Polymers

15 pages, 6177 KiB

Open AccessArticle

Agro-Waste Sweet Pepper Extract-Magnetic Iron Oxide Nanoparticles for Antioxidant Enrichment and Sustainable Nanopackaging

by Elisia María López-Alcántara, Grecia Marcela Colindres-Vásquez, Nouzha Fodil, Marlon Sánchez-Barahona, Octavio Rivera-Flores, Alberto Romero and Johar Amin Ahmed Abdullah

Polymers 2024, 16(4), 564; https://doi.org/10.3390/polym16040564 - 19 Feb 2024

Viewed by 1259

Abstract

This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. [...] Read more.

This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. Characterization techniques, including microscopy and spectroscopy, analyze the sweet pepper extract-magnetic iron oxide nanoparticles. Antioxidant capacities against 2,2-diphenyl-1-picrylhydrazyl are assessed, incorporating nanoparticles into banana-based bioplastic for grape preservation. Microscopy reveals cubic and quasi-spherical structures, and spectroscopy confirms functional groups, including Fe–O bonds. X-ray diffraction identifies cubic and monoclinic magnetite with a monoclinic hematite presence. Sweet pepper extract exhibits 100% inhibitory activity in 20 min, while sweet pepper extract-magnetic iron oxide nanoparticles show an IC₅₀ of 128.1 µg/mL. Furthermore, these nanoparticles, stabilized with banana-based bioplastic, effectively preserve grapes, resulting in a 27.4% lower weight loss rate after 144 h compared to the control group (34.6%). This pioneering study encourages institutional research into the natural antioxidant properties of agro-waste sweet pepper combined with magnetic iron and other metal oxide nanoparticles, offering sustainable solutions for nanopackaging and food preservation. Current research focuses on refining experimental parameters and investigating diverse applications for sweet pepper extract-magnetic iron oxide nanoparticles in varied contexts. Full article

(This article belongs to the Special Issue Metal Nanoparticles–Polymers Hybrid Materials III)

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39 pages, 5703 KiB

Open AccessArticle

Effect of End Groups on the Cloud Point Temperature of Aqueous Solutions of Thermoresponsive Polymers: An Inside View by Flory–Huggins Theory

by Thi To Nga Dang and Erik Nies

Polymers 2024, 16(4), 563; https://doi.org/10.3390/polym16040563 - 19 Feb 2024

Viewed by 774

Abstract

In an effort to gain insight into the origin of the effects of end groups on the cloud point temperature (

T_{c p}

) as a function of the polymer molar mass of thermoresponsive polymers with lower critical solution behavior in dilute [...] Read more.

In an effort to gain insight into the origin of the effects of end groups on the cloud point temperature (

T_{c p}

) as a function of the polymer molar mass of thermoresponsive polymers with lower critical solution behavior in dilute aqueous solutions, we use the Flory–Huggins (FH) theory amended for end groups. The theory was applied to available experimental data sets of poly(N-isopropylacrylamide) (PNIPAM), poly(4-vinylbenzyl methoxytris(oxyethylene) ether) (PTEGSt), and poly(α-hydro-ω-(4-vinylbenzyl)tetrakis(oxyethylene) ether) (PHTrEGSt). The theory relates the variations in

T_{c p} (M, ϕ_{c p})

for different end groups to the effective FH

χ

parameter of the end groups and explains the qualitative notion that the influence of the end groups is related to the hydrophobicity/hydrophilicity of the end groups relative to that of the so called intrinsic

T_{c p} (M, ϕ_{c p})

response of a polymer without end groups. The limits to the applicability of the FH theory are established, and a set of possible theoretical improvements is considered. The ultimate scrutiny of the simple FH theory and suggested improved theories must await the measurement of truly thermodynamic cloud points; the available cloud points are merely estimations of the thermodynamic cloud point, for which the deviation to the true cloud point cannot be established with sufficient accuracy. Full article

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13 pages, 3704 KiB

Open AccessArticle

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed

by Ramunas Tupciauskas, Zigmunds Orlovskis, Karlis Trevors Blums, Janis Liepins, Andris Berzins, Gunars Pavlovics and Martins Andzs

Polymers 2024, 16(4), 562; https://doi.org/10.3390/polym16040562 - 19 Feb 2024

Viewed by 1018

Abstract

The present study evaluates the mold fungal resistance of newly developed loose-fill thermal insulation materials made of wheat straw, corn stalk and water reed. Three distinct techniques for the processing of raw materials were used: mechanical crushing (Raw, ≤20 mm), thermo-mechanical pulping (TMP) [...] Read more.

The present study evaluates the mold fungal resistance of newly developed loose-fill thermal insulation materials made of wheat straw, corn stalk and water reed. Three distinct techniques for the processing of raw materials were used: mechanical crushing (Raw, ≤20 mm), thermo-mechanical pulping (TMP) with 4% NaOH and steam explosion pulping (SEP). An admixture of boric acid (8%) and tetraborate (7%) was applied to all processed substrates due to their anti-fungal properties. The fourth sample group was prepared from SEP substrates without added fungicide (SEP*) as control. Samples from all treatments were separately inoculated by five different fungal species and incubated in darkness for 28 days at 28 °C and RH > 90%. The highest resistance to the colonization of mold fungi was achieved by TMP and SEP processing, coupled with the addition of boric acid and tetraborate, where molds infested only around 35% to 40% of the inoculated sample area. The lowest mold fungi resistance was detected for the Raw and SEP* samples, each ~75%; they were affected by rich amount of accessible nutrients, suggesting that boric acid and tetraborate additives alone did not prevent mold fungal growth as effectively as in combination with TMP and SEP treatments. Together, the achieved fungal colonization scores after combined fungicide and pulping treatments are very promising for the application of tested renewable materials in the future development of thermal insulation products. Full article

(This article belongs to the Special Issue Advances in Wood-Based Materials and Wood Polymer Composites)

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Radial (a) and tangential (b) surfaces of pine sapwood specimens. Full article ">Figure 2
Microscopical surface view (25×, scale bar 1 mm) of mold fungal colonization on radial (above) and tangential (bottom) surfaces of pine sapwood specimens after 4 weeks incubation with (a) Trichoderma viride, (b) Chaetomium globulosum, (c) Paecilomyces variotii, (d) Penicillium pinophilum and (e) Aspergillus niger. Full article ">Figure 3
Mold fungal colonization (A–H2O, according to <a href="#polymers-16-00562-t001" class="html-table">Table 1</a>) of differently processed wheat straw samples. Error bars are one standard deviation of 4 specimens mean. Full article ">Figure 4
Microscopical surface view (10×, scale bar 3 mm) of mold fungal colonization on wheat straw samples after 4 weeks incubation: (a) WS-raw + A—Trichoderma viride, (b) WS-TMP + B—Chaetomium globulosum, (c) WS-SE + C—Paecilomyces variotii and (d) WS-SE* (H2O). Full article ">Figure 5
Mold fungal colonization (A–H2O, according to <a href="#polymers-16-00562-t001" class="html-table">Table 1</a>) on differently processed corn stalk samples. Error bars are one standard deviation of 4 specimens mean. Full article ">Figure 6
Microscopical surface view (10×, scale bar 3 mm) of mold fungal colonization on corn stalk samples after 4 weeks incubation: (a) Corn-raw + E—Aspergillus niger, (b) Corn-TMP (H2O), (c) Corn-SE + C—Paecilomyces variotii and (d) Corn-SE* + D—Penicillium pinophilum. Full article ">Figure 7
Mold fungal colonization (A–H2O, according to <a href="#polymers-16-00562-t001" class="html-table">Table 1</a>) of differently processed water reed samples. Error bars are one standard deviation of 4 specimens mean. Full article ">Figure 8
Microscopical surface view (10×, scale bar 3 mm) of mold fungal colonization on water reed samples after 4 weeks incubation: (a) Reed-raw + A—Trichoderma viride, (b) Reed-TMP (H2O), (c) Reed-SE + D—Penicillium pinophilum and (d) Reed-SE* + B—Chaetomium globulosum. Full article ">

12 pages, 11497 KiB

Open AccessArticle

Pretreating Recycled Carbon Fiber Nonwoven with a Sizing Formulation to Improve the Performance of Thermoplastic Recycled Fiber-Reinforced Composites

by Frederik Goethals, Elke Demeyer, Isabel De Schrijver and Myriam Vanneste

Polymers 2024, 16(4), 561; https://doi.org/10.3390/polym16040561 - 19 Feb 2024

Viewed by 1130

Abstract

Pyrolysis is already an established recycling method to recover the carbon fibers of end-of-life composites. However, the pyrolysis process removes the fiber sizing. Fiber sizing is a critical step in composite material production, influencing adhesion, protection and overall performance. In this study, recycled [...] Read more.

