<p>The adaptive system proposed by Williams et al. Figure reprinted with permission from Ref. [<a href="#B95-polymers-14-05321" class="html-bibr">95</a>] © The Optical Society.</p> Full article ">Figure 18
<p>Different categories of AO systems. Reprinted from Ref. [<a href="#B98-polymers-14-05321" class="html-bibr">98</a>] Progress in retinal and eye research, 68, S. A. Burns, A. E. Elsner, K. A. Sapoznik, R. L. Warner and T. J. Gast, Adaptive optics imaging of the human retina, pp. 1–30, Copyright (2019) with permission from Elsevier.</p> Full article ">Figure 19
<p>Binocular Shack–Hartmann wavefront sensor. A: aperture, L: lens (superscript represents focal length of the lens in mm), CBS: cube beamsplitter, PBS: pellicle beamsplitter, PM: plane mirror, HM: hot mirror. Figure reused from Ref. [<a href="#B102-polymers-14-05321" class="html-bibr">102</a>] under the terms of the OSA Open Access Publishing Agreement, © 2008 Optical Society of America.</p> Full article ">Figure 20
<p>Optical design of (<b>A</b>) Mini WELL and (<b>B</b>) Mini WELL PROXA. (Courtesy of SIFI SpA).</p> Full article ">Figure 21
<p>Theoretical Through-Focus Modulation Transfer Function (TF-MTF) curves of Mini WELL and Mini WELL PROXA with a 3 mm aperture and spatial frequency of 50 lp/mm. (Courtesy of SIFI SpA).</p> Full article ">Figure 22
<p>Maps of a post-RK eye. Top left: curvature map before simultaneous PRK–PTK. Top right: curvature map after simultaneous photorefractive keratectomy and phototherapeutic keratectomy (PRK–PTK). Bottom left: corneal wave aberration map before simultaneous PRK–PTK. Bottom right: corneal wave aberration map after simultaneous PRK–PTK. This figure was published in Ref. [<a href="#B112-polymers-14-05321" class="html-bibr">112</a>] <span class="html-italic">Journal of Cataract &amp; Refractive Surgery</span>, M. Camellin and S.A. Mosquera, Simultaneous aspheric wavefront-guided transepithelial photorefractive keratectomy and phototherapeutic keratectomy to correct aberrations and refractive errors after corneal surgery, 1173–1180, Copyright Elsevier (2010).</p> Full article ">Figure 23
<p>(<b>A</b>) Scheme of the scanning imaging system proposed by Guevara-Torres et al., composed of 5 pairs of afocal telescopes that relay coaligned beams for imaging and wavefront sensing. (<b>B</b>) The two possible scanning modes: (<b>i</b>) 2D raster scan and (<b>ii</b>) 1D line scan. See main text for more details. Figure reused from Ref. [<a href="#B119-polymers-14-05321" class="html-bibr">119</a>] under the terms of the OSA Open Access Publishing Agreement, © 2016 Optical Society of America.</p> Full article ">Figure 24
<p>Scheme of AO flood illumination ophthalmoscope. Figure reused from Ref. [<a href="#B124-polymers-14-05321" class="html-bibr">124</a>] under the terms of the OSA Open Access Publishing Agreement, © 2019 Optical Society of America.</p> Full article ">Figure 25
<p>The confocal configuration used to measure the shift in the focal spot. ND is a Neutral Density filter and DUT is the Device Under Test. Figure reprinted from Ref. [<a href="#B128-polymers-14-05321" class="html-bibr">128</a>] Charles Pelzman and Sang-Yeon Cho, “Wavefront detection using curved nanoscale apertures”, <span class="html-italic">Applied Physics Letters</span> 114, 183103 (2019), with the permission of AIP Publishing.</p> Full article ">Figure 26
<p>(<b>a</b>) Two-dimensional square lattice constituting an atomic Huygens surface with four atoms per unit cell. (<b>b</b>) An electric dipole moment, d (given by the vectorial sum of the individual dipole moments identified by the ticker blue arrows), is generated by the uniform polarization in the unit cell. (<b>c</b>) A magnetic dipole moment, m, is generated by the azimuthal polarization. Figure reused from Ref. [<a href="#B136-polymers-14-05321" class="html-bibr">136</a>] under the terms of the Creative Commons Attribution 4.0 International License.</p> Full article ">Figure 27
<p>Scheme of refractive surgery techniques. For more details, see Ref. [<a href="#B137-polymers-14-05321" class="html-bibr">137</a>].</p> Full article ">
16 pages, 6533 KiB  
Article
Structure and Properties of Epoxy Polysulfone Systems Modified with an Active Diluent
by Tuyara V. Petrova, Ilya V. Tretyakov, Alexey V. Kireynov, Alexey V. Shapagin, Nikita Yu. Budylin, Olga V. Alexeeva, Betal Z. Beshtoev, Vitaliy I. Solodilov, Gleb Yu. Yurkov and Alexander Al. Berlin
Polymers 2022, 14(23), 5320; https://doi.org/10.3390/polym14235320 - 5 Dec 2022
Cited by 9 | Viewed by 1827
Abstract
An epoxy resin modified with polysulfone (PSU) and active diluent furfuryl glycidyl ether (FGE) was studied. Triethanolaminotitanate (TEAT) and iso-methyltetrahydrophthalic anhydride (iso-MTHPA) were used as curing agents. It is shown that during the curing of initially homogeneous mixtures, heterogeneous structures are formed. The [...] Read more.
An epoxy resin modified with polysulfone (PSU) and active diluent furfuryl glycidyl ether (FGE) was studied. Triethanolaminotitanate (TEAT) and iso-methyltetrahydrophthalic anhydride (iso-MTHPA) were used as curing agents. It is shown that during the curing of initially homogeneous mixtures, heterogeneous structures are formed. The type of these structures depends on the concentration of active diluent and the type of hardener. The physico-mechanical properties of the hybrid matrices are determined by the structure formed. The maximum resistance to a growing crack is provided by structures with a thermoplastic-enriched matrix-interpenetrating structures. The main mechanism for increasing the energy of crack propagation is associated with the implementation of microplasticity of extended phases enriched in polysulfone and their involvement in the fracture process. Full article
(This article belongs to the Special Issue Mechanical Properties of Polymers)
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Figure 1
<p>Interferograms of the interdiffusion zones of the EO–FGE (<b>a</b>,<b>b</b>) and PSU–FGE (<b>c</b>,<b>d</b>) systems at 20 (<b>a</b>,<b>c</b>) and 160 °C (<b>b</b>,<b>d</b>).</p> Full article ">Figure 2
<p>Mechanical loss tangent angle tan δ (<b>a</b>) and elastic modulus E′ (<b>b</b>) of modified epoxy matrices cured with TEAT versus temperature T. The ratio of modifiers PSU/FGE: 1—P0/F0; 2—P20/F0; 3—P20/F10; 4—P20/F20; 5—P15/F20.</p> Full article ">Figure 3
<p>Mechanical loss tangent angle tan δ (<b>a</b>) and elastic modulus E′ (<b>b</b>) of modified epoxy matrices cured with iso-MTHPA versus temperature T. The ratio of modifiers PSU/FGE: 1—P0/ F0; 2—P20/F0; 3—P20/F10; 4—P20/F20; 5—P30/F20.</p> Full article ">Figure 4
<p>Strength σ, elastic modulus E and relative elongation ԑ at tension of epoxy systems EO + 20 wt. % of FGE, cured by TEAT, depending on the content of FGE: (<b>a</b>) 1—P0/F0, 2—P20/F0, 3—P20/F10; (<b>b</b>) 1 and 4—P0/F0, 2 and 5—P20/F0, 3 and 6—P20/F10. In (<b>b</b>) the upper curve corresponds to the modulus of elasticity, the lower curve corresponds to the relative elongation.</p> Full article ">Figure 5
<p>Strength σ, modulus of elasticity E and relative elongation ԑ at tension of epoxy systems EO + 20 wt. % FGE, cured iso-MTHPA, depending on the content of FGE: (<b>a</b>) 1—P0 /F0, 2—P20/F0, 3—P20/F10; (<b>b</b>) 1 and 4—P0/F0, 2 and 5—P20/F0, 3 and 6—P20/F10. In (<b>b</b>) the upper curve corresponds to the modulus of elasticity, the lower curve corresponds to the relative elongation.</p> Full article ">Figure 6
<p>Crack resistance G<sub>IR</sub> of epoxy systems EO + 20 wt. % FGE, cured with TEAT (<b>a</b>) or iso-MTHPA (<b>b</b>), modified with thermoplastic modifier PSU: 1—P0/F0; 2—P20/F0; 3—P20/F10.</p> Full article ">Figure 7
<p>Micrographs of the surface of cracks in the epoxy matrix cured with TEAT and modified PSU/FGE (wt. %): (<b>a</b>) 20/0; (<b>b</b>) 20/10; (<b>c</b>) 20/20; (<b>d</b>) 15/20.</p> Full article ">Figure 8
<p>Micrographs of the surface of cracks in the epoxy matrix cured with iso-MTHPA and modified with PSU/FGE (wt. %): (<b>a</b>) 20/0; (<b>b</b>) 20/10; (<b>c</b>) 20/20; (<b>d</b>) 30/20.</p> Full article ">Figure 9
<p>Schematic representation of PD in progress curing, where: 1—PD model systems PSU–EO; 2—model PD PSU–EO + FGE. o–figurative points of the curable systems PSU/FGE (wt. %): a—20/0, b—20/10, c—20/20, d—15/0. I, III—PD regions, where a “matrix-dispersion”; II—PD region, where a structure of the “interpenetrating phases” type is formed.</p> Full article ">
11 pages, 1882 KiB  
Review
Strategies for Improved Wettability of Polyetheretherketone (PEEK) Polymers by Non-Equilibrium Plasma Treatment
by Gregor Primc
Polymers 2022, 14(23), 5319; https://doi.org/10.3390/polym14235319 - 5 Dec 2022
Cited by 8 | Viewed by 3363
Abstract
Polyetheretherketone (PEEK) is the material of choice in several applications ranging from the automotive industry to medicine, but the surface properties are usually not adequate. A standard method for tailoring surface properties is the application of gaseous plasma. The surface finish depends enormously [...] Read more.
