bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moisture sorption of polyelectrolyte complex between poly(acrylic acid) and poly(4‐vinylpyridine)
Authors: Hirai Yoshiyuki , Nakajima Toshinari 
Published: April 2003

AbstractSuccessive differential sorptions have been measured for the system polyelectrolyte complex of poly(acrylic acid)/poly(4‐vinylpyridine) + water vapor. The sorption data revealed that the sorption process of water vapor in the complex is controlled not only by diffusion mechanism but also by relaxation mechanism of polymer chains. It has been considered that the complex is composed of a loosely crosslinked, slightly ionized, and relatively homogeneous network structure. The sorption–desorption kinetics have also been investigated for the region of intermediate and high vapor pressures. The interval sorption–desorption curves demonstrated that the complex has the nature of the hysteresis effect in sorptions. It has been concluded that the appearance of sorption hysteresis is due to the depression of mobility of polymer chains resulting from crosslinks between carboxyl groups and pyridine rings.
Cure studies of interpenetrating networks by microdielectrometry
Authors: Holmes Brenda S. , Trask Craig A. 
Published: April 2003

AbstractMicrodielectrometry has been used to follow the cure kinetics of interpenetrating polymer networks (IPNs). The rate of formation of a polyurethane–poly(n‐butyl acrylate) IPN has been characterized at three temperatures. The dielectric data indicate that the relative homonetwork formation rates dominate the resultant material properties.
Postcrosslinking of linear polyesters. I melt‐blend‐type UV‐induced crosslinking agents
Authors: Inata Hiroo , Morinaga Tsutou , Matsumura Shunichi 
Published: April 2003

AbstractPostcrosslinking of such linear polyesters as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are known to be attractive means to improve their thermal resistances without sacrificing their melt processibilities. Effective melt‐blend‐type ultraviolet‐induced crosslinking agents were investigated among allyl compounds. Such polyallyl compounds as triallyl cyanurate and triallyl isocyanurate were found to be practically promising agents from the viewpoints of crosslinkability and stability in the polyester melt. The crosslinkability of the ally compounds increased with increasing the number of the allyl groups in the molecule and electron‐withdrawing property of the neighboring group to which the allyl group was attached. The crosslinking mechanism likely includes both the polymerization of the allyl compound to form semi‐interpenetrating polymer networks in the polyester matrix and the reaction between the polyester and the allyl compound moiety. The crosslinked PET and PBT showed good mechanical properties even above the melting points of the ordinary PET and PBT.
Low‐pressure CO2 sorption in poly(vinyl benzoate) conditioned to high‐pressure CO2
Authors: Hirose Takuji , Mizoguchi Keishin , Naito Yasutoshi , Kamiya Yoshinori 
Published: April 2003

AbstractSorption of CO2 in poly(vinyl benzoate) was gravimetrically measured at pressures up to 1 atm. Sorption isotherms were determined above and below the glass transition temperature Tg from 5 to 85°C. The isotherms were analyzed by the dual‐mode sorption model assuming that the plasticizing effect of sorbed CO2 is negligible at this pressure range. The solubilities and Henry's law dissolution parameters were compared with those obtained by the high‐pressure sorption and permeation measurements. Henry's law dissolution parameters were in good agreement with one another. However, the solubilities first determined here were smaller than those determined by the high‐pressure sorption experiment at the same temperature. It was clear that the Langmuir capacity of the present specimen was smaller in spite of similar high‐pressure CO2 exposure. Relaxation of the polymer was expected to be one of the reasons. This expectation was confirmed from the observation and analysis of sorption isotherms after two kinds of treatments. After annealing above Tg, the Langmuir capacity was shown to be decreased to 1/2 or even to 1/3 from the sorption isotherms below 45°C. This means that the conditioning to the high‐pressure CO2 surely has a large effect on the nature of glassy polymer. Just after high‐pressure CO2 exposure at 25°C, increased solubility was observed. Furthermore, the slow decrease of solubility, that is, the decrease of conditioning effect, was also followed from the continual measurements at 25°C. This result reflects not only the characteristic of sorption capacity after high‐pressure CO2 exposure, but also the relaxation of polymer in glassy state.
ESCA analysis of partially converted lignocellulosic materials
Authors: Ahmed A. , Adnot A. , Kaliaguine S. 
Published: April 2003

