bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally stimulated depolarization current studies on PC/PTBF blends
Authors: Kalkar A. K. , Kundagol Shankar , Chand Suresh , Chandra Subhas 
Published: April 2003

AbstractThermally stimulated depolarization current (TSDC) studies have been carried out on blends of polycarbonate (PC) and poly(p‐t‐butyl phenolformaldehyde) (PTBF) using electric poling at temperatures ranging from 348°K to 383°K. The PC/PTBF blends poled at identical electric field (Ep) and temperature (Tp) exhibit a continuous distribution of polarizability (in general, in the range 300°K to 450°K) with a blend composition dependent single peak (TM). With increasing Ep and Tp, the TSDC peak of a blend shifts toward higher temperature with increasing peak current (IM) and charge (Q) associated with the peak. The effects of polarization field and temperature indicate that the polarization in the blend system is due to induced dipole formation. The activation energy decreases with increasing PTBF content in the blend, indicating shallow traps in PC/PTBF electret. The present blend electrets, however, comparative to its two components PC and PTBF, store more charge but decay faster. © 1994 John Wiley & Sons, Inc.
Structure/permeability relationships of polyamide‐imides
Authors: Gao Xuesong , Lu Fengcai 
Published: April 2003

AbstractStructure/permeability correlations for a family of aromatic polyamide‐imides are presented. The variations in chemical structure lead to significant changes in permeability. The crystallization of PAP results in a very low permeability. The introduction of bulky group tends to increase permeability without a corresponding decrease in permselectivity. This result contributes to the inhibition of chain packing and segmental mobility. Wide‐angle X‐ray diffraction measurements of average segmental spacing of the materials and fractional free volume calculations characterize the packing of the different polymers. © 1994 John Wiley & Sons, Inc.
Gas‐sweeping pervaporation: A method for studying the transport of solvent mixtures in polymers: Application to the methanol–propan‐1‐ol‐cellulose triacetate system
Authors: Nguyen X. Q. , Nguyen Q. T. , Clement R. , Uchytil P. 
Published: April 2003

AbstractA new method using a batch gas‐sweeping pervaporation was proposed for the measurement of different transport parameters of a polymer film to a solvent mixture. In addition to the total permeation flux and the selectivity of the film to the mixture, the diffusion coefficients and the permeation coefficients of the components can be determined. The method, which is based on new solutions of the second Fick law in which the upstream concentration is time‐dependent, was applied to the transport of methanol‐propan‐1‐ol mixtures through a cellulose triacetate membrane and their results were compared with those obtained in vacuum pervaporation. Both the methods give equivalent selectivity and permeation fluxes at all methanol contents. The diffusion coefficient of methanol, which was ca. 10−7 cm2/s in cellulose triacetate when pure methanol was used, was found to be much smaller when methanol was mixed with propan‐1‐ol (ca. 10−9cm2/s). From the practical viewpoint, the cellulose triacetate membrane shows a high permeation flux with a rather good selectivity to methanol. © 1994 John Wiley & Sons, Inc.
Comparison of thermal techniques for glass transition measurements of polystyrene and cross‐linked acrylic polyurethane films
Authors: Achorn Peter J. , Ferrillo Rosalie G. 
Published: April 2003

AbstractThere are few quantitative comparisons in the literature between glass transitions (Tg) measured by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMA). Also, in the case of DMA, two different operational definitions have been used to obtain the glass transition, namely, the loss modulus (E″) and damping (tan δ) peak temperatures. We propose a new DMA definition of Tg and demonstrate that it agrees with DSC Tg measurements within ±2°C for both thermoplastic polystyrene and thermoset cross‐linked acrylic polyurethane films with measurable tan δ peaks. The glass transitions for a single polystyrene standard and several cross‐linked acrylic polyurethane films were measured by DSC. Additionally, E″ and tan δ peak temperatures were measured by DMA as a function of frequency and temperature. Empirically, it was determined that the average of the E″ and tan δ peak temperatures measured at 1 rad/s oscillation frequency corresponds to the glass transition measured by the ASTM E1356 DSC test method. © 1994 John Wiley & Sons, Inc.
Preparation, characterization, and thermal behavior of MMA–N‐aryl maleimide copolymers
Authors: Bharel Renu , Choudhary Veena , Varma I. K. 
Published: April 2003