Polyetheretherketone (PEEK) is the material of choice in several applications ranging from the automotive industry to medicine, but the surface properties are usually not adequate. A standard method for tailoring surface properties is the application of gaseous plasma. The surface finish depends enormously on the processing parameters. This article presents a review of strategies adapted for improved wettability and adhesion of PEEK. The kinetics of positively charged ions, neutral reactive plasma species, and vacuum ultraviolet radiation on the surface finish are analyzed, and synergies are stressed where appropriate. The reviewed articles are critically assessed regarding the plasma and surface kinetics, and the surface mechanisms are illustrated. The directions for obtaining optimal surface finish are provided together with the scientific explanation of the limitations of various approaches. Super-hydrophilic surface finish is achievable by treatment with a large dose of vacuum ultraviolet radiation in the presence of oxidizing gas. Bombardment with positively charged ions of kinetic energy between about 100 and 1000 eV also enable high wettability, but one should be aware of excessive heating when using the ions. Full article
(This article belongs to the Special Issue Advances in Plasma Processes for Polymers II)
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<p>Schematic surface effects during PEEK treatment with weakly ionized oxygen plasma (<b>a</b>) and oxygen plasma afterglow (<b>b</b>).</p> Full article ">Figure 2
<p>Schematic of the surface effects during PEEK treatment with VUV radiation from an Xe excimer lamp.</p> Full article ">Figure 3
<p>Illustration of the surface effects upon irradiation of PEEK with Ar<sup>+</sup> ions in the absence of oxygen (<b>a</b>) and oxygen presence (<b>b</b>).</p> Full article ">Figure 4
<p>Schematic of the methods for super-hydrophilic surface finish of PEEK samples.</p> Full article ">Figure 5
<p>Schematic of the interaction between nitrogen plasma and PEEK surface at the beginning of treatment (<b>a</b>), after short (<b>b</b>) and long treatment time (<b>c</b>).</p> Full article ">
16 pages, 3097 KiB  
Article
Penetration Routes of Oxygen and Moisture into the Insulation of FR-EPDM Cables for Nuclear Power Plants
by Yoshimichi Ohki, Naoshi Hirai and Sohei Okada
Polymers 2022, 14(23), 5318; https://doi.org/10.3390/polym14235318 - 5 Dec 2022
Cited by 8 | Viewed by 1689
Abstract
The polymeric insulation used in nuclear power plants (NPPs) carries the risk of molecular breakage due to oxidation and hydrolysis in the event of an accident. With this in mind, tubular specimens of flame-retardant ethylene-propylene-diene rubber (FR-EPDM) insulation were obtained by taking conductors [...] Read more.
The polymeric insulation used in nuclear power plants (NPPs) carries the risk of molecular breakage due to oxidation and hydrolysis in the event of an accident. With this in mind, tubular specimens of flame-retardant ethylene-propylene-diene rubber (FR-EPDM) insulation were obtained by taking conductors out of a cable harvested from an NPP. Similar tubular specimens were made from a newly manufactured cable and those aged artificially using a method called the “superposition of time-dependent data.” The inner and outer surfaces of each tubular specimen were subjected to various instrumental analyses to examine their oxidation, moisture uptake, and cross-linking. As a result, it has become clear that oxygen penetrates the cable through gaps between the twisted conductor strands. Meanwhile, water vapor diffuses more often through the sheath than through gaps between the conductor strands. Of the two methods used to simulate design-based accidents in NPPs, the one used to simulate the designed loss-of-coolant accident is more severe to FR-EPDM than the one used to simulate the designed severe accident. In addition, the validity of the method called the “superposition of time-dependent data,” which is used to give artificial aging treatments to cable samples, was confirmed. Measurements of spin-spin relaxation time and residual dipolar coupling using time-domain nuclear magnetic resonance were found suitable to use to obtain information on the cross-linking of FR-EPDM insulation. Full article
(This article belongs to the Topic Polymers for Electrical Systems)
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<p>Conceptual drawing of the superposition of time-dependent data. Ordinate: elongation at break as an aging indicator. Abscissa: logarithmic aging time <span class="html-italic">t</span>. <span class="html-italic">T</span>: aging temperature. <span class="html-italic">D</span>: dose rate. α: shift factor.</p> Full article ">Figure 2
<p>Schematic image of the cross-sections, with different sizes, of the five cables A1, B0, B1, B2 and B3 used for research. Not to scale.</p> Full article ">Figure 3
<p>FT-MIR spectra observed on the outer surface (<b>a</b>) and the inner surface (<b>b</b>) of tubular specimens cut from cable B1L.</p> Full article ">Figure 4
<p>Normalized absorbance due to acid carbonyl, measured at each stage on various tubular specimens. The numeric letters on the abscissa represent the sample statuses; 1: new and unaged, 2: as removed from the NPP or aged equivalently, 3: after the radiation R<sub>L</sub>, 4: after the simulated LOCA, 5: after the radiation R<sub>S</sub>, 6: after the simulated SA. Refer also to <a href="#polymers-14-05318-t002" class="html-table">Table 2</a>. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> for sample symbols. Several data may overlap each other.</p> Full article ">Figure 5
<p>Normalized absorbance due to ester carbonyl measured at each stage on various tubular specimens. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols. Except for A1 and its treated stages, the absorbance in <a href="#polymers-14-05318-f005" class="html-fig">Figure 5</a>a is null.</p> Full article ">Figure 6
<p>Normalized absorbance due to OH groups measured at each stage on various tubular specimens. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols.</p> Full article ">Figure 7
<p>Weight losses measured at each stage in various tubular specimens due to the desorption of H<sub>2</sub>O in the range of 50 to 150 °C. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols. Several data may overlap each other.</p> Full article ">Figure 8
<p>Losses in total weight in a range of 50 to 900 °C, measured at each stage for various tubular specimens. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols. Several data may overlap each other.</p> Full article ">Figure 9
<p>Changes in gel fraction at each stage for various tubular specimens. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols. Several data may overlap each other.</p> Full article ">Figure 10
<p>Changes in the degree of swelling at each stage for various tubular specimens. Refer to <a href="#polymers-14-05318-t001" class="html-table">Table 1</a> and <a href="#polymers-14-05318-t002" class="html-table">Table 2</a> and <a href="#polymers-14-05318-f004" class="html-fig">Figure 4</a> for the meanings of the numerals on the abscissa and sample symbols. Several data may overlap each other.</p> Full article ">Figure 11
<p>Three transverse relaxation times of the five tubular samples and their dependence on gel fraction. (<b>a</b>) ●: <span class="html-italic">T</span>2(1) and <span style="color:red">▲</span>: <span class="html-italic">T</span>2(2), (<b>b</b>) <span style="color:#0070C0">■</span>: <span class="html-italic">T</span>2(3).</p> Full article ">Figure 12
<p>Residual dipolar coupling (RDC) measured for the five tubular samples as a function of gel fraction.</p> Full article ">
17 pages, 11376 KiB  
Article
Antibacterial Activity and Biocompatibility with the Concentration of Ginger Fraction in Biodegradable Gelatin Methacryloyl (GelMA) Hydrogel Coating for Medical Implants
by Seo-young Kim, Ae-jin Choi, Jung-Eun Park, Yong-seok Jang and Min-ho Lee
Polymers 2022, 14(23), 5317; https://doi.org/10.3390/polym14235317 - 5 Dec 2022
Cited by 9 | Viewed by 2399
Abstract
The gingerols and shogaols derived from ginger have excellent antibacterial properties against oral bacteria. However, some researchers have noted their dose-dependent potential toxicity. The aim of this study was to enhance the biofunctionality and biocompatibility of the application of ginger to dental titanium [...] Read more.
The gingerols and shogaols derived from ginger have excellent antibacterial properties against oral bacteria. However, some researchers have noted their dose-dependent potential toxicity. The aim of this study was to enhance the biofunctionality and biocompatibility of the application of ginger to dental titanium screws. To increase the amount of coating of the n-hexane-fractionated ginger on the titanium surface and to control its release, ginger was loaded in different concentrations in a photo-crosslinkable GelMA hydrogel. To improve coating stability of the ginger hydrogel (GH), the wettability of the surface was modified by pre-calcification (TNC), then GH was applied on the surface. As a result, the ginger fraction, with a high content of phenolic compounds, was effective in the inhibition of the growth of S. mutans and P. gingivalis. The GH slowly released the main compounds of ginger and showed excellent antibacterial effects with the concentration. Although bone regeneration was slightly reduced with the ginger-loading concentration due to the increased contents of polyphenolic compounds, it was strongly supplemented through the promotion of osteosis formation by the hydrogel and TNC coating. Finally, we proved the biosafety and superior biofunctionalities the GH−TNC coating on a Ti implant. However, it is recommended to use an appropriate concentration, because an excessive concentration of ginger may affect the improved biocompatibility in clinical applications. Full article
(This article belongs to the Special Issue Functional Polymer Biomaterials)
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<p>Description of the surface modification methods; (<b>A</b>) coating procedure and (<b>B</b>) group names.</p> Full article ">Figure 2
<p>Implantation of a surface-modified Ti screw in the tibial defect; (<b>A</b>) design of the Ti screw, (<b>B</b>) procedure of the surgery.</p> Full article ">Figure 3
<p>Characterization of ginger<sub>(sol)</sub> [extract vs fraction]; (<b>A</b>) content of main compounds (%), (<b>B</b>) MIC and MBC against <span class="html-italic">Streptococcus mutans</span> and <span class="html-italic">Porphyromonas gingivalis</span>], and (<b>C</b>) chemical structure with the concentration of ginger<sub>(fraction)</sub> in the GelMA hydrogel coating on the TNC surface.</p> Full article ">Figure 4
<p>(<b>A</b>) Analysis of the ginger<sub>(fraction)</sub>-loaded hydrogel by UV−vis [(<b>I</b>) peak-detection of materials, (<b>II</b>) standard curve of absorbance with the concentration of ginger at 287 nm, (<b>III</b>) release of ginger from the hydrogel at 15 days of immersion in DW], and (<b>B</b>) degradation of ginger<sub>(fraction)</sub>-loaded hydrogels depending on time.</p> Full article ">Figure 5
<p>Characterization of the GH−TNC surfaces (<b>A</b>,<b>C-I</b>) before and (<b>B</b>,<b>C-II</b>) after 10 days of immersion in HBSS; the morphologies and composition were obtained by FE-SEM and the crystal structure by XRD.</p> Full article ">Figure 6
<p>Bacterial viability (%) and morphology on the GH−TNC surfaces for <span class="html-italic">Streptococcus mutans</span> and <span class="html-italic">Porphyromonas gingivalis</span>.</p> Full article ">Figure 7
<p>(<b>A</b>) Proliferation of MC3T3-E1 cells in the extract media from the modified surfaces and (<b>B</b>) their morphologies. * It means that there is not significant difference (* <span class="html-italic">p</span> &gt; 0.05).</p> Full article ">Figure 8
<p>(<b>A</b>) SEM images on the surface and cross-section after GH−TNC coating on the Ti screw; (<b>B</b>) histological images after implantation of the surface-modified screw on the tibial defect of a rat for 2 and 6 weeks.</p> Full article ">
15 pages, 3405 KiB  
Article
High Multi-Environmental Mechanical Stability and Adhesive Transparent Ionic Conductive Hydrogels Used as Smart Wearable Devices
by Yuxuan Wu, Jing Liu, Zhen Chen, Yujie Chen, Wenzheng Chen, Hua Li and Hezhou Liu
Polymers 2022, 14(23), 5316; https://doi.org/10.3390/polym14235316 - 5 Dec 2022
Cited by 5 | Viewed by 1903
Abstract
Ionic conductive hydrogels used as flexible wearable sensor devices have attracted considerable attention because of their easy preparation, biocompatibility, and macro/micro mechanosensitive properties. However, developing an integrated conductive hydrogel that combines high mechanical stability, strong adhesion, and excellent mechanosensitive properties to meet practical [...] Read more.