AbstractFurther ESCA data of the solid residues obtained by supercritical extraction of Populus tremuloides are reported. The changes of the ESCA spectra with the severity of grinding are discussed. These data allow us to draw precise conclusions on the spatial distribution of carbonaceous recondensed material as thermal conversion proceeds. The C1s peaks are of special interest as the distribution of the four components in these peaks bears information on the nature of the chemical compounds present on the surface of the sample.
Polymerization of methyl methacrylate in micellar phase: A kinetic study
Authors: Panda Rahas B. , Patel N. , Sinha B. K. 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) using Ce(IV) as initiator in aqueous nitric acid solution in the presence of sodium lauryl sulphate (NaLS) has been studied kinetically at a temperature range of 25–35°C. The rate of polymerization (Rp) increases with increasing concentration of NaLS, and it was also proportional to [MMA]2; but, in the presence of NaLS, the change of Rp with respect to [Ce(IV)] and [H+] were not linear and similarly the rate of Ce(IV) disappearance was not proportional to its original concentration. The overall activation energy of the polymerization process in presence of 0.01M NaLS was found to decrease by ∼ 7.0 kcal mol−1. The monomer–micelle association constant has been calculated to be 5.135 × 104 mol−1 L. The polymer obtained in surfactant medium is sparingly soluble in benzene and DMSO. From infrared spectra clear evidence of vinyl polymerization was obtained.
Memory effects in polymers. I. Orientational memory in the molten state; its relationship to polymer structure and influence on recrystallization rate and morphology
Authors: Khanna Y. P. , Reimschuessel A. C. 
Published: April 2003

AbstractThe influence of polymer structure on the orientational memory in the molten state has been studied by observing the crystallization behavior of the molten polymer through differential scanning calorimetry. It is shown that polymers with strong intermolecular forces (e.g., H‐bonding) retain the orientation memory even at temperatures above their equilibrium melting temperatures. The retained orientation memory of the polymer melt is shown to influence its recrystallization rate and the morphology.
Polymerization and crystallization behavior of a LaRC‐TPI powder
Authors: Hou T. H. , Bai J. M. , St. Clair T. L. 
Published: April 2003

AbstractThe crystallization and polymerization behavior of a crystalline LaRC‐TPI powder at elevated temperatures have been studied. The characterization methods include differential scanning calorimetry and the measurements of inherent viscosity, ηinh, and viscoelastic properties of the fully imidized samples. The as‐Received material possesses an initial crystal melting peak temperature of 272°C. For the material annealed at temperatures below 320°C, a semicrystalline polymer can be obtained. On the other hand, a purely amorphous structure is realized in the samples annealed at temperatures above 320°C. Isothermal crystallization kinetics are studied by means of the simple. Avrami equation. The likely nucleation path is attributed as an intermolecular oligomer nucleation type. The isothermal polymerization behavior is quantified by inherent viscosity measurements. A single cure is found to correlate values of Tg and ηinh for samples experiencing different thermal histories. Fully imidized amorphous and semicrystalline LaRC‐TPI samples are successfully molded based on the information obtained from thermal analyses. The viscoelastic properties of these samples are also reported.
A constitutive equation for creep in polymer concretes and their resin binders
Authors: Dharmarajan N. , Kumar S. , Armeniades C. D. 
Published: April 2003

AbstractWe present here a method for superposing creep measurements on polymer concrete (PC), taken at different temperatures, imposed stresses, and resin contents, onto master curves, which describe the respective responses of various PC systems and their resin binders, to compressive, tensile, and flexural loads. This treatment is extended to systems reinforced with chopped glass fiber and montmorillonite (MMT). The general applicability of this superposition is tested with creep measurements by other investigators under tensile, compressive, and flexural loads. The results make it possible to predict the long‐term creep behavior of unfilled as well as reinforced glassy polymer systems at different temperatures and load conditions from limited, short‐term data. Success of the multiple superposition suggests a generalized constitutive equation, which describes the creep compliance of these systems as a product of separable functions of each parameter in the form of shift factors for temperature (αT), stress (ασ), resin content (αυ), fiber reinforcement (αF), and MMT reinforcement (αM): J(PC) = JrαTασαυαFαMtm, where Jr is an appropriately chosen reference creep compliance. The time exponent m does not depend on the chemical nature of the polymer matrix.
Polyamide–polyurethane interpenetrating polymer networks prepared by synthesis in the melt
Authors: Decurtins S. , Hourston D. J. 
Published: April 2003

