Witold Brostow | University of North Texas (original) (raw)

Papers by Witold Brostow

Polimeri : časopis za plastiku i gumu, 2009

U prvom dijelu rada o osnovama i va`nosti tribologije u prirodnim znanostima koje se bave materij... more U prvom dijelu rada o osnovama i va`nosti tribologije u prirodnim znanostima koje se bave materijalima i u in`enjerstvu materijala naglasak je na onom dijelu tribologije koji se bavi polimernim materijalima. Opisana su osnovna na~ela, uz navo|enje va`nosti kvantitativne ispitne metode vi{estrukog brazdanja povr{ine uzimaju}i u obzir viskoelasti~nost i krhkost polimernih materijala. Naime, utvr|eno je da ispitne metode koje se zasnivaju na mjerenju promjene mase i/ili volumena potro{enih ~estica nisu dovoljno pouzdane. Mogu}nost kvantitativne mjere tro{enja temelji se na metodi vi{estrukog brazdanja povr{ine polimernih materijala. Tribolo{ka svojstva u korelaciji su s energijom povr{ine materijala. KLJU^NE RIJE^I: faktor trenja otpornost na brazdanje tribologija polimernih materijala tro{enje

Chemistry and Chemical Technology, Mar 15, 2008

Polymerizable organic silane molecules 3-(trimethoxysilyl)propylmethacrylate (3MPS) and vinyltri(... more Polymerizable organic silane molecules 3-(trimethoxysilyl)propylmethacrylate (3MPS) and vinyltri(2-methoxyethoxy)silane (VTMES) have been introduced onto surfaces of high purity Boehmite (a commercial alumina) via hydroxyl groups on the oxides in order to obtain organic-inorganic hybrid macromonomers. Changes of surface characteristics have been determined using thermogravimetric analysis (TGA) and Fouriertransform infrared spectroscopy (FTIR). The influence of the type of silane used and modification conditions have been determined. Preheating was applied to some Boehmite samples; it leads to lower concentrations of OH groups on the powder surface and the adsorption yields lower than in samples without preheating. Modification leads to surface hydrophobicity and thus reduces significantly water adsorption; in TGA we see desorption of water below 423 K only in unmodified Boehmite.

Materiali in tehnologije, 2020

Using a hydrosilylation reaction of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane (D4 ... more Using a hydrosilylation reaction of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane (D4 H) with 2.2.3.3-tetrafluoropropyl acrylate and vinyltriethoxysilane at a 1:3:1 ratio of the initial compounds in the presence of platinum catalysts, a new D4 RR' type fluorine-containing methylorganocyclosiloxane was obtained. Via a ring-opening co-polymerization reaction of D4 R,R' type methylorganocyclotetrasiloxane in a solution, in the presence of catalysts, anhydrous powder-like potassium hydroxide, or tetramethylammonium fluoride, new comb-type siloxane matrices with pendant ethyl tetrafluopropionate side groups and cross-linkable triethoxysilane moieties were obtained. The synthesized comb-type polymers were analysed with FTIR, 1 H, 13 C, and 29 Si NMR spectroscopy as well as the DSC and GPC methods. Sol-gel reactions of polymers doped with lithium trifluoromethanesulfonate (triflate) and lithium bis(trifluoromethanesulfonyl)imide were studied and solid polymer electrolyte membranes were obtained. The ion conductivity of the membranes was determined via electrical impedance spectroscopy.

Resources, Conservation and Recycling, 2018

The trend to recycle materials in industry has increased over the last few years as manufacturers... more The trend to recycle materials in industry has increased over the last few years as manufacturers seek ways to decrease material costs and reduce their environmental footprints. In the wire and cable manufacturing industry, excess wire and cable is shredded into a mixture commonly known as fluff. Because fluff is comprised of different metals as well as polymers of varying physical and chemical properties, it cannot be recycled into a usable product until the different components comprising fluff have been separated. Metallic components could possibly be used for recovery of metals from zinc-carbon and alkaline spent batteries. However, the amount of metals in fluff is low from the economical point of view. Polymeric components might be used in the production of aggregate in concreteconsidered for this application together with fly ash. We have employed different concentrations and combinations of frothers, wetting agents, and inorganic materials, encouraging the separation of the different components of fluff by taking advantage of each component's physical properties. An essential stage of the operation was separating metals from polymers. Among polymers, the main component of fluff was PVCthat we successfully reclaimed and then verified our results through the use of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Success in this endeavor would spell dramatic reductions in unrecyclable wire and cable waste, increase reclamation of materials, and further improve our understanding of the pros and cons of different density-based separation methods.

