Witold Brostow
University of North Texas, Materials Science and Engineering, Faculty Member
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Authors describe the network structure of octadecylacrylate (ODA)-co-acrylic acid (AA) cross-linked with divinyl benzene (DVB). Crosslinked xerogels comprised of ODA/AA, with ODA molar composition ranging from 50 to 90%, were synthesised... more
Authors describe the network structure of octadecylacrylate (ODA)-co-acrylic acid (AA) cross-linked with divinyl benzene (DVB). Crosslinked xerogels comprised of ODA/AA, with ODA molar composition ranging from 50 to 90%, were synthesised by radical initiation copolymerisation in different concentrations (1–10%) of DVB utilising either bulk or suspension techniques in two solvents. Atomic force microscopy images of the xerogels reveal a variety of porous morphologies. The average molecular weight between the cross-links and polymer-toluene interaction parameter of xerogels were determined from swelling measurements. The efficiency of DVB as a cross-linking agent for ODA/AA was also determined. An increase of concentration of AA in the copolymers enhances the thermal stability of the copolymers at elevated temperatures determined by thermogravimetric analysis (TGA). Moreover, the increase in AA concentration increases the average molecular weight between cross-links and thus enhances swelling of the copolymer by toluene; this is true for any of our copolymerisation procedures.
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In situ copolymerization of diglycidyl ether of 4, 4′-dihydroxybiphenol (DGE-DHBP) with diglycidyl ether of bisphenol F (DGEBP-F) networks using an anhydride curing agent has been investigated. DGEBP-F is a commercial epoxy while cured... more
In situ copolymerization of diglycidyl ether of 4, 4′-dihydroxybiphenol (DGE-DHBP) with diglycidyl ether of bisphenol F (DGEBP-F) networks using an anhydride curing agent has been investigated. DGEBP-F is a commercial epoxy while cured DGE-DHBP shows liquid crystal transitions. Curing kinetics are determined using differential scanning calorimetry (DSC). The data were fitted using an autocatalytic curing model for both pure and mixed components. Isothermal and non-isothermal methods were compared. The glass ...
Research Interests: Engineering, Materials Science, Kinetics, Scanning Electron Microscopy, Polymer Blends, and 12 morePolymer, Differential scanning calorimetry, Activation Energy, Epoxy, CHEMICAL SCIENCES, Glass Transition, Liquid Crystal, Epoxy Resin, Fracture Toughness, Failure Mechanism, Dynamic Mechanical Analysis, and Liquid Crystalline
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We have applied six different fillers to a typical polymer cement. Silica fume, furnace slag, fly ash, marble powder, natural sand and boron were used at different percentages mixed in a commercial epoxy. The concentration of the fillers... more
We have applied six different fillers to a typical polymer cement. Silica fume, furnace slag, fly ash, marble powder, natural sand and boron were used at different percentages mixed in a commercial epoxy. The concentration of the fillers varied from 10 to 50 wt.% at 10% intervals. The composites were subjected to 3-point bending and compression testing. Weight loss of each sample was evaluated in a hydrochloric acid bath. There are differences in densities or weights of the samples that need to be taken into account when considering mechanical parameters. Boron and fly ash powders provide flexural strength determined by 3-point bending higher than the neat epoxy. Some fillers lower the flexural strength of the cement, a result of the filler agglomeration. Fly ash, furnace slag and boron increase the elastic modulus in compression; so does also silica fume but only at 30 wt.% concentration. Marble powder has a small negative effect on the compressive modulus while natural sand has little effect. However, when one takes into account densities or specific weights, only 10% boron enhances the compressive performance per unit weight. Weight losses in hydrochloric acid solutions are the largest for natural sand (13 wt.%), for boron up to 11%, for marble powder up to 8%, for furnace slag also near 8%. Silica fume and fly ash have the changes below 1.8%.
