bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peculiar thermal behavior of diallyl oxalate prepolymer
Authors: Yamawaki Masataka , Matsumoto Akira , Oiwa Masayoshi 
Published: April 2003

AbstractFirst, the thermal behavior of diallyl oxalate prepolymer (PDAO) at 130–300°C was preliminarily compared with diallyl phthalate prepolymer; PDAO was self‐curable and degraded easily accompanying the evolution of gas. Next, the thermal degradation of PDAO was investigated in detail by TG. The TG curve of PDAO compared with those of various diallyl dicarboxylate prepolymers was peculiar suggesting two stages of thermal degradation processes with two maximum degradation temperatures, although the first stage is relevant to the significant release of carbon dioxide. In addition, the effect of the structural units, involving uncyclized, cyclized, and crosslinked units, on the thermal degradation of PDAO was examined; the thermal degradation rate was reduced with an increase in the cyclized units and was independent of the content of crosslinked units. From these results, the thermal degradation mechanism of PDAO is briefly discussed in terms of a radical mechanism.
Grafting onto polyester fibers. IV. Synergism during graft copolymerization of binary mixtures of vinyl monomers onto polyester fibers
Authors: Lokhande H. T. , Teli M. D. , Rao K. N. , Rao M. H. 
Published: April 2003

AbstractGraft‐copolymerization reactions of binary mixtures of vinyl monomers (acrylamide–acrylic acid and acrylonitrile–acrylic acid) with polyester fibers have been studied by chemical initiation technique using benzoyl peroxide as an initiator. The total graft add‐on was determined gravimetrically, while the modified Kjeldahl's method for N‐estimation was employed to determine acrylamide and acrylonitrile grafts in their mixtures with acrylic acid grafts. Synergism of very high order was noticed during the graft‐copolymerization reactions. In the case of the acrylamide–acrylic acid system a very high order of synergism (129.15%) was noticed at equimolar proportions of the monomers in the grafting bath. Both acrylamide and acrylic acid showed synergistic influence over each other during graft‐copolymerization reactions. In the case of the acrylonitrile–acrylic acid system, however, the presence of acrylonitrile reduced the graft yield of the acrylic acid component showing a negative synergism; but acrylic acid enhanced the acrylonitrile graft yield to a considerable extent. The results have been explained in terms of reactivity ratios of the monomers. The conductivity results of the monomer mixtures also supported the experimental results.
Microphase state of oligobutadienediol‐based polyurethaneureas
Authors: Lipatov Yu. S. , Dmitruk N. V. , Tsukruk V. V. , Shilov V. V. , Priss L. S. , Dashevsky L. I. 
Published: April 2003

AbstractStructural studies of oligobutadienediol‐based polyurethanes with various degrees of crosslinking were carried out. From absolute small‐angle X‐ray scattering, the degree of segregation of components was determined. It was concluded that a complete microphase separation of the different components is realized in all samples irrespective of the degree of crosslinking, and these polymers are two‐phase systems. While stretching, the fibrillar structure is formed.
New polyisobutylene‐based model elastomeric ionomers. VI. The effect of excess neutralizing agents on solid‐state mechanical properties
Authors: Mohajer Y. , Bagrodia S. , Wilkes G. L. , Storey R. F. , Kennedy J. P. 
Published: April 2003

AbstractThe role of excess neutralizing agents on the mechanical properties of three‐arm star polyisobutylene‐based model ionomers is discussed. The stress level, particularly at high elongations, is significantly affected by the presence of excess neutralizing agents, and these effects are observed with different cations such as potassium, calcium, and zinc. A morphological model is proposed that can account for the observed mechanical behavior.
Grafting vinyl monomers onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers using vanadyl acetyl acetonate complex
Authors: Samal Shashadhar , Sahu Gangadhar , Nayak P. L. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate (MMA) onto native and reduced Indian Chokla wool fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, and the solvent composition of the reaction medium. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10−5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. MMA was found to be the most active monomer when compared to other vinyl monomers. Grafting increases with increasing concentration of HClO4 and with increasing temperature. Reduced and oxidized wools were found to be better substrates than untreated, esterified, crosslinked, and trinitrophenylated wools. The extent of grafting was mostly dependent upon the concentration of SH groups in case of reduced wool. A suitable reaction scheme has been proposed and the activation energy was calculated from Arrhenius plot.
Water absorption isotherms for cured bisphenol A type epoxy resins: Effects of isotherm temperature and resin hardener
Authors: Ellis Bryan , Rashid H. U. 
Published: April 2003

