bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new synergistic combination of safe accelerators for the improvement of physical properties in gum and filled vulcanizates
Authors: Debnath Subhas Chandra , Mandal Swapan Kumar , Basu Dipak Kumar 
Published: April 2003

AbstractThe synergistic activity of bis(diisopropyl) thiophosphoryl disulfide (DIPDIS) in the presence of dithio bis(N‐β‐OH ethyl piperazine) (DTEP), a safe amine‐based accelerator, has been studied both in gum and filled stock vulcanization of NR. This study, concerning the effect of variation of sulfur concentration on the gum vulcanization of NR, reveals that, although modulus values of the vulcanizates increase with the level of sulfur, the tensile strength values attain a maximum at 1.5 phr sulfur for an equimolar (4.5:4.5) concentration of DIPDIS and DTEP. The concentration of accelertors was varied from 6 mmol to 18 mmol phr, keeping the molar ratio at 1:1. It was noticed that, although the torque and modulus values increased, the tensile strength values decreased after attaining a maximum at 12 mmolar concentration of DIPDIS and DTEP accelerators, when the sulfur concentration was fixed at 1.5 phr. The synergistic activity of DIPDIS‐DTEP accelerated mixes is considered to arise from the generation of some intermediate accelerators that are governed by the proportion of accelerators, sulfur, filler, etc., present in the mix. Some investigations were also carried out to optimize the amount of carbon black at these fixed levels of accelerators and sulfur. A regarding tensile strength, it increased up to a loading of 50 phr carbon black, but beyond this level a gradual fall in the value was noticed. However, modulus, torque, and hardness increased with the concentration of carbon black. The optimum dispersion of carbon black for this system was obtained following Lee's method. © 1995 John Wiley & Sons, Inc.
Measurements of mutual diffusivities in concentrated solutions of membrane‐forming polyamides and cellulose acetate
Authors: Cheng Liao‐Ping , Dwan An‐Hwa , Gryte Carl C. 
Published: April 2003

AbstractMutual diffusivities at 25°C were measured in the range of the polymer weight fraction of 0.15–0.5, using differential interference microscopy. Diffusivities of atactic polystyrene in toluene at 25°C for 0.35‐0.5 polymer weight fractions showed good agreement with the prediction of Vrentas and Duda. Polyamides (nylon‐6, nylon‐66, and a nylon‐6, ‐66, and ‐610 amorphous terpolymer) in formic acid all exhibited very similar diffusivities. Although slightly higher in magnitude, the mutual diffusivities of cellulose acetate (39.8 wt% acetyl) in acetone had a compositional dependence that was parallel to the data for the polyamides. In the range of composition studied, there was an unanticipated very weak dependence of mutual diffusivity on the polymer weight fraction. © 1995 John Wiley & Sons, Inc.
Protolytic and complexing properties of microcrystalline chitosan with Co(II), Zn(II), and Cu(II) ions
Authors: Bodek Kazimiera Henryka , Kufelnicki Aleksander 
Published: April 2003

AbstractIt has been evidenced that microcrystalline chitosan (MCCh) with a determined (by the potentiometric method in nonaqueous medium) degree of deacetylation of 0.87 acts as a polymeric chelating agent with cobalt(II) and zinc(II). The predomination of hydrolytic reactions, in the case of copper(II) ions, has been attributed to a change in crystalline character of the ligand. The protolytic reactions have been studied using the Katchalsky–Spitnik equation. The pH profiles have been shown for Co(II)–MCCh and Zn(II)–MCCh systems and the corresponding equilibrium constants have been determined as well. Both the amino and hydroxyl groups are involved in Co2+ complexation, whereas for Zn2+, the complexes are formed only via amino nitrogen. © 1995 John Wiley & Sons, Inc.
Morphology of gel‐spun polyethylene fibers
Authors: Khosravi Nasrin , Warner S. B. , Murthy N. S. , Kumar Satish 
Published: April 2003