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Publisher Summary Efforts to determine the failure mechanisms of polymers have followed different “viewpoints.” Material properties are seen to affect failure through consideration of molecular aspects. Mechanisms of crack propagation are... more
Publisher Summary Efforts to determine the failure mechanisms of polymers have followed different “viewpoints.” Material properties are seen to affect failure through consideration of molecular aspects. Mechanisms of crack propagation are viewed through interpretation of propensity of the material for crazing, shear yielding, or their combination. Macroscopic failure evaluation relies on fracture mechanics. The existence of all these distinct methods of interpretation behooves to establish the relation between the properties of crack propagation and the material structure. The technique of thermal wave imaging was applied earlier to a thermoplastic olefin (TPO). This chapter examines the effect of material properties on the failure. To do so, experiments are conducted on the TPO (a blend of polypropylene (PP), ethylenepropylene diene rubber, and polyethylene) as well as its constituent PP. The effect of rubber modification on the temperature field surrounding the propagating crack is thus established. The technique of thermal wave imaging utilizes the radiation heat transfer. The overlap of heat radiation wavelengths with that of infrared wavelength results in potential benefits of utilizing IR thermometry to interpret the temperatures generated in the emitting material. It is found that thermal wave imaging is an excellent technique to probe the structure-property relationships in polymers. Modification of PP is accompanied by an increase in the temperature associated with the deformation. The effects are because of the larger isobaric expansivity of the rubber–modified system.
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Abstract This study presents investigation on microstructural, mechanical, durability and thermal characteristics of hemp fibers (HFs) reinforced foam concrete with fly ash (FA) and Taguchi optimization approach. Three series of foam... more
Abstract This study presents investigation on microstructural, mechanical, durability and thermal characteristics of hemp fibers (HFs) reinforced foam concrete with fly ash (FA) and Taguchi optimization approach. Three series of foam concretes mixtures were produced with foam contents of 50, 75 and 100 kg/m3. There is a reference mixture without HFs and FA. Thus, mixtures contain FA as cement replacement at the concentrations of 0%, 10%, 20%, 30%, 40% and 50%. HFs with varying fiber length were introduced into mixes at concentrations of 0.75%, 1.5% and 3% by weight of cement. Slump test was done to see workability. Compression and flexural properties were determined at 7, 28 and 91 days. Durability was investigated by high temperature, freeze–thaw and sulphate exposures. Thermal conductivity, drying shrinkage, porosity, water absorption and dry unit weight properties of foam concretes were also investigated. Experimental results were analyzed using Taguchi optimization approach. Addition of HFs provides very large compressive and flexural strength enhancements. FA addition reduces the drying shrinkage and thermal conductivity while it increases the high temperature resistance of foam concretes.
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The effect of coreacting diglycidyl ether of bisphenol F (DGEBP-F) with diglycidyl ether of 4, 4′-dihydroxybiphenol (DGE-DHBP) on mechanical properties is investigated. DGE-DHBP shows a liquid crystal (LC) transition upon curing. Tensile,... more
The effect of coreacting diglycidyl ether of bisphenol F (DGEBP-F) with diglycidyl ether of 4, 4′-dihydroxybiphenol (DGE-DHBP) on mechanical properties is investigated. DGE-DHBP shows a liquid crystal (LC) transition upon curing. Tensile, impact and fracture toughness test results are evaluated. Dynamic mechanical analysis is conducted to determine the effect of the DGE-DHBP component. Scanning electron microscopy of fracture surfaces shows changes in failure mechanisms compared to the pure components. The results indicate ...