AbstractThe work describes the synthesis and characterization of copolymers of methyl methacrylate (MMA) and N‐o‐tolyl maleimide (MO)/N‐p‐tolyl maleimide (MP)/4‐maleimido benzoic acid (MB). The copolymers were synthesized by varying the mol fraction of N‐aryl maleimides from 0.1 to 0.5 in the initial feed using azobisisobutyronitrile (AIBN) as an initiator and tetrahydrofuran as the solvent. The copolymer composition was determined from the 1H‐NMR spectra by taking the ratio of proton resonance signals due to OCH3 of MMA (δ=3.59 ppm) and the aromatic protons (δ=7.0–7.3 ppm) of N‐aryl maleimides. The monomer reactivity ratios of MMA–MP were r1=0.926±0.001 and r2=0.47±0.03 and MMA–;MO were r1=1.37±0.005 and r2=0.31±0.01. The initial decomposition temperature of copolymers and glass transition temperatures increased with increasing N‐aryl maleimide content in the backbone. © 1994 John Wiley & Sons, Inc.
Some mechanical properties of solvent‐treated polypropylene films
Authors: Ugbolue S. C. O. , Uzomah T. C. 
Published: April 2003

AbstractThe amount of polypropylene (PP) extracted by hot solvent extraction increased with increasing naphtha in a naphtha/reformate solvent blend. The stress–strain curves formed the basis for the calculation of several mechanical properties of the residual film. The yield stress, the natural draw ratio, secant modulus, breaking factor, and work expended in drawing were maximum at a 10/90 naphtha/reformate composition. These were explained in terms of extraction of low molecular weight and atactic materials leaving a more stereoregular block, giving maximum properties with the least removal of polymer materials. Further increases in the naphtha component, however, decreased these properties, possibly due to the greater solubilizing effect of naphtha for the PP chains. © 1995 John Wiley & Sons, Inc.
Elastomer–carbon black interaction: Influence of elastomer chemical structure and carbon black surface chemistry on bound rubber formation
Authors: Roychoudhury A. , De P. P. 
Published: April 2003

AbstractThe contribution of elastomer polarity and reactivity to bound rubber formation has been investigated. In this study, a number of elastomers of different chemical nature have been tested. The surface of the carbon black (N110) has also been modified by nitric acid oxidation in order to increase the concentration of surface functional groups. The experimental results have shown that the bound rubber formation is barely related to the polarity of the polymers. It is the reactive sites in both the elastomer and carbon black which are mainly responsible for bound rubber formation. It therefore appears that the elastomer/carbon black interaction leading to the formation of bound rubber is essentially a chemical process involving primary bond formation between elastomer and carbon black. The oxidized carbon black exhibits a higher surface activity which may be due to an increased concentration of oxygen‐containing reactive surface sites, namely, phenolic hydroxyl, carboxyl, lactone, and quinone groups. © 1995 John Wiley & Sons, Inc.
Cross‐linking of poly(methyl methacrylate) by aminolysis of ester functions with diamines
Authors: Pavlinec J. , Lazar M. 
Published: April 2003

AbstractThe cross‐linking of poly(methyl methacrylate) (PMMA) macromolecules by primary aliphatic diamines was carried out at 413–473 K, above the polymer glass transition temperature. The spherical grains of the suspension‐prepared polymer (0.25–0.8 mm) and the molar ratio to amine above 20 were used. The reaction is characterized by an induction period before the macroscopic gel was observed and by fast network formation. Both phenomena are temperature‐dependent (87± 2 kJ mol−1). The rate of gelation is dependent also on the type of diamine; the shorter induction period of gelation and the higher rate of cross‐linking were observed when amino groups were separated with longer alkyl chains. From the kinetics of amine uptake with PMMA, however, it can be concluded that gel formation is influenced also by the reactivity of amine in the transamination reaction and by the amount of bounded diamine. Aminolysis of PMMA ester groups proceeds from the very beginning of heating of the reaction charge. The polymer cross‐linking prevails when there is more than 60% of diamine attached to PMMA in dependence on the amine type used. © 1995 John Wiley & Sons, Inc.
Crosslinked hydroxypropyl cellulose films retaining cholesteric liquid crystalline order. I. Effects of cast conditions and heat treatment on the textures and order of films
Authors: Suto Shinichi , Suzuki Kuniaki 
Published: April 2003