Pyrolysis is already an established recycling method to recover the carbon fibers of end-of-life composites. However, the pyrolysis process removes the fiber sizing. Fiber sizing is a critical step in composite material production, influencing adhesion, protection and overall performance. In this study, recycled carbon nonwoven reinforcements made from pyrolyzed carbon fibers were pretreated to improve the mechanical properties of polyamide and polypropylene composites. The pretreatment involved applying specific coatings (sizings) on the nonwoven by spraying. Pretreated and non-pretreated composites were prepared by compression molding to investigate the impact of the fiber pretreatment on the tensile properties and interlaminar shear strength. The tests were performed in the 0° and 90° directions of the composite plate. The results revealed that pretreatment had little effect on the polyamide composites. However, significant improvements were obtained for the polypropylene composites, as an increase of more than 50% in tensile strength was achieved in the 0° direction and more than 35% in the 90° direction. In addition, the interlaminar shear strength increased from 11.9 MPa to 14.3 MPa in the 0° direction and from 14.9 MPa to 17.8 MPa in the 90° direction. Full article

(This article belongs to the Section Polymer Fibers)

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Applying the sizing formulation. Full article ">Figure 2
SEM images of treated carbon nonwoven: (a) bottom of sample treated with Form 1; (b) middle of sample treated with Form 1. Full article ">Figure 3
SEM images of treated carbon nonwoven: (a) bottom of sample treated with Form 5; (b) middle of sample treated with Form 5. Full article ">Figure 4
Tensile strength of carbon/PA6 and carbon/PP composites containing different fiber sizings. In black are the results obtained in the 0° direction and in gray are the results obtained in the 90° direction of the composite plate. Full article ">Figure 5
Tensile modulus of carbon/PA6 and carbon/PP composites containing different fiber sizings. In black are the results obtained in the 0° direction and in gray are the results obtained in the 90° direction of the composite plate. Full article ">Figure 6
Interlaminar shear strength of carbon/PA6 and carbon/PP composites containing different fiber sizings. In black are the results obtained in the 0° direction and in gray are the results obtained in the 90° direction of the composite plate. Full article ">Figure 7
SEM images of the cross section of (a) non-pretreated PA6 composite (no-sizing PA), (b) pretreated PA6 composite (COM 4), (c) non-pretreated PP composite (no-sizing PP) and (d) pretreated PP composite (COM 6). Full article ">

17 pages, 12960 KiB

Open AccessArticle

Photopolymerization Pattern of New Methacrylate Cellulose Acetate Derivatives

by Ioana-Sabina Trifan, Andreea L. Chibac-Scutaru, Violeta Melinte and Sergiu Coseri

Polymers 2024, 16(4), 560; https://doi.org/10.3390/polym16040560 - 19 Feb 2024

Viewed by 1018

Abstract

Polymeric photocrosslinked networks, of particular interest in the design of materials with targeted characteristics, can be easily prepared by grafting light-sensitive moieties, such as methacrylates, on polymeric chains and, after photochemical reactions, provide materials with multiple applications via photopolymerization. In this work, photopolymerizable [...] Read more.

Polymeric photocrosslinked networks, of particular interest in the design of materials with targeted characteristics, can be easily prepared by grafting light-sensitive moieties, such as methacrylates, on polymeric chains and, after photochemical reactions, provide materials with multiple applications via photopolymerization. In this work, photopolymerizable urethane–methacrylate sequences were attached to free hydroxyl units of cellulose acetate chains in various proportions (functionalization degree from 5 to 100%) to study the properties of the resulting macromolecules and the influence of the cellulosic material structure on the double bond conversion degree. Additionally, to manipulate the properties of the photocured systems, the methacrylate-functionalized cellulose acetate derivatives were mixed with low molecular weight dimethacrylate derivatives (containing castor oil and polypropylene glycol flexible chains), and the influence of UV-curable composition on the photopolymerization parameters being studied. The achieved data reveal that the addition of dimethacrylate comonomers augmented the polymerization rates and conversion degrees, leading to polymer networks with various microstructures. Full article

(This article belongs to the Collection Biopolymers: Synthesis and Properties)

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14 pages, 2264 KiB

Open AccessArticle

Experimental and Theoretical Insights into the Effect of Dioldibenzoate Isomers on the Performance of Polypropylene Catalysts

by Huasheng Feng, Changxiu Li, Junling Zhou, Xiaofan Zhang, Shuxuan Tang, Xiangya Xu and Zhihui Song

Polymers 2024, 16(4), 559; https://doi.org/10.3390/polym16040559 - 19 Feb 2024

Viewed by 837

Abstract

Experimental investigations and density functional theory (DFT) calculations were carried out to study the comprehensive effect of different 3,5-heptanedioldibenzoate (HDDB) optical isomers as the internal electron donor on the catalytic performance of Ziegler−Natta catalysts. The experimental catalytic activity of HDDB has a positive [...] Read more.

Experimental investigations and density functional theory (DFT) calculations were carried out to study the comprehensive effect of different 3,5-heptanedioldibenzoate (HDDB) optical isomers as the internal electron donor on the catalytic performance of Ziegler−Natta catalysts. The experimental catalytic activity of HDDB has a positive correlation with the relative content of the mesomer incorporated during catalyst preparation, while the hydrogen response of HDDB displayed a negative correlation with the relative content of the mesomer. In order to apply the DFT calculation results to the macroscopic activity of the catalyst, the content of the active centers of the catalyst was analyzed. Assuming that the content of the active centers is proportional to the internal electron donor content of the catalyst, binary linear regression was carried out, which showed a good linear correlation between experimental activity data and internal electron donor content. Furthermore, the fitted activity of the single active centers aligned well with the calculated activation energies. These results revealed that the catalytic activity of polypropylene (PP) catalysts is dependent on both the active center content and the catalytic activity of an individual active center. Additionally, the lower hydrogen response of HDDB leads to a higher molecular weight of polypropylene obtained from the RS-containing catalyst compared to the SS-containing catalyst. Further study reveals that the hydrogen transfer reactions of 2,4-pentanediol dibenzoate (PDDB)/HDDB are influenced by the orientation of the methyl/ethyl groups in different isomers, which affect the activation energy differences between the hydrogen transfer reaction and the propylene insertion reaction, and finally influence the molecular weight of PP. Full article

(This article belongs to the Special Issue Catalytic Olefin Polymerization and Polyolefin Materials)

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Figure 1
The optimized DFT geometries for the HDDB stereoisomers in the free state (red: oxygen; grey: carbon; hydrogen is omitted). Full article ">Figure 2
The trans-a adsorption modes of HDDB stereoisomers and TiCl4 on the (110)-facet of MgCl2 (red: oxygen; grey: carbon; green: chlorine; yellow: magnesium; hydrogen is omitted). Full article ">Figure 3
Structures of HDDB–catalyst–propylene complexes (red: oxygen; grey: carbon; green: chlorine; yellow: magnesium; hydrogen is omitted). Full article ">Figure 4
The transition state structures of HDDB–catalyst–propylene (si-insertion) complexes (red: oxygen; grey: carbon; green: chlorine; yellow: magnesium; hydrogen is omitted). Full article ">Figure 5
The changes of macroscopic activity for the active centers with (a) PDDB and (b) HDDB ID when increasing the stereoisomer content. The residuals are distributed according to the relative content percent of the RS or SS stereoisomers. The slope represents the catalytic activity for the active centers per unit. Full article ">Figure 6
The transition state structures of HDDB stereoisomer catalysts in the hydrogen transfer reaction (red: oxygen; grey: carbon; green: chlorine; yellow: magnesium; hydrogen is omitted). Full article ">

15 pages, 6448 KiB

Open AccessArticle

Preparation and Mechanical Properties of Flexible Prepreg Resin with High Strength and Low Creep

by Zhaoyi Sun, Zhiyuan Mei, Zheng Huang and Guorong Wang

Polymers 2024, 16(4), 558; https://doi.org/10.3390/polym16040558 - 18 Feb 2024

Cited by 1 | Viewed by 1025

Abstract

In this study, aiming at the problem of low strength and high creep caused by medium–low modulus flexible resin based on the formulation design idea of high-molecular-weight epoxy resin (E12)-reinforced flexible epoxy-terminated urethane resin (EUR), a flexible epoxy prepreg resin with high strength [...] Read more.

In this study, aiming at the problem of low strength and high creep caused by medium–low modulus flexible resin based on the formulation design idea of high-molecular-weight epoxy resin (E12)-reinforced flexible epoxy-terminated urethane resin (EUR), a flexible epoxy prepreg resin with high strength and low bending creep was prepared to be suitable for hot melt processing technology. Flexible EUR was synthesized by grafting flexible polyurethane segments onto the epoxy side chain by urethane bonding. By adjusting the ratio of E12 and EUR, the effects of different ratios of the two components on the mechanical properties and viscoelasticity of the resin were systematically studied with dicyandiamide as the latent curing system. Research has found that when the E12 content is between 20%wt and 40%wt, the resin system has the best coating viscosity at 65 °C to 85 °C. The molecular weight and the content of aromatic heterocyclic groups of the resin determine the strength and creep behavior of the resin. When the content of E12 in the system is less than 50%wt, modulus and strength increase linearly, but after more than 50%wt E12 content, the modulus is almost unchanged and the strength begins to decrease. By increasing the content of E12 in the resin, the creep behavior of the resin is greatly reduced. When the content of E12 increases to 50%wt, the bending creep is the lowest. Full article

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15 pages, 4535 KiB

Open AccessArticle

Effect of Heat Treatment under Different Atmospheres on the Bonding Properties and Mechanism of Ceramiziable Heat-Resistant Adhesive

by Qingke Wang, Jiadong Tao, Huawei Shan, Tangyin Cui, Jie Ding and Jianghang Wang

Polymers 2024, 16(4), 557; https://doi.org/10.3390/polym16040557 - 18 Feb 2024

Viewed by 976

Abstract

In this study, a heat-resistant adhesive was prepared using molybdenum-phenolic (Mo-PF) resin as the matrix and TiB₂ particle as the ceramizable filler for bonding Al₂O₃ ceramic substrates. Firstly, Fourier transform infrared (FTIR) was used to characterize the chemical structure [...] Read more.

