bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on oxidative photodegradation of epoxy resins by IR‐ATR spectroscopy
Authors: Zhang G. , Pitt W. G. , Goates S. R. , Owen N. L. 
Published: April 2003

AbstractThis article describes studies on oxidative‐photodegradation of cured Epolite epoxy resin using techniques of IR spectroscopy with attenuated total reflectance optics and scanning electron microscopy. The results show that the oxidative‐photodegradation of this epoxy system is characterized by the formation and subsequent decomposition of carbonyl groups and by epoxy ring opening. The carbonyl bonds are apparently formed in the initial stage of photodegradation and then decomposed upon further aging. Changes in the surface morphology of the samples during degradation suggest that there is significant scissioning of the cross‐linked polymer structure. This phenomenon was reproduced using three different UV lamps that differed in spectral properties. Our studies provide clues to the mechanism of epoxy polymer degradation by solar light. © 1994 John Wiley & Sons, Inc.
Synthesis of liquid crystalline triheptyl cellulose and its blend thin‐film composite membrane for air separation
Authors: Huang Mei‐Rong , Li Xin‐Gui 
Published: April 2003

AbstractLiquid crystalline triheptyl cellulose (THC) was synthesized directly from cellulose acetate and heptyl bromide with dimethyl sulfoxide as a single‐component solvent. Synthetic conditions were studied with respect to reaction temperature, time, and yield. The molecular structure and liquid crystalline character of the THC obtained as sticky, soft, and birefringent solids at room temperature were investigated by IR, NMR, elemental analysis, and a polarizing microscope. The composite membranes consisting of a THC/ethyl cellulose blend as a dense thin selective layer and polyethersulfone as a porous thick support layer were fabricated and their air‐separation performances were studied by a constant pressure–variable volume method. The data show that the air‐separation performances increase dramatically with operating parameters such as pressure and temperature. No apparent dependence of air‐separation ability on operating time and THC/ethyl cellulose ratio was observed. © 1994 John Wiley & Sons, Inc.
Shear and elongational flow of some branched polyethylenes
Authors: Chohan R. K. 
Published: April 2003

AbstractThe elongational properties of some branched polyethylenes are studied. Experimental results of their flow behavior are presented. The Cogswell technique of calculating the elongational viscosity together with another approach based on the work of Huang and Shroff are utilized. The results show close agreement between these two methods. Certain parameters related to material elasticity are employed. Results suggest that the elastic parameters achieve relatively high levels only if the molecular weights are sufficiently high. © 1994 John Wiley & Sons, Inc.
Preparation and structures of ethyl–cyanoethyl cellulose/cross‐linked polystyrene composites
Authors: Jiang S. H. , Huang Y. 
Published: April 2003

AbstractEthyl–cyanoethyl cellulose [(E–CE)C]/cross‐linked polystyrene (PS) composites were prepared via polymerization of styrene in (E–CE)C/styrene solution with glycol diacrylate as a cross‐linking reagent. The polymerization of the solution, morphology, and miscibility of (E–CE)C/PS composites were studied with polarizing microscopy, small‐angle light scattering (SALS), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). It was found that the mixing state of the (E–CE)C/PS system and the thermal stability of composites were modified by cross‐linking of PS. In the intensively cross‐linked composite prepared from the anisotropic solution, there existed cylindrical domains in which (E–CE)C spherulites were dispersed in PS. © 1994 John Wiley & Sons, Inc.
Polymer drying. X. A recondsideration of the kinetics of evaporation from polymer–liquid systems during the interval of transition from the rubbery to a glassy state
Authors: Errede L. A. , Henrich P. J. , Tiers George V. D. 
Published: April 2003

AbstractThis kinetic restudy of the physical changes that occur during evaporation‐induced transition from the rubbery to a glassy state of polystyrene–liquid systems shows that such transitions occur via two mechanistic pathways. The first is random nucleation of microdomains of self‐associated polymer segments owing to a time‐dependent logarithmic decrease in the number of adsorbed volatile molecules per phenyl group of residual mobile polymer segments. The second is a therodynamically driven self‐association of adjacent monomer units with concomitant explusion of the adsorbed molecules, which appears to propagate via a “dominolike” chain reaction. Conceptually this is a three‐dimensional “zippering‐up” of suitably close polymer segments to produce the corresponding macrostructural network of self‐associated polymer. The kinetics of the latter is zero‐order, and this dominates the overall kinetics of evaporation during the latter portion of the transition interval, presumably owing to changes in entropy of the system as it progresses from the mobility characteristic of the rubbery state to the rigidity characteristic of a glassy state. © 1994 John Wiley & Sons, Inc.
Structural changes of cellulose, wood, and paper under shear deformation and high pressure
Authors: Teeäär R. , Lippmaa E. , Gravitis J. , Kokorevics A. , Kreituss A. , Zharov A. 
Published: April 2003