AbstractWater‐sorption isotherms have been determined for some bisphenol‐A‐type epoxy resins cured with either 4,4′‐diamino diphenyl methane (DDM), phthalic anhydride, or polyamide, Versamid 115. The absorption isotherms for the diamine‐cured resin are reversible and that at 0.2°C is linear for the whole accessible range of relative pressures (0 ⩽ h ⩽ 1). With increase in temperature deviations from Henry's law occur at successively lower relative pressures. It is shown that these deviations from Henry's law are related to a concentration dependence of the isosteric heat of absorption. Sorption by both the polyamide and phthalic‐anhydride‐cured resins is not reversible; there are weight increases following an absorption–desorption cycle.
Preparation and properties of graft and block copolymers of poly(p‐phenylene terephthalamide) with polybutadiene
Authors: Takayanagi Motowo , Goto Kohei 
Published: April 2003

AbstractGraft copolymers of polybutadiene (PBD) onto poly(p‐phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N‐metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino‐group‐terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with Tg of PBD for both graft and block copolymers. The Tg's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.
Effects of complexation on the water vapor sorption of polymer alloys
Authors: Oyama Hideko Tamaru , Nakajima Toshinari 
Published: April 2003

AbstractWater sorption measurements of the polyion complex between poly(p‐styrenesulfonic acid) (PStS) and poly(4‐vinylpyridine) (PVP) were carried out to study the effect of the Coulombic interactions between a polyanion and a polycation. The properties of the polyion complex were examined using infrared spectroscopy (IR), X‐ray diffraction, X‐ray photoelectron spectroscopy (XPS), and elemental analysis.It was found that the ionic bonds between and groups led to the formation of a 1:1 polyion complex between PStS and PVP. The nitrogen 1s level in the PStS/PVP polyion complex increased 2.1 eV above its level for PVP, indicating protonation of the pyridine group. In addition, at 293 K and 303 K the water sorption of the complex was larger than that of the sum of the component polymers. In the preceding paper, the water sorption properties of the polyion complex between poly(acrylic acid) (PAA) and PVP were studied. Compared to this complex, the PStS/PVP complex absorbed more water relative to its components. This may be due to the stronger acid strength of the
over the COOH groups.
Sensitivity analysis of a batch polymerization reactor
Authors: Thomas Isabelle M. , Kiparissides Costas 
Published: April 2003

AbstractThe sensitivity of model output variables for a batch polymerization reactor to uncertainties in the kinetic parameters and initial conditions is studied. Differential equations that describe the time variation of sensitivity coefficients for the batch reactor are derived. Numerical integration of the sensitivity equations reveals that the system output responses are very sensitive to parameter variations especially when the polymerization exhibits an autoacceleration of the reaction rate.
Absorption of dicumyl peroxide by extruded polyethylene: Difference between surface and bulk morphology
Authors: Gupta J. P. , Sefton Michael V. 
Published: April 2003