AbstractTo eliminate the shear‐induced band texture and wrinkled texture observed on the free surface of cellulosic solid cast films retaining cholesteric liquid crystalline order, we proposed a storing process of the cast solutions: the solution is stored in the same solvent vapor atmosphere as the solution. The effect of cast conditions (the storing time) on those textures and the cholesteric liquid crystalline order was determined using the lyotropic liquid crystalline solution of hydroxypropyl cellulose in methanol with crosslinker. Furthermore, the effect of heat treatment on the liquid crystalline order in the cast films was determined. The resultant crosslinked films were observed with a polarized microscope and a scanning electron microscope, and were investigated with circular dichroism. Our findings showed that the proposed storing process is needed before starting the cast process. During the process the textures vanished, due to the relaxation of the residual stress in the solution, the cholesteric liquid crystalline order became stable, and the cholesteric pitch decreased with increasing storing time. The heat treatment also affected the liquid crystalline order of the films; the peak in the circular dichroism spectrum sharpened and shifted with heat treatment, and the shift in peak seemed to depend on the crosslinker concentration. Furthermore, the crosslinking proceeded with heat treatment. © 1995 John Wiley & Sons, Inc.
Hydrolytic aging of polycarbonate. I. Physical aspects
Authors: Ghorbel I. , Thominette F. , Spiteri P. , Verdu J. 
Published: April 2003

AbstractThe hydrolytic aging of an unstabilized industrial sample of polycarbonate was studied at 40, 70, 80, and 90°C, 100% RH. The water absorption characteristics show that, at equilibrium, the polymer absorbs about 0.04 mol water per ester group and that the equilibrium is reached after about 10–40 h exposure, i.e., far before irreversible changes of physical properties are observed. Differential scanning calorimetry reveals the combined effects of hydrolytic chain scission and physical aging on glass transition temperature. Investigations on tensile yield properties showed that hydrolytic chain scission leads to a significant decrease of the apparent Eyring's activation volume. These observations strongly support the hypothesis that there are preexisting or hydrolysis‐induced defects responsible for an heterogeneous distribution of chain scissions that would be concentrated into localized microdomains. © 1995 John Wiley & Sons, Inc.
Effects of poly(vinyl acetate) and poly(methyl methacrylate) low‐profile additives on the curing of unsaturated polyester resins. I. Curing kinetics by DSC and FTIR
Authors: Huang Yan‐Jyi , Su Chin‐Cheng 
Published: April 2003

AbstractThe effects of two low‐profile additives (LPA), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) on the curing kinetics during the cure of unsaturated polyester (UP) resins at 110°C were investigated by using a differential scanning calorimeter (DSC) and a Fourier transform infrared spectrometer (FTIR). The effects of temperature, molar ratio of styrene to polyester CC bonds, and LPA content on phase characteristics of the static ternary systems of styrene–UP–PVAc and styrene–UP–PMMA prior to reaction were presented. Depending on the molar ratio of styrene to polyester CC bonds, a small shoulder or a kinetic‐controlled plateau in the initial portion of the DSC rate profile was observed for the LPA‐containing sample. This was due to the facilitation of intramicrogel crosslinking reactions since LPA could enhance phase separation and thus favor the formation of clearly identified microgel particles. FTIR results showed that adding LPA could enhance the relative conversion of polyester CC bonds to styrene throughout the reaction. Finally, by use of a microgel‐based kinetic model and static phase characteristics of styrene–UP–LPA systems at 25°C, the effects of LPA on reaction kinetics regarding intramicrogel and intermicrogel crosslinking reactions, relative conversion of styrene to polyester CC bonds, and the final conversio have been explained. © 1995 John Wiley & Sons, Inc.
UV‐curable acrylic resins for production of glass laminates
Authors: Decker C. , Moussa K. 
Published: April 2003

