bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrolysis of poly(acrylamide)–starch graft copolymer
Authors: Khalil M. I. , Farag S. , Fattach S. Abd El
Published: April 2003

Poly(acrylamide)–starch graft copolymer was treated independently with sodium hydroxide and different acid solutions. The different acids include phosphoric, hydrochloric, and sulphuric acid. The treatment was carried out under a variety of conditions including sodium hydroxide concentration, time, and duration of hydrolysis as well as type of acid used. The extent of hydrolysis was assessed by estimating amide and carboxyl content as well as the acrylate and starch content before and after treatment. It was found that the increment in carboxyl content is equal to the decrement in amide on using sodium hydroxide concentration up to 1N, while using higher concentration than 1N leads to a difference in formed carboxyl and decreased amide groups. The magnitude of this difference depends on sodium hydroxide concentration as well as temperature and duration of hydrolysis. The maximum value of carboxyl content obtained was 593 meq/100 g sample. The acidic treatment of the starch copolymer does not affect the conversion of amide groups to carboxyl groups, and the sole effect was hydrolysis of starch component of the copolymer. Evaluation of the alkali‐treated copolymer as cation exchanger was carried out. The absorption efficiency % of different cations depends on the associated anions and follow the order: Cu2+ > Zn2+ > Co2+ > Mg2+. © 1995 John Wiley & Sons, Inc.
UV and fluorescence characterization of styrene and methyl methacrylate polymerization
Authors: Kim You Shin , Sung Chong Sook Paik
Published: April 2003

Polymerization of styrene and methyl methacrylate (MMA) were studied by UV and fluorescence spectroscopic techniques. Using a sharp decrease in the extinction coefficient at 250 nm and the fluorscence quantum yield at 308 nm of styrene following polymerization, styrene conversion in solution polymerization by UV and fluorescence measurements were found to correlate well with IR results monitoring the disappearance of vinyl groups, at three different temperatures (65, 70, and 75°C). The activation energy of about 6 kcal/mol was obtained. Using the decrease in UV absorbance of MMA during polymerization, solution polymerization of MMA was studied and compared with IR results. Due to the solvent absorbance, the UV method underestimates the conversion to a certain extent. When a small amount of styrene is added in MMA polymerization as a reactive extrinsic comonomer, the conversion of styrene measured by fluorescence is found to be faster than MMA, due to the characteristic reactivity ratios of MMA and styrene. The correlation curve could be used to estimate MMA conversion from styrene fluorescence, providing a method more sensitive than the viscosity‐dependent fluorescence probe technique. Bulk polymerization of styrene was studied by bifurcated fiber‐optic fluorescence. Due to self‐quenching, little fluorescence of styrene is observed up to 75% conversion, but increases sharply from 75 to 85% conversion, followed by a drastic decrease during the last 15% conversion. In comparison to other methods of following vinyl polymerization such as refractive index, density, and gel permeation chromatography, these spectroscopic techniques provide real‐time in situ capability as well as better sensitivity, especially in the later stages of polymerization. © 1995 John Wiley & Sons, Inc.
Curing reaction of diglycidylesters containing alicyclic imide structures with anhydrides and amines as hardeners
Authors: Galià M. , Serra A. , Mantecón A. , Cádiz V.
Published: April 2003

The cure reaction of diglycidyl esters containing bicyclo[2.2.2]oct‐7‐ene units with phthalic annhydride, hexahydrophthalic anhydride, bis(4‐aminophenyl)methane, and bis(4‐aminophenyl)ethane as hardeners was studied by differential scanning calorimetry. The use of 4‐dimethylaminopyridine as a catalyst agent for the anhydride–epoxide reaction was also investigated. Depending on the curing agent, anhydride or amine, and the concentration of the catalyst, differences in activation energies were found, but negligible changes are observed between both anhydrides and the two primary amines. Thermal properties of the final product were unaltered by the hardener used. © 1995 John Wiley & Sons, Inc.
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

The 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

Mutual 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

It 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

Nitric 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

The 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

Electroinitiated 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

A 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

UV‐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

Blends 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

A 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

The 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

Membranes 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

This 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

Blends 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

A 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

Simple 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

This 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

The 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

Atomic 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.
Gas permeabilities and permselectivity of photochemically crosslinked polyimides
Authors: Liu Ye , Ding Mengxian , Xu Jiping
Published: April 2003