Ionic conductive hydrogels used as flexible wearable sensor devices have attracted considerable attention because of their easy preparation, biocompatibility, and macro/micro mechanosensitive properties. However, developing an integrated conductive hydrogel that combines high mechanical stability, strong adhesion, and excellent mechanosensitive properties to meet practical requirements remains a great challenge owing to the incompatibility of properties. Herein, we prepare a multifunctional ionic conductive hydrogel by introducing high-modulus bacterial cellulose (BC) to form the skeleton of double networks, which exhibit great mechanical properties in both tensile (83.4 kPa, 1235.9% strain) and compressive (207.2 kPa, 79.9% strain) stress–strain tests. Besides, the fabricated hydrogels containing high-concentration Ca2+ show excellent anti-freezing (high ionic conductivities of 1.92 and 0.36 S/m at room temperature and −35 ∘C, respectively) properties. Furthermore, the sensing mechanism based on the conductive units and applied voltage are investigated to the benefit of the practical applications of prepared hydrogels. Therefore, the designed and fabricated hydrogels provide a novel strategy and can serve as candidates in the fields of sensors, ionic skins, and soft robots. Full article
(This article belongs to the Special Issue Polymer Based Electronic Devices and Sensors II)
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<p>(<b>a</b>) Schematic diagram of hydrogel structure. (<b>b</b>) SEM images of P(AA-AMPS), P(AA-AMPS)-TA@BC, P(AA-AMPS)-TA@BC-Ca<sup>2+</sup> hydrogel. (<b>c</b>) AFM images of BC and TA@BC cellulose. (<b>d</b>) Thickness distribution curve of BC and TA@BC in AFM.</p> Full article ">Figure 2
<p>The FT-IR spectra of AA, AMPS, TA, BC, TA@BC, P(AA-AMPS), P(AA-AMPS)-TA@BC, and P(AA-AMPS)-TA@BC.</p> Full article ">Figure 3
<p>Tensile properties of hydrogel. (<b>a</b>) Tensile stress–strain curves of P(AA-AMPS)-TA@BC-Ca<sup>2+</sup> hydrogels with different concentrations of TA@BC; (<b>b</b>) stretch–release cycle (600%, 5 cycles) of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel; (<b>c</b>) tensile stress–strain histogram of P(AA-AMPS), P(AA-AMPS)-TA@BC<sub>0.5</sub>, and P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogels (black columns: stress, red columns: strain); (<b>d</b>) tensile stress–strain histogram of P(AA-AMPs)-TA@BC-Ca<sup>2+</sup> hydrogels with different concentrations of Ca<sup>2+</sup> ions (black columns: stress, red columns: strain).</p> Full article ">Figure 4
<p>Anti-freezing and moisturizing properties of the hydrogel. (<b>a</b>) DSC curves of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogels with different Ca<sup>2+</sup> concentrations during the heating process; (<b>b</b>) optical images of P(AA-AMPS) and P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel at −20 °C; (<b>c</b>) stress–strain curves of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel before and after being stored at −20 °C for 24 h; (<b>d</b>) mass curves of P(AA-AMPS) and P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogels at room temperature; (<b>e</b>) optical images of P(AA-AMPS) and P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel in room temperature; (<b>f</b>) stress–strain curves before and after 120 h storage in room temperature.</p> Full article ">Figure 5
<p>Adhesion properties of the hydrogel. (<b>a</b>) Optical images of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel adhesion to different substrate materials; (<b>b</b>) schematic illustrations of the adhesion mechanism; (<b>c</b>) tensile adhesion strength of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel to different matrix materials; (<b>d</b>) adhesion energy of P(AA-AMPS)-TA@BC<sub>0.5</sub>-Ca<sup>2+</sup> hydrogel on different matrix materials.</p> Full article ">Figure 6
<p>Mechanosensitive performances of the hydrogel. (<b>a</b>) The brightness of LED lamp observed at different hydrogel strains; (<b>b</b>) the RRCs of hydrogel strip at the elongation form 2.5% to 30%; (<b>c</b>) the RRCs of hydrogel strip at the elongation form 100 to 900%; (<b>d</b>) mechanical response performance of hydrogel with 1M Ca<sup>2+</sup> concentration under 10% to 500% strain; (<b>e</b>) mechanical response performance of hydrogel with 2M Ca<sup>2+</sup> concentration under 10% to 500% strain; (<b>f</b>) comparison of RRCs values of hydrogels with different Ca<sup>2+</sup> concentrations; (<b>g</b>) under 1 V, mechanical sensing under 10% to 500% strain; (<b>h</b>) under 1.5 V, mechanical sensing under 10% to 500% strain; (<b>i</b>) comparison of RRC values of hydrogels under diverse voltage.</p> Full article ">Figure 7
<p>(<b>a</b>) RRCs from finger motion of different angles (0°, 30°, 60°, 90°). (<b>b</b>) RRC values change under continuous and slow bending; (<b>c</b>) optical picture corresponding to finger bending; (<b>d</b>) corresponding curve of bending angle and RRC value; (<b>e</b>) schematic illustration of the setup for handwriting sensing; (<b>f</b>) RRCs for “1”, “2”, and “3” written on the PET film; (<b>g</b>) RRCs of the pulse beating before and after running for 5 min.</p> Full article ">
14 pages, 2951 KiB  
Article
Novel Non-Viral Vectors Based on Pluronic® F68PEI with Application in Oncology Field
by Inês Silva, Cátia Domingues, Ivana Jarak, Rui A. Carvalho, Rosemeyre A. Cordeiro, Marília Dourado, Francisco Veiga, Henrique Faneca and Ana Figueiras
Polymers 2022, 14(23), 5315; https://doi.org/10.3390/polym14235315 - 5 Dec 2022
Cited by 1 | Viewed by 1948
Abstract
Copolymers composed of low-molecular-weight polyethylenimine (PEI) and amphiphilic Pluronics® are safe and efficient non-viral vectors for pDNA transfection. A variety of Pluronic® properties provides a base for tailoring transfection efficacy in combination with the unique biological activity of this polymer group. [...] Read more.
Copolymers composed of low-molecular-weight polyethylenimine (PEI) and amphiphilic Pluronics® are safe and efficient non-viral vectors for pDNA transfection. A variety of Pluronic® properties provides a base for tailoring transfection efficacy in combination with the unique biological activity of this polymer group. In this study, we describe the preparation of new copolymers based on hydrophilic Pluronic® F68 and PEI (F68PEI). F68PEI polyplexes obtained by doping with free F68 (1:2 and 1:5 w/w) allowed for fine-tuning of physicochemical properties and transfection activity, demonstrating improved in vitro transfection of the human bone osteosarcoma epithelial (U2OS) and oral squamous cell carcinoma (SCC-9) cells when compared to the parent formulation, F68PEI. Although all tested systems condensed pDNA at varying polymer/DNA charge ratios (N/P, 5/1–100/1), the addition of free F68 (1:5 w/w) resulted in the formation of smaller polyplexes (<200 nm). Analysis of polyplex properties by transmission electron microscopy and dynamic light scattering revealed varied polyplex morphology. Transfection potential was also found to be cell-dependent and significantly higher in SCC-9 cells compared to the control bPEI25k cells, as especially evident at higher N/P ratios (>25). The observed selectivity towards transfection of SSC-9 cells might represent a base for further optimization of a cell-specific transfection vehicle. Full article
(This article belongs to the Special Issue New Polymers as Nanovehicles for Several Therapeutic Applications: Current Advances and Future Perspectives)
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<p>Synthesis and characterization of F68PEI copolymer. (<b>a</b>) Synthesis scheme; (<b>b</b>) <sup>1</sup>H NMR spectra of F68, PEI, intermediary F68CDI and copolymer F68PEI. Insert shows the aromatic region with imidazole multiplets. Some multiplet resonances are assigned; (<b>c</b>) IR spectra of F68, PEI, intermediary F68CDI and copolymer F68PEI. Vertical lines indicate the appearance of characteristic peaks of new functional groups during F68PEI synthesis: introduction of a carboxylic group in F68CDI (1761 cm<sup>−1</sup>) and the appearance of vibrations characteristic of PEI in F68PEI (1569 and 3282 cm<sup>−1</sup>).</p> Full article ">Figure 2
<p>Buffering capacity of F68PEI and bPEI1.8k determined by titration with NaOH (0.1 M) within the range of pH 3–10. Colored inserts under the titration curves indicate NaOH volume needed to increase pH from 4.5 to 6.5, which is the physiological pH range of the endosomal system from lysosomes (pH 4.5) to early endosomal compartment (pH 6.5), in addition to indicating the buffering capacity, which is relevant for endosomal escape according to the “proton sponge” theory.</p> Full article ">Figure 3
<p>DNA complexation ability of F68PEI without and with the addition of free F68 (1:5 <span class="html-italic">w/w</span>) determined by agarose gel electrophoresis. For F68PEI and F68PEI/F68 1:5, N/P ratios between 5 and 100 were tested. For the control bPEI25k N/P ratios between 10 and 25 were tested.</p> Full article ">Figure 4
<p>Cell viability of (<b>a</b>) SCC-9 and (<b>b</b>) U2OS cells exposed to polyplexes prepared with different F68PEI formulations: F68PEI, F68PEI/F68 1:2 and F68PEI/F68 1:5. Cells were exposed to the formulations for 4 h and analyzed after an additional 48 h. Data are expressed as the percentage of cell viability with respect to the control (nontreated cells) and shown as the mean ± standard deviation. * Statistically different groups (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>Transfection efficiency of F68PEI-based polyplexes in (<b>a</b>) SCC-9 and (<b>b</b>) U2OS cells. The following F68PEI formulations were tested: F68PEI, F68PEI/F68 1:2 and F68PEI/F68 1:5. Increasing polymer concentrations were mixed with 1 μg of pCMV.Luc plasmid to achieve the desired N/P ratios (5–100). Data are expressed as the relative light unit (RLU) of luciferase per mg of total cell protein and shown as the mean ± standard deviation. * Statistically different groups (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 6
<p>TEM images showing morphologies of polyplexes formed with (<b>a</b>) F68PEI and (<b>b</b>) F68PEI/F68 1:5 at N/P 50. The bar represents 500 nm.</p> Full article ">
18 pages, 7005 KiB  
Article
Facile Fabrication of Superhydrophobic and Flame-Retardant Coatings on Cotton Fabrics
by Shiwei Li, Luyan Yu, Jianhua Xiong, Ying Xiong, Shuguang Bi and Heng Quan
Polymers 2022, 14(23), 5314; https://doi.org/10.3390/polym14235314 - 5 Dec 2022
Cited by 11 | Viewed by 2407
Abstract
The hydrophilicity and inherent flammability of cotton textiles severely limit their usage. To solve these drawbacks, a superhydrophobic and flame-retardant (SFR) coating made of chitosan (CH), ammonium polyphosphate (APP), and TiO2-SiO2-HMDS composite was applied to cotton fabric using simple [...] Read more.