Wear, 2017

Abstract We have created inorganic-organic hybrid composites and antibiocorrosive coatings based ... more Abstract We have created inorganic-organic hybrid composites and antibiocorrosive coatings based on an epoxy modified with silicon-containing polyepoxies and bioactive coordination compounds. The scratch resistance was determined using a conical diamond indenter with linearly increased load. Repetitive scratching along the same groove (sliding wear determination) was also performed. Whether in single or in repetitive scratching, for most hybrids the residual depth is shallower than for the pure epoxy. Dynamic friction was determined on a pin-on-disk tribometer using steel pins. Lower friction is accompanied by higher scratch resistance. Surface morphology seen in scanning electron microscopy (SEM) shows that increasing modifier content causes more ductile behavior with less crack nucleation; no debris formation is observed. The composites were also characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Isothermal aging and water absorption ability (WH2O) of the hybrids were determined. The hybrids are optically transparent, visually homogeneous, with smooth surfaces.

Polymer Testing, 2017

Varying concentrations of maleic anhydride (MAH) were grafted onto three types of polypropylene (... more Varying concentrations of maleic anhydride (MAH) were grafted onto three types of polypropylene (PP) in the presence of dicumyl peroxide (DCP). Pull-off adhesive strength from a copper substrate, tensile Young's modulus, and tensile strain-at-break were determined and SEM observations made as a function of the MAH concentration for each PP. One of the PPs plus 3 wt.% MAH provides a high value of the adhesive strength along with the Young modulus and the strain-at-break sufficient for the use as a coating for copper wires and cables.

European Polymer Journal, 2016

The goal of the work was improvement of mechanical and tribological properties of high density po... more The goal of the work was improvement of mechanical and tribological properties of high density polyethylene (HDPE) while finding use for wood sawdust (wood flour). Two chemical modification methods have been used for wood sawdust treatment to improve compatibility between the HDPE matrix and wood sawdust. Traditional silane coupling was used as a first approach to modify the sawdust by 3-methacryloxypropyl-trimethoxysilane (3MPS) and thereby forming CAOASi bonds. As a second method, we decided to combine sol-gel process with 3MPS treatment to form SiAOASi and CAOASi linkages. Silica nanoparticles are filling wood fiber cells and silica rods formation is seen; as a result, thermal expansivity decreases. As expected, the enthalpy of fusion and the degree of crystallinity go down with increasing filler concentration. Tensile modulus goes up as result of filler loading while the tensile strain at break goes down. As the result, brittleness B goes up somewhat, but overall the values of B are quite low. With one exception, residual depth in scratch resistance testing decreases as a consequence of introduction of the fillers. Addition of unmodified wood results in increasing dynamic friction, chemical modification of wood particles results in lowering friction. Combination of focused ion beam milling with scanning electron microscopy shows clearly positive effects of modification on adhesion between the phases.

Chemistry and Chemical Technology, Dec 24, 2023

We have obtained an equation for polymers relating their flexibility Y defined in 2019 to the lin... more We have obtained an equation for polymers relating their flexibility Y defined in 2019 to the linear isobaric thermal expansivity a L. This way we have connected quantitatively a thermodynamic property to a mechanical one. The expansivity is important since different materials expand at different rates on the increase of temperature; the same applies to contraction resulting from cooling. Thus, a temperature change can cause disintegration of a composite with no mechanical force involved.

Sustainability

Phosphonic acid functionalization of gellan gum and chitosan biopolymers was successfully perform... more Phosphonic acid functionalization of gellan gum and chitosan biopolymers was successfully performed. In the first step, the sorption was investigated using La(III) ions before testing for the recovery of rare earth elements (REEs) from pretreated industrial acidic leachate. The sorbent was characterized by Fourier-transform infrared (FTIR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), and pH of zero charge (pHPZC) determination. FTIR and EDX results show efficient grafting of phosphoryl groups. The sorption was determined for the crude materials before functionalization (PGEG) and after phosphorylation (TBP-PGEG). More efficient sorption was seen for phosphorylated sorbent than for the crude composite. The sorption capacity is 0.226 mmol La g−1 for the PGEG while the value is 0.78 mmol La g−1 for the TBP-PGEG. We infer that phosphonate groups participate in the sorption. The most effecti...

Macromolecular Symposia, 2016

New compositions based on arsenic oxide nanoparticles and poly(vinyl chloride) (PVC) were prepare... more New compositions based on arsenic oxide nanoparticles and poly(vinyl chloride) (PVC) were prepared. Sufficient antibacterial activity has been achieved for Escherichia coli and Pseudomonas syringae. The antibacterial materials so obtained are non-irritant. At the same time, the PVC-based composites have high thermal stability as demonstrated by thermogravimetric analysis and aging of samples; crosslinking enhances thermal stability. Still further, we have determined scratch resistance in a microscratch tester. High scratch resistance has been demonstrated, including strong viscoelastic scratch recovery (the bottom of the groove goes up inside of 2 minutes).

Materials Research Innovations, 2016

The authors have used an Air Void Analyzer (AVA) designed for concretes and applied it to polymer... more The authors have used an Air Void Analyzer (AVA) designed for concretes and applied it to polymeric foams. Similarly as with air voids in concretes, there is a kinetic process of foam cell formation and growth. Good results have been obtained for polyurethane foams. There seems to be no limitation in using AVA for other polymeric foams formation.