In this study, a heat-resistant adhesive was prepared using molybdenum-phenolic (Mo-PF) resin as the matrix and TiB₂ particle as the ceramizable filler for bonding Al₂O₃ ceramic substrates. Firstly, Fourier transform infrared (FTIR) was used to characterize the chemical structure of the Mo-PF. Subsequently, thermo gravimetric analysis (TGA) and shear strength testing were employed to investigate the effects of heat treatment in different atmospheres on the thermal stability and residual bonding properties of the adhesive. To further explore the bonding mechanism of the adhesive after heat treatment in different atmospheres, scanning electron microscopy (SEM), compressive strength testing, and X-ray diffraction (XRD) were utilized to analyze the microstructure, mechanical strength, and composition evolution of the adhesive at different temperatures. The bonding strength of Al₂O₃ joints showed a trend of initially decreasing and then increasing after different temperature heat treatment in air, with the shear strength reaching a maximum value of 25.68 MPa after treatment at 1200 °C. And the bonding strength of Al₂O₃ joints decreased slowly with the increase of temperature in nitrogen. In air, the ceramicization reaction at a high temperature enabled the mechanical strength of the adhesive to rise despite the continuous pyrolysis of the resin. However, the TiB₂ filler in nitrogen did not react, and the properties of the adhesive showed a decreasing tendency with the pyrolysis of the resin. Full article

(This article belongs to the Special Issue Advanced Research on Thermal Properties and Flame Retardancy of Polymer Composites)

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22 pages, 6087 KiB

Open AccessArticle

Effect of Silica Fume Utilization on Structural Build-Up, Mechanical and Dimensional Stability Performance of Fiber-Reinforced 3D Printable Concrete

by Hatice Gizem Şahin, Ali Mardani and Hatice Elif Beytekin

Polymers 2024, 16(4), 556; https://doi.org/10.3390/polym16040556 - 18 Feb 2024

Cited by 5 | Viewed by 1023

Abstract

It is known that 3D printable concrete mixtures can be costly because they contain high dosages of binder and that the drying-shrinkage performance may be adversely affected. Mineral additives and fibers are generally used to control these negative aspects. In this study, the [...] Read more.

It is known that 3D printable concrete mixtures can be costly because they contain high dosages of binder and that the drying-shrinkage performance may be adversely affected. Mineral additives and fibers are generally used to control these negative aspects. In this study, the use of silica fume, a natural viscosity modifying admixture, was investigated to improve the rheological and thixotropic behavior of 3D printable concrete mixtures reinforced with polypropylene fiber (FR-3DPC). The effect of increasing the silica fume utilization ratio in FR-3DPC on the compressive strength (CS), flexural strength (FS), and drying-shrinkage (DS) performance of the mixtures was also examined. A total of five FR-3DPC mixtures were produced using silica fume at the rate of 3, 6, 9, and 12% of the cement weight, in addition to the control mixture without silica fume. As a result of the tests, the dynamic yield stress value decreased with the addition of 3% silica fume to the control mixture. However, it was found that the dynamic yield stress and apparent viscosity values of the mixtures increased with the addition of 6, 9, and 12% silica fume. With the increase in the use of silica fume, the CS values of the mixtures were generally affected positively, while the FS and DS behavior were affected negatively. Full article

(This article belongs to the Special Issue Functional Polymer-Associated Self-Healing Materials)

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26 pages, 7011 KiB

Open AccessReview

A Review of Polymer-Based Environment-Induced Nanogenerators: Power Generation Performance and Polymer Material Manipulations

by Shuanghong Xie, Huping Yan and Ronghui Qi

Polymers 2024, 16(4), 555; https://doi.org/10.3390/polym16040555 - 18 Feb 2024

Viewed by 1713

Abstract

Natural environment hosts a considerable amount of accessible energy, comprising mechanical, thermal, and chemical potentials. Environment-induced nanogenerators are nanomaterial-based electronic chips that capture environmental energy and convert it into electricity in an environmentally friendly way. Polymers, characterized by their superior flexibility, lightweight, and [...] Read more.

Natural environment hosts a considerable amount of accessible energy, comprising mechanical, thermal, and chemical potentials. Environment-induced nanogenerators are nanomaterial-based electronic chips that capture environmental energy and convert it into electricity in an environmentally friendly way. Polymers, characterized by their superior flexibility, lightweight, and ease of processing, are considered viable materials. In this paper, a thorough review and comparison of various polymer-based nanogenerators were provided, focusing on their power generation principles, key materials, power density and stability, and performance modulation methods. The latest developed nanogenerators mainly include triboelectric nanogenerators (TriboENG), piezoelectric nanogenerators (PENG), thermoelectric nanogenerators (ThermoENG), osmotic power nanogenerator (OPNG), and moist-electric generators (MENG). Potential practical applications of polymer-based nanogenerator were also summarized. The review found that polymer nanogenerators can harness a variety of energy sources, with the basic power generation mechanism centered on displacement/conduction currents induced by dipole/ion polarization, due to the non-uniform distribution of physical fields within the polymers. The performance enhancement should mainly start from strengthening the ion mobility and positive/negative ion separation in polymer materials. The development of ionic hydrogel and hydrogel matrix composites is promising for future nanogenerators and can also enable multi-energy collaborative power generation. In addition, enhancing the uneven distribution of temperature, concentration, and pressure induced by surrounding environment within polymer materials can also effectively improve output performance. Finally, the challenges faced by polymer-based nanogenerators and directions for future development were prospected. Full article

(This article belongs to the Special Issue High Performance Polymer Membranes II)

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24 pages, 4634 KiB

Open AccessArticle

Cellulose Acetate–Ionic Liquid Blends as Potential Polymers for Efficient CO₂ Separation Membranes

by Giannis Kontos, Costas Tsioptsias and Ioannis Tsivintzelis

Polymers 2024, 16(4), 554; https://doi.org/10.3390/polym16040554 - 18 Feb 2024

Viewed by 1103

Abstract

CO₂ capture, applied in CO₂ separation from natural gas or in CO₂/N₂ separation from power plant flue gas streams, is of great importance for technical, economic, and environmental reasons. The latter seems important because CO₂, as [...] Read more.

CO₂ capture, applied in CO₂ separation from natural gas or in CO₂/N₂ separation from power plant flue gas streams, is of great importance for technical, economic, and environmental reasons. The latter seems important because CO₂, as a greenhouse gas, is considered the main contributor to global warming. Using polymeric membranes for CO₂ separation presents several advantages, such as low energy demand, small equipment volume, and the absence of liquid waste. In this study, two ionic liquids (ILs) were used for the preparation of cellulose acetate (CA)–IL blend membranes for potential CO₂ capture applications, namely, 1-butyl-3-methylimidazolium hydrogen sulfate (

[{Bmim}^{+}]

[

{H SO}_{4}^{-}

]) and choline glycine (

[{Ch}^{+}] [{Gly}^{-}]

), as they present adequate CO₂ dissolution ability. The first IL is commercially available, whereas the latter was synthesized by a novel route. Several composite membranes were prepared through the solvent casting technique and characterized by a variety of methods, including thermogravimetry, calorimetry, FTIR spectroscopy, and X-ray diffraction. The CO₂ sorption in the composite membranes was experimentally measured using the mass loss analysis (MLA) technique. The results showed that the ILs strongly interacted with the C=O groups of CA, which exhibited high affinity with CO₂. In the case of

[{Bmim}^{+}]

[

{H SO}_{4}^{-}

], a reduction in the available sites that allow strong intermolecular interactions with CO₂ resulted in a decrease in CO₂ sorption compared to that of pure CA. In the case of

[{Ch}^{+}] [{Gly}^{-}]

, the reduction was balanced out by the presence of specific groups in the IL, which presented high affinity with CO₂. Thus, the CA-

[{Ch}^{+}] [{Gly}^{-}]

blend membranes exhibited increased CO₂ sorption capability, in addition to other advantages such as non-toxicity and low cost. Full article

(This article belongs to the Section Polymer Membranes and Films)

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34 pages, 11139 KiB

Open AccessArticle

Kraft (Nano)Lignin as Reactive Additive in Epoxy Polymer Bio-Composites

by Christina P. Pappa, Simone Cailotto, Matteo Gigli, Claudia Crestini and Konstantinos S. Triantafyllidis

Polymers 2024, 16(4), 553; https://doi.org/10.3390/polym16040553 - 18 Feb 2024

Cited by 1 | Viewed by 2124

Abstract

The demand for high-performance bio-based materials towards achieving more sustainable manufacturing and circular economy models is growing significantly. Kraft lignin (KL) is an abundant and highly functional aromatic/phenolic biopolymer, being the main side product of the pulp and paper industry, as well as [...] Read more.