The hydrophilicity and inherent flammability of cotton textiles severely limit their usage. To solve these drawbacks, a superhydrophobic and flame-retardant (SFR) coating made of chitosan (CH), ammonium polyphosphate (APP), and TiO2-SiO2-HMDS composite was applied to cotton fabric using simple layer-by-layer assembly and dip-coating procedures. First, the fabric was alternately immersed in CH and APP water dispersions, and then immersed in TiO2-SiO2-HMDS composite to form a CH/APP@TiO2-SiO2-HMDS coating on the cotton fabric surface. SEM, EDS, and FTIR were used to analyze the surface morphology, element composition, and functional groups of the cotton fabric, respectively. Vertical burning tests, microscale combustion calorimeter tests, and thermogravimetric analyses were used to evaluate the flammability, combustion behavior, thermal degradation characteristics, and flame-retardant mechanism of this system. When compared to the pristine cotton sample, the deposition of CH and APP enhanced the flame retardancy, residual char, heat release rate, and total heat release of the cotton textiles. The superhydrophobic test results showed that the maximal contact angle of SFR cotton fabric was 153.7°, and possessed excellent superhydrophobicity. Meanwhile, the superhydrophobicity is not lost after 10 laundering cycles or 50 friction cycles. In addition, the UPF value of CH/APP@TiO2-SiO2-HMDS cotton was 825.81, demonstrating excellent UV-shielding properties. Such a durable SFR fabric with a facile fabrication process exhibits potential applications for both oil/water separation and flame retardancy. Full article
(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)
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<p>Schematic illustration of the fabrication process of SFR coating on cotton fabric.</p> Full article ">Figure 2
<p>SEM images of pristine cotton (<b>a<sub>1</sub></b>–<b>a<sub>3</sub></b>), CH/APP cotton (<b>b<sub>1</sub></b>–<b>b<sub>3</sub></b>), CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton (<b>c<sub>1</sub></b>–<b>c<sub>3</sub></b>).</p> Full article ">Figure 3
<p>(<b>a</b>) FTIR of spectra of the pristine cotton, CH/APP cotton and CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton, (<b>b</b>) X-ray diffraction spectra of the pristine cotton, CH/APP cotton and CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton.</p> Full article ">Figure 4
<p>The TGA (<b>a</b>) and DTG curves (<b>b</b>) of the pristine cotton, CH/APP cotton, and CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton under nitrogen.</p> Full article ">Figure 5
<p>HRR curves of pristine cotton, CH/APP cotton, and CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton samples from MCC.</p> Full article ">Figure 6
<p>Vertical flame test optical images of cotton samples.</p> Full article ">Figure 7
<p>Combustion test optical images of CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS ((<b>a</b>). 0 laundering cycle, (<b>b</b>). 50 laundering cycles).</p> Full article ">Figure 8
<p>SEM images of char residues after flame exposure for 12 s of pristine cotton (<b>a<sub>1</sub></b>–<b>a<sub>3</sub></b>), CH/APP cotton (<b>b<sub>1</sub></b>–<b>b<sub>3</sub></b>), CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton (<b>c<sub>1</sub></b>–<b>c<sub>3</sub></b>).</p> Full article ">Figure 9
<p>Photographic images of water droplet on the different cotton samples surface. Pristine cotton (<b>a</b>), CS/APP cotton (<b>b</b>), 0.15 g TiO<sub>2</sub> amounts of TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton (<b>c</b>), different TiO<sub>2</sub> amounts ((<b>d</b>). 0.15 g, (<b>e</b>). 0.45 g, (<b>f</b>). 0.75 g) of CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton, different HMDS amounts ((<b>g</b>). 3 mL, (<b>h</b>). 6 mL, (<b>i</b>). 7.5 mL) of CH/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton.</p> Full article ">Figure 10
<p>Effect of laundering cycles (<b>a</b>) and friction cycles (<b>b</b>) times on the CA of the CS/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS.</p> Full article ">Figure 11
<p>Photographs of antifouling ability test and self-cleaning property test for pristine cotton fabric (<b>a<sub>1</sub>–a<sub>5</sub></b>), CS/APP cotton fabric (<b>b<sub>1</sub>–b<sub>5</sub></b>) and CS/APP@TiO<sub>2</sub>-SiO<sub>2</sub>-HMDS cotton fabrics (<b>c<sub>1</sub>–c<sub>5</sub></b>).</p> Full article ">
16 pages, 6954 KiB  
Article
Modelling of Web-Crippling Behavior of Pultruded GFRP I Sections at Elevated Temperatures
by Lingfeng Zhang, Qianyi Li, Ying Long, Dafu Cao and Kai Guo
Polymers 2022, 14(23), 5313; https://doi.org/10.3390/polym14235313 - 5 Dec 2022
Cited by 1 | Viewed by 1262
Abstract
The concentrated transverse load may lead to the web crippling of pultruded GFRP sections due to the lower transverse mechanical properties. Several investigations have been conducted on the web-crippling behavior of the GFRP sections under room temperature. However, the web-crippling behavior is not [...] Read more.
The concentrated transverse load may lead to the web crippling of pultruded GFRP sections due to the lower transverse mechanical properties. Several investigations have been conducted on the web-crippling behavior of the GFRP sections under room temperature. However, the web-crippling behavior is not yet understood when subjected to elevated temperatures. To address this issue, a finite element model considering the temperature-dependent material properties, Hashin failure criterion and the damage evolution law are successfully developed to simulate the web-crippling behavior of the GFRP I sections under elevated temperatures. The numerical model was validated by the web-crippling experiments at room temperature with the end-two-flange (ETF) and end bearing with ground support (EG) loading configurations. The developed model can accurately predict the ultimate loads and failure modes. Moreover, it was found that the initial damage was triggered by exceeding the shear strength at the web-flange junction near the corner of the bearing plate and independent of the elevated temperatures and loading configurations. The ultimate load and stiffness decreased obviously with the increasing temperature. At 220 °C, the ultimate load of specimens under ETF and EG loading configurations significantly decreased by 57% and 62%, respectively, whereas the elastic stiffness obviously reduced by 87% and 88%, respectively. Full article
(This article belongs to the Special Issue Fibre-Reinforced Polymer Composite II)
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<p>Appearance of the specimen: (<b>a</b>) front view; (<b>b</b>) side view and (<b>c</b>) top view.</p> Full article ">Figure 2
<p>Loading configurations of (<b>a</b>) ETF and (<b>b</b>) EG.</p> Full article ">Figure 3
<p>Test set-up of specimens under ETF loading configuration.</p> Full article ">Figure 4
<p>Failure modes of the specimens (<b>a</b>) ETF139.7-b50-2; (<b>b</b>) EG139.7-b50-2.</p> Full article ">Figure 5
<p>Load-displacement curves of specimens under (<b>a</b>) ETF and (<b>b</b>) EG loading conditions.</p> Full article ">Figure 6
<p>Transverse strains of the specimens (<b>a</b>) ETF139.7-b50-1 and (<b>b</b>) EG139.7-b50-2.</p> Full article ">Figure 7
<p>Geometry, mesh and boundary condition of the specimen under (<b>a</b>) ETF and (<b>b</b>) EG loading conditions.</p> Full article ">Figure 8
<p>Equivalent stress-equivalent displacement relationship for damage evolution.</p> Full article ">Figure 9
<p>The experimental and numerical load-displacement curves of the specimens under (<b>a</b>) ETF and (<b>b</b>) EG loading conditions at room temperature.</p> Full article ">Figure 10
<p>Comparison between the experimental failure mode and numerical damage pattern at room temperature.</p> Full article ">Figure 11
<p>Temperature-dependent material properties: (<b>a</b>) modulus; (<b>b</b>) strength.</p> Full article ">Figure 12
<p>Validation of the developed numerical model by the experimental failure modes at 100 °C: (<b>a</b>) 10° off-axis tension (shear); (<b>b</b>) uniaxial tension [<a href="#B40-polymers-14-05313" class="html-bibr">40</a>].</p> Full article ">Figure 13
<p>The influence of elevated temperatures on the load-displacement curve under (<b>a</b>) ETF and (<b>b</b>) EG loading configurations.</p> Full article ">Figure 14
<p>The matrix compressive damage distributions in case of ETF at different temperatures under the initial damage state and ultimate load state.</p> Full article ">Figure 15
<p>The matrix compressive damage distributions in the case of EG at different temperatures under the initial damage state and ultimate load state.</p> Full article ">Figure 16
<p>The transverse compressive stress and in-plane shear stress distributions in the case of ETF under different temperatures under initial damage state.</p> Full article ">Figure 17
<p>The transverse compressive stress (S22) and in-plane shear stress (S12) distributions in the case of EG at different temperatures under initial damage state.</p> Full article ">
11 pages, 3755 KiB  
Article
Self-Powered Gradient Hydrogel Sensor with the Temperature-Triggered Reversible Adhension
by Dong Sun, Cun Peng, Yuan Tang, Pengfei Qi, Wenxin Fan, Qiang Xu and Kunyan Sui
Polymers 2022, 14(23), 5312; https://doi.org/10.3390/polym14235312 - 5 Dec 2022
Cited by 4 | Viewed by 1892
Abstract
The skin, as the largest organ of human body, can use ions as information carriers to convert multiple external stimuli into biological potential signals. So far, artificial skin that can imitate the functionality of human skin has been extensively investigated. However, the demand [...] Read more.