AbstractUnder some conditions, the absorption of dicumyl peroxide (DICUP) at 70°C by extruded low density polyethylene (LDPE) displayed features which are characteristic of two‐stage sorption. For example, the initial slope of the DICUP absorption curve (plot of Mt/M∝ against \documentclass {article}\pagestyle{empty}\begin{document}$\sqrt t$\end{document} ) reflecting diffusion in the surface region was 2.5 times higher than the slope of the second stage (reflecting diffusion in the bulk) for 4‐mm‐diameter LDPE rods extruded at 130°C and 180 rpm (die pressure = 6000 psig). Only a single stage curve was evident in the same rod with its surface removed or in smaller diameter extrudate. Increasing the screw speed from 10 to 45 rpm at nearly constant extrusion pressure (1800–2380 psig) resulted in an approximately 50% decrease in the initial (first stage) slope with a negligible effect on the second stage slope. Increasing the die pressure (4900–6000 psig), by decreasing the extrusion temperature, at constant screw speed (125 rpm) resulted in an almost threefold decrease in the second stage slope without apparent effect on the first stage slope. Photomicrographs demonstrated the presence of distinct surface and bulk morphologies with evidence of a transcrystalline surface layer oriented prependicular to the surface at low screw speeds and larger spherulites in the bulk of the high pressure extrudate. Such morphological features and the observed dependence of the two stage sorption curves on extrusion conditions are consistent with the surface and bulk morphology of the extruded LDPE rod being dependent on the screw speed and die pressure, respectively. These uptake curves were determined by modifying the classical sorption technique to separate the measurement of the equilibrium uptake from the continuous recording of the slow changes in mass during absorption. This technique may be useful in the characterization of the migration process in other plastic/penetrant systems where diffusion is too slow to be measured by conventional means.
Effects of coupling agent on the rheological behavior and processability of polypropylene
Authors: Han Chang Dae , Kwack Tae Hoon , Luo Hong‐Lie 
Published: April 2003

AbstractAn investigation was made into the effect of coupling agents on the rheological behavior and processability of polypropylene. For the study, each of the following three commercially available coupling agents, a titanate coupling agent (Kenrich Petrochemicals, KR‐TTS) and two silane coupling agents (Union Carbide, A1100 and Y9187), was melt‐blended with polypropylene (PP). Melt blending was performed using a twin‐screw compounding machine. It was found that the zero‐shear viscosity of polypropylene was decreased by 1 order of magnitude after it had been extruded through the twin‐screw compounding machine and that, when coupling agents were added to it, its viscosity was higher than that of the PP without the coupling agents, undergoing the same deformation history through the twin‐screw compounding machine. Independent measurements of the molecular weight of the materials show that the weight‐average molecular weight (MW) of the extruded PP is 3.77 × 105, whereas the MW of the virgin PP (before extrusion) is 4.80 × 105, indicating that considerable molecular degradation occurred during extrusion and the MW of the PP extruded with coupling agent is greater than that of the PP extruded without coupling agent. In other words, the molecular weight measurement supports the viscosity measurements of the PP investigated with and without coupling agent. Also measured were the elongational viscosity of the PP with and without coupling agent, which was then correlated to the melt drawability of the materials investigated.
Permeability coefficient of proton‐irradiated poly(ethylene terephthalate) thin films
Authors: Bassani L. C. , Santos W. M. S. , Maréchal B. 
Published: April 2003

AbstractThe principle of operation of an apparatus developed to study gas permeation through thin films is described, and the measurement method is discussed. Use is made of diffusion theory to obtain an expression for the permeability coefficient as a function of the rate of increase of the pressure in the receiving volume. The activation energy for permeation of helium through PET is determined. The permeability coefficient for helium is found to increase significantly with the range of the implanted protons although the incident charge has been kept constant. The hypothesis of structural modifications of the proton implanted PET seems to be confirmed by small‐angle X‐ray scattering experiments on the irradiated samples.
Structure–property relationship in heat‐set poly(ethylene terephthalate) fibers. I. Structure and morphology
Authors: Gupta V. B. , Ramesh C. , Gupta A. K. 
Published: April 2003