AbstractNitric acid etching studies have been conducted on samples of commercially available highly oriented gel‐spun polyethylene fibers: SpectraTM 900 and 1000 from AlliedSignal Inc. The results show that the acid attacks the fiber, increases crystallinity as observed by X‐ray diffraction, increases the enthalpy of melting of unconstrained fibers by 13–25%, and removes topological constrains thus facilitating the crystallization of chain segments in the noncrystalline regions. The acid functionalizes the fiber, creating various oxygen and nitrogen‐containing moieties, specifically (CO),CC, and NO2 groups. The small weight loss upon etching, less than 2%, and the fact that fibers weaken but do not fragment suggests that the gel‐spun and ‐drawn morphology is more resistant to acid attack than are other morphologies of polyethylene. Photomicroscopy shows that acid etching opens cracks normal to the fiber axis. That the acid can attack the gel‐spun fibers indicates the presence of structural imperfections such as folds, molecular kinks, or uncrystallized regions within the fibers. Infrared analysis on virgin fibers shows the absence of absorption bands normally associated with the presence of chains lying within amorphous regions in polyethylene. These and other morphological features are integrated into a description of the structure of commercial gel‐spun polyethylene fibers. © 1995 John Wiley & Sons, Inc.
Proton exchange membranes by radiation grafting of styrene onto FEP films. IV. Evaluation of the states of water
Authors: Gupta Bhuvanesh , Haas Otto , Scherer Günther G. 
Published: April 2003

AbstractThe nature of water in proton exchange membranes, obtained by radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films and subsequent sulfonation, was investigated by differential scanning calorimetry. It was found that the membranes contained three different types of water, which were categorized as freezing‐free, freezing‐bound, and nonfreezing water. The degree of grafting had a considerable influence on the relative ratios of these three types of water molecules. The nonfreezing water per ion‐exchange site ratio was found to be independent of the degree of grafting. However, freezing‐free and freezing‐bound water per ionic site ratios increased with increasing graft levels. A correlation between the water uptake and the structural changes occurring in the membrane as a function of the degree of grafting was established. © 1995 John Wiley & Sons, Inc.
Polymer coatings by electropolymerization of some vinyl monomers
Authors: Lee Chi S. , Bell James P. 
Published: April 2003

AbstractElectroinitiated polymerization coatings are uniform, thin, tightly adherent, conformal, and economical to produce. This article describes use of a novel (for electropolymerization) persulfate initiator to rapidly polymerize a moderate Tg crosslinked acrylic coating. Polymer coatings derived from the monomers acrylamide, acrylonitrile, and N,N′‐methylenebisacrylamide were synthesized on an aluminum cathode by persulfate electroinitiated polymerization at room temperature. The crosslinked polymer was brittle (Tg = 239°C) but thermally stable (degradation temperature = 310°C). The coatings were spongy and contained some small cracks when polymerized at low current density (0.1 mA/cm2). However, thicker coatings with fewer cracks were obtained at higher current densities. Persulfate was found to be an effective initiator for polymerization in this system, and the initiation mechanism was confirmed to be free radical. In general, it appears possible to produce thin, uniform coatings on aluminum by this route. © 1995 John Wiley & Sons, Inc.
Pervaporation of aqueous alcohol mixtures through a membrane prepared by grafting of polar monomer onto nylon 4
Authors: Lee Kueir‐Rarn , Lai Juin‐Yih 
Published: April 2003

AbstractA hydrophilic pervaporation membrane was prepared via a homografting polymerization of N,N′‐(dimethylamino)ethyl methacrylate (DMAEM) onto nylon 4 backbone, DMAEM‐g‐N4. The water permselectivity was improved by the ammonium quaterization of the pendant N,N′‐dimethylamino group on the DMAEM‐g‐N4 membrane using demethyl sulfate, DMAEMQ‐g‐N4. The separation factor and permeation rate for both chemically modified nylon 4 membranes were higher than those of the unmodified nylon 4 membrane. The effects of feed composition, feed temperature, and molar volume of the alcohols on pervaporation performance were investigated. Optimum pervaporation was obtained by a DMAEMQ‐g‐N4 membrane with a degree of grafting of 12.7% for a 90 wt % ethanol feed concentration, giving a separation factor of 36 and a permeation rate of 564 g/m2h. © 1995 John Wiley & Sons, Inc.
Mechanical and thermal properties of glycidyl methacrylate grafted cotton cellulose
Authors: Shukla S. R. , Athalye A. R. 
Published: April 2003