Research Interests: Engineering, Materials Science, Kinetics, Polymer Blends, Polymer, and 15 moreDifferential scanning calorimetry, bisphenol A, Activation Energy, Epoxy, Composite Material, CHEMICAL SCIENCES, Glass Transition, Scanning Electron Microscope, Liquid Crystal, Epoxy Resin, Fracture Toughness, Failure Mechanism, Dynamic Mechanical Analysis, Liquid Crystalline, and Mechanical Property
This study aimed to develop a Rule Based Mamdani Type Fuzzy Logic (RBMFL) model to predict the flexural strengths and compressive strengths of blended cements under elevated temperatures. Clinoptilolite was used as cement substitution... more
This study aimed to develop a Rule Based Mamdani Type Fuzzy Logic (RBMFL) model to predict the flexural strengths and compressive strengths of blended cements under elevated temperatures. Clinoptilolite was used as cement substitution material in the experimental stage. Substitution ratios in the cement mortar mix designs were selected as 0% (reference), 5%, 10%, 15% and 20%. The data used in the modeling process were obtained experimentally, after mortar specimens having reached the age of 90 days and exposed to 300°C, 400°C, 500°C temperatures for 3 hours. In the RBMFL model, temperature (C°) and substitution ratio of clinoptilolite (%) were inputs while the compressive strengths and flexural strengths of mortars were outputs. Results were compared by using some statistical methods. Statistical comparison results showed that rule based Mamdani type fuzzy logic can be an alternative approach for the evaluation of the mechanical properties of concrete under elevated temperature.
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Materials with higher strength and high performanceprovide excellent benefits. But after a very short useful-life become waste and contribute to environmental degradation. Some investigations are focused on recycling by using innovative... more
Materials with higher strength and high performanceprovide excellent benefits. But after a very short useful-life become waste and contribute to environmental degradation. Some investigations are focused on recycling by using innovative and clean technologies. In this work, waste and recycled materials as well as gamma radiation are proposed as tools for improving mechanical properties of concrete; polyethylene terephthalate of bottles, automotive tire rubber as well as cellulose of Tetra Pak packages are studied as materials.
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EN AW-AlCu4MgSi(A) aluminium alloy is widely used as a structural material in aerospace and automotive applications. We have subjected it to grinding, polishing and ball burnishing. We have performed ball-on-disk tribological tests. We... more
EN AW-AlCu4MgSi(A) aluminium alloy is widely used as a structural material in aerospace and automotive applications. We have subjected it to grinding, polishing and ball burnishing. We have performed ball-on-disk tribological tests. We have also determined normalized 3D roughness parameters. High surface smoothness turns out to be obtainable. Favorable effect of the ball burnishing on the tribological properties of the alloy are seen. Results will be presented at the Conference.
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We have developed novel antibiocorrosive multifunctional hybrid materials based on functionalizedperfluoroalkylmethacrylate copolymerswith epoxy groups in main chainsand selected biologically active compounds.The hybrids are transparent,... more
We have developed novel antibiocorrosive multifunctional hybrid materials based on functionalizedperfluoroalkylmethacrylate copolymerswith epoxy groups in main chainsand selected biologically active compounds.The hybrids are transparent, showgood adhesion to various surfaces (plastic, wood),high viscoelastic recovery in scratch testing,low wear rates and glass transitions above 323 K. No phase separation is seen in scanning electron micrography. Enhanced mechanical strength and good abrasion resistance are advantages for uses of our protective and antibiocorrosive coatings in various applications including protection of cultural heritage.