AbstractPoly(ethylene terephthalate) (PET) fibers having a range of structure and morphology were prepared by heat‐setting commercial PET yarn at temperatures of 100–250°C for 5 min under two conditions, while the yarn was free to relax and when it was held taut at constant length. The crystallinity, crystallinity orientation, and crystallite size were determined by X‐ray diffraction while birefringence was measured with the help of optical microscopy. The amorphous orientation factor was computed from the structural parameters. The coupling between the crystalline and amorphous regions was determined using the Takayanagi model. While crystallinity and crystallite orientation values for the corresponding samples of the free‐annealed and taut‐annealed series did not show very large differences, the free‐annealed samples had much lower amorphous orientation, especially when heat‐set at higher temperatures. Also while the free‐annealed samples showed a predominantly series type of coupling between the crystalline and amorphous regions, the taut‐annealed samples showed a significant degree of parallel coupling. It is shown that samples in which there is distinct phase separation between the crystalline and amorphous regions have a predominantly series type coupling.
The mechanism for enhanced autoadhesion in azoester‐modified polybutadienes
Authors: Roland C. M. , Böhm G. G. A. 
Published: April 2003

AbstractThe addition of IAD pendant groups to PB molecules results in a larger effective chain crosssectional area with consequent decrease in chain entanglements. This causes the rubber to be more complaint at low strains and strain rates. Simultaneously, the IAD structures give rise to polar and H‐bond interactions which cause the material to exhibit strong adhesion and to possess high green strength. As a result, the IAD‐PB is a relatively rare example of a synthetic polymer with good autoadhesive properties.
Force–temperature behavior of rigid rod polymeric fibers
Authors: Pottick L. A. , Allen S. R. , Farris R. J. 
Published: April 2003

AbstractThe force versus temperature behavior (at constant length) of poly(p‐phenylene benzobisthiazole) fibers (PBT) and Kevlar fibers has been investigated. Thermal expansion coefficients are evaluated for heat treated PBT (PBT‐HT) and Kevlar 49, to be −1.1 × 10−6/°C and −3.2 × 10−6/°C, respectively. Kevlar 49, PBT‐HT, and steel fibers exhibit a linear thermal elastic behavior whereas Kevlar 29 and as‐spun PBT do not. Material changes which occur during heat treatment processing are detected in the force‐temperature profile. A correspondence between the thermal and mechanical energy input which induces these material changes has been found.
Effect of absorbed water on dynamic modulus for short fiber–CR composites
Authors: Ashida Michio , Noguchi Toru , Mashimo Satoshi 
Published: April 2003

AbstractShort fiber–elastomer composites with 10 vol % fiber, nylon 6–CR and PET–CR composites, absorbed water either in the moisture atmosphere or in water. The effect of absorbed water on the viscoelastic properties for these composites was investigated. The temperature dependence of tan σ for the nylon–CR composite showed that the α‐dispersion peak of nylon shifted to lower temperatures with increasing absorbed water content and that after displacement of the α‐dispersion peak the additional small hump appeared at about 90°C. For the PET composite, the α‐dispersion peak of PET shifted slightly to lower temperatures and the small shoulder at 90°C diminished with increasing absorbed water. The additional dispersion probably was caused by the interface between fiber and CR matrix and was independent of fiber orientation. The results suggested that nylon fiber absorbed a larger amount of water than CR matrix, while the water absorption for PET fiber was considerably less than for nylon fiber. The absorbed water in nylon fiber bonded stronger than that in CR matrix and was only slightly diminished by heat treatment under 100°C.
Compatibility of polypeptide blends of poly(γ‐butyl glutamate)/poly(γ‐benzyl glutamate)
Authors: Tsujita Yoshiharu , Ikenouchi Masami , Inukai Masahiko , Takizawa Akira 
Published: April 2003

AbstractThe compatibility of poly(γ‐butyl glutamate)/poly(γ‐benzyl glutamate) blend was examined by the estimation of the side chain dispersion of polypeptides in terms of the condition of preparation of blend films and the blend ratio. The polypeptide blend prepared for very short casting time exhibited an apparent compatibility. On the other hand, the polypeptide blend cast for long time did show incompatibility, irrespective of the blend ratio or mole fraction. The structures of the separated phase changed around mole fraction of 0.5 with the increasing mole fraction. The poly(γ‐butyl glutamate) island phase transformed into the poly(γ‐benzyl glutamate) island phase with increasing mole fraction of poly(γ‐benzyl glutamate) according to the calculation of the simple island‐matrix model by Takayanagi et al.
Chemical etching of poly(ethylene terephthalate) filaments
Authors: Chauhan R. S. , Rao M. V. S. , Dweltz N. E. 
Published: April 2003