Photosensitive polyimide BTDA‐3MPDA was modified by UV irradiation. The structure of UV‐irradiated polyimides was investigated by FTIR and gel fraction measurements. The results showed that longer UV exposure time resulted in a higher extent of crosslinking. The gas permeabilities of hydrogen, oxygen and nitrogen through UV‐irradiated polyimides were characterized in a temperature range from 30°C to 90°C. Photocrosslinking resulted in a sharp decline in gas permeability for hydrogen, oxygen, and nitrogen through polyimide in the initial stage of photocrosslinking. Then, as the crosslinked benzophenone percentage amounted to 28–38% for hydrogen, 17–31% for oxygen and 3–28% for nitrogen, the gas permeabilities showed another sharp decline. Gas permselectivity increased significantly with the progress of photocrosslinking, and it can be adjusted in a wide range by controlling the extent of crosslinking. Arrhenius plots of gas permeability for hydrogen and oxygen through UV‐irradiated polyimides are straight lines; for nitrogen, however, change in the slope of the straight line is observed and activation energies for hydrogen and oxygen permeation show abrupt increases when crosslinked benzophenone percentage amounts to about 30%. UV‐irradiated polyimides with simultaneous high gas permeability and permselectivity make them ideal candidate materials for gas separation. © 1995 John Wiley & Sons, Inc.
Morphology control in reaction‐induced phase‐separated polymeric systems
Authors: Kim S. , An J. H.
Published: April 2003

In this article the morphology control of poly(ethyl acrylate)/poly(methyl methacrylate) (PMMA) semi‐interpenetrating polymer networks (IPNs) has been attempted either by changing reaction temperature or by adding the third component at the initial stage of phase separation. The morphological variation was followed via dynamic mechanical behavior and electron microscopy. It was found that raising the polymerization temperature of PMMA or adding linear PMMA to the initial mixture facilitates phase separation during the semi‐IPNs formation process. However, the phase separation was further induced by annealing, which indicates that kinetically controlled morphology was not at its equilibrium state. © 1995 John Wiley & Sons, Inc.
Compatibility in immiscible poly(ether ether ketone)/poly(ether sulfone) blends
Authors: Arzak A. , Eguiazábal J. I. , Nazábal J.
Published: April 2003

Both as‐molded and annealed poly(ether ether ketone) (PEEK)/poly(ether sulfone) (PES) blends have been prepared by direct injection molding. The system has been found to be immiscible at all compositions; however, as a result mainly of the produced morphology, it surprisingly maintains to a very great extent the excellent mechanical performance of both of the pure components. This mechanical response is compared with that of the compression molded blends. The ductility of these blends when quenched appears close to the linear between that of the two components. Leaving aside possible morphological and excess free volume of mixing effects, it is in part attributed to the nature of the blend itself. © 1995 John Wiley & Sons, Inc.
Effect of chemical interaction between surface oxidized carbon black and carboxylated nitrile rubber on dynamic properties
Authors: Bandyopadhyay Sumanda , De P. P. , Tripathy D. K. , De S. K.
Published: April 2003

Monsanto rheometric, dynamic mechanical, and solvent swelling studies indicate that functional groups of oxidized carbon black chemically react with carboxylated nitrile rubber (XNBR) when heated at high temperature for prolonged time. The reinforcing ability of the surface oxidized carbon black, measured by failure and hysteresis properties, is higher than the nonoxidized counterpart. © 1995 John Wiley & Sons, Inc.
PET synthesis in the presence of lanthanide catalysts
Authors: Ignatov Vladimir N. , Pilati Francesco , Berti Corrado , Tartari Vittorio , Carraro Claudio , Nadali Giampietro , Fiorini Maurizio , Toselli Maurizio
Published: April 2003

Syntheses of poly(ethylene terephthalate), PET, by transesterification of dimethyl terephthalate with ethylene glycol in the presence of well‐known catalysts and various lanthanide compounds were performed. Lanthanide catalysts appeared to be much more efficient in the first stage of the process (transesterification in the presence of an excess of ethylene glycol), and less active in polycondensation. PET produced with lanthanides was found to possess enhanced thermal and hydrolytic stability as compared to PET synthesized with well‐known catalysts and commercial PET. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of pH‐sensitive and biodegradable hydrogels prepared by γ irradiation using microbial poly(γ‐glutamic acid) and poly(ϵ‐lysine)
Authors: Choi Hyuk Joon , Yang Ryung , Kunioka Masao
Published: April 2003