The skin, as the largest organ of human body, can use ions as information carriers to convert multiple external stimuli into biological potential signals. So far, artificial skin that can imitate the functionality of human skin has been extensively investigated. However, the demand for additional power, non-reusability and serious damage to the skin greatly limits applications. Here, we have developed a self-powered gradient hydrogel which has high temperature-triggered adhesion and room temperature-triggered easy separation characteristics. The self-powered gradient hydrogels are polymerized using 2-(dimethylamino) ethyl metharcylate (DMAEMA) and N-isopropylacrylamide (NIPAM) under unilateral UV irradiation. The prepared hydrogels achieve good adhesion at high temperature and detachment at a low temperature. In addition, according to the thickness-dependent potential of the gradient hydrogel, the hydrogels can also sense pressure changes. This strategy can inspire the design and manufacture of self-powered gradient hydrogel sensors, contributing to the development of complex intelligent artificial skin sensing systems in the future. Full article
(This article belongs to the Special Issue Recent Trends in Polymer Membranes: Fabrication Technique, Characterization, Functionalization, and Applications in Environmental Science)
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<p>Preparation of self-powered gradient hydrogels with a reversible adhesion capacity.</p> Full article ">Figure 2
<p>Characterization of the self-powered gradient hydrogel. (<b>a</b>) Cross-sectional SEM images of the gradient PDMAEMA/PNIPAM hydrogel. (<b>b</b>) Wide-scan survey XPS spectra of the HD side and LD side for the gradient PDMAEMA/PNIPAM hydrogel, and the insert is the atomic percentage of carbon, nitrogen, and oxygen at the HD side and LD side. (<b>c</b>) Transmittance vs. temperature for the LCST-type hydrogels with different monomer mass ratios (DMAEMA/NIPAM). (<b>d</b>) The optical images of hydrogel at room temperature and after heating. (<b>e</b>) Stress–strain curves of the hydrogel with different DMAEMA/NIPAM mass ratios at room temperature. (<b>f</b>) Stress–strain curves of the hydrogel with different DMAEMA/NIPAM mass ratios after heating. Stress–strain cycle curves of hydrogels with different concentrations. (<b>g</b>) DMAEAM:NIAPM = 5:1, (<b>h</b>) DMAEAM:NIAPM = 10:1, (<b>i</b>) DMAEAM:NIAPM = 15:1.</p> Full article ">Figure 3
<p>Adhesion performance of self-powered gradient hydrogel based on PDMAEAM/PNIPAM. Photos of hydrogels adhered on (<b>a</b>) platinum, (<b>b</b>) copper, (<b>c</b>) silicone rubber and (<b>d</b>) glass. (<b>e1</b>) Peeling force curves and (<b>e2</b>) interface toughness of hydrogel with different proportions at room temperature and high temperature in binding platinum; (<b>f1</b>) peeling force curves and (<b>f2</b>) interface toughness of hydrogel with different proportions at room temperature and high temperature in binding copper; (<b>g1</b>) peeling force curves and (<b>g2</b>) interface toughness of hydrogel with different proportions at room temperature and high temperature in binding silicone rubber; (<b>h1</b>) peeling force curves and (<b>h2</b>) interface toughness of hydrogel with different proportions at room temperature and high temperature in binding glass.</p> Full article ">Figure 4
<p>Schematic diagram of pressure and sensing mechanism of self-powered gradient hydrogel.</p> Full article ">Figure 5
<p>Pressure- and strain-sensing performance of the self-powered hydrogel sensors. (<b>a</b>) Output voltage of sensors as a function of pressure. (<b>b</b>) Output voltage under a 2 kPa static pressure. (<b>c</b>) Output voltage at different pressures. (<b>d</b>) Repeated loading/unloading of 5 kPa pressure for 200 cycles. (<b>e</b>) Gradually increased tensile strain and (<b>f</b>) different tensile strain. (<b>g</b>) Current signals of sensor in response to the 5 kPa pressure. Recorded voltage signals of the sensors in response to (<b>h</b>) finger joint motions and (<b>i</b>) wrist joint motions.</p> Full article ">
16 pages, 4922 KiB  
Article
Structural Characterization and Glycosaminoglycan Impurities Analysis of Chondroitin Sulfate from Chinese Sturgeon
by Mei Zhao, Yong Qin, Ying Fan, Xu Wang, Haixin Yi, Xiaoyu Cui, Fuchuan Li and Wenshuang Wang
Polymers 2022, 14(23), 5311; https://doi.org/10.3390/polym14235311 - 5 Dec 2022
Cited by 1 | Viewed by 1856
Abstract
Chinese sturgeon was an endangered cartilaginous fish. The success of artificial breeding has promoted it to a food fish and it is now beginning to provide a new source of cartilage for the extraction of chondroitin sulfate (CS). However, the structural characteristics of [...] Read more.
Chinese sturgeon was an endangered cartilaginous fish. The success of artificial breeding has promoted it to a food fish and it is now beginning to provide a new source of cartilage for the extraction of chondroitin sulfate (CS). However, the structural characteristics of sturgeon CS from different tissues remain to be determined in more detail. In this study, CSs from the head, backbone, and fin cartilage of Chinese sturgeon were individually purified and characterized for the first time. The molecular weights, disaccharide compositions, and oligosaccharide sulfation patterns of these CSs are significantly different. Fin CS (SFCS), rich in GlcUAα1-3GalNAc(4S), has the biggest molecular weight (26.5 kDa). In contrast, head CS (SHCS) has a molecular weight of 21.0 kDa and is rich in GlcUAα1-3GalNAc(6S). Most features of backbone CS (SBCS) are between the former two. Other glycosaminoglycan impurities in these three sturgeon-derived CSs were lower than those in other common commercial CSs. All three CSs have no effect on the activity of thrombin or Factor Xa in the presence of antithrombin III. Hence, Chinese sturgeon cartilage is a potential source for the preparation of CSs with different features for food and pharmaceutical applications. Full article
(This article belongs to the Special Issue Biobased and Biodegradable Polymer Blends and Composites)
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<p>Analysis of GAG-lyase-treated CS preparations by gel filtration chromatography. SHCS (<b>A</b>), SBCS (<b>B</b>), and SFCS (<b>C</b>) were treated with CSase ABC, Hepases, and CSase B, respectively, and the resultants were analyzed by gel filtration with a UV detector. Mono-S, the monosulfated disaccharides; Non-S, non-sulfated disaccharides. To determine the content of KS impurity in commercial CS-A, CS-C (<b>D</b>), or three CS preparations (<b>E</b>), each CS sample was digested with KSase and CSase ABC, respectively, and the product was labeled with 2-AB followed by analysis by gel filtration with a fluorescence detector. 2AB-2S, 2AB-labeled disulfated disaccharides; 2AB-1S, 2AB-labeled monosulfated disaccharides; 2AB-0S, 2AB-labeled non-sulfated disaccharides.</p> Full article ">Figure 2
<p>Analysis of Chinese sturgeon cartilage CSs by PAGE. The CS preparations from head, backbone, and fin cartilages of Chinese sturgeon were analyzed and compared with commercial CSs by PAGE using 18.3% polyacrylamide gels followed by staining with Alcian Blue, as described under “<a href="#sec2-polymers-14-05311" class="html-sec">Section 2</a>”. Lane A: CS-A; Lane B: CS-C; Lane C: CS-D; Lane D: SHCS; Lane E: SBCS; Lane F: SFCS.</p> Full article ">Figure 3
<p>Molecular mass analysis by MALS. The molecular mass of SHCS (<b>A</b>), SBCS (<b>B</b>), or SFCS (<b>C</b>) was measured by size exclusion chromatography with a multi-angle light scattering (MALS) detector and a refractive index (RI) detector, as described under “<a href="#sec2-polymers-14-05311" class="html-sec">Section 2</a>”.</p> Full article ">Figure 4
<p>Disaccharide composition analysis by anion-exchange HPLC. CS (2 μg) from the cartilage of head (<b>A</b>), backbone (<b>B</b>), or fins (<b>C</b>) were digested with CSase ABC, labeled by 2-AB, and analyzed by an anion-exchange HPLC column with a fluorescence detector. All samples were analyzed by HPLC on a YMC-Pack PA-G column using a NaH<sub>2</sub>PO<sub>4</sub> gradient (indicated by the dashed line). The elution positions of authentic 2-AB-labeled unsaturated disaccharides are indicated by arrows. 1, Δ<sup>4,5</sup>HexUAα1-3GalNAc; 2, Δ<sup>4,5</sup>HexUAα1-3GalNAc(6S); 3, Δ<sup>4,5</sup>HexUAα1-3GalNAc(4S).</p> Full article ">Figure 5
<p>NMR analysis of three CSs and CS-A. (<b>A</b>) <sup>1</sup>H NMR spectra. (<b>B</b>) <sup>13</sup>C NMR spectra.</p> Full article ">Figure 6
<p>Preparation of size-defined oligosaccharides. SHCS (<b>A</b>), SBCS (<b>B</b>), or SFCS (<b>C</b>) was digested with hyaluronidase, and after 2-AB labeling, the digest was fractionated on a Superdex<sup>TM</sup> Peptide 10/300GL column as described under “<a href="#sec2-polymers-14-05311" class="html-sec">Section 2</a>”. Vo, void volume. The elution positions of 2AB-labeled authentic unsaturated CS-derived standard oligosaccharides determined are indicated by arrows as follows: 1, CS-dodecasaccharides; 2, CS-decasaccharides; 3, CS-octasaccharides; 4, CS-hexasaccharides; 5, CS-tetrasaccharides.</p> Full article ">Figure 7
<p>Analysis of tetrasaccharide fractions by anion-exchange HPLC. The tetrasaccharide fractions prepared from SHCS (<b>A</b>), SBCS (<b>B</b>), and SFCS (<b>C</b>) were analyzed by anion-exchange HPLC on a YMC-Pack PA-G column using a NaH<sub>2</sub>PO<sub>4</sub> gradient (indicated by the dashed line).</p> Full article ">Figure 8
<p>Analysis of hexasaccharide fractions by anion-exchange HPLC. The hexasaccharide fractions prepared from SHCS (<b>A</b>), SBCS (<b>B</b>), and SFCS (<b>C</b>) were analyzed as described in the caption of <a href="#polymers-14-05311-f005" class="html-fig">Figure 5</a>. All samples were analyzed by HPLC on a YMC-Pack PA-G column using a NaH<sub>2</sub>PO<sub>4</sub> gradient (indicated by the dashed line).</p> Full article ">Figure 9
<p>The effect of CSs from sturgeon cartilage to the effect of residual FIIa (<b>A</b>) or FXa (<b>B</b>) activity in the presence of ATIII. The standard Hep (□) was set as a reference (Insert). (●) SHCS; (■), SBCS; (▲) SFCS.</p> Full article ">
16 pages, 2719 KiB  
Article
Biobased Castor Oil-Based Polyurethane Foams Grafted with Octadecylsilane-Modified Diatomite for Use as Eco-Friendly and Low-Cost Sorbents for Crude Oil Clean-Up Applications
by Helanka J. Perera, Anjali Goyal, Saeed M. Alhassan and Hussain Banu
Polymers 2022, 14(23), 5310; https://doi.org/10.3390/polym14235310 - 5 Dec 2022
Cited by 6 | Viewed by 2697
Abstract
Herein we report the synthesis and characterization of novel castor oil-based polyurethane (PU) foam functionalized with octadecyltrichlorosilane (C18)-modified diatomaceous earth (DE) particles, exhibiting superior hydrophobicity and oil adsorption, and poor water absorption, for use in effective clean-up of crude oil spillage in water [...] Read more.
