bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of polarity of polymer on inorganic particle dispersion in dielectric particle/polymer composite systems
Authors: Nagata Kazuya , Kodama Souji , Kawasaki Hitoshi , Deki Shigehito , Mizuhata Minoru 
Published: April 2003

AbstractThe influence of the polarity of polymers on the degree of dispersion of BaTiO3 particles in BaTiO3/polymer composite systems was investigated. The BaTiO3 polymer composite systems were prepared from BaTiO3 particles and low‐density polyethylene (LDPE) or ethylene vinyl acetate copolymer (EVA) with 7 and 15 wt % vinyl acetate. Scanning electron microscopy observation showed that BaTiO3 particles aggregated in the polymer matrices and dispersed more readily into the EVA matrix than into LDPE. The shift of the β‐peak temperature by ca. +5°C in the temperature dispersion of the loss modulus was observed for EVA–BaTiO3 composite systems in dynamic mechanical property measurement. On the other hand, the β‐peak temperature of the polymers filled with graphite particles, which have hydrophobic surfaces, was almost constant in a volume fraction region of 0–0.3. The ellipsoidal axes' ratios given by comparison of experimental dielectric constant values and theoretical ones using the Maxwell equation were 4.2, 3.6, and 3.1 for LDPE/BaTiO3, EVA(7%)/BaTiO3, and EVA(15%)/BaTiO3 composite systems, respectively. The axes' ratio decreased by the introduction of polar vinyl acetate groups into nonpolar LDPE. The results confirmed that the polarity of the polymers was one of the key factors governing the dispersibility of BaTiO3 particles in the polymer matrix. © 1995 John Wiley & Sons, Inc.
The compatibility of the blends of PUs with PVC and the adhesion behavior of PU to PVC
Authors: Zhu Y. Q. , Huang Y. J. , Chi Z. G. 
Published: April 2003

AbstractThree series of polyurethane adhesives—polyethyleneadipateurethane (PEAU), polybuthyleneadipateurethane (PBAU), and polyhexyleneadipateurethane (PHAU)—with the same MW and hard/soft segment ratio, based on the three polyesters polyethyleneadipate (PEA), polybuthyleneadipate (PBA), polyhexyleneadipate (PHA), with 4,4′‐diphnylmethane diisocyanate (MDI), and butendiol were synthesized by solution polymerization. The crystallinity of these polyesters and polyurethanes (PUs) and the compatibility of blends of PUs with PVC were studied by means of wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMA), testing of solubility, and phase contrast microscopy. The results indicated that PBAU/PVC and PHAU/PVC were compatible systems, but PEAU/PVC was incompatible. The adhesive strengths of the three adhesives were quite different from one another, in the order of PBAU ≥ PHAU ≫ PEAU. The influences of crystallinity and compatibility on adhesion were discussed, and the Diffusion Theory for PU‐PVC systems was recommended. © 1995 John Wiley & Sons, Inc.
New method of lifetime prediction for brittle fracture of polyethylene
Authors: Chudnovsky A. , Shulkin Y. , Baron D. , Lin K. P. 
Published: April 2003

AbstractA new method for predicting the time to brittle failure of polyethylenes is proposed. The method includes modeling slow crack growth in polyethylenes and the experimental determination of material parameters for the model. The model is based on the concept of the crack layer, i.e., a system consisting of the strongly interacting crack and process zone and the kinetic equations which govern the crack layer growth. The process zone in polyethylenes usually appears to be a thin strip of drawn material extending along the crack line. This permits a characterization of the crack layer by two parameters: the crack and process zone lengths. The two‐parameter crack layer kinetic model allows description of slow crack growth as the discontinuous (stepwise) process which is commonly observed in the brittle fracture of polyethylenes. The model also predicts a relationship between time to failure and applied stress, identical to that established experimentally. The material parameters of the kinetic model can be determined by experiments on smooth specimens, i.e., are independent of slow crack growth and require relatively short‐term observations. Thus, the combination of the material testing and the mathematical modeling of the crack layer evolution is proposed as a method for lifetime prediction in the brittle fracture of polyethylenes. © 1995 John Wiley & Sons, Inc.
Copolymerization of the silane‐modified polyvinylimidazole(1) as a metal corrosion inhibitor
Authors: Jang Jyongsik , Kim Hyuncheol 
Published: April 2003