AbstractTwo types of interpenetrating polymer networks based on polyamide (nylon 12) and a polyurethane formed in the polyamide melt were prepared. The first type (A), which could be regarded as a semi‐2‐IPN, consisted of a polyurethane component crosslinked with trimethylolpropane whereas for the second type (B), which would meet the definition of a thermoplastic IPN, the polyurethane component was chain‐extended with butane‐1,4‐diol only. The phase morphologies of these IPNs were investigated using electron microscopy, dynamic mechanical analysis, tensile testing, and sonic velocity measurements. Electron micrographs were compared by using the conventional TEM technique and a Robinson‐type backscattered electron detector in combination with a SEM. It was concluded that the materials are phase separated, but with a fine continuous‐dispersed phase structure. For a 44 wt % polyurethane IPN a cocontinuous phase structure with a subcellular texture was indicated. One physically blended sample was compared with the analogous IPN‐type sample.
Study on the effect of dibenzylidene sorbitol as a nucleating agent on the crystallization and morphology of poly(ethylene terephthalate)
Authors: Mitra Debaprasad , Misra Ashok 
Published: April 2003

AbstractThe effect of dibenzylidene sorbitol (DBS) as a nucleating agent on the crystallization of poly(ethylene terephthalate) (PET) has been studied. It has been found that DBS, when incorporated into the polyester, at a 0.5–1.0 wt % level, significantly lowers the induction period and reduces the half‐time of crystallization. Thermal studies clearly show that the addition of DBS results in decreasing the temperature of crystallization, Tch, when heated from the glassy state as well as increasing the temperature of crystallization, Tcc, when cooled from the melt. Maximum spherulitic radius at 110°C has been determined for pure and nucleated PET. The spherulitic size has been found to decrease slightly with the increase in the level of DBS. Optical transmittance measurements reveal that PET containing 0.5–0.7 wt % of DBS gives the best clarity, and, beyond this level of DBS, the clarity decreases. This is probably due to the formation of agglomerates of DBS which in turn scatter visible light, thus making the film appear more hazy.
Polymer thin film integrated optics: Fabrication and characterization of polystyrene waveguides
Authors: Ives J. T. , Reichert W. M. 
Published: April 2003

AbstractThe fabrication and characterization of 1–3 μm polystyrene thin film integrated optical (IO) waveguides is presented. The polymer films were spun‐cast onto quartz and glass microscope slides, yielding waveguides of varying quality. The majority of defects in the polymer films appeared to be introduced during the curing process. Laser light (488 nm) was coupled into the polymer films using the prism coupling technique. The collected Raman emission was used to characterize physical and light guiding properties of acceptable polymer films. The Raman intensity spectra collected as a function of the coupling angle supplied data for the calculation of polymer film thickness and refractive index as well as providing general measure of waveguide suitability. The intensity loss due to scatter of several waveguides was also determined to rigorously evaluate waveguide quality.
Toughened mica‐filled polypropylene systems
Authors: Faulkner Douglas L. 
Published: April 2003

AbstractA family of rubber‐toughened, mica‐filled polypropylene materials was developed. The rubber modifier used was an ethylene‐propylene‐diene monomer (EPDM) compound. A unique feature of this rubber‐modified system is that it can be directly molded from a dry blend. This simplifies processing by eliminating the need for melt compounding which, in turn, contributes to greater flexural moduli since attrition of the mica platelets is reduced. In addition, impact measurements were conducted as a function of temperature for EPDM/polypropylene and EPM D/poly(propylene‐ethylene) copolymer blends. The low temperature impact resistance was improved for both systems; however, the modified copolymer system maintained ductile behavior to a far lower temperature than the corresponding homopolymer system.
Molecular weight distribution control in a semibatch living‐anionic polymerization. II. Experimental study
Authors: Alassia L. M. , Couso D. A. , Meira G. R. 
Published: April 2003