Herein we report the synthesis and characterization of novel castor oil-based polyurethane (PU) foam functionalized with octadecyltrichlorosilane (C18)-modified diatomaceous earth (DE) particles, exhibiting superior hydrophobicity and oil adsorption, and poor water absorption, for use in effective clean-up of crude oil spillage in water bodies. High-performance and low-cost sorbents have a tremendous attraction in oil spill clean-up applications. Recent studies have focused on the use of castor oil as a significant polyol that can be used as a biodegradable and eco-friendly raw material for the synthesis of PU. However, biobased in-house synthesis of foam modified with C18-DE particles has not yet been reported. This study involves the synthesis of PU using castor oil, further modification of castor oil-based PU using C18 silane, characterization studies and elucidation of oil adsorption capacity. The FTIR analysis confirmed the fusion of C18 silane particles inside the PU skeleton by adding the new functional group, and the XRD study signified the inclusion of crystalline peaks in amorphous pristine PU foam owing to the silane cross-link structure. Thermogravimetric analysis indicated improvement in thermal stability and high residual content after chemical modification with alkyl chain moieties. The SEM and EDX analyses showed the surface’s roughness and the incorporation of inorganic and organic elements into pristine PU foam. The contact angle analysis showed increased hydrophobicity of the modified PU foams treated with C18-DE particles. The oil absorption studies showed that the C18-DE-modified PU foam, in comparison with the unmodified one, exhibited a 2.91-fold increase in the oil adsorption capacity and a 3.44-fold decrease in the water absorbing nature. From these studies, it is understood that this novel foam can be considered as a potential candidate for cleaning up oil spillage on water bodies. Full article
(This article belongs to the Special Issue Functional Polymer Foam and Composite Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Powder XRD spectra of PU (bottom), DE, C18-DE particles and PU-C18-DE (top). XRD spectra of PU-C18-DE show an increment in crystallinity due to the incorporation of modified silane DE particles in amorphous PU foam.</p> Full article ">Figure 2
<p>SEM images on different scales: (<b>a1</b>–<b>a3</b>) pristine PU synthesized foam, (<b>b1</b>–<b>b3</b>) C18-DE, (<b>c1</b>–<b>c3</b>) modified PU-C18-DE foam, EDX graph mapping and elemental analysis for all three samples, respectively, (<b>a4</b>), (<b>b4</b>), (<b>c4</b>).</p> Full article ">Figure 3
<p>TGA (<b>left</b> image) and the corresponding DTA curve (<b>right</b> image) of PU and PU-C18-DE.</p> Full article ">Figure 4
<p>FTIR spectrum represents the structural changes of C18 grafted DE particles and synthesized PU foam before and after modification with C18-DE particles.</p> Full article ">Figure 5
<p>The water contact angle of (<b>A</b>) unmodified PU is 85.5°, (<b>B</b>) C18-DE is 137.2° (<b>C</b>) C18-DE-PU is 129.8°.</p> Full article ">Figure 6
<p>Represents the oil absorption studies in the biobased PU (<b>a</b>) unmodified PU, (<b>b</b>) PU-C18-DE, after in contact with crude oil for 20 min, (<b>c</b>) unmodified PU and (<b>d</b>) PU-C18-DE.</p> Full article ">Figure 7
<p>This figure illustrates the oil adsorption capacity of castor oil-based PU foam modified with DE-C18 studied by layering 1 g of crude oil (1–2 mm in thickness) on distilled water; the oil absorption at initial (<b>a</b>), 0 min (<b>b</b>), 2 min (<b>c</b>), 4 min (<b>d</b>), and after 20 min (<b>e</b>), respectively.</p> Full article ">
17 pages, 4146 KiB  
Article
Study on the Relationship between Textile Microplastics Shedding and Fabric Structure
by Hong Cui and Changquan Xu
Polymers 2022, 14(23), 5309; https://doi.org/10.3390/polym14235309 - 5 Dec 2022
Cited by 10 | Viewed by 3254
Abstract
Microplastics refer to plastic fibers, particles or films less than 5 mm in diameter. Textile microplastics are an important form of microplastics, which can harm the ecological environment and human health. This paper studies the relationship between textile microplastic shedding and fabric structure [...] Read more.
Microplastics refer to plastic fibers, particles or films less than 5 mm in diameter. Textile microplastics are an important form of microplastics, which can harm the ecological environment and human health. This paper studies the relationship between textile microplastic shedding and fabric structure to reduce microplastics pollution and reduce its impact on humans and the natural environment. Firstly, household washing is simulated by considering the main fabric type, the number of steel balls used in the washing, washing temperature, washing time and other influencing factors. An orthogonal test of the mixing level of the four factors is designed by selecting the fabric type, the number of steel balls used in washing, washing temperature and washing time, and the influencing factors is analyzed, and the best washing scheme is obtained. Then, under optimal washing conditions, the three factors and three levels of orthogonal test are designed to analyze the influence of fabric structure and external factors on the shedding of microplastics by changing the amounts of friction and insolation time. The results show that the microplastics released by knitted fabrics are significantly more under the same washing conditions than that of woven fabrics. Satin fabrics released the most microplastics and plain fabrics the least. In addition, among the external factors, the amount of friction significantly affects the production of microplastics. Full article
(This article belongs to the Special Issue Textile Materials and Textile Design)
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<p>All-polyester knitted fabric.</p> Full article ">Figure 2
<p>All-polyester woven fabric.</p> Full article ">Figure 3
<p>Plain fabric.</p> Full article ">Figure 4
<p>Twill fabric.</p> Full article ">Figure 5
<p>Satin fabric.</p> Full article ">Figure 6
<p>(<b>a</b>) Three-dimensional surface diagram of fabric type and washing time; (<b>b</b>) contour plot of fabric type and washing time; (<b>c</b>) three-dimensional surface diagram of fabric type and washing temperature; (<b>d</b>) contour plot of fabric type and washing temperature; (<b>e</b>) three-dimensional surface diagram of fabric type and steel ball count; (<b>f</b>) contour plot of fabric type and steel ball count. (The blue dots and black dots in the figure represent the positions of the values of the 16 experimental points respectively).</p> Full article ">Figure 7
<p>(<b>a</b>) Three-dimensional surface diagram of fabric structure and amount of friction; (<b>b</b>) contour plot of fabric structure and amount of friction; (<b>c</b>) three-dimensional surface diagram of fabric structure and insolation time; (<b>d</b>) three-dimensional surface diagram of fabric structure and insolation time; (<b>e</b>) three-dimensional surface diagram of the amount of friction and sunshine duration; (<b>f</b>) contour plot of the amount of friction and sunshine duration. (The blue dots and black dots in the figure represent the positions of the values of the 9 experimental points respectively).</p> Full article ">Figure 8
<p>Fibers released from woven fabrics.</p> Full article ">Figure 9
<p>Fibers released from knitted fabrics.</p> Full article ">
10 pages, 2767 KiB  
Article
Hemp Shives as a Raw Material for the Production of Particleboards
by Radosław Auriga, Marta Pędzik, Robert Mrozowski and Tomasz Rogoziński
Polymers 2022, 14(23), 5308; https://doi.org/10.3390/polym14235308 - 5 Dec 2022
Cited by 13 | Viewed by 3594
Abstract
Increased demand for wood affects its price and thus contributes to the growing interest in raw materials that can be used as a partial or total substitute for wood in the production of particleboard. One of the raw materials for the production of [...] Read more.
Increased demand for wood affects its price and thus contributes to the growing interest in raw materials that can be used as a partial or total substitute for wood in the production of particleboard. One of the raw materials for the production of particleboard can be Cannabis sativa or, more precisely, hemp shives. In this work, 7 variants of panels with a density of 650 kg/m3 with 10 and 25% hemp shives substitution in different layers were produced. Particleboards containing hemp shives were characterized by lower density compared to conventional particleboards. The shares of hemp shives at the levels of 10% and 25% have a slight impact on the MOR and MOE; additional IB showed no statistically significant differences between the conventional particleboards and particleboards with a share of hemp shives. For particleboards with 25% hemp shives, a reduction in swelling was observed relative to particleboards made entirely of industrial wood particles. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Particle size for each layer of the board: (<b>A</b>) industrial particles for the core layer, (<b>B</b>) industrial particles for the surface layers, (<b>C</b>) hemp shives for the core layer, (<b>D</b>) hemp shives for surface layers.</p> Full article ">Figure 2
<p>Cross-section of the manufactured particleboard variants. (<b>A</b>–<b>G</b>) letters designations according to the variant letters in <a href="#polymers-14-05308-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 3
<p>Density profile of manufactured particleboards.</p> Full article ">Figure 4
<p>Modulus of rapture of particleboards. a,b—homogenous group by Tukey test.</p> Full article ">Figure 5
<p>Modulus of elasticity of particleboards. a,b,c—homogenous group by Tukey test.</p> Full article ">Figure 6
<p>Internal bond of particleboards. a—homogenous group by Tukey test.</p> Full article ">Figure 7
<p>Thickness swelling and water absorption after 2 and 24 h of soaking in water. a,b,c,d—homogenous group by Tukey test.</p> Full article ">
12 pages, 11669 KiB  
Article
Liquid Fraction Effect on Foam Flow through a Local Obstacle
by Oksana Stennikova, Natalia Shmakova, Jean-Bastien Carrat and Evgeny Ermanyuk
Polymers 2022, 14(23), 5307; https://doi.org/10.3390/polym14235307 - 5 Dec 2022
Cited by 1 | Viewed by 2200
Abstract
An experimental study of quasi-two-dimensional liquid foams with varying liquid fractions is presented. Experiments are conducted in a Hele-Shaw cell with a local permeable obstacle placed in the center and filling 35, 60 and 78% of the cell gap. Foam velocity is calculated [...] Read more.