AbstractStructural changes of wood and its components have been studied after shear deformation under high pressure (SDHP) at up to 6 GPa. Cellulose amorphization and chain depolymerization was observed. Approximately 30% of microcrystalline cellulose was soluble in water after a 360‐degree twist of the Bridgman anvils. The water‐insoluble part was re‐crystallized into cellulose II lattice. Repeated treatment applied to the nondissolved part of the sample, the so‐called cascade experiment, permits the dissolving of about 30% of the residual nondissolved material once again. Extraction with water, followed by 10% sodium hydroxide, allows almost complete dissolving of microcrystalline cellulose (98%). Water‐soluble saccharides were studied by HPLC and 13C NMR. It was found that destruction of the wood lignin network needs more severe treatment conditions than cellulose destruction does. Lignin domains in wood act as “grinding stones” during cellulose destruction. Long‐living lignin free radicals have been detected with EPR after SDHP. 13C NMR CP/MAS spin diffusion studies showed that SDHP leads to separation of wood components into different biopolymer domains, which turns the system toward thermo‐dynamic equilibrium. SDHP does not permit achievement of initial compulsary compatibility of components in native wood. SDHP technique appears as a promising method for wood delignification and carbohydrate saccharification in the solid state without using harmful chemical reagents of solvents, which is important for technological safety and ecology. © 1994 John Wiley & Sons, Inc.
Selective crosslinking in polymer blends. II. Its effect on impact strength and other mechanical properties of polypropylene/unsaturated elastomer blends
Authors: Inoue Toshio 
Published: April 2003

AbstractThe effect of selective crosslinking of the unsaturated elastomer particles in polypropylene (PP) matrix was investigated. The crosslink system comprised N,N′‐m‐phenylene‐bismaleimide and 6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroqinoline or polymerized‐(2,2,4‐trimethyl‐1,2‐dihydroquinoline). The system, which produces only carbon radicals, crosslinks the elastomer particles selectively without causing excessive degradation of the PP matrix. The reaction was carried out under a dynamic crosslinking process using a twin extruder on PP/EPDM, PP/SBS, and PP/SIS blends, all of which comprised 80 wt % of PP and 20 wt % of the elastomer. After the crosslinking, the impact strength of the blends increased. Especially remarkable increase is obtained at 23°C where PP is above its Tg. The increase of interfacial adhesion caused by production of PP/elastomer graft copolymer at the interface is considered to be the most important factor in the improvement. It permits the interactions of the stress concentrate zone developed at the elastomer particles and causes shear yielding of the PP matrix. Impact fracture energy absorption can be thus changed by adjusting the degree of the interfacial adhesion even at essentially the same morphology. The crosslinked elastomer particles also play the role of a nucleation agent. The selective cross‐linking of the elastomer particles in PP/elastomer blends is demonstrated to be an excellent technique to produce a high‐impact, high‐modulus PP. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of methyl methacrylate–EPDM–styrene graft terpolymer
Authors: Park Duck‐Jei , Ha Chang‐Sik , Cho Won‐Jei 
Published: April 2003

AbstractThe graft copolymerizations of methyl methacrylate (MMA) and styrene (St) onto ethylene–propylene–diene terpolymer (EPDM) were carried out with benzoyl peroxide (BPO) as an initiator in toluene. The effects of EPDM concentration, mol ratio of St to MMA, reaction time, reaction temperature, and initiator concentration on the graft copolymerizations were examined. The synthesized MMA–EPDM–St graft terpolymers (MES) were identified by IR and 1H‐NMR spectra. The number‐average molecular weight (Mn) was 110,000. The thermal stability, tensile strength, light resistance, and weatherability of MES were considerably better than those of the acrylonitrile–butadiene–St (ABS) copolymer. © 1994 John Wiley & Sons, Inc.
Synthesis of nonionic flocculants by gamma irradiation of mixtures of polyacrylamide and poly(ethylene oxide)
Authors: Deng Yulin , Pelton Robert , Xiao Huining , Hamielec Archie 
Published: April 2003