The demand for high-performance bio-based materials towards achieving more sustainable manufacturing and circular economy models is growing significantly. Kraft lignin (KL) is an abundant and highly functional aromatic/phenolic biopolymer, being the main side product of the pulp and paper industry, as well as of the more recent 2nd generation biorefineries. In this study, KL was incorporated into a glassy epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and an amine curing agent (Jeffamine D-230), being utilized as partial replacement of the curing agent and the DGEBA prepolymer or as a reactive additive. A D-230 replacement by pristine (unmodified) KL of up to 14 wt.% was achieved while KL–epoxy composites with up to 30 wt.% KL exhibited similar thermo-mechanical properties and substantially enhanced antioxidant properties compared to the neat epoxy polymer. Additionally, the effect of the KL particle size was investigated. Ball-milled kraft lignin (BMKL, 10 μm) and nano-lignin (NLH, 220 nm) were, respectively, obtained after ball milling and ultrasonication and were studied as additives in the same epoxy system. Significantly improved dispersion and thermo-mechanical properties were obtained, mainly with nano-lignin, which exhibited fully transparent lignin–epoxy composites with higher tensile strength, storage modulus and glass transition temperature, even at 30 wt.% loadings. Lastly, KL lignin was glycidylized (GKL) and utilized as a bio-based epoxy prepolymer, achieving up to 38 wt.% replacement of fossil-based DGEBA. The GKL composites exhibited improved thermo-mechanical properties and transparency. All lignins were extensively characterized using NMR, TGA, GPC, and DLS techniques to correlate and justify the epoxy polymer characterization results. Full article

(This article belongs to the Collection Lignin)

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12 pages, 9342 KiB

Open AccessArticle

Flame-Retardant Thermoplastic Polyether Ester/Aluminum Butylmethylphosphinate/Phenolphthalein Composites with Enhanced Mechanical Properties and Antidripping

by Xue Yang, Yan Zhang, Jia Chen, Liyong Zou, Xuesong Xing, Kangran Zhang, Jiyan Liu and Xueqing Liu

Polymers 2024, 16(4), 552; https://doi.org/10.3390/polym16040552 - 18 Feb 2024

Cited by 1 | Viewed by 857

Abstract

Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the current study. The thermal properties, flame retardancy, crystallization and mechanical properties of TPEE/AiMBP with or without phenolphthalein were investigated using [...] Read more.

Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the current study. The thermal properties, flame retardancy, crystallization and mechanical properties of TPEE/AiMBP with or without phenolphthalein were investigated using various characterizations, including the limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis TG, differential scanning calorimetry, microcombustion calorimeter (MCC), scanning electron microscopy (SEM), and mechanical tests. The results revealed that AiBMP alone is an efficient flame retardant of TPEE. Adding 15 wt.% AiBMP increases the LOI value of TPEE from 20% to 36%. The formula TPEE-15 AiBMP passed the UL 94 V-0 rating with no dripping occurring. The MCC test shows that AiBMP depresses the heat release of TPEE. In comparison with pure TPEE, the heat release rate at peak temperature and the heat release capacity of TPEE-15AiBMP are reduced by 46.1% and 55.5%, respectively. With the phenolphthalein added, the formula TPEE/13AiBMP/2Ph shows a higher char yield at high temperatures (>600 °C), and the char layer is stronger and more condensed than TPEE-15AiBMP.The tensile strength and elongation at break values of TPEE-13AiBMP-2Ph are increased by 29.63% and 4.8% in comparison with TPEE-15AiBMP. The SEM morphology of the fracture surface of the sample shows that phenolphthalein acts as a plasticizer to improve the dispersion of AiBMP within the matrix. The good char charming ability of phenolphthalein itself and improved dispersion of AiBMP make the TPEE composites achieve both satisfying flame retardancy and high mechanical properties. Full article

(This article belongs to the Special Issue Advance in Polymer Composites: Fire Protection and Thermal Management)

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(a) XRD spectra, (b)XRF, (c) morphology and (d) FTIR spectra of AiBMP. Full article ">Figure 2
Heat release rate vs. temperature of samples. Full article ">Figure 3
(a) TG and (b) DTG curves of TPEE, phenolphthalein and AiBMP in N2. (c) TG and (d) DTG curves of TPEE composites in N2. (c′) TG curves of TPEE composites between 500–700 °C in N2, (d′) DTG curves of TPEE composites between 300–450 °C in N2. Full article ">Figure 4
SEM (upper) and digital photos (bottom) of the residues TPEE (a), TPEE-15AiBMP (b) and TPEE-13AiBMP-2Ph (c) obtained by heating samples at 500 °C for 5 min. Full article ">Figure 5
DSC curves of heating and subsequent cooling for samples. Full article ">Figure 6
Tensile properties of samples at a crosshead speed of 25 mm/min. Full article ">Figure 7
SEM images of fractured surface for TPEE (a), TPEE-15AiBMP (b) and TPEE-13AiBMP-2Ph (c). Full article ">

17 pages, 5363 KiB

Open AccessArticle

Lignocellulosic Membranes Grafted with N-Vinylcaprolactam Using Radiation Chemistry: Load and Release Capacity of Vancomycin

by Maite Rentería-Urquiza, Guadalupe Gabriel Flores-Rojas, Belén Gómez-Lázaro, Felipe López-Saucedo, Ricardo Vera-Graziano, Eduardo Mendizabal and Emilio Bucio

Polymers 2024, 16(4), 551; https://doi.org/10.3390/polym16040551 - 18 Feb 2024

Viewed by 941

Abstract

Radiation chemistry presents a unique avenue for developing innovative polymeric materials with desirable properties, eliminating the need for chemical initiators, which can be potentially detrimental, especially in sensitive sectors like medicine. In this investigation, we employed a radiation-induced graft polymerization process with N-vinylcaprolactam [...] Read more.

Radiation chemistry presents a unique avenue for developing innovative polymeric materials with desirable properties, eliminating the need for chemical initiators, which can be potentially detrimental, especially in sensitive sectors like medicine. In this investigation, we employed a radiation-induced graft polymerization process with N-vinylcaprolactam (NVCL) to modify lignocellulosic membranes derived from Agave salmiana, commonly known as maguey. The membranes underwent thorough characterization employing diverse techniques, including contact angle measurement, degree of swelling, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), nuclear magnetic resonance (CP-MAS ¹³C-NMR), X-ray photoelectron spectroscopy (XPS), and uniaxial tensile mechanical tests. The membranes’ ability to load and release an antimicrobial glycopeptide drug was assessed, revealing significant enhancements in both drug loading and sustained release. The grafting of PNVCL contributed to prolonged sustained release by decreasing the drug release rate at temperatures above the LCST. The release profiles were analyzed using the Higuchi, Peppas–Sahlin, and Korsmeyer–Peppas models, suggesting a Fickian transport mechanism as indicated by the Korsmeyer–Peppas model. Full article

(This article belongs to the Special Issue Polymers in Pharmaceutical Technology II)

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25 pages, 5890 KiB

Open AccessArticle

Sustainable Innovation: Fabrication and Characterization of Mycelium-Based Green Composites for Modern Interior Materials Using Agro-Industrial Wastes and Different Species of Fungi

by Worawoot Aiduang, Kritsana Jatuwong, Praween Jinanukul, Nakarin Suwannarach, Jaturong Kumla, Wandee Thamjaree, Thana Teeraphantuvat, Tanut Waroonkun, Rawiwan Oranratmanee and Saisamorn Lumyong

Polymers 2024, 16(4), 550; https://doi.org/10.3390/polym16040550 - 18 Feb 2024

Cited by 2 | Viewed by 1805

Abstract

Mycelium-based bio-composites (MBCs) represent a sustainable and innovative material with high potential for contemporary applications, particularly in the field of modern interior design. This research investigates the fabrication of MBCs for modern interior materials using agro-industrial wastes (bamboo sawdust and corn pericarp) and [...] Read more.

Mycelium-based bio-composites (MBCs) represent a sustainable and innovative material with high potential for contemporary applications, particularly in the field of modern interior design. This research investigates the fabrication of MBCs for modern interior materials using agro-industrial wastes (bamboo sawdust and corn pericarp) and different fungal species. The study focuses on determining physical properties, including moisture content, shrinkage, density, water absorption, volumetric swelling, thermal degradation, and mechanical properties (bending, compression, impact, and tensile strength). The results indicate variations in moisture content and shrinkage based on fungal species and substrate types, with bamboo sawdust exhibiting lower shrinkage. The obtained density values range from 212.31 to 282.09 kg/m³, comparable to traditional materials, suggesting MBCs potential in diverse fields, especially as modern interior elements. Water absorption and volumetric swelling demonstrate the influence of substrate and fungal species, although they do not significantly impact the characteristics of interior decoration materials. Thermal degradation analysis aligns with established patterns, showcasing the suitability of MBCs for various applications. Scanning electron microscope observations reveal the morphological features of MBCs, emphasizing the role of fungal mycelia in binding substrate particles. Mechanical properties exhibit variations in bending, compression, impact, and tensile strength, with MBCs demonstrating compatibility with traditional materials used in interior elements. Those produced from L. sajor-caju and G. fornicatum show especially promising characteristics in this context. Particularly noteworthy are their superior compression and impact strength, surpassing values observed in certain synthetic foams multiple times. Moreover, this study reveals the biodegradability of MBCs, reaching standards for environmentally friendly materials. A comprehensive comparison with traditional materials further supports the potential of MBCs in sustainable material. Challenges in standardization, production scalability, and market adoption are identified, emphasizing the need for ongoing research, material engineering advancements, and biotechnological innovations. These efforts aim to enhance MBC properties, promoting sustainability in modern interior applications, while also facilitating their expansion into mass production within the innovative construction materials market. Full article

(This article belongs to the Special Issue Polymer Composites in Waste Recycling)

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10 pages, 837 KiB

Open AccessArticle

Effect of Different Post-Curing Methods on the Degree of Conversion of 3D-Printed Resin for Models in Dentistry

by Scott Kirby, Igor Pesun, Anthony Nowakowski and Rodrigo França

Polymers 2024, 16(4), 549; https://doi.org/10.3390/polym16040549 - 18 Feb 2024

Cited by 2 | Viewed by 1190

Abstract

The aim was to investigate the effects of different post-curing units on the chemical properties (degree of conversion) of 3D-printed resins for producing models in dentistry. The goal is to determine whether less-expensive post-curing units can be a viable alternative to the manufacturer’s [...] Read more.