AbstractThe free radical copolymerization of vinyl imidazole (VI) with γ‐methacryloxypropyltrimethoxy silane (γ‐MPS) by using azobisisobutyronitrile (AIBN) as an initiator was carried out in benzene at 68°C. The copolymer compositions at various monomer feeds were investigated by elemental analysis. The reactivity ratios of two monomers were determined by the Finemann‐Ross method: r1(VI) = 0.22, r2 (γ‐MPS) = 3.18. From these results, it could be concluded that silane‐modified polyvinylimidazoles were random copolymers (0<r1r2<1). Thermal stability of decomposition of the copolymer increased with increasing the mole ratio of VI in the copolymer. Thermal decomposition of the copolymer was caused by the decomposition of the γ‐MPS unit. However, thermal stability above 300°C and maximum thermal decomposition temperature increased with increasing the mole ratio of γ‐MPS due to the crosslinking reaction of hydrolyzed γ‐MPS unit. © 1995 John Wiley & Sons, Inc.
Effects of denaturing agents on the molecular association of dextran. I. Aqueous solutions
Authors: Güner Ali̇ 
Published: April 2003

AbstractMolecular association of aqueous dextran solutions have been investigated by viscosimetric measurements. Intrinsic viscosities of different concentrations of aqueous solutions of dextran with a variety of denaturing agents have been determined. Intrinsic viscosity numbers and Huggins constants of dextran solutions decreased with the addition of denaturing agents. The reducing effect of denaturing agents on the intrinsic viscosities and Huggins constants decreased in the order guanidinium sulfate > guanidinium carbonate > guanidinium chloride > thiourea > urea. The effect of temperature on the intrinsic viscosities of dextran and dextran denaturing agent solutions have also been investigated. A small change in the intrinsic viscosity values was observed for dextran in 1M of guanidinium carbonate and sulfate solutions with the increase of the temperature from 25 to 40 °C. Aqueous dextran solutions, however, showed a significant decrease in the intrinsic viscosities in the same temperature range. © 1995 John Wiley & Sons, Inc.
Effect of blend rheology on the transport property of oriented poly(ethylene terephthalate) blends
Authors: Gopalakrishnan Rajagopalan , Schultz Jerold M. , Gohil Ramesh M. 
Published: April 2003

AbstractRheological studies were performed to delineate appropriate stretching windows, and poly(ethylene terephthalate)/poly(ethylene‐co‐vinyl alcohol) blend films were extruded biaxially within such processing windows. The morphology and oxygen permeability properties of these films, with and without a compatibilizer, were characterized. The intent of this study was to achieve a blend oxygen permeability value (OPV) of less than 1. At a fixed draw ratio and draw temperature, appropriate rheological matching could lead to an increase in the aspect ratio of the EVOH phase and, thereby, of oxygen barrier properties. This study concludes that by melt viscosity matching it is not possible to obtain blends with OPV of less than 1. The model of Fricke, used to predict blend permeability, was found to be more accurate at the higher draw temperatures, with the measured values deviating increasingly negatively from the predicted values as the draw temperature is decreased. © 1995 John Wiley & Sons, Inc.
Biodegradation of low‐density polyethylene, polystyrene, polyvinyl chloride, and urea formaldehyde resin buried under soil for over 32 years
Authors: Otake Yoshito , Kobayashi Tomoko , Asabe Hitoshi , Murakami Nobunao , Ono Katsumichi 
Published: April 2003

AbstractThe biodegradation of several polymers that had been buried under soil for over 32 years was examined. No evidence of biodegradation was found for polystyrene, polyvinylchloride, and urea formaldehyde resin. A remarkable degradation was indicated for low density polyethylene thin films which were directly in contact with soil. Severely degraded parts of the film is characterized by whitening. Many small holes were recognized on the surface of the whitened part. The whitened part is specific for the growth of hyphae. FT‐IR spectra of the whitened part showed a characteristic band in the vicinity of 1640 cm−1 which was assigned to the stretching vibration of CC bond. Although the part which was not in contact with soil was clear, it also showed evidence of degradation from the presence of carbonyl band in FT‐IR. It was suggested that the degradation of the clear part is due to the usual thermo‐oxidative process, while the degradation of the whitened part is due to the biotic process. © 1995 John Wiley & Sons, Inc.
Evolution of the molecular weight distribution and linear viscoelastic rheological properties during the reactive extrusion of polypropylene
Authors: Mead D. W. 
Published: April 2003