AbstractThe synthesis of polyacrylamide (PAM) graft poly(ethylene oxide) (PEO) has been investigated and the reaction conditions were varied by gamma irradiation to optimize polystyrene latex flocculation by the copolymers. The effects of the gamma ray dosage, the PEO chain length, the ratio of PEO to PAM, and the crosslinking degree of copolymer were studied. The most effective flocculant was obtained by exposing a mixture of 1.2 wt % PAM (Mw = 5 × 106) and 0.94 wt % PEO (Mw = 5000) to 816 krad of gamma radiation. The resulting copolymer contained 24 wt % PEO. Crosslinking to give insoluble gels was an undesirable side reaction increased with γ‐ray dose and decreased with PEO addition. The most effective flocculants contained more than 15 wt % PEO with little crosslinking. The grafting behavior of triblock copolymer, poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide) (EmPnEm, where m and n are oxyethylene and oxypropylene unit, respectively), onto PAM by gamma radiation was also studied; grafting occurred but effective flocculants were not obtained. © 1994 John Wiley & Sons, Inc.
Chemical modification of of polypyrrole. I. Preparation and structural characterization of polypyrrole electrophically substituted with phthalic anhydride and pyromellitic dianhydride
Authors: Biswas Mukul , Roy Anindita 
Published: April 2003

AbstractPolypyrrole (PPY) prepared in ether and in aqueous medium has been modified by polycondensation with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA) in presence of Friedel–Crafts catalysts such as anhydrous zinc chloride and anhydrous ferric chloride at high temperature. The substitution reaction between PPY and the anhydrides presumably proceeds by intra‐and interchain resulting in the formation of intractable products. The characterstic carbonyl absorption band expected for CO and diketone groups in the proposed structure for the polycondensates has been observed in spectra of the anhydride‐modified poly‐condensates. XRD pattern of the polycondensates is totally amorphous. © 1994 John Wiley & Sons, Inc.
Drawing behavior of polyblend fibers from polypropylene and liquid crystal polymers
Authors: Qin Yimin 
Published: April 2003

AbstractPolyblend fibers were made from mixtures of polypropylene (PP) and thermotropic liquid crystal polymers (LCPs). The as‐spun fibers were drawn to produce the oriented structure for the PP matrix. The LCPs were found to exist in thin and long fibrils in the as‐spun fibers; after drawing, they were split into short fragments. From a simplified model whereby a single LCP fibril is embedded in a PP matrix fiber, it was calculated out that the length of the LCP fibril in the drawn fiber is directly proportional to the fibril diameter and tenacity, and is reversely proportional to the compressional stress on the fibril and the friction coefficient between the fibril and the surrounding matrix. With regard to the drawing conditions, it was found that a long length of the LCP fibrils can be preserved by increasing the drawing temperature, or by reducing the draw rate. The effect of two‐stage drawing on the LCP phase morphology was also studied in the present work. © 1994 John Wiley & Sons, Inc.
Swelling bahavior of hydroxyethylemethacrylate hydrogels modified by copolymerization with furfuryl acrylate
Authors: Peniche Carlos , Zaldíiver Dionisio , Agallardo Alaberto , Román Julio San 
Published: April 2003

AbstractHydrogels of biomedical interest were prepared by the free redical copolymerization of 2‐hydroxyethylmethacrylate, H, with furfuryl acrylate, A, at low and high conversion. The microstructural analysis of the copolymer system was carried out by nuclear magnetic resonance (NMR) spectroscopy, taking into consideration statistical perameters according to the Mayo–Lewis copolymerization model. The hydration process in physsiological conditions was studied gravimetrically at 37°C, following the kinetics of swelling of homogeneous thin films. A diffusion mechanism based on the stress relaxation model of copolymer chains accounts satisfactorily for the expermental data obtained. The diffusion coefficents determined according to the classical to the Fickian uptake kinetics are very sensitive to the copolymer's composition. © 1994 John Wiley & Sons, Inc.
Preparation of fine polymer particles containing metallocene derivatives
Authors: Sakurai Hiroyuki , Tamai Hisashi , Nishiyama Fumitaka , Yasuda Hajime 
Published: April 2003