AbstractUV‐radiation‐induced graft‐copolymerization of cotton cellulose was carried out with glycidyl methacrylate (GMA) using ceric ammonium nitrate (CAN) as a photoinitiator as well as a chemical initiator. With increase in the graft add‐on, breaking load and moisture regain of cotton decreased, so also its thermal stability. The fiber surface changes due to grafting were ascertained by X‐ray diffraction and scanning electron microscopy. © 1995 John Wiley & Sons, Inc.
Degradation of poly(vinyl chloride) in the presence of 9‐(2,3‐epoxypropane)carbazole studied by means of TGA/FTIR
Authors: Pielichowski Krzysztof , Pielichowski Jan , Hamerton Jan 
Published: April 2003

AbstractBlends containing poly(vinyl chloride) and 9‐(2,3‐epoxypropane)carbazole in different weight ratios were subjected to investigations using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The effect of additive on the polymer degradation process was studied. It was found that 9‐(2,3‐epoxypropane)carbazole causes an increase in the onset temperature of hydrogen chloride emission by about 20–25°C. Finally, the mechanisms of stabilization were proposed. © 1995 John Wiley & Sons, Inc.
Minimum‐time strategy to produce nonuniform emulsion copolymers. I. Theory
Authors: De La Cal Jose C. , Echevarria Antonio , Meira Gregorio R. , Asua Jose M. 
Published: April 2003

AbstractA method for calculating the optimal monomer addition policy to produce emulsion copolymers with a given composition profile is presented. The approach allows the calculation of the time evolution of the monomer feed rates that ensure the formation of the desired copolymer composition profile in a minimum process time. The method was applied by simulation to obtain widely different copolymer composition profiles during the emulsion copolymerization of butyl acrylate and styrene. The results were compared with those obtained by means of the power feed method. In these calculations, it was assumed that both the kinetic model and the values of the kinetic parameters are available. The implementation of this approach to real emulsion copolymerization systems in which only a limited kinetic information is available is presented in the second article of this series. © 1995 John Wiley & Sons, Inc.
The properties of polymer protective coatings of optical fibers. II. The influence of curing time on adhesion of UV‐curable coatings to fused silica surface
Authors: Rayss J. , Podkościelny W. M. , Gorgol A. , Widomski J. , Ryczkowski J. 
Published: April 2003

AbstractThe dependence of adhesion of four various UV‐curable protective coatings of optical fibers to the surface of fused silica on the time of UV irradiation was investigated. The maxima of adhesion were observed in short periods of time of curing. Comparison of adhesion values to the hardness, gel content, and contact angles of water measured on the polymer surface revealed that adhesion of epoxyacrylate protective coatings of optical fibers depended on the inner structure of the polymer rather than on its surface properties. This observation was confirmed by IR studies. © 1995 John Wiley & Sons, Inc.
Polyacrylonitrile‐reinforced poly(vinyl alcohol) membranes: Mechanical and dialysis performance
Authors: Paul Willi , Sharma Chandra P. 
Published: April 2003

AbstractMembranes used for hemodialysis should have good mechanical strength to withstand the maximum transmembrane pressure. Although crosslinked poly(vinyl alcohol) membrane has superior permeability to solutes, its wet breaking strength is low. Mechanical strength, dry and wet, of membranes made from crosslinked blendmers of poly(vinyl alcohol) and polyacrylonitrile was investigated. The possibilities of these membranes for the application as dialysis membranes were evaluated by estimating its solute permeabilities. The optimum membrane selected shows permeability and mechanical properties comparable with the commercial regenerated cellulose membrane. Polyelectrolyte grafting made the membrane more blood‐compatible. © 1995 John Wiley & Sons, Inc.
Hydrolytic degradation of polyamides based on L‐tartaric acid and diamines
Authors: Ruiz‐Donaire P. , Bou J. J. , Muñoz‐Guerra S. , Rodriguez‐Galan A. 
Published: April 2003

AbstractThis article describes the hydrolytic degradation of a series of nylons based on methylated L‐tartaric acid and diamines. These polytartaramides were prepared by a solution polycondensation process using bis(pentachlorophenyl)‐2,3‐O‐dimethyl‐L‐tartrate and N,N′‐bis(trimethylsilyl)alkanediamines with 6, 8, or 12 methylene groups. The stereoregular optically active polyamides obtained were soluble in chloroform and showed intrinsic viscosities between 1.0 and 2.7 dL g−1. The degradation of these polytartaramides in the form of discs has been investigated in buffered salt solutions of pH 2.3, 7.4, and 10.6, and at temperatures of 37, 55, and 70°C. The degradation was monitored by following the changes in molecular weight, mass loss, chemical constitution, and thermal properties. Our results show that these polytartaramides degrade slowly at 37°C, with a degradation rate highly depending upon the number of methylenes in the diamine unit of the polyamide. The pH of the medium has also a great influence on degradation, as well as the temperature, with an important hydrolysis rate enhancement at 70°C. © 1995 John Wiley & Sons, Inc.
Effects of radiation on mechanical properties of polybutadiene/polystyrene blends
Authors: Spiegelberg Stephen H. , Cohen Robert E. , Argon Ali S. 
Published: April 2003