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Ecologically friendly composites have been made on the basis of wood sawdust and sillylated styrene as the binder. That binder acts simultaneously as a reinforcing agent. The surface structures were studied by a scanning electron... more
Ecologically friendly composites have been made on the basis of wood sawdust and sillylated styrene as the binder. That binder acts simultaneously as a reinforcing agent. The surface structures were studied by a scanning electron microscopy and energy dispersive X-ray microanalysis. The bending strength increases with the increase in temperature from 453 to 493 K at the constant pressure of 15 MPa. Likely we have heterogeneous reactions between active groups of triethoxysilylated styrene and sawdust, which lead to increasing of the spatial (per specific volume) concentration of chemical bonds. Impact viscosity increases in the same temperature range from 14.6 to 25.8 kJ/m2. Water absorption determined after 3 and 24 h varies over a wide range in the function of the composition. The lowest value is 4.1 wt% water after 24 h
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We have obtained composites on the basis of dry bamboo powders and in turn several binders, including polyethylene (PE) and alkoxysilanes. The composites were studied by Fourier transformation infrared spectroscopy (FTIR), optical and... more
We have obtained composites on the basis of dry bamboo powders and in turn several binders, including polyethylene (PE) and alkoxysilanes. The composites were studied by Fourier transformation infrared spectroscopy (FTIR), optical and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Some mechanical properties were determined along with thermal stability by thermogravimetry; water absorption was also determined. FTIR results show formation of primary chemical bonds between bamboo surface active groups and the binders. Mechanical property improvement goes symbatically with the thermal stability.
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Hydrosilylation of a,o-bis(trimethylsiloxy)methylhydrosiloxane to alkenes in the presence of a catalyst was performed at several temperatures (30-708C). Combtype methylsiloxane oligomers with various alkyl substituted groups in the side... more
Hydrosilylation of a,o-bis(trimethylsiloxy)methylhydrosiloxane to alkenes in the presence of a catalyst was performed at several temperatures (30-708C). Combtype methylsiloxane oligomers with various alkyl substituted groups in the side chains have been obtained. Not all active BSiÀ ÀH groups participate in the reaction. The reaction order, activation energies, and rate constants have been determined. The synthesized oligomers were characterized by 1 H, 13 C, 1 H COSY NMR, and FTIR spectroscopy. Calculations using the quantum-chemical semiempirical AM1 method for modeling reaction between methyldimethoxysilane [Me(MeO) 2 SiH] and hexene-1 were performed to evaluate possible reaction paths. For all initial, intermediate, and final products, enthalpies of formation as a function of the distance between BCÀ ÀSiB bonds are calculated. The hydride addition is energetically more favorable according to the anti-Markovnikov rule than according to the Markovnikov rule. Comb-type oligomers were characterized by gel-permeation chromatography, differential scanning calorimetry, thermogravimetry, and wide-angle X-ray diffractometry.
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Research Interests: Chemical Engineering, Materials Science, Crystallization, Tribology, Block Copolymer, and 15 moreTheoretical Morphology (in Biology), Polypropylene, Polystyrene, Composite Material, Crystallinity, Thermophysical Properties, Polymer Blend, Copolymer, Tensile Test, Dynamic Mechanical Analysis, Styrene, Wear Mechanism, Ultimate Tensile Strength, Mechanical Property, and Enthalpy of Fusion
Research Interests: Engineering, Materials Science, Chemical, Starch, Multidisciplinary, and 12 morePolymer, Sliding wear, Poly (lactic acid), Nanocomposite, Maleic Anhydride, Mechanical Testing, CHEMICAL SCIENCES, Glass Transition, Glass Transition Temperature, Lactic Acid, Dynamic Mechanical Analysis, and Mechanical Property
A simulation of the mechanical behavior of a carbon nanotubes-reinforced polymeric composite, based on Flory’s statistical segment approach, is presented. The material is modeled at the micro and nano levels. Interactions between... more
A simulation of the mechanical behavior of a carbon nanotubes-reinforced polymeric composite, based on Flory’s statistical segment approach, is presented. The material is modeled at the micro and nano levels. Interactions between molecules are Morse-like potentials, as well as Van der Walls forces. Traditional simulations involve Molecular Dynamics by solving Newton’s equations of motion, Instead, we apply here a finite element approach, involving nonlinear elements to take into account the potential interactions. Amorphous polymer chains are represented by statistical segments, in which several repeating units of a chain are treated as single and independent components. This model allows the simulation at a large scale as compared to those using the unit-atom model or those performed at the atomistic level.