AbstractThis work constitutes an indirect verification of a theoretical method that allows the production of polymers with prespecified molecular weight distributions (MWDs), through semibatch living‐anionic homopolymerizations. The chemical system consisted of styrene with sec‐butyllithium, in a solvent mixture of cyclohexane and tetrahydrofurane (THF). The necessary flow profiles were applied by a pair of computer‐controlled pumps, and the produced MWDs were measured by size exclusion chromatography, with correction for nonuniform instrumental spreading. The main difficulty was the estimation of the initial moles of initiator and of the concentration of impurities in the monomer solution. For such estimation, a precalibration experiment was implemented.
Water sorption, membrane potentials, and ion permeability of styrene‐grafted Bombyx mori silk fibroin membrane
Authors: Demura Makoto , Kitamura Aio , Shibamoto Akio , Asakura Tetsuo 
Published: April 2003

AbstractCharacterization of styrene‐grafted Bombyx mori silk fibroin membrance was investigated. It was revealed from the water sorption and 1H nuclear magnetic resonance (NMR) measurements that the amounts of water adsorbed on the silk fibroin membranes decreased by the styrene grafting and the states of water adsorbed on the styrene‐grafted silk fibroin membranes were not homogeneous; the presence of two components of water adsorbed on the membranes at 60% relative humidity was observed. In addition, the fraction of the fast component decreased with increasing styrene grafting. The membrane potentials increased with increasing of the grafting. The KCl permeability of the membrane strongly depends on the degree of styrene grafting.
Modified wheat flour–natural rubber blends. II
Authors: Hota Arun K. , Maiti Mrinal M. 
Published: April 2003

AbstractEffect of cyanoethylation of starch on the properties of starch xanthide–NR vulcanizates has been studied. Significant improvements in compounding, tensile modulus, tensile strength, and retention of wet strength of the vulcanizates have been recorded. Equilibrium swelling of vulcanizates by water is also greatly suppressed. The role of cyanoethylation of starch in imparting such specific effects has been analyzed in the light of the polarity of the cyanoethyl group and its effect in lowering the critical yield stress of the modified starch for efficient dispersive mixing in NR matrix.
Viscosity and molecular weight distribution of ultrahigh molecular weight polyethylene using a high temperature low shear rate rotational viscometer
Authors: Wagner H. L. , Dillon J. G. 
Published: April 2003

AbstractTo obtain accurate measurements of the limiting viscosity number (LVN) or the intrinsic viscosity [η] of solutions of ultrahigh molecular weight polyethylene (UHMWPE), a low shear floating‐rotor viscometer of the Zimm‐Crothers type was constructed to measure viscosities at elevated temperatures (135°C) and near zero shear rate. The zero shear rate measurements for UHMWPE whole polymer and UHMWPE fractionated by hydrodynamic crystallization were compared with viscosity measurements at moderate and high shear rates (up to 2000s−1) carried out in a capillary viscometer. The limiting viscosity number of UHMWPE decreases, as expected, with shear rate. The higher shear rate data could not be extrapolated to yield the correct zero‐shear rate viscosities. Fractionation of UHMWPE gave 10 fractions ranging in LVN from 9 to 50 dL/g. A tentative integral molecular weight distribution for the whole polymer was calculated on the basis of the Mark‐Houwink equation, but because it had been previously established only for lower molecular weight polyethylenes, it may not be accurate. A correlation was found between the LVNs for the fractions in the two types of viscometers.
Macromolecular complexes consisting of poly(aluminum chloride), [2‐(diethylamino)ethyl]dextran hydrochloride, and potassium poly(vinyl sulfate)
Authors: Kikuchi Yasuo , Kubota Naoji 
Published: April 2003