AbstractHomogeneous and nonhomogeneous reactive extrusion of polypropylene is modeled using random chain scission statistics coupled with the double reptation mixing rule. In this manner, the evolution of both the molecular weight distribution and the linear viscoelastic material properties is quantitatively predicted for the reactive extrusion–pelletization process. Dispersion in the level of random chain scission has little impact on the MFI for a given average level of chain scission; however, dispersion does generate a marked increase in the recoverable compliance (melt elasticity) relative to the ideal homogeneous random chain scission case. Methods to quantitatively determine the degree of cracking dispersion in processing equipment are identified. Quality control issues such as blending materials of known linear viscoelastic properties to obtain a desired property set is considered in the context of known empirical relations consistent with the double reptation model. Simple mixing rules for the melt flow index and the steady‐state recoverable compliance involving only single component MFI and Je information are derived. © 1995 John Wiley & Sons, Inc.
Optimization of an industrial semibatch nylon 6 reactor
Authors: Sareen R. , Kulkarni M. R. , Gupta S. K. 
Published: April 2003

AbstractAn industrial semibatch nylon 6 reactor has been optimized using a one‐variable (at a time) search technique. The vapor release rate from the reactor and the final monomer conversion have been constrained to lie very close to the values currently present. The degree of polymerization of the product is , similarly, constrained to lie at a value of 152. The optimal pressure histories for two values of the jacket fluid temperature, Tj, have been evaluated using two objective functions, I1 and I3, namely, the total reaction time (I1 = tf) and the concentration of the cyclic dimer (I3 = [C2]f) in the product. It is observed that as Tj is increased from 270 to 280°C, I1 improves while I3 worsens simultaneously. This suggests that these two optimal points lie on the Pareto set for the two‐objective function problem. © 1995 John Wiley & Sons, Inc.
Synthesis and metal binding properties of poly(hydroxamic acid) resins from poly(ethyl acrylate‐co‐divinylbenzene) beads
Authors: Lee Taek Seung , Hong Sung Il 
Published: April 2003

AbstractPoly(hydroxamic acid) resins from crosslinked poly(ethyl acrylate)s were prepared and their metal binding properties were investigated. The metal binding capacities of this type resin for metal ions were determined at specific pH. In the acidic region, the chelating resin showed high adsorption capacity for copper, iron, vanadium, and uranium. Metal adsorption capacities varied according to polymerization condition, i.e. crosslinking ratio and degree of dilution. Equilibration rates of the chelating resins were investigated to evaluate their use as materials for chromatographic separation. Selectivity for various metals was also observed from the mixed metal solution. © 1995 John Wiley & Sons, Inc.
Computer simulation of phase separation in binary polymer mixtures
Authors: Matsuoka Takaaki , Yamamoto Satoru 
Published: April 2003

AbstractPhase separation of binary polymer mixtures was numerically simulated by solving the time‐dependent Langevin equation with Flory–Huggins free energy in two dimensions by using a finite difference method. Spinodal decomposition following structure coarsening was calculated. Simulation results were verified by evaluating the evolution of the wave number obtained from the calculated phase structure by Fourier transformation. Then, computer experiments were carried out to investigate effects of volume fraction and polymer characters, the number of segments, and solubility parameter on morphology. The phase separation time, when the phase began to separate, decreased with deviating volume fraction from 0.5 and with decreasing number of segments and difference between solubility parameters. The difference between solubility parameters had the largest influence on the phase separation time among them and had two effects, the acceleration of phase separation and the restriction of structure coarsening. © 1995 John Wiley & Sons, Inc.
High density polyethylene/acrylonitrile butadiene rubber blends: Morphology, mechanical properties, and compatibilization
Authors: George Josephine , Joseph Reethamma , Thomas Sabu , Varughese K. T. 
Published: April 2003