AbstractChemical etching of poly(ethylene terephthalate) filaments with aqueous methylamine has revealed a complex stress—cracking behavior, which varied with orientation and thermal crystallization conditions. The appearance of both longitudinal and transverse cracks, can be explained on the basis of the existence of two types of domains, where the stresses are preferentially concentrated. They are explained on the basis of Prevorsek's structural model. In heat‐set fibers, there exists a skin to core differentiation in the internal stress distribution. The crack pattern also varied depending on whether the fibers were heat‐set in the taut or slack conditions. This chemical etching technique can prove to be a very useful tool, for the study of the internal stress distribution induced in fibers by various fabrication processes or post mechanical deformations.
The influence of reactor type and operating conditions on the molecular weight distribution in vinyl acetate polymerization
Authors: Taylor T. W. , Reichert K. H. 
Published: April 2003

AbstractThe vinyl acetate polymerization system was investigated with respect to the breadth of the molecular weight distribution (MWD) in batch, continuous segregated, and continuous micromixed reactors. Models were developed employing a complex kinetic scheme including polymer transfer and terminal double bond polymerization, without neglecting initiation and termination steps. Inclusion of a gel effect for terminal double bond polymerization gave better agreement with experimental molecular weight data in suspension polymerization. Simulation results showed the MWD order in the three reactor types is not fixed, but a function of reactant concentrations and the importance of chain branching. In some cases changing the initiator type and concentration will change the MWD order.
Annealing of polypropylene/poly(ethylene‐co‐propylene) blend. II. Influence of the structure and properties of poly(ethylene‐co‐propylene) and blended polyethylene on impact strength
Authors: Ito Junichi , Mitani Katsuo , Mizutani Yukio 
Published: April 2003

AbstractThe effect of annealing on the impact strength of PP/poly(ethylene‐co‐propylene) (PEP) and PP/PEP/PE blends was studied with regard to the structure of PEP and the polyethylene crystallinity. The tensile impact strength of annealed blends was remarkably affected by the PEP structure such as molecular weight and comonomer composition and the annealing temperature, while the brittle temperature was scarcely affected. For the PP/PEP/PE blends, annealing at temperatures above the melting point of PE lowers the tensile impact strength in a similar manner as the PP/crystalline PEP blend. These phenomena were explained on the basis of the deformation mechanism presented in the previous article, that is, a thicker interfacial layer of PP and PEP forms by means of annealing to increase the energy needed to deform the interface. By using a scanning electron microscope, the transition layer was observed at the interface between amorphous PEP and PE in the PP/amorphous PEP/PE blend after etching with nitric acid. The formation of a thicker transition layer between amorphous PEP and PE and a sizeable increase in PE particle size by annealing was observed. The phenomena should be correlated with the impact sensitivity, especially tensile impact strength, in the PP/crystalline PEP and PP/amorphous PEP/PE blends. A reasonable explanation of the microstructure in PP/PEP blends has been developed in terms of comonomer composition and melting property of PEP.
Biodegradation of gelatin graft copolymers. III
Authors: Kumar G. Sudesh , Kalpagam V. , Nandi U. S. 
Published: April 2003

AbstractGelatin‐g‐poly(methyl acrylate) and gelatin‐g‐poly(acrylonitrile) copolymers were prepared in an aqueous medium using K2S2O8 initiator. A plausible mechanism has been put forward for the observed grafting behavior of monomers. Gelatin‐g‐PAN showed a greater resistance to mixed bacterial inolucum compared to gelatin‐g‐PMA samples. The rate of degradation decreased with the increase in grafting efficiency. A parallel set of experiments carried out by employing the samples as the only source of both carbon and nitrogen showed a marginal but definite increase in the utilization of the polymer. The nitrogen analysis also showed the utilization of the polymer. Scanning electron micographs of the polymer films do show extensive pitting after microbiological testing.