AbstractThis article deals with preparations of fine particles of metallocene copolymers by emulsifierfree emulsion polymerization of vinylferrocene (VFc), ferrocenylmethyl methacrylate (FMMA), 1‐ferrocenylethyl methacrylate (1‐FEMA), 2‐ferrocenylethyl methacrylate (2‐FEMA), and 1‐ruthenocenylethyl methacrylate (1‐REMA) with acrylonitrile (AN), styrene (St), and methyl methacrylate (MMA) in water/ethanol medium. As a result, spherical copolymer particles containing metallocene derivatives have been successfully synthesized in the particle size of ca. 120 to 600 nm. The contents of ferrocenyl or ruthenocenyl groups in copolymer particles increased with increasing concentration of charged metallocene derivatives, while the amounts of metallocene derivatives incorporated into particles are much lower than the charged ratio. © 1994 John Wiley & Sons, Inc.
Studies on a new binary accelerator system containing TMTD and amidinothiourea in sulfur vulcanization of natural rubber
Authors: Mathew Cyriac , Mini Varghese T. Elizabeth , Kuriakose A. P. , Francis D. Joseph 
Published: April 2003

AbstractIt is well known that the use of binary accelerator systems in rubber vulcanization provide better physical and chemical properties to the vulcanizates. The present work reports the results obtained on the study of amidinothiourea as a secondary accelerator along with tetramethyl thiuram disulfide (TMTD) in the sulfur vulcanization of natural rubber. Vulcanizates containing amidinothiourea have an appreciable increase in mechanical properties and better retention of these properties after aging compared to the reference mixes used. These mixes containing amidinothiourea showed appreciable reduction in optimum cure time as well. This suggests a nucleophilic reaction mechanism in the vulcanization reactions under review. Mixes with varying concentrations of amidinothiourea were tried; and the optimum level of amidinothiourea required has been derived based on the cure characteristics of the mixes and physical properties of the vulcanizates. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of two kinds of amphiphilic graft copolymers with well‐defined structure
Authors: Xie Hong‐Quan , Wu Xiang‐Dong , Guo Jun‐She 
Published: April 2003

AbstractPolyacrylamide with well‐defined polystyrene grafts (PAM‐g‐PS) and poly(methacrylic acid) with well‐defined poly(methyl methacrylate) grafts (PMAA‐g‐PMMA) were synthesized via macromer techniques. Polymerization conditions and reactivity ratios for the copolymerizations were studied. The graft copolymers were purified by extractions and characterized with IR spectra. Structural parameters of PMAA‐g‐PMMA were determined by measurement of number average molecular weight of both macromers and copolymers. Both kinds of the graft copolymers are amphiphilic, exhibiting good emulsifying properties. When PAM‐g‐PS was mixed with PMAA‐g‐PMMA in a molar ratio of PAM/PMAA = 1, an intermolecular complex membrane was formed. This behaves as a chemical valve; its permeability can be controlled reversibly by changing the pH value. © 1994 John Wiley & Sons, Inc.
Enantiomer enrichment of oxprenolol through cellulose tris(3,5‐dimethylphenylcarbamate) membrane
Authors: Yashima Eiji , Noguchi Junko , Okamoto Yoshio 
Published: April 2003

AbstractEnantioselective enrichment of racemic oxprenolol dissolved in a hexane‐2‐propanol mixture was achieved with a solid chiral polymer membrane consisting of cellulose tris(3,5‐dimethylphenylcarbamate) coated on a Teflon membrane filter. The oxprenolol obtained through the membrane was rich in (S)‐isomer up to about 50% ee at initial stage and (R) enrichment of a source phase (23% ee) was achieved. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical analysis and interpretation of molecular motions in polyarylates
Authors: Charati S. G. , Jog J. P. , Kulkarni S. S. , Kulkarni M. G. 
Published: April 2003

AbstractMolecular motions in polyarylates synthesized from substituted bisphenols have been investigated by dynamic mechanical analysis. Substitution at the ring carbon atom results in a more pronounced enhancement in glass transition temperature (Tg) as compared to substitution at the bridge carbon atom. The enhancement in mono and disubstituted polyarylates is more consistent than that in the case of polycarbonates and polysulfones. The β transition has been shown to result from defects in the polymer samples. The molecular motion responsible for the τ transition in polyarylates has been shown to be more iocalized than in the case of polycarbonates. Introduction of the phthalide ring in the isopropylidene unit of bisphenol‐A molecule results in splitting of the τ transition peak into two. The results have been compared with those reported for other bisphenol‐based polymers, viz. polycarbonates and polysulfones, and explained on the basis of the structural attributes of the polymers. © 1994 John Wiley & Sons, Inc.
Blends of cellulosic esters with poly(caprolactone): Characterization by DSC, DMA, and WAXS
Authors: Vázquez‐Torres H. , Cruz‐Ramos C. A. 
Published: April 2003