AbstractBlends containing 3 wt % low molecular weight polybutadiene (PB) in a polystyrene (PS) matrix were prepared via a precipitation technique that yielded spherical, submicron pools of PB. Tensile specimens made from these blends were then irradiated with high energy electrons in air at dose levels from 0 to 70 Mrads. The blends, which previously showed high levels of toughness approaching that of high impact PS, lost all enhanced toughness when irradiated above 10 Mrads. Analysis of pure PS specimens irradiated over the dose range from 0 to 45 Mrads showed no appreciable dependence of mechanical behavior on dose level. Molecular weight studies of the polybutadiene demonstrated only a very modest increase in molecular weight in the dose range studied here; therefore, reduced mobility of the PB in the blends was not the reason for the dramatic drop in toughness with radiation dose. It was concluded that radiation‐induced scission of the PS near the surface of the blends resulted in a significant local reduction in molecular weight. This degraded layer led to premature craze failure and hence a low level of toughness. It was demonstrated that the absence of oxygen during the irradiation process or the removal of the scissioned surface layer via mechanical abrasion resulted in a recovery of toughness. © 1995 John Wiley & Sons, Inc.
Melt blending of linear low‐density polyethylene and polystyrene in a Haake internal mixer. II. Morphology‐processing relationships
Authors: Yang Li‐Ying , Bigio David , Smith Theodore G. 
Published: April 2003

AbstractA measure of the effective shear rate range for dispersive mixing in the Haake mixer has been developed, which is more representative of shearing conditions than that currently used. In addition, the effects of processing conditions, composition, and compatibilizer on linear low‐density polyethylene and polystyrene (LLDPE/PS) blend morphology were studied. Fiber/stratified morphologies form with blends when the minor phase has low viscosity and is present at its higher concentration. The influence of the viscosity ratio on phase size was found to be a minor effect for mixtures having a low fraction of the dispersed phase (20% PS). The effect of shear intensity, however, was found to be more important at a low composition of the dispersed phase or in compatibilized blends. During Haake blending, an optimal time for adding compatibilizer to stabilize phase morphology was found to be when the final morphology of an incompatible blend had developed. Further studies have concluded that the addition of styrene–ethylene/butylene–styrene (SEBS) stabilized the blend morphology of LLDPE/PS more efficiently than styrene–ethylene/propylene (SEP) on different blending conditions and compositions. At high temperatures, the addition of SEP to a LLDPE/PS blend did not modify the dispersed phase size. On the other hand, SEBS stabilized the dispersion so that the final domain size is independent of composition. © 1995 John Wiley & Sons, Inc.
Surfactant‐modified epoxy resins as novel negative‐acting deep UV photoresists
Authors: Everett J. , Piechocki C. , Argitis P. , Hatzakis M. 
Published: April 2003

AbstractSimple cresol epoxy novolac resins have been modified with hydrophilic chains producing surfactant‐modified epoxy resins. They have been formulated with catalytic amounts of photoacid generator and solvent and subsequently exposed to deep UV light. With respect to their photochemistry, they behave as conventional chemically amplified negative acting materials, however, their overall lithography is somewhat more novel. For example, they have high contrast behavior and unexposed regions swell in aqueous base developer and peel‐off into solution through an apparent adhesion loss at the wafer–photoresist interface. © 1995 John Wiley & Sons, Inc.
Adsorption behavior and potential interfacial morphology: Impact of adsorbing hydrophobic groups in polymers with weakly adsorbing main backbones
Authors: Kelly Michelle S. , Santore Maria M. 
Published: April 2003