An experimental study of quasi-two-dimensional liquid foams with varying liquid fractions is presented. Experiments are conducted in a Hele-Shaw cell with a local permeable obstacle placed in the center and filling 35, 60 and 78% of the cell gap. Foam velocity is calculated using a standard cross-correlation algorithm. Estimations of the liquid fraction of the foam are performed using a new simplified method based on a statistical analysis of foam cell structures. The pattern of the foam velocity field varies with increasing liquid fraction, responsible for significant variation of the foam’s rheology. The local permeability decreases with increasing obstacle height and liquid fraction. In case of high liquid fraction (5.8×10−2), the permeability coefficient tends to zero for obstacles filling more than 78% of the cell gap. Full article
(This article belongs to the Special Issue Polymer Theory and Simulation)
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<p>(<b>a</b>) Experimental setup: a Hele-Shaw cell consisting of two glass plates with a gap of <math display="inline"><semantics> <mrow> <mi>G</mi> <mo>=</mo> <mn>1.15</mn> </mrow> </semantics></math> mm, the tank (in situ foam generator) attached to the bottom plate with holes for air and fluid injection, the light source below the cell and the camera above it; the air from the compressor is partially used for pressing the glass plates; compressed air passing filters enters the air flow regulator and the tank via the needle. The water pump controls the soap solution flow rate. (<b>b</b>) Raw image of the foam flow zoomed in on the permeable obstacle area (obstacle diameter <math display="inline"><semantics> <mrow> <mi>a</mi> <mo>=</mo> <mn>30</mn> </mrow> </semantics></math> mm) and (<b>c</b>) its binarization, with the red circle corresponding to the position of the permeable obstacle.</p> Full article ">Figure 2
<p>Method used to find the critical distance <math display="inline"><semantics> <msub> <mi>L</mi> <mi>c</mi> </msub> </semantics></math> before rearrangement (or T1 event) occurs: (<b>a</b>) selection of a bubble and all its neighbors, which are located at a distance less than <math display="inline"><semantics> <mrow> <mn>2</mn> <msub> <mi>d</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> </mrow> </msub> </mrow> </semantics></math> from its center; (<b>b</b>) an example of sorted distances between the foam cells in the ascending order, the red star indicates <math display="inline"><semantics> <msub> <mover accent="true"> <mi>L</mi> <mo>^</mo> </mover> <mi>c</mi> </msub> </semantics></math>—the critical distance plus border width; (<b>c</b>) histogram of bubble areas superposed with a Gaussian fit (Normal distribution with <math display="inline"><semantics> <mrow> <mi>s</mi> <mo>=</mo> <mn>12.28</mn> <mspace width="0.277778em"/> <msup> <mi>mm</mi> <mn>2</mn> </msup> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>σ</mi> <mo>=</mo> <mn>0.59</mn> <mspace width="0.277778em"/> <msup> <mi>mm</mi> <mn>2</mn> </msup> </mrow> </semantics></math>).</p> Full article ">Figure 3
<p>Original images of the foam (on the left) and longitudinal velocity component averaged over 125 s with subtracted mean velocity <math display="inline"><semantics> <mrow> <mi>u</mi> <mo>−</mo> <msub> <mi>U</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> </mrow> </msub> </mrow> </semantics></math> (color) together with the velocity vector field <math display="inline"><semantics> <mrow> <mi mathvariant="bold">U</mi> <mo>−</mo> <msub> <mi>U</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> </mrow> </msub> </mrow> </semantics></math> (on the right) for various liquid fraction <math display="inline"><semantics> <mi mathvariant="sans-serif">Φ</mi> </semantics></math>: (<b>a</b>,<b>b</b>) <math display="inline"><semantics> <mrow> <mn>3.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math>, (<b>c</b>,<b>d</b>) <math display="inline"><semantics> <mrow> <mn>1.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math>, (<b>e</b>,<b>f</b>) <math display="inline"><semantics> <mrow> <mn>3.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> and (<b>g</b>,<b>h</b>) <math display="inline"><semantics> <mrow> <mn>5.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Analytical calculation of a two-dimensional potential flow passing a circular obstacle with the longitudinal velocity <math display="inline"><semantics> <mrow> <mi>u</mi> <mo>−</mo> <msub> <mi>U</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> </mrow> </msub> </mrow> </semantics></math> in color and the vector field <math display="inline"><semantics> <mrow> <mi mathvariant="bold">U</mi> <mo>−</mo> <msub> <mi>U</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> </mrow> </msub> </mrow> </semantics></math> shown with black arrows.</p> Full article ">Figure 5
<p>Profiles of the normalized longitudinal velocity <math display="inline"><semantics> <mover accent="true"> <mi>u</mi> <mo>^</mo> </mover> </semantics></math> along the <span class="html-italic">x</span>-axis for obstacle heights <math display="inline"><semantics> <mrow> <mi>H</mi> <mo>/</mo> <mi>G</mi> </mrow> </semantics></math> of (<b>a</b>) 0.35, (<b>b</b>) 0.6 and (<b>c</b>) 0.78 and liquid fractions of <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Φ</mi> <mo>=</mo> <mn>3.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (blue), <math display="inline"><semantics> <mrow> <mn>4.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (green), <math display="inline"><semantics> <mrow> <mn>1.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (red), <math display="inline"><semantics> <mrow> <mn>3.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (yellow) and <math display="inline"><semantics> <mrow> <mn>5.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (purple).</p> Full article ">Figure 6
<p>Maximum normalized longitudinal velocity <math display="inline"><semantics> <msup> <mover accent="true"> <mi>u</mi> <mo>^</mo> </mover> <mo>*</mo> </msup> </semantics></math> with respect to the foam liquid fraction for <math display="inline"><semantics> <mrow> <mi>H</mi> <mo>/</mo> <mi>G</mi> <mo>=</mo> <mn>0.35</mn> <mo>,</mo> <mn>0.6</mn> </mrow> </semantics></math> and 0.78.</p> Full article ">Figure 7
<p>Profiles of the normalized longitudinal velocity <math display="inline"><semantics> <mover accent="true"> <mi>u</mi> <mo>^</mo> </mover> </semantics></math> along the <span class="html-italic">y</span>-axis for the obstacle height <math display="inline"><semantics> <mrow> <mi>H</mi> <mo>/</mo> <mi>G</mi> <mo>=</mo> <mn>0.78</mn> </mrow> </semantics></math> and the liquid fractions <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Φ</mi> <mo>=</mo> <mn>3.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (blue), <math display="inline"><semantics> <mrow> <mn>4.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (green), <math display="inline"><semantics> <mrow> <mn>1.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (red), <math display="inline"><semantics> <mrow> <mn>3.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (yellow) and <math display="inline"><semantics> <mrow> <mn>5.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (purple).</p> Full article ">Figure 8
<p>Permeability factor <span class="html-italic">Q</span> calculated using Equation (<a href="#FD2-polymers-14-05307" class="html-disp-formula">2</a>) with respect to the normalized obstacle height <math display="inline"><semantics> <mrow> <mi>H</mi> <mo>/</mo> <mi>G</mi> </mrow> </semantics></math> for liquid fractions <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Φ</mi> <mo>=</mo> <mn>3.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (purple), <math display="inline"><semantics> <mrow> <mn>4.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (yellow), <math display="inline"><semantics> <mrow> <mn>1.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (red), <math display="inline"><semantics> <mrow> <mn>3.7</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (green) and <math display="inline"><semantics> <mrow> <mn>5.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (blue) and the data from [<a href="#B24-polymers-14-05307" class="html-bibr">24</a>] for <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Φ</mi> <mo>=</mo> <mn>7.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics></math> (black triangles) and <math display="inline"><semantics> <mrow> <mn>1.4</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> (black squares).</p> Full article ">
19 pages, 2929 KiB  
Article
Production of 3D Printed Bi-Layer and Tri-Layer Sandwich Scaffolds with Polycaprolactone and Poly (vinyl alcohol)-Metformin towards Diabetic Wound Healing
by Sena Harmanci, Abir Dutta, Sumeyye Cesur, Ali Sahin, Oguzhan Gunduz, Deepak M. Kalaskar and Cem Bulent Ustundag
Polymers 2022, 14(23), 5306; https://doi.org/10.3390/polym14235306 - 5 Dec 2022
Cited by 12 | Viewed by 3390
Abstract
Type 2 diabetes mellitus (T2DM) is a chronic disease characterized by impaired insulin secretion, sensitivity, and hyperglycemia. Diabetic wounds are one of the significant complications of T2DM owing to its difficulty in normal healing, resulting in chronic wounds. In the present work, PCL/PVA, [...] Read more.