AbstractPolymer blends based on high‐density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two‐phase structure in which NBR phase was dispersed as domains up to 50% of its concentration in the continuous HDPE matrix. However, 70 : 30 NBR/HDPE showed a cocontinuous morphology. The tensile strength, elongation at break, and hardness of the system were measured as a function of blend compostion. As the polymer pair is incompatible, technological compatibilization was sought by the addition of maleic‐modified polyethylene (MAPE) and phenolic‐modified polyethylene (PhPE). The interfacial activity of MAPE and PhPE was studied as a function of compatibilizer concentration by following the morphology of the blend using scanning electron micrographs. Domain size of the dispersed phase showed a sharp decrease by the addition of small amounts of compatibilizers followed by a leveling off at higher concentrations. Also, more uniformity in the distribution of the dispersed phase was observed in compatibilized systems. The tensile strength of the compatibilized systems showed improvement. The mechanical property improvement, and finer and uniform morphology, of compatibilized systems were correlated with the improved interfacial condition of the compatibilized blends. The experimental results were compared with the current theories of Noolandi and Hong. © 1995 John Wiley & Sons, Inc.
Use of epoxy reactivity for compatibilization of PP/PBT and PP/LCP blends
Authors: Holsti‐Miettinen Riitta M. , Heino Markku T. , Seppälä Jukka V. 
Published: April 2003

AbstractBinary blends of a reactive ethylene‐based terpolymer with polybutylene terephthalate (PBT) and with a liquid crystalline polyester (LCP) were studied to clarify the possible interactions between the blended polymers. The aim was to determine the suitability of the reactive terpolymer containing epoxy reactivity as a compatibilizer in blends of polypropylene (PP) and these two polyesters. The binary blends exhibited increased viscosity during blending, changes in the crystallization of the PBT phase, and an intimate contact between the blended polymers, which pointed to strong interactions or chemical reactions between the compatibilizer and both PBT and LCP. FTIR analysis confirmed the reaction of the epoxide and formation of new esters. Most probably the carboxyl end groups of the polyesters reacted with the epoxy group of the compatibilizer. In the second part of the work the same terpolymer was shown to act as a compatibilizer in PP/PBT and PP/LCP blends. This behavior was based on good mixing with the PP phase and on the chemical reactivity or strong interactions with the polyesters demonstrated in the investigations on binary blends. Addition of 5 wt% of the compatibilizer improved the impact strength, especially in PP/PBT blends where synergistic behavior was found at compositions of 80/20 and 20/80. In PP/LCP blends, the compatibilizer significantly improved the impact strength of unnotched samples at 20 wt % LCP content. In both blends, the compatibilizer reduced the size of the dispersed domains and caused them to attach better in the matrix. © 1995 John Wiley & Sons, Inc.
Cationic conduction in oligoether salt–comblike polyether complex
Authors: Zheng Yungui , Wan Guoxiang 
Published: April 2003

AbstractPolymeric solid electrolytes, with excellent cationic conductivity, were prepared from the complexation of lithium methoxyoligo(oxyethylene) sulfate and lithium methoxyoligo(oxyethylene) sulfonate with poly[methoxyoligo(oxyethylene)methacrylate‐co‐acrylamide]. The electrolytes exhibit low glass transition temperature and have almost no crystal. Their ionic conductivities at 25°C are over 10−5 S/cm. The carrier number in the complex decreases while ionic mobility increases considerably with increasing considerably with increasing temperature. The polarization reversing method confirms that the cationic transference numbers are all over 0.9. The electrolytes have single ion conduction characteristics in DC polarization. © 1995 John Wiley & Sons, Inc.
Toughening of epoxy resin by reacting with functional terminated‐polyurethanes
Authors: Wang Huei‐Hsiung , Chen Jung‐Chieh 
Published: April 2003