The aim was to investigate the effects of different post-curing units on the chemical properties (degree of conversion) of 3D-printed resins for producing models in dentistry. The goal is to determine whether less-expensive post-curing units can be a viable alternative to the manufacturer’s recommended units. Forty-five samples were fabricated with an LCD printer (Phrozen Sonic Mini, Phrozen 3D, Hsinchu City, Taiwan) using MSLA Dental Modeling Resin (Apply Lab Work, Torrance, CA, USA). These samples were divided randomly into four different groups for post-curing using four distinct curing units: Phrozen Cure V2 (Phrozen 3D, Hsinchu City, Taiwan), a commercial acrylic nail UV LED curing unit (SUNUV, Shenzhen, China), a homemade curing unit created from a readily available UV LED light produced (Shenzhen, China), and the Triad^® 2000™ tungsten halogen light source (Dentsply Sirona, York, PA, USA). The degree of conversion was measured with FTIR spectroscopy using a Nicolet 6700 FTIR Spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). Phrozen Cure V2 had the highest overall mean degree of conversion (69.6% with a 45 min curing time). The Triad^® 2000 VLC Curing Unit had the lowest mean degree of conversion value at the 15 min interval (66.2%) and the lowest mean degree of conversion at the 45 min interval with the homemade curing unit (68.2%). The type of light-curing unit did not yield statistically significant differences in the degree of conversion values. There was a statistically significant difference in the degree of conversion values between the 15 min and 45 min curing intervals. When comparing individual light-curing units, there was a statistically significant difference in the degree of conversion for the post-curing units between the 15 min and 45 min curing time (p = 0.029). Full article

(This article belongs to the Special Issue 3D Printing Polymer: Processing and Fabrication)

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26 pages, 3071 KiB

Open AccessArticle

Impact of Eco-Friendly Plaster Using Epoxy Resin and Epoxy Hardener on Mechanical Properties under Compression and Tension

by Mohammed A. Albadrani and Ahmed D. Almutairi

Polymers 2024, 16(4), 548; https://doi.org/10.3390/polym16040548 - 18 Feb 2024

Viewed by 1254

Abstract

BISCO plaster (BRP) is an environmentally friendly material with high mechanical properties and is considered a great elective to conventional materials such as gypsum and cement. Our investigation seeks to examine BISCO plaster (BRP) and a mixture of resin and hardener in three [...] Read more.

BISCO plaster (BRP) is an environmentally friendly material with high mechanical properties and is considered a great elective to conventional materials such as gypsum and cement. Our investigation seeks to examine BISCO plaster (BRP) and a mixture of resin and hardener in three proportions (30%, 45%, and 60%) to achieve our ultimate goal, which is to preserve the environment and achieve the vision of the Kingdom of Saudi Arabia 2030 to reach zero carbon emissions by 2060? Emissions tests were performed, and although the CO₂ level was zero, they emitted SO₂ sulfur dioxide and NO₂ nitrogen dioxide, and 60% was the lowest emission rate. We also used ANSYS 2023 R1 software to compare them with their mechanical properties resulting from tensile and compression testing. In this study, we looked closely at the mechanical characteristics of different materials designed for wall coverings, with particular emphasis on their environmental sustainability. We carried out experiments to gauge the tensile and compressive stress on samples with varying mixing ratios. Our main objective was on crucial mechanical properties such as the modulus of elasticity, ultimate tensile strength, yield strength, yield strain, modulus of resilience, and ductility. Through meticulous scrutiny, we determined that the amalgamation of these mechanical attributes at the 30% mixing ratio provides an optimal combination for attaining structural integrity, adaptability, and resilience in wall coverings. Significantly, this ratio also underscores a commitment to environmentally conscious material selection. Our study offers important new insights into the selection of wall covering materials by providing a detailed understanding of their mechanical behavior under various stress conditions. It aligns with the increasing significance of environmental responsibility in contemporary design and construction. By emphasizing the 30% mixing ratio, our findings establish a foundation for informed decision making, promoting the utilization of sustainable materials that achieve a balance between strength, flexibility, and longevity. This ensures optimal performance in practical applications while simultaneously minimizing the environmental impact. Full article

(This article belongs to the Section Polymer Applications)

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20 pages, 5061 KiB

Open AccessArticle

In Situ Study and Improvement of the Temperature Increase and Isothermal Retention Stages in the Polyacrylonitrile (PAN) Fiber Pre-Oxidation Process

by Ye Cui, Lizhi Liu, Lixin Song, Sanxi Li, Ying Wang, Ying Shi and Yuanxia Wang

Polymers 2024, 16(4), 547; https://doi.org/10.3390/polym16040547 - 18 Feb 2024

Cited by 2 | Viewed by 905

Abstract

The pre-oxidation process of Polyacrylonitrile (PAN) fibers is a complex procedure involving multiple stages of temperature increase and isothermal temperature retention. However, the impact of the temperature increase stage on PAN fiber has often been overlooked. To address this, samples were collected before [...] Read more.

The pre-oxidation process of Polyacrylonitrile (PAN) fibers is a complex procedure involving multiple stages of temperature increase and isothermal temperature retention. However, the impact of the temperature increase stage on PAN fiber has often been overlooked. To address this, samples were collected before and after the temperature increase and isothermal retention stages, treating them as separate influencing factors. Therefore, the pre-oxidation process can be divided into four distinct stages: (1) A temperature increase stage before the cyclization reactions: the PAN fiber’s small-size crystals melt, and the crystal orientation changes under fixed tension, leading to shrinkage and increased orientation of the micropore. (2) An isothermal retention stage before the cyclization reactions: The crystal structure maintains well, resulting in minimal micropore evolution. The PAN fiber’s crystal orientation and micropore orientation increased under fixed tension. (3) A temperature increase stage after the cyclization reactions: The PAN fiber’s crystal melts again, reducing the average chord length and relative volume of the micropore. However, the PAN fiber can recrystallize under fixed tension. (4) An isothermal retention stage after the cyclization reactions: Significant crystal melting of the PAN fiber occurs, but the highly oriented crystals are maintained well. The average chord length and relative volume of the micropore increase. Recommendations for improving the pre-oxidation process are made according to these stages. Full article

(This article belongs to the Special Issue Polymer-Based Carbon Fiber Composites)

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31 pages, 7722 KiB

Open AccessReview

Advances in Monte Carlo Method for Simulating the Electrical Percolation Behavior of Conductive Polymer Composites with a Carbon-Based Filling

by Zhe Zhang, Liang Hu, Rui Wang, Shujie Zhang, Lisong Fu, Mengxuan Li and Qi Xiao

Polymers 2024, 16(4), 545; https://doi.org/10.3390/polym16040545 - 18 Feb 2024

Cited by 2 | Viewed by 2020

Abstract

Conductive polymer composites (CPCs) filled with carbon-based materials are widely used in the fields of antistatic, electromagnetic interference shielding, and wearable electronic devices. The conductivity of CPCs with a carbon-based filling is reflected by their electrical percolation behavior and is the focus of [...] Read more.

Conductive polymer composites (CPCs) filled with carbon-based materials are widely used in the fields of antistatic, electromagnetic interference shielding, and wearable electronic devices. The conductivity of CPCs with a carbon-based filling is reflected by their electrical percolation behavior and is the focus of research in this field. Compared to experimental methods, Monte Carlo simulations can predict the conductivity and analyze the factors affecting the conductivity from a microscopic perspective, which greatly reduces the number of experiments and provides a basis for structural design of conductive polymers. This review focuses on Monte Carlo models of CPCs with a carbon-based filling. First, the theoretical basis of the model’s construction is introduced, and a Monte Carlo simulation of the electrical percolation behaviors of spherical-, rod-, disk-, and hybridfilled polymers and the analysis of the factors influencing the electrical percolation behavior from a microscopic point of view are summarized. In addition, the paper summarizes the progress of polymer piezoresistive models and polymer foaming structure models that are more relevant to practical applications; finally, we discuss the shortcomings and future research trends of existing Monte Carlo models of CPCs with carbon-based fillings. Full article

(This article belongs to the Section Polymer Chemistry)

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13 pages, 4076 KiB

Open AccessArticle

Preparation of MoS₂@PDA-Modified Polyimide Films with High Mechanical Performance and Improved Electrical Insulation

by Xian Cheng, Chenxi Wang, Shuo Chen, Leyuan Zhang, Zihao Liu and Wenhao Zhang

Polymers 2024, 16(4), 546; https://doi.org/10.3390/polym16040546 - 17 Feb 2024

Viewed by 977

Abstract

Polyimide (PI) has been widely used in cable insulation, thermal insulation, wind power protection, and other fields due to its high chemical stability and excellent electrical insulation and mechanical properties. In this research, a modified PI composite film (MoS₂@PDA/PI) was obtained [...] Read more.