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... Jeziorny (29); O - Chou ea (10); A - Benson and Lewis (32); V - Gedde ea (33); - Hedmark (M) ? O - Jackson and Kuhfuss (15) ; and H - Kricheldorf and Schwarz (35). ... 1982, 20, 719. 19. Noel, C. In Polymeric Liquid Crystals;... more
... Jeziorny (29); O - Chou ea (10); A - Benson and Lewis (32); V - Gedde ea (33); - Hedmark (M) ? O - Jackson and Kuhfuss (15) ; and H - Kricheldorf and Schwarz (35). ... 1982, 20, 719. 19. Noel, C. In Polymeric Liquid Crystals; Blumstein, A. (Ed.) Plenum: New York 1985; p.21. 20. ...
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In this study, the effect of Fe powder on the physical and mechanical properties of high density polyethylene (HDPE) was investigated experimentally. HDPE and HDPE containing 5, 10, and 15 vol % Fe metal–polymer composites were prepared... more
In this study, the effect of Fe powder on the physical and mechanical properties of high density polyethylene (HDPE) was investigated experimentally. HDPE and HDPE containing 5, 10, and 15 vol % Fe metal–polymer composites were prepared with a twin screw extruder and injection molding. After this, fracture surface, the modulus of elasticity, yield and tensile strength, % elongation, Izod impact strength (notched), hardness (Shore D), Vicat softening point, heat deflection temperature (HDT), melt flow index (MFI), and melting temperature (Tm) were determined, for each sample. When the physical and mechanical properties of the composites were compared with the results of unfilled HDPE, it was found that the yield and tensile strength, % elongation, and Izod impact strength of HDPE decreased with the vol % of Fe. As compared with the tensile strength and % elongation of unfilled HDPE, tensile strength and % elongation of 15 vol % Fe filled HDPE were lower, about 17.40% and 94.75% respectively. On the other hand, addition of Fe into HDPE increased the modulus of elasticity, hardness, Vicat softening, MFI, and HDT values, such that 15 vol % Fe increased the modulus of elasticity to about 48%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
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Structure and several properties of AgNO3 and As2O3 doped polymer composites have been investigated, including their antibacterial activity against E. coli, S. aureus, C. albicans and S. epidermidis. New silver or arsenic doped polymer... more
Structure and several properties of AgNO3 and As2O3 doped polymer composites have been investigated, including their antibacterial activity against E. coli, S. aureus, C. albicans and S. epidermidis. New silver or arsenic doped polymer composites have been characterized by an X-ray diffraction (XRD), a scanning electron microscopy combined with an energy dispersive X-ray spectroscopy (SEM/EDS) and ion release studies. The antibacterial evaluation of each of the composite samples was conducted using S. aureus in the liquid broth culture, with 10, 20 and 30 % of liquid extract added to the bacterial culture. Control S. aureus stocks were used for comparison at each time period and were recorded at 100 % at each time period. For samples with the PLA plasticizer the bacterial viability was significantly reduced for each composition containing Ag/As and was similar for each dosage concentration.
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Thermoelectric (TE) devices have one main disadvantage: short service lifetime.
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We have performed mechanical finishing operations on Sverker 21 (traditional) and Vanadis 6 (advanced powder) steel surfaces: grinding, turning, and turning followed by slide burnishing. Then each specimen was subjected in turn to focused... more
We have performed mechanical finishing operations on Sverker 21 (traditional) and Vanadis 6 (advanced powder) steel surfaces: grinding, turning, and turning followed by slide burnishing. Then each specimen was subjected in turn to focused ion beams of helium or krypton up to fluences of 1015 ions/cm2 and finally to scratch resistance testing. Acoustic signals show that krypton implantation reduces microcracks. Helium ions act even more strongly as homogenizers—almost completely eliminating the imperfections. Optical microscopy during scratch testing shows the force level when debris formation begins. Helium ions fitting between the iron atoms increase the resistance against scratching; larger krypton ions produce the opposite effect.