AbstractThis study examined the adsorption isotherm behavior within a homologous series of fluorescently end‐labeled hydrophobically end‐modified (“fluorophobe”) poly(ethylene oxide)s (PEOs) on hydrophobic polystyrene (PS) latex. Results were then compared with a model for the adsorption of end‐modified chains and previous adsorption studies of associative thickeners, PEOs containing hydrophobes on both ends in addition to regularly spaced weak internal hydrophobes. For both PEO series, an increase in end‐group hydrophobicity yielded higher isotherm plateau coverages by up to a factor of 5 over control samples without end hydrophobes. For the fluorophobe‐PEOs, an increased end‐group hydrophobicity also led to a steeper slope in the low‐concentration regime of the isotherm, reflecting the influence of the end group on the net adsorption energy (to the extent that the initial isotherm slope reflected an equilibrium partitioning between the interphase and the bulk). In contrast for the associative thickeners, the impact of end‐group hydrophobicity on the initial isotherm slope was not apparent, and the initial slopes for the associative thickeners were generally much steeper than for any of the fluorophobe PEOs. These differences in isotherm shapes were thought to reflect differences in the molecular architecture between the fluorophobe‐PEO and associative thickener series, and the impact of molecular architecture on the interaction with the substrate. In addition to altering the coverage, the end‐group hydrophobes alter the interfacial morphology and the surface selectivity for specific molecular weight populations within a polydisperse PEO sample. © 1995 John Wiley & Sons, Inc.
Core‐shell structured latex particles. III. Structure–properties relationship in toughening of polycarbonate with poly(n‐butyl acrylate)/poly(benzyl methacrylate–styrene) structured latex particles
Authors: Segall I. , Dimonie V. L. , El‐Aasser M. S. , Soskey P. R. , Mylonakis S. G. 
Published: April 2003

AbstractThe performance of the designed structured core‐shell latex particles in toughening polycarbonate (PC) matrix was examined. Izod impact testing of the PC‐core‐shell latex blends were used to evaluate the influence of parameters related to the core‐shell latex particles on toughening polycarbonate. Among these parameters are the particle size and levels of crosslinking of the core rubber particles, composition and molecular weight of the shell polymer, and weight ratio of shell to core polymers as well as the particle morphology. In this work, core‐shell structured latex particles with thinner shells of higher molecular weight polymers were found to improve the impact resistance of polycarbonate. The role of chain entanglements in increased adhesion between the discrete rubbery phase and the continuous glassy matrix and the importance of surface‐to‐surface interparticle distance for toughening at various temperatures are discussed. © 1995 John Wiley & Sons, Inc.
Characterization of the particle–matrix interface in rubber‐modified epoxy by atomic force microscopy
Authors: Shaffer O. L. , Bagheri R. , Qian J. Y. , Dimonie V. , Pearson R. A. , El‐Aasser M. S. 
Published: April 2003

AbstractAtomic force microscopy (AFM) was used to study the interphase regions in rubber‐toughened epoxy polymers. The nature of the interphase region was varied by either the adducting of reactive oligomers or by crosslinking the shell polymer on core/shell latex particles. The adducted reactive oligomers were comprised of carboxyl‐terminated, butadiene‐actrylonitrile copolymers (CTBN) prereacted with either (1) a low molecular weight diglycidyl ether of bisphenol A‐based epoxy, which results in an interphase with increased crosslink density, or (2) a high molecular weight epoxy based on the diglycidyl ether of propylene glycol (DEGP), which results in an interphase with decreased crosslink density. The second type of rubber particles is custom‐made submicron core/shell latex particles of a poly(butadiene‐co‐styrene)[P(BS)] core with an acrylate shell. Two acrylate shells were (1) PMMA/AN shell containing 25% acrylonitile and (2) a similar PMMA/AN with 5% divinyl benzene. The toughness of these blends was characterized using linear elastic fracture mechanics. The features on the fracture surfaces were examined using both AFM and FESEM (field emission scanning electron microscopy). AFM was able to detect features not observed in SEM and also to quantify all of the fracture surface features. In particular, the height‐to‐width ratio of the rim surrounding cavitated particles provided a useful means for determining the ductility of the interphase region. Attempts were made to determine the size of the interphase region using the frictional mode and the tip‐adhesion forces. Unfortunately, the results of both approaches are inconclusive at the present time; this is most likely due to the deformation surrounding the rubber particles detected in the fast fracture regions. © 1995 John Wiley & Sons, Inc.