AbstractBinary blends of poly(caprolactone) (PCL) with cellulosic esters [cellulose diacetate (CDA), cellulose acetate–butyrate (CAB), and cellulose triacetate (CTA)] were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide‐angle X‐ray scattering (WAXS) techniques, and qualitative comparison was made with the results obtained by polarizing optical microscopy. The PCL–CAB system was proved to be partially miscible, whereas PCL–CDA and PCL–CTA appeared to be immiscible. A double‐melting behavior was showed for PCL–CAB and PCL–CTA blends. As these peaks did not shift by varying the heating rate of DSC runs, this behavior can be due to melting of two populations of crystals of PCL, which may be different in size. On the other hand, blends of PCL containing a low amount of CAB or CDA seem to develop more crystallinity for the PCL than this polymer alone. The solvent seems to have a certain influence on the thermal and morphological behaviors of the as‐cast blends of these three systems, affecting the extent of crystallinity of PCL, as well as itsTmand ΔHf. This finding is discussed in the light of WAXS and polarizing optical microscopy results. © 1994 John Wiley & Sons, Inc.
Accelerated hydrothermal weathering of silicone rubber, EPDM, and their blends
Authors: Kole S. , Srivastava S. K. , Tripathy D. K. , Bhowmick A. K. 
Published: April 2003

AbstractHydrothermal weathering of the peroxide vulcanized specimens of silicone rubber, EPDM rubber, and their 50 : 50 blend carried out for various durations at different temperatures reveals that silicone is very susceptible to degradation. For example, the modulus, the strength, and the elongation at break consistently fall with aging period. For 72 h of aging at 210°C, it practically loses its rubberiness (elongation < 50%); while EPDM and the 50 : 50 blend maintain more than 100% elongation at break during the times and temperatures. While hydrolytic chain scission is the main degradation mechanism for silicone, EPDM undergoes a predominantly crosslinking reaction. The kinetics study reveals that the better retention of properties of the blends over silicone is due to an increase in the activation energy of degradation in the presence of EPDM rubber, and this protection effect is higher in liquid‐phase weathering than in steam‐phase weathering. © 1994 John Wiley & Sons, Inc.
Gas permeation and sorption in brominated poly(1‐trimethylsilyl‐1‐propyne) membrane
Authors: Nagai Kazukiyo , Higuchi Akon , Nakagawa Tsutomu 
Published: April 2003

AbstractBrominated poly(1‐trimethylsilyl‐1‐propyne) (Br–PMSP), which was prepared by immersing a poly(1‐trimethylsilyl‐1‐propyne) membrane in bromine water, had a new endothermic peak between 70°C and 80°C in its DSC curves. After storage in air at room temperature,the endothermic peak shifted to the low temperature side with time, and occurred between 30°C and 40°C. A distinct change in slopes near the endothermic temperature determined by the DSC analysis was observed in the Arrhenius plots of the permeability coefficients for various gases in all Br–PMSP membranes. However, the slope's change did not clearly appear with storage under the same conditions. The Br–PMSP membrane had a pressure‐dependence of the permeability coefficients not only below the endothermic temperature, but also above one. The sorption behavior for propane in the Br–PMSP membrane was similar to that for other glassy polymers, and there was little change in the sorption behavior with time. In the case of carbon dioxide, a different behavior was observed at first; that is, the same isotherm shape in glassy polymers appeared below 20 atm, but it showed an upward curve above that. After storage in air, the upward behavior disappeared, and the isotherm showed the general shape in glassy polymers. © 1994 John Wiley & Sons, Inc.
Synthesis of core‐shell emulsion copolymer of poly(butyl acrylate)/α‐methyl styrene‐co‐methyl acrylate, with application as processing aid of poly(vinyl chloride)
Authors: Li Zhiting , Gao Jungang , Deng Kuilin , Zhu Hong Guo 
Published: April 2003

AbstractThe core‐shell grafting copolymer of α‐methyl styrene‐methyl acrylate on poly(butyl acrylate) was synthesized. The particle morphology of latex and core‐shell grafting polymerization was investigated as a function of: (a) reaction temperature; (b) initiator concentration used in the secondary polymerization; (c) monomer to polymer ratio; (d) emulsifier concentration. The compatibility of this copolymer with poly(vinyl chloride) (PVC) was determined by the method of solubility parameter and scanning electron microscopy. The rheological behavior of the blend of this copolymer with PVC was investigated. The mechanical properties of the blend were determined. The results show that this copolymer can be used as processing aid for PVC. © 1994 John Wiley & Sons, Inc.