Polyimide (PI) has been widely used in cable insulation, thermal insulation, wind power protection, and other fields due to its high chemical stability and excellent electrical insulation and mechanical properties. In this research, a modified PI composite film (MoS₂@PDA/PI) was obtained by using polydopamine (PDA)-coated molybdenum disulfide (MoS₂) as a filler. The low interlayer friction characteristics and high elastic modulus of MoS₂ provide a theoretical basis for enhancing the flexible mechanical properties of the PI matrix. The formation of a cross-linking structure between a large number of active sites on the surface of the PDA and the PI molecular chain can effectively enhance the breakdown field strength of the film. Consequently, the tensile strength of the final sample MoS₂@PDA/PI film increased by 44.7% in comparison with pure PI film, and the breakdown voltage strength reached 1.23 times that of the original film. It can be seen that the strategy of utilizing two-dimensional (2D) MoS₂@PDA nanosheets filled with PI provides a new modification idea to enhance the mechanical and electrical insulation properties of PI films. Full article

(This article belongs to the Section Polymer Applications)

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12 pages, 3087 KiB

Open AccessArticle

Flame-Retardant GF-PSB/DOPO-POSS Composite with Low Dk/Df and High Thermal Stability for High-Frequency Copper Clad Applications

by Ke Zheng, Yizhi Zhang, Jiaxiang Qiu, Guanqun Xie, Zengbiao Huang, Wei Lin, Zhimeng Liu, Qianfa Liu and Xiaoxia Wang

Polymers 2024, 16(4), 544; https://doi.org/10.3390/polym16040544 - 17 Feb 2024

Viewed by 1150

Abstract

In the field of high-frequency communications devices, there is an urgent need to develop high-performance copper clad laminates (CCLs) with low dielectric loss (Df) plus good flame retardancy and thermal stability. The hydrocarbon resin styrene-butadiene block copolymer (PSB) was modified with the flame-retardant [...] Read more.

In the field of high-frequency communications devices, there is an urgent need to develop high-performance copper clad laminates (CCLs) with low dielectric loss (Df) plus good flame retardancy and thermal stability. The hydrocarbon resin styrene-butadiene block copolymer (PSB) was modified with the flame-retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide/polyhedral oligomeric silsesquioxanes (DOPO-POSS) to meet the demands of high-frequency and high-speed applications. The resulting DOPO-POSS-modified PSB was used as the resin matrix along with other additives to fabricate PSB/DOPO-POSS laminates. At a high-frequency of 10 GHz, the laminates containing 20 wt.% of DOPO-POSS and with a thickness of 0.09 mm exhibited a Df of 0.00328, which is much lower compared with the commercial PSB/PX-200 composite (Df: 0.00498) and the PSB without flame retardancy (Df: 0.00453). Afterwards, glass fiber cloth (GF) was used as a reinforcing material to manufacture GF-PSB/DOPO-POSS composite laminates with a thickness of 0.25 mm. The flame retardancy of GF-PSB/DOPO-POSS composite laminate reached vertical burning (UL-94) V-1 grade, and GF-PSB/DOPO-POSS exhibited higher thermal and dynamic mechanical properties than GF-PSB/PX-200. The results of a limited oxygen index (LOI) and self-extinguishing time tests also demonstrated the superior flame-retardant performance of DOPO-POSS compared with PX-200. The investigation indicates that GF-PSB/DOPO-POSS composite laminates have significant potential for use in fabricating a printed circuit board (PCB) for high-frequency and high-speed applications. Full article

(This article belongs to the Special Issue Development in Flame-Retardant Polymer Composites)

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16 pages, 8947 KiB

Open AccessArticle

Performance of Particleboard Made of Agroforestry Residues Bonded with Thermosetting Adhesive Derived from Waste Styrofoam

by Tati Karliati, Muhammad Adly Rahandi Lubis, Rudi Dungani, Rijanti Rahaju Maulani, Anne Hadiyane, Alfi Rumidatul, Petar Antov, Viktor Savov and Seng Hua Lee

Polymers 2024, 16(4), 543; https://doi.org/10.3390/polym16040543 - 17 Feb 2024

Cited by 1 | Viewed by 918

Abstract

This paper investigated the upcycling process of thermoplastic waste polystyrene (WPS) into thermosetting particleboard adhesive using two cross-linkers, namely methylene diphenyl diisocyanate (MDI) and maleic anhydride (MA). The WPS was dissolved in an organic co-solvent. The weight ratio of WPS/co-solvent was 1:9, and [...] Read more.

This paper investigated the upcycling process of thermoplastic waste polystyrene (WPS) into thermosetting particleboard adhesive using two cross-linkers, namely methylene diphenyl diisocyanate (MDI) and maleic anhydride (MA). The WPS was dissolved in an organic co-solvent. The weight ratio of WPS/co-solvent was 1:9, and 10% of cross-linkers based on the WPS solids content were added subsequently at 60 °C under continuous stirring for 30 min. The adhesive properties, cohesion strength, and thermo-mechanical properties of WPS-based adhesives were examined to investigate the change of thermoplastic WPS to thermosetting adhesives. The bonding strength of WPS-based adhesives was evaluated in particleboard made of sengon (Falcataria moluccana (Miq.) Barneby & J.W. Grimes) wood and rice straw particles at different weight ratios according to the Japanese Industrial Standard (JIS) A 5908:2003. Rheology and Dynamic Mechanical Analysis revealed that modification with MDI and MA resulted in thermosetting properties in WPS-based adhesives by increasing the viscosity at a temperature above 72.7 °C and reaching the maximum storage modulus above 90.8 °C. WPS modified with MDI had a lower activation energy (Ea) value (83.4 kJ/mole) compared to the WPS modified with MA (150.8 kJ/mole), indicating the cross-linking with MDI was much faster compared with MA. Particleboard fabricated from 100% sengon wood particles bonded with WPS modified with MDI fulfilled the minimum requirement of JIS A 5908:2003 for interior applications. Full article

(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)

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20 pages, 3284 KiB

Open AccessArticle

Synapse-Mimicking Memristors Based on 3,6-Di(tpy)-9-Phenylcarbazole Unimer and Its Copolymer with Cobalt(II) Ions

by Ambika Pandey, Andrei Chernyshev, Yadu Ram Panthi, Jiří Zedník, Adriana Šturcová, Magdalena Konefał, Olga Kočková, Stephen H. Foulger, Jiří Vohlídal and Jiří Pfleger

Polymers 2024, 16(4), 542; https://doi.org/10.3390/polym16040542 - 17 Feb 2024

Cited by 1 | Viewed by 1628

Abstract

The title compound, unimer U (tpy stands for 2,2′:6′,2″-terpyridin-4′-yl end-group), by itself shows the memristor effect with a retention time of 18 h and persistence of 11 h. Its coordination copolymer with Co(II) ions, [CoU]_n, exhibits multimodal resistance changes similar [...] Read more.

The title compound, unimer U (tpy stands for 2,2′:6′,2″-terpyridin-4′-yl end-group), by itself shows the memristor effect with a retention time of 18 h and persistence of 11 h. Its coordination copolymer with Co(II) ions, [CoU]_n, exhibits multimodal resistance changes similar to the synaptic responses observed in biological systems. More than 320 cycles of potentiation and depression measured in continuous sequence occurred without observing a significant current change, confirming the operational stability and reproducibility of the device based on the [CoU]_n polymer. The synaptic effect of a device with an indium tin oxide (ITO)/[CoU]_n/top-electrode (TE) configuration is more pronounced for the device with TE = Au compared to devices with TE = Al or Ga. However, the latter TEs provide a cost-effective approach without any significant compromise in device plasticity. The detected changes in the synaptic weight, about 12% for pair-pulse facilitation and 80% for its depression, together with a millisecond trigger and reading pulses that decay exponentially on the time scale typical of neurosynapses, justify the device’s ability to learn and memorize. These properties offer potential applications in neuromorphic computation and brain-inspired synaptic devices. Full article

(This article belongs to the Special Issue Emerging Smart Applications of Functional Polymeric Materials)

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18 pages, 6580 KiB

Open AccessArticle

Fluorescent Carbon Dioxide-Based Polycarbonates Probe for Rapid Detection of Aniline in the Environment and Its Biomarkers in Urine

by Yun Liu, Wen-Zhen Wang, Zhi-Ping Zhang, Chun-Bao Du, Lei-Lei Li, Chen Zhao, Hong-Jiu Li and Qing Huang

Polymers 2024, 16(4), 541; https://doi.org/10.3390/polym16040541 - 17 Feb 2024

Viewed by 956

Abstract

Aniline compounds, as a class of widely used but highly toxic chemical raw materials, are increasingly being released and accumulated in the environment, posing serious threats to environmental safety and human health. Therefore, developing detection methods for aniline compounds is of particular significance. [...] Read more.