Poly(γ‐glutamic acid) (PGA) and poly(ϵ‐lysine) (PL) solutions were used as components to prepare mixed hydrogels by γ irradiation. A PGA and PL mixed solution was crosslinked to form a hydrogel with specific water content (weight of absorbed water/weight of dry gel) of 10–100 when the 5 wt % solution of mixed polymer was exposed to γ radiation of 87 kGy dosage under N2 atmosphere. The specific water content increased with increasing PGA content of the PGA/PL mixed gel. The influence of pH and salt concentration on equilibrium swelling was studied. A characteristic pH‐sensitive swelling behavior was obtained using compositional changes of PGA and PL in the gel. PGA/PL 50/50 wt % mixed gel swelling in acid (pH < 4.0) and alkaline (pH > 6.0) conditions and was deswelled between pH 4.0 and 6.0 due to the ionic composition changes of the gel network. With an increase in the ratio of PGA to PL, the hydrogels showed increasing sensitivity to salt solutions (NaCl, Na2SO4, and CaCl2). In addition, degradation of PGA/PL gel by protease produced from Aspergillus oryzae was investigated at 40°C and pH 7.0. PL gel was degraded completely within 2 days. An increase in the ratio of PAG in the PGA/PL mixed gel led to a decrease in the degree of degradation as expected. Some subtle degradation changes were found in the 50/50 and 80/20 wt % (PGA/PL) gels that were degraded by only 3.5 and 3.8% by protease, respectively. © 1995 John Wiley & Sons, Inc.
Changes in mechanical behavior during fatigue of semicrystalline thermoplastics
Authors: Lesser Alan J.
Published: April 2003

The tensile fatigue behavior of two engineering thermoplastics (polyacetal and nylon6,6) were studied by measuring changes in the dynamic viscoelastic response together with changes in potential energy density, strain energy density, and irreversible work. The results show that both stress softening and hardening can occur in controlled load cyclic conditions. At high stress levels and/or frequencies, both the polyacetal and nylon6,6 show evidence of thermal softening as characterized by changes in their dynamic viscoelastic properties and decrease in storage modulus with corresponding increases in loss modulus and loss tangent. This effect is supported by observed decreases in the overall crystallinity as measured in DSC experiments. At lower stress levels (the mechanically dominated region), all results indicate that, although fatigue crack propagation (FCP) is one of the mechanisms governing the fatigue life, its contribution is minor and crack initiation time constitutes the majority of the fatigue life. Also, during the initiation stage, both materials become less viscoelastic and more elastic. This phenomenon is evidenced by overall reductions in the loss modulus, loss tangent, and irreversible work densities while the storage modulus is maintained. © 1995 John Wiley & Sons, Inc.
Extraction fractionation of segmented polyurethanes according to composition
Authors: Šimek Lubomír , Bohdanecký Miloslav
Published: April 2003

Extraction of solid polyester‐based segmented polyurethanes by chloroform and its mixtures with an increasing amount of N,N‐dimethylformamide is described. Unlike the precipitation in a solvent‐nonsolvent system, where fractionation according to the molecular weight dominates, the extraction can resolve the copolymer into fractions differing in the content of diisocyanate units. © 1995 John Wiley & Sons, Inc.
Modification of waterborne polyurethanes by acrylate incorporations
Authors: Kim Byung Kyu , Lee Jong Cheol
Published: April 2003

Waterborne polyurethanes (PUs) were hydrophobically modified using various types of acrylate monomers. PUs having hydroxy ethylacrylate (HEA) terminal groups were first obtained following a prepolymer mixing process. These PU base polymers were then chain extended with acrylate monomers via a radical polymerization mechanism. The effect of the overall composition, base polymer molecular weight, and type of acrylate were studied in terms of water swell and contact angle, as well as mechanical and dynamic mechanical properties of the emulsion cast film. It was found that water resistance, hardness, modulus, and tensile strength of the waterborne PU can be dramatically increased by acrylate incorporation. The reinforcing effect was more pronounced with multifunctional monomers, probably due to the crosslinking effect. © 1995 John Wiley & Sons, Inc.
Toughening of nylon 6 with grafted rubber impact modifiers
Authors: Lu M. , Keskkula H. , Paul D. R.
Published: April 2003