AbstractGlass laminates have been readily obtained by photocuring at ambient temperature of an acrylic adhesive consisting either of a liquid resin or a solid thermoplastic polymer. The light‐induced polymerization process was followed by real‐time infrared spectroscopy. Close to 100% conversion was reached within a few seconds of exposure, by taking as the photoinitiator an α‐hydroxy alkylphenone or an aryl phosphine oxide. A liquid formulation containing an aliphatic polyurethane–acrylate oligomer, acrylic acid, and butyl acrylate gives the best performance in terms of reactivity, adhesion, impact resistance, and transparency. The impact resistance was further increased by introducing a polycarbonate core between the two glass plates. The solid thermoplastic polymer was obtained either by casting from a solution containing an aliphatic polyurethane, an acrylate oligomer, and the photoinitiator or by mixing these compounds in the molten state and further extrusion. The glass assembly was heated above the softening temperature (80°C) under a 1 MPa pressure and cured by a 1 min exposure to UV radiation to give a strongly adhesive laminate showing good transparency and long term weatherability. © 1995 John Wiley & Sons, Inc.
Studies on the preparation and properties of conductive polymers. VIII. Use of heat treatment to prepare metallized films from silver chelate of PVA and PAN
Authors: Chang Liang‐Tau , Yen Chih‐Chao 
Published: April 2003

AbstractMetallized polymer films were prepared from polyacrylonitrile or poly(vinyl alcohol) silver chelate solution by heat treatment. These metallized film exhibited low surface resistivity around 100Ω/cm2. The surface of these conductive films was proved to be metallized using X‐ray analysis. The metal adhered on the film was believed to be responsible for the improvement of electrical conductivity. The effects of types and concentrations of silver salt, types and volume of solvent, and drying time on the conductivity of metallized films were investigated. © 1995 John Wiley & Sons, Inc.
Microstructure and mechanical properties studies of poly(vinyl alcohol)–lead salts complexes
Authors: Bakr N. A. , Abdel‐Hamid M. I. , El‐Hanafy O. 
Published: April 2003

AbstractPoly(vinyl alcohol) (PVA) was found to form complexes with PbCl2, Pb(NO3)2, and Pb(CH3COO)2. Different complex compositions were prepared by casting technique. Microdomains were observed in the case of the PbCl2‐PVA system. Complexes of PbCl2‐PVA system are somicrystalline over the entire composition range. PbCl2‐PVA complexes are stable to temperatures greater than 350°C in comparison to 225°C of pure PVA. The general features of the microdomains depends upon the temperature and the salt concentration. The hardness properties of the binary mixture were found to change in a nonlinear mode exhibiting a maximum value with the increase of the PbCl2 content and in a linear mode for the other salts. © 1995 John Wiley & Sons, Inc.
Short coir fiber‐reinforced natural rubber composites: Effects of fiber length, orientation, and alkali treatment
Authors: Geethamma V. G. , Joseph Reethamma , Thomas Sabu 
Published: April 2003

AbstractNatural rubber is reinforced with untreated coir fiber chopped to different lengths, viz., 6, 10, and 14 mm. Mixes were also prepared using 10 mm‐long coir fibers treated with 5% sodium hydroxide solution for different time intervals, viz., 4, 24, 48, and 72 h. These composites were vulcanized at 150°C. The vulcanization parameters, processability characteristics, and stress–strain properties of these composites were analyzed. The rubbercoir interface bonding was improved by the addition of a resorcinol–hexamethylenetetramine dry‐bonding system. The reinforcing property of the alkali‐treated fiber was compared with that of the untreated one. The extent of fiber orientation in the composite was determined from green strength measurements. From anisotropic swelling studies, the extent of fiber alignment and the strength of fiber–rubber interface adhesion were analyzed. Scanning electron microscopic studies were carried out to investigate the fiber surface morphology, fiber pullout, and fiber–rubber interface. © 1995 John Wiley & Sons, Inc.
Thermal and mechanical properties of phenolphthalein polyethersulfone/poly(phenylene sulfide) blends
Authors: Yang Yuming , Li Binyao , Zhang Yingjun , Zhang Yan , Zhuang Guoqing 
Published: April 2003

AbstractThe thermal and mechanical properties of phenolphthalein polyethersulfone/poly(phenylene sulfide) (PES‐C/PPS) blends were studied using a differential scanning calorimeter, a dynamic mechanical analyzer, and mechanical characterization. The morphologies of fracture surfaces were observed by scanning electron microscopy. The blends are multiphase systems with strong interaction between the two phases. It is of interest that, although the strength and ductility of PPS are lower than those of PES‐C, the addition of PPS can improve markedly the impact strength of PES‐C without changing its higher strength. The PPS can also act as a flow aid for PES‐C. © 1995 John Wiley & Sons, Inc.
Applications of computer difference spectroscopy in ion‐exchange resins analysis
Authors: Rodriguez A. S. , Flores R. Ma. E. 
Published: April 2003