AbstractHydroxyl‐, amine‐, and anhydride‐terminated polyurethane (PU) prepolymer which were synthesized from polyether (PTMG) diol, 4,4′‐diphenylmethane diisocyanate (MDI), and a coupling agent bisphenol‐A, 4,4′‐diaminodiphenyl sulfone (DDS), or benzophenonetetracarboxylic dianhydride (BTDA) were used to modify the toughness of bisphenol‐A diglycidyl ether epoxy resin (DGEBA) cured with 4,4′‐diaminodiphenyl sulfone. From the experimental results, it was shown that the modified resin displayed a significant improvement in fracture energy (GIC) and also in its interfacial shear strength with polyaramid fiber. It was more enhanced with increase of the PU modifier wt % content. The hydroxyl‐terminated PU was found to be the most effective among those three prepolymers. In addition, the toughening mechanism was discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by transmission (TEM) and scanning electron microscopy (SEM) revealed that the modified resin had a two‐phase structure. The existence of an unclean fiber surface after its fiber pullout test suggested that a ductile fracture might have occurred. © 1995 John Wiley & Sons, Inc.
Quantitative measurement of interdiffusion at polymer–polymer interfaces with TEM/EDS and EELS
Authors: Jabbari Esmaiel , Peppas Nikolaos A. 
Published: April 2003

AbstractTransmission electron microscopy and energy dispersive spectroscopy (TEM/EDS) were used to map the concentration profile at the interface of a poly(vinyl chloride) and poly(methyl methacrylate) bilayer. Thin sections in the order of 800 Å were cut using an ultramicrotome, examined with TEM, and the concentration profile was mapped with EDS. The intensity of fluorescene X‐rays was adjusted for sample thickness variation by measuring the relative thickness across the interface with electron energy‐loss spectroscopy (EELS). The interfacial thickness of the bilayer after 6 h at 120°C was 1.5 μm, whereas the interdiffusion coefficient was determined as 8.0 × 10−14 cm2/s. © 1995 John Wiley & Sons, Inc.
Monomer reactivity ratios in UV‐initiated free‐radical copolymerization reactions
Authors: Ramelow Ulku S. , Qiu Qing Hua 
Published: April 2003

AbstractThe homopolymers of styrene (S) and vinyl acetate (VA) and their copolymers were prepared in bulk by ultraviolet (UV)‐radiation‐initiated free‐radical polymerization with azobisisobutyronitrile (AIBN) as an initiator. The reacitivity ratios for these copolymerizations were determined by analyzing the monomer content in the copolymers by UV spectroscopy. The same method was extended to other copolymers of styrene such as styrene–methyl methacrylate and styrene–ethyl acrylate. A new analysis method was developed to measure reactivity ratios. For this purpose, UV light was used as a photochemical initiator and UV absorption spectroscopy was used for the determination of the instantaneous composition of copolymers. Nuclear magnetic resonance (NMR) was used to calculate percent conversion. © 1995 John Wiley & Sons, Inc.
Melting behavior of polypropylene fibers studied by differential scanning calorimetry
Authors: Andreassen Erik , Grøstad Kristin , Myhre Ole Jan , Braathen Marianne D. , Hinrichsen Einar L. , Syre Anne Marie V. , Løvgren Tor Bertel 
Published: April 2003

AbstractPolypropylene fibers produced in a compact‐spinning process were studied by differential scanning calorimetry (DSC). With unrestrained fibers, the onset of melting increases with decreasing draw ratio, increasing Mw/Mn, decreasing extrusion temperature, increasing annealing ratio, and increasing draw‐down ratio. These trends are discussed in terms of restraints and reorganization. The onset of melting is shifted to lower temperatures as the heating rate increases for all combinations of material and processing parameters, indicating suppressed reorganization. At low draw ratios, the height and width of the endotherm are affected by the spinline stress, and a secondary peak or shoulder is observed on the high temperature side of the main peak. The magnitude of the secondary peak increases with decreasing Mw/Mn, increasing draw ratio, decreasing draw‐down ratio, and decreasing heating rate, but its position mainly depends on the heating rate. This indicates that the secondary peak may be due to the melting of structures that have been reorganized during the heating scan. As the draw ratio increases, the melting regime broadens, especially towards lower temperatures, and several maxima emerge on the DSC curve. Reorganization and shrinkage during heating may explain these observations. © 1995 John Wiley & Sons, Inc.