Recent work has shown that nylon 6/acrylonitrile–butadiene–styrene (ABS) blends can be made tough by the addition of some polymer additives that are chemically reactive with nylon 6 and physically compatible with the styrene‐acrylonitrile copolymer (SAN) phase of ABS. Imidized acrylic polymers (IA) represent a successful example of such additives that improve the dispersion of ABS in the nylon 6 matrix and render the blends tough. This article examines the possibility of toughening nylon 6 with ethylene/propylene/diene elastomer grafted with SAN copolymer (EPDM‐g‐SAN). This EPDM‐g‐SAN consists of 50% rubber and 50% SAN by weight. However, it was found that the same IA that works well to disperse ABS materials of similar rubber content is not as effective for EPDM‐g‐SAN, primarily because the EPDM forms the continuous phase, not SAN, and, thus, interfaces with nylon 6 during melt blending. Maleated elastomers like maleic anhydride grafted ethylene–propylene copolymer (EPR‐g‐MA) and styrene–(ethylene‐co‐butylene)–styrene triblock copolymer (SEBS‐g‐MA) were more effective for dispersing EPDM‐g‐SAN in the nylon 6 matrix than IA. Various mechanisms that improve the dispersion are discussed. © 1995 John Wiley & Sons, Inc.
Barrier properties of surface sulfonated HDPE films
Authors: Sabne M. B. , Thombre S. M. , Patil A. S. , Patil S. D. , Idage S. B. , Vernekar S. P.
Published: April 2003

Films of high‐density polyethylene (HDPE) have been sulfonated by solid–gas phase reaction using gaseous sulfur trioxide (SO3) of different concentrations in nitrogen. The effect of concentration of SO3 in an SO3 + N2 gas mixture and time of sulfonation on solvent and gas barrier properties of sulfonated HDPE films was studied by determining toluene and oxygen permeability of HDPE films sulfonated with different concentrations of SO3 for different times. The color developed in sulfonated HDPE films during sulfonation could be bleached by aqueous sodium hypochloride solution. The effect of sodium hypochloride solution treatment on oxygen permeability of sulfonated HDPE films was also studied. © 1995 John Wiley & Sons, Inc.
Moisture‐activated, electrically conducting bioadhesive hydrogels as interfaces for bioelectrodes: Effect of film hydration on cutaneous adherence in wet environments
Authors: Woolfson A. D. , Mccafferty D. F. , Mccallion C. R. , Mcadams E. T. , Anderson J. McC.
Published: April 2003

The water contents of bioadhesive polymeric films of poly(methylvinyl ether–maleic anhydride) copolymer, stored at two humidities and at two temperatures, have been determined by continuous gravimetry. The water contents of the films increased under storage conditions of increasing humidity. The bioadhesion of these films was assessed using an in vitro bioadhesive tester previously validated in our laboratory. Water uptake during the bioadhesive test was taken into account and the final water content of films recorded as a “corrected equilibrium water content” (CEWC). A good quality second‐order polynomial relationship between bioadhesion and the CEWC of films stored at both 23 and 35°C was developed using standard curve fitting analyses. A 2 × 2 factorial design experiment revealed that there was a synergistic relationship between temperature and percentage relative humidity with regard to their effect on the bioadhesion of polymeric films, presumably due to their combined effect on film water content. These findings have implications for both the storage and packaging of hydrophilic polymeric films. © 1995 John Wiley & Sons, Inc.
The effect of carbon black on tetramethylthiuram disulfide accelerator sulfur vulcanization of polyisoprene
Authors: McGill W. J. , Shelver S. R.
Published: April 2003

Polyisoprene was vulcanized with the tetramethylthiuram disulfide/sulfur/ZnO system in the presence and absence of N330 carbon black. Crosslinking was carried out in a DSC at a programmed heating rate, the reaction stopped at points along the thermal curve, and the system analyzed. Residual curatives and reaction intermediates were determined by HPLC and crosslink densities by swelling in benzene. Combinations of the powdered curatives were also heated with and without carbon black and analyzed. It is shown that the step in the vulcanization sequence, influenced by carbon black, is the formation of tetramethylthiuram polysulfides that act as the active sulfurating agent in vulcanization. Carbon black catalyzes their formation, and to a lesser extent, the formation of accelerator terminated polysulfidic pendent groups on the chain. © 1995 John Wiley & Sons, Inc.
Relationships between the properties of fibers and thermally bonded nonwoven fabrics made of polypropylene
Authors: Andreassen Erik , Myhre Ole Jan , Hinrichsen Einar L. , Braathen Marianne D. , Grøstad Kristin
Published: April 2003