Type 2 diabetes mellitus (T2DM) is a chronic disease characterized by impaired insulin secretion, sensitivity, and hyperglycemia. Diabetic wounds are one of the significant complications of T2DM owing to its difficulty in normal healing, resulting in chronic wounds. In the present work, PCL/PVA, PCL/PVA/PCL, and metformin-loaded, PCL/PVA-Met and PCL/PVA-Met/PCL hybrid scaffolds with different designs were fabricated using 3D printing. The porosity and morphological analysis of 3D-printed scaffolds were performed using scanning electron microscopy (SEM). The scaffolds’ average pore sizes were between 63.6 ± 4.0 and 112.9 ± 3.0 μm. Molecular and chemical interactions between polymers and the drug were investigated with Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Mechanical, thermal, and degradation analysis of the scaffolds were undertaken to investigate the physico-chemical characteristics of the scaffolds. Owing to the structure, PCL/PVA/PCL sandwich scaffolds had lower degradation rates than the bi-layer scaffolds. The drug release of the metformin-loaded scaffolds was evaluated with UV spectrometry, and the biocompatibility of the scaffolds on fibroblast cells was determined by cell culture analysis. The drug release in the PCL/PVA-Met scaffold was sustained till six days, whereas in the PCL/PVA-Met/PCL, it continued for 31 days. In the study of drug release kinetics, PCL/PVA-Met and PCL/PVA-Met/PCL scaffolds showed the highest correlation coefficients (R2) values for the first-order release model at 0.8735 and 0.889, respectively. Since the layered structures in the literature are mainly obtained with the electrospun fiber structures, these biocompatible sandwich scaffolds, produced for the first time with 3D-printing technology, may offer an alternative to existing drug delivery systems and may be a promising candidate for enhancing diabetic wound healing. Full article
(This article belongs to the Special Issue Advances in 3D Printing of Polymer Composites)
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Figure 1

Figure 1
<p>Production and characterization of the scaffolds using 3D printing and demonstration of their role in the wound healing process.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of the morphology of the scaffolds: PCL/PVA (<b>A</b>,<b>E</b>), PCL/PVA/PCL (<b>B</b>,<b>F</b>), PCL/PVA-Met (<b>C</b>,<b>G</b>), and PCL/PVA-Met/PCL (<b>D</b>,<b>H</b>).</p> Full article ">Figure 3
<p>FTIR spectra of metformin ((<b>A</b>)), a), PVA ((<b>A</b>), b), PCL ((<b>A</b>), c), PCL/PVA ((<b>A</b>), d), PCL/PVA/PCL ((<b>A</b>), e), PCL/PVA-Met ((<b>A</b>), f), and PCL/PVA-Met/PCL ((<b>A</b>), g) scaffolds. XRD results of the PCL ((<b>B</b>), a), PVA ((<b>B</b>), b), metformin ((<b>B</b>), c) and PCL/PVA ((<b>B</b>), d), PCL/PVA/PCL ((<b>B</b>), e), PCL/PVA-Met ((<b>B</b>), f), and PCL/PVA-Met/PCL ((<b>B</b>), g) scaffolds; DSC curves of PCL/PVA ((<b>C</b>), a), PCL/PVA/PCL ((<b>C</b>), b), PCL/PVA-Met ((<b>C</b>), c), and PCL/PVA-Met/PCL ((<b>C</b>), d) scaffolds.</p> Full article ">Figure 4
<p>Degradation rates of 3D-printed scaffolds.</p> Full article ">Figure 5
<p>In vitro drug release of scaffolds: (<b>A</b>) Absorption spectra of metformin at 6 different concentrations, (<b>B</b>) encapsulation efficiency of the scaffolds, (<b>C</b>) release profiles of metformin from PCL/PVA-Met and (<b>D</b>) PCL/PVA-Met/PCL scaffolds.</p> Full article ">Figure 6
<p>In vitro release kinetic models of the PCL/PVA-Met and PCL/PVA-Met/PCL scaffolds (please see <a href="#polymers-14-05306-t002" class="html-table">Table 2</a> for further details).</p> Full article ">Figure 7
<p>In vitro cell viability analysis using MTT assay of the fabricated scaffolds (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">Figure 8
<p>Morphology of the fibroblast cells attached on the scaffolds post 7 day incubation: SEM images of (<b>A</b>,<b>E</b>) PCL/PVA, (<b>B</b>,<b>F</b>) PCL/PVA/PCL, (<b>C</b>,<b>G</b>) PCL/PVA-Met, and (<b>D</b>,<b>H</b>) PCL/PVA-Met/PCL.</p> Full article ">Figure 9
<p>Fluorescent microscopy images of the DAPI stained fibroblast cells attached to the hybrid scaffolds, days 3 and 7 post-cell culture.</p> Full article ">
13 pages, 2661 KiB  
Article
Polyurethane Adhesives Based on Oxyalkylated Kraft Lignin
by Fernanda Rosa Vieira, Nuno Gama, Sandra Magina, Ana Barros-Timmons, Dmitry V. Evtuguin and Paula C. O. R. Pinto
Polymers 2022, 14(23), 5305; https://doi.org/10.3390/polym14235305 - 5 Dec 2022
Cited by 12 | Viewed by 2467
Abstract
Lignin-based polyol was obtained via oxyalkylation reaction with propylene carbonate using eucalyptus kraft lignin isolated from the industrial cooking liquor by the Lignoboost® procedure. This lignin-based polyol (LBP) was used without purification in the preparation of polyurethane (PU) adhesives combined with polymeric [...] Read more.
Lignin-based polyol was obtained via oxyalkylation reaction with propylene carbonate using eucalyptus kraft lignin isolated from the industrial cooking liquor by the Lignoboost® procedure. This lignin-based polyol (LBP) was used without purification in the preparation of polyurethane (PU) adhesives combined with polymeric 4,4′-methylenediphenyl diisocyanate (pMDI). A series of adhesives were obtained by varying the NCO/OH ratio of PU counterparts (pMDI and LBPs) and their performance was evaluated by gluing wood pieces under predefined conditions. The adhesion properties of the novel PU adhesive were compared with those of a commercial PU adhesive (CPA). The occurrence and extent of curing reactions and changes in the polymeric network of PA were monitored by Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis. Although the lap shear strength and glass transition temperature of the lignin-based PU adhesives have increased steadily with the NCO/OH ratio ranging from 1.1–2.2, chemical aging resistance can be compromised when the NCO/OH is very low. It was found that the lignin-based PU adhesive with an NCO/OH ratio of 1.3 showed better chemical resistance and adhesion efficiency than CPA possibly because the NCO/OH in the latter is too high as revealed by FTIR spectroscopy. Despite some lower thermal stability and shorter gelation time of lignin-based PU than CPA, the former revealed great potential to reduce the use of petroleum-derived polyols and isocyanates with potential application in the furniture industry as wood bonding adhesive. Full article
(This article belongs to the Special Issue Properties and Applications of Natural Polymers)
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Figure 1
<p>Lap shear test versus curing exposure period of lignin-based PU adhesive formulated with NCO/OH = 1.1 (PU 1.1).</p> Full article ">Figure 2
<p>Normalized FTIR spectra of crude LBP, CPA, and lignin−based PU adhesives with different NCO/OH ratios (PU 1.1,1.3, 1.6, and 2.2).</p> Full article ">Figure 3
<p>Effect of NCO/OH ratio on average lap shear strength of the lignin-based PU adhesives compared with CPA.</p> Full article ">Figure 4
<p>Examples of (<b>a</b>) adhesive failure (AF), (<b>b</b>) cohesive failure (CF), and (<b>c</b>) substrate failure (SF).</p> Full article ">Figure 5
<p>DMA results of lignin-based PU adhesives with different NCO/OH ratios (PU1.1 to PU 2.2) and CPA obtained at frequency 1 Hz.</p> Full article ">Figure 6
<p>(<b>a</b>) TGA curves of PU 1.1, PU 1.3, and CPA, (<b>b</b>) Derivatives of mass loss (dw/dt) of PU 1.1, PU 1.3, and CPA.</p> Full article ">Figure 7
<p>Chemical resistance of PU 1.1, 1.3, and CPA.</p> Full article ">
12 pages, 2501 KiB  
Article
High-Efficiency Carbon Fiber Recovery Method and Characterization of Carbon FIBER-Reinforced Epoxy/4,4′-Diaminodiphenyl Sulfone Composites
by Yong-Min Lee, Kwan-Woo Kim and Byung-Joo Kim
Polymers 2022, 14(23), 5304; https://doi.org/10.3390/polym14235304 - 4 Dec 2022
Cited by 3 | Viewed by 2931
Abstract
Globally, the demand for carbon fiber-reinforced thermosetting plastics for various applications is increasing. As a result, the amount of waste from CFRPs is increasing every year, and the EU Council recommends recycling and reuse of CFRPs. Epoxy resin (EP) is used as a [...] Read more.
Globally, the demand for carbon fiber-reinforced thermosetting plastics for various applications is increasing. As a result, the amount of waste from CFRPs is increasing every year, and the EU Council recommends recycling and reuse of CFRPs. Epoxy resin (EP) is used as a matrix for CFRPs, and amine hardeners are mainly used. However, no research has been conducted on recycling EP/4,4’-diaminodiphenyl sulfone (DDS)-based CFRP. In this study, the effect of steam and air pyrolysis conditions on the mechanical properties of re-cycled carbon fiber (r-CF) recovered from carbon fiber-reinforced thermosetting (epoxy/4,4′-diaminodiphenyl sulfone) plastics (CFRPs) was investigated. Steam pyrolysis enhanced resin degradation relative to N2. The tensile strength of the recovered r-CF was reduced by up to 35.12% due to oxidation by steam or air. However, the interfacial shear strength (IFSS) tended to increase by 9.18%, which is considered to be due to the increase in functional groups containing oxygen atoms and the roughness of the surface due to oxidation. The recycling of CFRP in both a steam and an air atmosphere caused a decrease in the tensile strength of r-CF. However, they were effective methods to recover r-CF that had a clean surface and increased IFSS. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymer Composites: Mechanical Properties and Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Curing temperature of epoxy/4,4′-diaminodiphenyl sulfone mixture using differential scanning calorimetry.</p> Full article ">Figure 2
<p>Chemical structures of epoxy and 4,4′-diaminodiphenyl sulfone.</p> Full article ">Figure 3
<p>Schematics of physical properties test; (<b>a</b>) tensile strength and (<b>b</b>) interfacial shear strength.</p> Full article ">Figure 4
<p>TGA and DTG graphs of as-received carbon fiber and epoxy resin pyrolysis under gas atmosphere: (<b>a</b>) cured epoxy/4,4′-diaminodiphenyl sulfone and (<b>b</b>) carbon fiber.</p> Full article ">Figure 5
<p>Weight loss of as-received carbon fiber and epoxy resin pyrolysis under gas atmosphere: (<b>a</b>) N<sub>2</sub>, (<b>b</b>) steam, and (<b>c</b>) air.</p> Full article ">Figure 6
<p>Scanning electron microscopy images of the as-received and recycled carbon fibers under varying pyrolysis conditions; (<b>a</b>) Ar-CF, (<b>b</b>) 50, (<b>c</b>) 55, (<b>d</b>) 60, (<b>e</b>) 50-50-10, (<b>f</b>) 50-55-10, (<b>g</b>) 50-60-10, (<b>h</b>) 55-60-10, and (<b>i</b>) 60-60-10.</p> Full article ">Figure 7
<p>Physical properties of the as-received and recycled carbon fibers under varying pyrolysis conditions: (<b>a</b>) tensile strength and (<b>b</b>) interfacial shear strength.</p> Full article ">Figure 8
<p>Fourier-transform infrared spectra of the as-received and recycled carbon fibers with varying pyrolysis conditions.</p> Full article ">
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