Aniline compounds, as a class of widely used but highly toxic chemical raw materials, are increasingly being released and accumulated in the environment, posing serious threats to environmental safety and human health. Therefore, developing detection methods for aniline compounds is of particular significance. Herein, we synthesized the fluorescent third monomer cyano-stilbene epoxide M and ternary copolymerized it with carbon dioxide (CO₂) and propylene oxide (PO) to synthesize carbon dioxide-based polycarbonate (PPCM) with fluorescence recognition functions, as well as excellent performance, for the first time. The results revealed that the PPCM fluorescent probe exhibited typical aggregation-induced luminescence properties and could be quenched by aniline compounds. The probe presented anti-interference-specific selectivity for aniline compounds, and the detection limit was 1.69 × 10⁻⁴ M. Moreover, it was found to be a highly sensitive aniline detection probe. At the same time, the aniline biomarker p-aminophenol in urine could also be detected, which could expand the potential applications of polymers in the fluorescence-sensing field. Full article

(This article belongs to the Special Issue Novel Polymers in Sensors)

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15 pages, 3277 KiB

Open AccessArticle

Novel Conductive AgNP-Based Adhesive Based on Novel Poly (Ionic Liquid)-Based Waterborne Polyurethane Chloride Salts for E-Textiles

by Haiyang Liao, Yeqi Xiao, Tiemin Xiao, Hongjin Kuang, Xiaolong Feng, Xiao Sun, Guixin Cui, Xiaofei Duan and Pu Shi

Polymers 2024, 16(4), 540; https://doi.org/10.3390/polym16040540 - 17 Feb 2024

Viewed by 931

Abstract

The emergence of novel e-textile materials that combine the inherent qualities of the textile substrate (lightweight, soft, breathable, durable, etc.) with the functionality of micro/nano-electronic materials (conductive, dielectric, sensing, etc.) has resulted in a trend toward miniaturization, integration, and intelligence in new electronic [...] Read more.

The emergence of novel e-textile materials that combine the inherent qualities of the textile substrate (lightweight, soft, breathable, durable, etc.) with the functionality of micro/nano-electronic materials (conductive, dielectric, sensing, etc.) has resulted in a trend toward miniaturization, integration, and intelligence in new electronic devices. However, the formation of a conductive network by micro/nano-conductive materials on textiles necessitates high-temperature sintering, which inevitably causes substrate aging and component damage. Herein, a bis-hydroxy-imidazolium chloride salt as a hard segment to synthesize a waterborne polyurethane (WPU) adhesive is designed and prepared. When used in nano-silver-based printing coatings, it offers strong adherence for coatings, reaching 16 N cm⁻¹; on the other hand, the introduction of chloride ions enables low-temperature (60 °C) chemical sintering to address the challenge of secondary treatment and high-temperature sintering (>150 °C). Printed into flexible circuits, the resistivity can be controlled by the content of imidazolium salts anchored in the molecular chain of the WPU from a maximum resistivity of 3.1 × 10⁷ down to 5.8 × 10⁻⁵ Ω m, and it can conduct a Bluetooth-type finger pulse detector with such low resistivity. As a flexible circuit, it also offers high stability against washing and adhesion, which the resistivity only reduces less than 20% after washing 10 times and adhesion. Owing to the adjustability of the resistivity, we fabricated an all-textile flexible pressure sensor that accurately differentiates different external pressures (min. 10 g, ~29 Pa), recognizes forms, and detects joint motions (finger bending and wrist flexion). Full article

(This article belongs to the Special Issue Advanced Conductive Polymers for Electrochemical Applications)

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(a) Schematic illustration for fabrication of AgNP-based printed conductive pattern; (b) SEM image of the as-prepared AgNPs; (c) TEM image of as-prepared AgNPs and insert image shows the HR-TEM image; and (d) FTIR spectrum of CA-Na and AgNPs. Full article ">Figure 2
(a) TG curves of AgNPs and conductive adhesive and WPU[Cl−]; (b) particle size distribution of AgNPs; (c) particle size distribution of WPU[Cl−]; (d) FTIR spectra of conductive adhesive and WPU[Cl−]; (e) XPS spectra of AgNP-based conductive adhesive with 2 mmol of WPU[Cl−]; (f) photo of printed pattern on textile; (g) microscopic photograph of the demarcation line of a printed pattern; differences in the morphology of patterns printed on textile; (h) SEM image of unprinted site; and (i) SEM image of printed site. Full article ">Figure 3
(a) Resistivity of as-prepared AgNP-based printed conductive coatings based on different contents of OH-IL[Cl−]-OH in WPU[Cl−]; (b) photo of printed conductive pattern based on 4 mmol of OH-IL[Cl−]-OH in a WPU[Cl−]application in conductive wire for connecting the LEDs; morphology of printed pattern based on different contents of OH-IL[Cl−]-OH in WPU[Cl−]: (c) 0 mmol, (d) 2 mmol, and (e) 4 mmol; and XPS spectra of different elements: (f) Ag 3d, (g) N 1s, and (h) Cl 2d. Full article ">Figure 4
(a) Structure and photographs of textile pressure sensors based on AgNP-based conductive adhesive; (b) real-time resistance curve of the textile pressure sensor for detection of different weights with 10 g, 20 g, and 50 g; (c) real-time resistance curve of the PET-FPS to thumb bending; (d) stability of the PET-FPS on weight detection (50 g); (e) real-time resistance curve of PET-FPS on monitoring wrist vibration; and (f) the PET-FPS on area recognition. Full article ">Figure 5
Conductive AgNP-based printed circuits for electrical component integration. Full article ">

15 pages, 14632 KiB

Open AccessArticle

Ligand-Induced Synthesis of Highly Stable NM88(DB)@COF-JLU19 Composite: Accelerating Electron Flow for Visible-Light-Efficient Degradation of Tetracycline Hydrochloride

by Jinxia Zhao, Jingchao Liu, Zenghe Li and Yilin Yin

Polymers 2024, 16(4), 539; https://doi.org/10.3390/polym16040539 - 17 Feb 2024

Cited by 1 | Viewed by 806

Abstract

In recent years, the response of new porous materials to visible light and their potential applications in wastewater treatment has received extensive attention from the scientific community. Metal Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) have been the focus of attention due [...] Read more.

In recent years, the response of new porous materials to visible light and their potential applications in wastewater treatment has received extensive attention from the scientific community. Metal Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) have been the focus of attention due to their strong visible light absorption, high specific surface area, well-regulated pore structures, and diverse topologies. In this study, a novel MOF@COF composite with a high surface area, high crystallinity, and structural stability was obtained using the covalent bond formation strategy from COF-JLU19 and NH2-MIL-88B(Fe). Under visible light irradiation, the degradation of tetracycline hydrochloride by this material reached more than 90% within 10 min and was completely degraded within 30 min, which exceeded the degradation rate of individual materials. Remarkably, the catalytic activity decreased by less than 5% even after five degradation cycles, indicating good structural stability. The excellent photocatalytic performance of the NM88(DB)@COF-JLU19 hybrids was attributed to the formation of covalent bonds, which formed a non-homogeneous interface that facilitated effective charge separation and promoted the generation of hydroxyl radicals. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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17 pages, 12429 KiB

Open AccessArticle

Artificial Neural Network Approach for Assessing Mechanical Properties and Impact Performance of Natural-Fiber Composites Exposed to UV Radiation

by Khaled Nasri and Lotfi Toubal

Polymers 2024, 16(4), 538; https://doi.org/10.3390/polym16040538 - 17 Feb 2024

Cited by 1 | Viewed by 889

Abstract

Amidst escalating environmental concerns, short natural-fiber thermoplastic (SNFT) biocomposites have emerged as sustainable materials for the eco-friendly production of mechanical components. However, their limited durability has prompted research into the experimental evaluation of the deterioration of the mechanical characteristics of SNFT biocomposites, particularly [...] Read more.

Amidst escalating environmental concerns, short natural-fiber thermoplastic (SNFT) biocomposites have emerged as sustainable materials for the eco-friendly production of mechanical components. However, their limited durability has prompted research into the experimental evaluation of the deterioration of the mechanical characteristics of SNFT biocomposites, particularly under the influence of ultraviolet rays. However, conducting tests to evaluate the mechanical properties can be time-consuming and expensive. In this study, an artificial neural network (ANN) model was employed to predict the mechanical properties (tensile strength) and the impact performance (resistance and absorbed energy) of polypropylene reinforced with 30 wt.% short flax or wood pine fibers (referred to as PP30-F or PP30-P, respectively). Eight parameters were collected from experimental studies. The ANN input parameters comprised nondestructive test results, including mass, hardness, roughness, and natural frequencies, while the output parameters were the tensile strength, the maximum impact load, and absorbed energy. The model was developed using the ANN toolbox in MATLAB. The linear coefficient of correlation and mean squared error were selected as the metrics for evaluating the performance function and accuracy of the ANN model. They calculate the relationship and the average squared difference between the predicted and actual values. The data analysis conducted by the models demonstrated exceptional predictive capability, achieving an accuracy rate exceeding 96%, which was deemed satisfactory. For both the PP30-F and PP30-P biocomposites, the ANN predictions deviated from the experimental data by 3, 5, and 6% with regard to the impact load, absorbed energy, and tensile strength, respectively. Full article

(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)

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14 pages, 3532 KiB

Open AccessArticle

Strategies to Cope with Inferior Long-Term Photostability of Bentonite Polyolefin Nanocomposites

by Erik Westphal, Guru Geertz, Michael Großhauser, Elke Metzsch-Zilligen and Rudolf Pfaendner

Polymers 2024, 16(4), 535; https://doi.org/10.3390/polym16040535 - 17 Feb 2024

Viewed by 1094

Abstract

This study provides insight into the causes of inferior long-term stability of nanocomposites based on organic layered silicates (OLSs) used for cable mantles. A hierarchy was established by analyzing bentonite products and their respective polyolefin nanocomposites. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), gas [...] Read more.