AbstractInfrared spectra demonstrate the use of computer difference spectroscopy and other dataprocessing routines to derive and enhance the difference spectra that relates the concentration of a resin to the concentration of other resins in the mixture. Therefore, a simple quantitative treatment accounting for the resin concentration has been determined. © 1995 John Wiley & Sons, Inc.
The stability of poly(ether urethane)/polydimethylsiloxane interpenetrating polymer networks
Authors: Ali S. A. M. , Hourston D. J. , Manzoor K. , Williams D. F. 
Published: April 2003

AbstractInterpenetrating polymer networks (IPNs) are a special type of polymer blend consisting of two polymer networks synthesized and/or cross‐linked independently within each other. One potential approach for the preparation of composite materials from polymers having desirable physical characteristics obtained by modifying their surfaces with physiologically acceptable polymers involves IPN technology. An IPN based on a poly(ether urethane) and polydimethylsiloxane has been synthesized and charaterized using optical microscopy, dynamic mechanical analysis, and scanning electron microscopy. The stability of poly(ether urethane)/polydimethylsiloxane composites were studied in hydroxyl radical aqueous solutions over 30 weeks. The data suggest that these composites have good potential for biomedical applications. © 1995 John Wiley & Sons, Inc.
Direct use of mixing data for modeling high‐viscosity, melt‐phase, condensation polymer reactors
Authors: Neogi Swati , Sampson Kendree J. 
Published: April 2003

AbstractMathematical models for simultaneous reaction and mass transfer occurring in the manufacture of high‐viscosity condensation polymers are considered. Particle tracking experiments are used to estimate convective flow rates and mixing volumes in a disc‐ring reactor configuration. These results are incorporated directly into a mixing‐cell model without resorting to the use of restrictive assumptions regarding the convective mixing. Both a penetration theory model and a flash evaporation model are used to simulate the transport at the liquid–vapor interface. Although widely used in previous studies, the penetration theory model is ultimately rejected because it underpredicts the overall reactivity. Model results predict interactions between agitation rate, residence time, and the overall reaction rate for commercial‐scale systems producing poly(ethylene terephthalate). The model is partially verified by comparison with degassing data. © 1995 John Wiley & Sons, Inc.
Large transient shearing of molten polymers: Predictions of rate‐dependent and nonaffine network models
Authors: Xu Y. Z. , De Kee D. , Fong C. F. Chan Man 
Published: April 2003

AbstractAnalytical expressions of shear stress evolution for arbitrary transient flows are obtained, based on a rate‐dependent network (RDN) model as well as on a nonaffine network (NAN) model. Predictions of both models are evaluated for various step histories against experimental results on linear and branched polyethylene melts (LDPE and HDPE). Agreement with experiments justifies the usefulness of the computed stress functions regarding the predictions of shear responses in melt processing. A slow transient process is more adequately simulated by an NAN model than by an RDN model. The very slow reentanglement process following cessation of flow is poorly described by either model. This fact implies that additional relaxation mechanisms are involved. In the linear viscoelasticity of small deformation, elastic relaxation occurs. In processes involving large shear rates, additional parameters are needed to account for the structural changes accompanying the relaxation process. © 1995 John Wiley & Sons, Inc.
Role of PbO in covulcanization of carboxylated nitrile–polyacrylic rubber blend in the presence of ethylene thiourea or mercaptobenzothiazole
Authors: Chowdhury P. , Chakravorti M. C. , Das C. K. 
Published: April 2003

AbstractThe effects of metal oxide (PbO) on covulcanization of the blend [carboxylated nitrile rubber (XNBR)–Polyacrylic rubber (ACM) = 50 : 50] in the presence of 2‐mercaptobenzothiazole (MBT) or ethylene thiourea (ETU) have been evaluated to elucidate the curing mechanism. The optimum mole ratio of ETU–PbO and MBT–PbO with respect to cure characteristics and physical properties have been found to be 1 : 1.5 and 1 : 0.5, respectively. The examination of infrared (IR) spectra reveals that crosslinking occurs at the CCl cure site of the ACM and COOH cure site of the XNBR. Based on the optimum mole ratios and Spectral analysis a scheme of reactions has been proposed. © 1995 John Wiley & Sons, Inc.