Electronic Journal of Biotechnology, 2018

Background: The use of novel materials as an artificial extracellular matrix for stem cell growth... more Background: The use of novel materials as an artificial extracellular matrix for stem cell growth is a current strategy of increasing interest for regenerative medicine. Here, we prepare thermal-remolded membrane scaffolds from poly(3-hydroxybutyrate) grafted with 2-amino-ethyl methacrylate hydrochloride. However, it is unclear whether these membranes are useful for tissue engineering. Results: The mechanical properties, tribology, and morphology of the dense membranes were assessed. The results show that tensile strain at break and roughness of the compressed membrane decrease with increasing graft degree. Moreover, graft copolymer membranes showed lower resistance to scratching, greater degree of swelling and higher brittleness than un-grafted P(3HB) films. Thus, it effectively supports the growth of dermal fibroblast, as demonstrated by epifluorescence microscopy. Conclusions: It is concluded that the developed membrane can be properly used in is the restoration of skin tissue. How to cite: González-Torres M, Sánchez-Sánchez R, Solís-Rosales SG, et al. Poly(3-hydroxybutyrate) graft copolymer dense membranes for human mesenchymal stem cell growth.

Journal of the European Ceramic Society, 2012

The utilization of silicon-based polymers as a source of amorphous non- oxide ceramics obtained u... more The utilization of silicon-based polymers as a source of amorphous non- oxide ceramics obtained upon pyrolytic treatment of them is increasingly gaining attention in research and is currently expanding into the field of commercial products. This work is focused on the near-net shaped fabrication, mechanical and tribological properties of a polymer-derived Si/C/N system. Small sub-millimetre thick ceramic test discs and bars were fabricated by casting of polysilazane and/or polycarbosilane precursor mixtures into elastomeric polydimethylsiloxane forms, thermal cross-linking and subsequent pyrolysis. Additional carbon was introduced on the molecular level using triphenylvinylsilane as the precursor, its cross-linking with the polymers via hydrosilylation prohibits phase separation of graphite. The characteristic strength of nearly 700 MPa along with stable low friction coefficients in sliding against similar polymer-derived ceramics testifies to their potential in micro electro mechanical system applications.

Polímeros, 2015

Polymer surface coatings provide superior adhesion to substrates, some flexibility and corrosion ... more Polymer surface coatings provide superior adhesion to substrates, some flexibility and corrosion resistance. On the other hand, 400,000 ton of boron wastes are generated each year. We have developed polymer composites based on epoxy resins containing up to 50 wt. % of boron wastes and determined their pin-on-disk dynamic friction, wear, Shore D hardness and surface roughness. The hardness and wear resistance increase with increasing boron waste concentration. An equation, with parameters dependent on the load, relating wear rate to hardness is provided. Dynamic friction increases with increasing surface roughness, as represented by the equation. Further, dynamic friction is an increasing function of the wear rate. Micrographs of pure epoxy without fillers shows traces after pin-on-disk testing, with tears, breaks and cracks. For the composites, we observe simpler and relatively homogeneous surfaces.

Chemistry and Chemical Technology, Dec 22, 2022

1 Since neat PVC is rigid, in all applications a plasticizer is added. Migration of the plasticiz... more 1 Since neat PVC is rigid, in all applications a plasticizer is added. Migration of the plasticizer results in brittleness of flexible PVC and environmental pollution. We have used three types of cross-linking agent blended with commercial PVC, plasticizer and thermal stabilizer. Heat treatments at 100 С, 121 С and 136 C were performed. We made tensile tests, dynamic friction tests, wear rate determination, scratch resistance determination, water absorption tests and SEM analysisto make selection of compositions suitable for sufficient crosslinking for long term applications.

APS March Meeting Abstracts, Mar 1, 2003

Inorganic biomedical materials are of great interest in the biomedical field. One such material, ... more Inorganic biomedical materials are of great interest in the biomedical field. One such material, hydroxyapatite (HAP), is the main inorganic substance in the hard tissue of bones and teeth in the human body. Until recently, studies of the mechanical properties of HAP by uniaxial tension testing and compression molecular dynamics (MD) simulation had remained difficult. In addition, electric charges used in such simulations alter the molecular structure of HAP. Here, we present the mechanical properties and new charges of the monoclinic form of HAP using the self-consistent charge equilibration (QEq) scheme proposed by Rappé and Goddard in 1991 (J Phys Chem 95:3358-3363), and a successful MD simulation of the uniaxially tensile and compressive properties of monoclinic HAP. Also presented is the change in potential energy in the cell and how temperature and strain rate affect the uniaxial tension and compressive properties of HAP. Additionally, we compare the mechanical properties of this substance along different directions, and some conclusions useful for further studies of the mechanical properties of HAP composite materials are discussed.

한국고분자학회 학술대회 연구논문 초록집, Apr 1, 1992