This study provides insight into the causes of inferior long-term stability of nanocomposites based on organic layered silicates (OLSs) used for cable mantles. A hierarchy was established by analyzing bentonite products and their respective polyolefin nanocomposites. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), gas adsorption, energy-dispersive spectroscopy (SEM-EDX), and infrared spectroscopy (IR) provided evidence for the adsorption of stabilizers onto the filler surface and thus their reduction in activity, promoting polymer oxidation. This behavior corresponds to the specific surface area of the incorporated OLS. Therefore, it can be stated that gas adsorption and XRD are especially useful for the evaluation of long-term photostability. It was revealed that photocatalytically active iron is of secondary importance since iron-rich bentonites still formed the most stable nanocomposite. This also applies to the Hofmann elimination products of the modifying agent, where higher contents do not accelerate the degradation process. No elimination products could be traced within the composites. Due to the polymer-filler interface being essential for long-term photostability, prior analysis of the filler surface properties can be used to estimate the stability of the respective nanocomposite as a rationale for product selection in the early stages of development. The reasons identified in this work for decreasing the long-term photostability of OLS nanocomposites compared with unfilled formulations is an important step toward increasing their stability. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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Figure 1
TG and DTG curves for OLS and unmodified bentonite samples. TG and DTG curves are denoted by the solid and dashed lines, respectively. Full article ">Figure 2
SEM micrographs at 500× magnification, covering an area of 270 × 270 µm2 for (a) OLS Dellite CW9, (b) OLS MAX CT 4260, (c) OLS Cloisite 20A, and (d) unmodified bentonite Cloisite 116. Full article ">Figure 2 Cont.
SEM micrographs at 500× magnification, covering an area of 270 × 270 µm2 for (a) OLS Dellite CW9, (b) OLS MAX CT 4260, (c) OLS Cloisite 20A, and (d) unmodified bentonite Cloisite 116. Full article ">Figure 3
Particle size distribution of bentonite sample inferred by SEM imaging. The solid lines represent distribution curves and were fitted to the data evaluated by image analysis. Full article ">Figure 4
Results of XRD analysis depicting d001 distances of bentonite products. Full article ">Figure 5
XRD analysis of bentonite-filled nanocomposites. Full article ">Figure 6
Carbonyl index during weathering of model composites. Full article ">Figure 7
Iron content obtained by SEM-EDX analysis, normalized by (a) Si content and (b) Si content and organo-modifier content obtained by TGA, each with corresponding CI and the end of weathering. Full article ">

18 pages, 4312 KiB

Open AccessArticle

Stability in Aqueous Solution of a New Spray-Dried Hydrocolloid of High Andean Algae Nostoc sphaericum

by David Choque-Quispe, Carlos A. Ligarda-Samanez, Yudith Choque-Quispe, Sandro Froehner, Aydeé M. Solano-Reynoso, Elibet Moscoso-Moscoso, Yakov Felipe Carhuarupay-Molleda and Ronald Peréz-Salcedo

Polymers 2024, 16(4), 537; https://doi.org/10.3390/polym16040537 - 16 Feb 2024

Cited by 1 | Viewed by 1055

Abstract

There is a growing emphasis on seeking stabilizing agents with minimal transformation, prioritizing environmentally friendly alternatives, and actively contributing to the principles of the circular economy. This research aimed to assess the stability of a novel spray-dried hydrocolloid from high Andean algae when [...] Read more.

There is a growing emphasis on seeking stabilizing agents with minimal transformation, prioritizing environmentally friendly alternatives, and actively contributing to the principles of the circular economy. This research aimed to assess the stability of a novel spray-dried hydrocolloid from high Andean algae when introduced into an aqueous solution. Nostoc sphaericum freshwater algae were subject to atomization, resulting in the production of spray-dried hydrocolloid (SDH). Subsequently, suspension solutions of SDH were meticulously prepared at varying pH levels and gelling temperatures. These solutions were then stored for 20 days to facilitate a comprehensive evaluation of their stability in suspension. The assessment involved a multifaceted approach, encompassing rheological analysis, scrutiny of turbidity, sedimentation assessment, ζ-potential, and measurement of particle size. The findings from these observations revealed that SDH exhibits a dilatant behavior when in solution, signifying an increase in with higher shear rate. Furthermore, it demonstrates commendable stability when stored under ambient conditions. SDH is emerging as a potential alternative stabilizer for use in aqueous solutions due to its easy extraction and application. Full article

(This article belongs to the Special Issue Advances in Sustainable Polymeric Materials II)

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13 pages, 7954 KiB

Open AccessArticle

Flowing Liquid-Based Triboelectric Nanogenerator Performance Enhancement with Functionalized Polyvinylidene Fluoride Membrane for Self-Powered Pulsating Flow Sensing Application

by Duy Linh Vu, Quang Tan Nguyen, Pil Seung Chung and Kyoung Kwan Ahn

Polymers 2024, 16(4), 536; https://doi.org/10.3390/polym16040536 - 16 Feb 2024

Cited by 1 | Viewed by 973

Abstract

Pulsating flow, a common term in industrial and medical contexts, necessitates precise water flow measurement for evaluating hydrodynamic system performance. Addressing challenges in measurement technologies, particularly for pulsating flow, we propose a flowing liquid-based triboelectric nanogenerator (FL-TENG). To generate sufficient energy for a [...] Read more.

Pulsating flow, a common term in industrial and medical contexts, necessitates precise water flow measurement for evaluating hydrodynamic system performance. Addressing challenges in measurement technologies, particularly for pulsating flow, we propose a flowing liquid-based triboelectric nanogenerator (FL-TENG). To generate sufficient energy for a self-powered device, we employed a fluorinated functionalized technique on a polyvinylidene fluoride (PVDF) membrane to enhance the performance of FL-TENG. The results attained a maximum instantaneous power density of 50.6 µW/cm², and the energy output proved adequate to illuminate 10 white LEDs. Regression analysis depicting the dependence of the output electrical signals on water flow revealed a strong linear relationship between the voltage and flow rate with high sensitivity. A high correlation coefficient R² within the range from 0.951 to 0.998 indicates precise measurement accuracy for the proposed FL-TENG. Furthermore, the measured time interval between two voltage peaks precisely corresponds to the period of pulsating flow, demonstrating that the output voltage can effectively sense pulsating flow based on voltage and the time interval between two voltage peaks. This work highlights the utility of FL-TENG as a self-powered pulsating flow rate sensor. Full article

(This article belongs to the Special Issue Polymer Materials in Sensors, Actuators and Energy Conversion II)

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Schematic diagram of the procedure for functionalizing the PVDF membrane and diagram description of the FL-TENG device. Full article ">Figure 2
Schematic diagram of the experimental set up of the FL-TENG device. Full article ">Figure 3
(a) Schematic diagram of contact electrification and the forming of EDL. (b) Output electrical signals of the SE-WTENG when water flows through the cell at a flow rate of 390 cc/min. Full article ">Figure 4
FE-SEM and AFM images of (a) PVDF membrane and (b) F-PVDF membrane; the inset image shows a contact angle; (c) frequency dependence of dielectric constant, and (d) output current of PVDF and F-PVDF-based TENG. Full article ">Figure 5
(a) Voltage and (b) transferred charge of the F-PVDF-based TENG depending on the flow rate (Different colors correspond to different flow rates shown as in the x-axis), (c) comparison of voltages measured at different resistances and flow rates, (d) voltage and power, and (e) power density and energy density of the F-PVDF-based TENG, measured at various resistances from 1 kW to 10 MW at a flow rate of 1170 mL/min, (f) charging of 4.7μF, 22μF, and 47μF capacitor by F-PVDF-based TENG. Full article ">Figure 6
Electrical performance of F-PVDF-based TENG, depending on water flow conditions at a flow rate of (a) 130, (b) 390, and (c) 780 mL/min; regression analyses of the electrical response of FL-TENG based on (d) voltage and (e) time interval between two voltage peaks with different flow rates. Full article ">Figure 7
(a) Time interval between two voltage peaks and (b) output voltage, depending on the flow rate with different FL-TENG pipe sizes; regression analyses of the electrical response of (c) 3 mm-pipe, (d) 5 mm-pipe, (e) 8 mm-pipe-FL-TENG based on time interval between two voltage peaks and flow rates; regression analyses of the electrical response of (f) 3 mm-pipe, (g) 5 mm-pipe, and (h) 8 mm-pipe-FLTENG based on voltage and flow rate. Full article ">

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Polymers, Volume 16, Issue 4 (February-2 2024) – 119 articles

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