Typical polypropylene fibers for use in light nonwoven fabrics were produced in a full scale compact‐spinning line. Molecular weight distribution (MWD), extrusion temperature, draw‐down ratio, and draw ratio were varied. The fibers were thermally bonded (welded) into nonwoven fabrics, at different bonding temperatures, using a pilot calender line. The tensile properties of the fabrics are influenced by the MWD and the processing conditions of the fibers, and the effects of these fiber parameters increase with increasing bonding temperature. The fabric strength increases with increasing Mw/Mn, decreasing draw ratio, and increasing extrusion temperature, while in all these cases the fiber strength generally follows the opposite trend. Furthermore, the fabric strength, as well as the fiber strength, have a maximum as a function of draw‐down ratio. The tensile properties of the fabrics seem to be governed by the bonding properties of the constituent fibers, not the fiber strength per se. Bond characteristics are discussed in terms of skin‐core structures. Some details of the macroscopic fracture mechanisms of fabrics were revealed by scanning electron microscopy and the shape of load‐elongation curves. © 1995 John Wiley & Sons, Inc.
Prediction of service lifetime and performance of a prosthetic thermoplastic
Authors: Chiu C.‐H. , Lautenschlager E. P. , Greener E. H. , Childress D. S. , Healy K. E.
Published: April 2003

The service lifetime and performance for a prosthetic and orthotic thermoplastic, SubortholenTM, was measured using correlations between artificial and natural weathering degradation data of (1) the accumulated carbonyl compound concentration at the polymer surface, (2) changes in thickness of the surface reaction zone, and (3) changes in hardness and tensile properties. An empirical, mathematical relationship between artificial and natural weathering exposures is presented. Results show that the hardness degradation is a useful parameter to estimate the different stages in clinical performance of Subortholen. Corroborating hardness, tensile properties, and weathering exposure time, the service lifetime for Subortholen was determined to be 4–6 years. This finding indicates that the correlation between artificial and natural weathering degradation may provide an effective way to calculate the most appropriate time to replace a worn prosthetic or orthotic device before the device passes into a dangerous stage. © 1995 John Wiley & Sons, Inc.
Differential scanning calorimetry and dynamic mechanical analysis of amine‐modified urea–formaldehyde adhesives
Authors: Ebewele R. O.
Published: April 2003

Urea–formaldehyde (UF) resins are susceptible to stress rupture and hydrolytic degradation, particularly under cyclic moisture or warm, humid conditions. Modification of UF resins with flexible di‐ and trifunctional amines reduces this problem. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the thermal behavior of modified and unmodified adhesives to identify the physical and morphological factors responsible for the improved performance. A UF resin modified by incorporating urea–capped poly(propyleneoxidetriamine) during resin synthesis exhibited a higher cure rate and greater cure exotherm than the unmodified resin. Resins cured with a hexamethylenediamine hydrochloride curing agent had slower cure rates than those cured with NH4Cl. DMA behavior indicated that modified adhesives were more fully cured and had a more homogeneous crosslink density than unmodified adhesives. DMA behavior changed with storage of specimens at 23°C and 50% relative humidity, after previous heating for approximately 20 min at 105°C to 110°C. The initial changes were postulated to occur because of physical aging (increase in density) and continued cure. These were followed by physical breakdown (microcracking) and possibly cure reversion. © 1995 John Wiley & Sons, Inc.
Flocculation of clay suspensions with water‐insoluble starch grafting acrylamide/sodium allylsulfonated copolymer powder
Authors: Chan Wu‐Chung , Chiang Chen‐Yen
Published: April 2003

Use of water‐soluble and ‐insoluble starch grafting acrylamide/sodium allylsulfonated copolymers as flocculants to flocculate the clay suspension was investigated. The composition of acrylamide (AM), sodium allylsulfonated (SAS), and starch (St) repeating units in the water‐soluble and ‐insoluble starch‐grafted copolymer is about 0.718, 0.022, and 0.260 and 0.439, 0.014, and 0.547, respectively. For the water‐soluble starch‐grafted copolymer, the fast initial Ar decreasing rate and the lowest final Ar value occur at pH 2, 80 mg/L water‐soluble starch‐grafted copolymer and 100 mg/L clay suspension. As the suspension contains 1000 mg/L Na+ ion, the flocculating capability would be increased. For the water‐insoluble starch‐grafted copolymer, the initial Ar decreasing rate and the final Ar value are 1.6 times and 0.4 times, respectively, that of the water‐soluble starch‐grafted copolymer at the same test suspension. © 1995 John Wiley & Sons, Inc.
Functionalization of poly(vinyl chloride) through radiation‐induced grafting
Authors: Pande C. S. , Single Sanjay , Gupta N.
Published: April 2003

Poly(vinyl chloride) was irradiated in air with γ‐rays. The hydroperoxidized poly(vinyl chloride) when heated with acrylic acid in water was grafted with poly(acrylic acid), thus introducing the elements of glutaric acid on the polymer. Percentage weight gain was investigated as a function of total dose, monomer concentration, and time of reaction. The effect of adding methanol to water as a medium of reaction was studied in terms of percentage weight gain on grafting. © 1995 John Wiley & Sons, Inc.