AbstractThe mixture of poly(aluminum chloride) (PAC) and [2‐(diethylamino)ethyl]dextran hydrochloride (EA) were allowed to react with potassium poly(vinyl sulfate) (PVSK) to form many different water‐insoluble macromolecular complexes (MCs) in aqueous solution at various hydrogen ion concentrations. According to elemental analyses, IR spectroscopy, and solubilities of MCs, molecular structures of each MC depend on [H+]. It is suggested that the MCs obtained at pH 1.0 are products consisting of EA, PVSK, and aluminum aquo‐complex having coordination water whereas the MCs at pH 4.0 are higher molecular products consisting of EA, PVSK, and basic aluminum maltidentate complex. This result is attributable to change with [H+] in the degree of dissociation and conformation of EA, PVSK, and the dissociation of hydrated coordination of PAC. MC membranes were made by casting solutions of all kinds of MCs, and active, selective transport phenomena through a membrane of the MC prepared in a solution of pH 1.0 HCl were investigated under various conditions. Transport ratio of Na+ and the electric potential difference between the left and right sides of the membrane were measured, with a result that the higher value the membrane potential difference was long allowed to maintain, the higher the transport ratio became. According to this result, the driving force of transport is dependent on the membrane potential, Donnan potential, and diffusion potential, between both sides of the membrane. The Cl− exclusion (Donnan exclusion), however, is small due to the small cation‐exchange capacity, so that the membrane potential difference is caused to decrease rather rapidly by Cl− permeation. It was also suggested that the affinity of the carrier and both the chemical and physical properties of the MC membrane controlled the selective transport through the membrane.
Modeling of butadiene polymerization using cobalt octoate/DEAC/water catalyst
Authors: Estrada J. M. Vela , Hsu C. C. , Bacon D. W. 
Published: April 2003

AbstractTwo‐level fractional factorial designs were employed to study the solution polymerization of butadiene in a batch reactor using cobalt octoate/DEAC/water as catalyst. Conversion and molecular weight data obtained as functions of time were used to develop a kinetic model, and the estimated kinetic parameters were correlated empirically with four operating variables: temperature and concentrations of cobalt octoate, DEAC, and water. The experimental data indicate that at high water concentration a significant amount of oligomers is formed during early stages of polymerization, and the molecular weight of polymer increases with time. Analysis of the data suggests instantaneous initiation, first order propagation with cobalt and monomer, and transfer to monomer. Models which do not take account of the branching are shown to be incapable of fitting data for both Mn and Mw. The catalyst decay seems to follow a first‐order mechanism, but the evidence is somewhat inconclusive.
Solute diffusion in swollen membranes. IX. Scaling laws for solute diffusion in gels
Authors: Lustig Steven R. , Peppas Nikolaos A. 
Published: April 2003

AbstractA scaling law was developed for the diffusion coefficient of spheroidal and ellipsoidal solutes in nonporous, equilibrium‐swollen hydrogels. The law relates the solute diffusion coefficient to the solute size, the gel mesh size, and the gel equilibrium volume degree of swelling. The law was verified by appropriate data of low and high molecular weight solute diffusion through hydrogels such as swollen networks of poly(vinyl alcohol), poly(2‐hydroxyethyl methacrylate), cellulose, and others. An additional scaling law was developed which relates the rate of release of a small or large molecule from an equilibrium swollen hydrogel with time and with morphological characteristics of the polymeric network.
Thermal and dynamic mechanical properties of hydroxypropyl cellulose films
Authors: Rials Timothy G. , Glasser Wolfgang G. 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were used to characterize the morphology of solvent cast hydroxypropyl cellulose (HPC) films. DSC results were indicative of a semicrystalline material with a melt at 220°C and a glass transition at 19°C (T1), although an additional event was suggested by a baseline inflection at about 80°C (T2). Corresponding relaxations were found by DMTA. A secondary relaxation at −55°C was attributed to the interaction between hydroxyl groups of the polymer and residual diluent. The tan δ peak at T2 was found to arise from an organized phase, presumably from a liquid‐crystal mesophase formed while in solution. Crosslinking with a diisocyanate increased the peak temperature of the two primary relaxations, and resulted in a more clearly defined peak for the T2 transition. From this behavior it was concluded that both T1 and T2 are similar to glass transitions (Tg's) associated with an amorphous component and a more highly ordered phase (due to a residual liquid crystal superstructure) in the HPC bulk.