bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical and physical investigation of alkyd resin in the course of its preparation. I. Determination of composition of reaction mixture using volatile monocarboxylic acid for alkyd synthesis
Authors: Kaštánek Alois , Hájek Karel , Dufka Oldřich 
Published: April 2003

AbstractThe extent of esterification between isocaprylic acid, phthalic anhydride, glycerol, and pentaerythritol was followed by analysis of reaction mixture. Acid numbers, hydroxyl numbers, and saponification numbers of alkyd samples were determined at different stages of the reaction. A way of calculation of the losses of volatile monomer reactants from liquid reaction mixture was proposed. The amounts of condensed water experimentally measured during alkyd synthesis correspond to the amounts of water losses from the batch that were calculated.
Chemical modification of Kevlar fiber surfaces and of model diamides
Authors: Wu Yulong , Tesoro Guiliana C. 
Published: April 2003

AbstractOrganic reactions of aromatic diamides as models for PPTA fibers have been investigated to select reagents and conditions suitable for surface‐controlled heterogeneous reactions on Kevlar filaments and fabrics. Amine functional groups have been incorporated into fiber surfaces by bromination followed by ammonolysis and by nitration followed by reduction. Modification of filaments has been attained without impairment of fiber properties. Preliminary experiments have also shown that the presence of amino groups on Kevlar fabric can provide remarkably improved peel strength and apparent interlaminar shear strength in epoxy laminates, suggesting a significant role of covalent bonding in improving adhesion in aramidepoxy composites.
Selective transport of inorganic ions along CA membranes
Authors: Yellin N. , Ben‐Dor L. , Zelingher N. 
Published: April 2003

AbstractTransport of inorganic ions along asymmetric cellulose acetate (CA) membrane from aqueous binary systems with a common ion: KCl–NaCl, Na2SO4–CuSO4, K2CrO4–KNO3, KCl–CaCl2, and NaCl–LiCl was studied. The transport proceeds via the support matrix of the membrane and can be measured by the growth of whiskers on its exposed surface and the change of composition of the solution. Differences in the growth rates resulted from differences in transport rates of the various ions. The selectivity of the membrane is attributed to the interaction support matrix–water–ion.
Polymers from renewable sources. IV. Polyurethane elastomers based on myrcene polyols
Authors: Cawse J. L. , Stanford J. L. , Still R. H. 
Published: April 2003

AbstractTwo hydroxy‐functionalized liquid rubbers, one a commercially available polybutadiene (PB) and the other a specially synthesized polymyrcene (PM), have been converted into homopolyurethane elastomers by reaction with 4,&4prime;‐diphenylmethane diisocyanate (MDI). Additionally, PB and PM, each in admixture with various amounts of 1,4‐butane diol, were reacted with MDI to yield two series of segmented copolyurethanes having different hard‐block contents (0–30% w/w). The physical properties of these elastomers have been compared by stress–strain, thermal, and dynamic mechanical analyses, and by swelling experiments. The two series of segmented copolyurethanes have similar morphologies being almost completely phaseseparated and variations in physical properties have been empirically related to hard block contents. The PM‐based elastomers exhibited higher Tg values, ultimate elongations, and larger swelling ratios, but were softer and possessed lower tensile strenghts in comparison with elastomers based on PB. These differences have been related to solfraction contents, the nature and distribution of molecular species present in the parent liquid rubbers and hence to polyol functionalities (f̄n). Analysis of the stress–strain data from the homopolyurethanes using the Mooney–Rivlin expression enabled the relationship between f̄n and elastomer structure to be quantified in terms of the molar mass (M̄c) of the polyurethane network chains forming the soft blocks.
Nitrogen–phosphorous antagonism in flame‐retardant cotton
Authors: Davies D. , Horrocks A. R. 
Published: April 2003

AbstractPhosphorous, as sodium dihydrogen phosphate, and nitrogen, in the form of a urea–for‐maldehyde condensate, were applied to cotton fabric. The flame‐retarding character of each treated fabric was assessed by determining the respective limiting oxygen index. Analysis of the results showed that at the lowest levels of applied phosphorous (P = 2%), the presence of nitrogen produced less than an additive combined flame‐retarding effect. At higher phosphorous levels, this deviation from additivity increased until at P > 6%, the presence of nitrogen antagonized the flame‐retarding effect of the phosphorous. These observations are discussed within the current ideas of nitrogen–phosphorous interaction in flame‐retardant systems, for cotton‐containing fabrics.
Carbon tetrachloride absorption in L‐O‐W‐density polyethylene pellets: Mathematical analysis of concentration profiles
Authors: Gupta J. P. , Sefton M. V. 
Published: April 2003

AbstractConcentration profiles of carbon tetrachloride in low‐density polyethylene pellets were analyzed mathematically to estimate the concentration dependence of the diffusivity. Profiles were measured by electron microprobe analysis and energy dispersive x‐ray spectroscopy (EDAX) and found to be sharper than expected. However, the diffusion front position was proportional to \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt t $\end{document} rather than t as might have been expected if case II diffusion applied. The mathematical model assumed a constant diffusivity behind the diffusion front and zero diffusivity in advance of the front. The resulting moving boundary problem was solved by integral methods, yielding concentration profiles consistent with the essential features of the experimental profiles. The difference in shape between experimental and calculated profiles was attributed to the concentration dependence of the diffusivity, which was estimated by a curve‐fitting procedure. The resulting integral average diffusivity was 1.28 × 10−6cm2/s, four times that estimated assuming standard fickian absorption from the mass uptake curves. This difference was attributed to the inapplicability of the standard relationships to this system in which a discontinuous diffusivity concentration relationship was presumed to apply.
Morphological, structural, and interfacial changes produced in composites on the basis of polypropylene and surface‐treated sepiolite with organic acids II. Thermal properties
Authors: Acosta J. L. , Ojeda M. C. , Morales E. , Linares A. 
Published: April 2003

AbstractHeat capacity and thermal expansion measurements in composites have been relatively little used as research procedures. In recent times, however, they are beginning to be increasingly utilized in morphological studies. This motivated the application of both techniques to composites on the basis of polypropylene and sepiolite that had been surface treated with linear organic acids. Assessment of our results allows for the interference that the incorporation of these sepiolites produces important structural changes in the polypropylene containing them. These changes can be explained by the complex interface (mesophase) theory.
The preparation and properties of vinyl cellulose
Authors: Träskman B. , Tammela V. 
Published: April 2003

AbstractThe vinylation of cellulose by acetylene under alkaline conditions was optimized with respect to both DS and DP. Shortening the reaction time reduced the harmful alkaline depolymerization of cellulose during the reaction and gave products with higher DP values. Thus cellulose, activated by KOH, was vinylated for 180 min at 431K and 5.5 MPa to yield 72.1% of a product with DS 1.46 and DPw 175. Results of vinyl cellulose analysis by new and old methods were in good agreement with each other. Trimethylsilylated vinyl cellulose was prepared for proton NMR and GPC measurements. It was found that vinyl cellulose slowly loses its vinyl groups when stored in light and air.
Sorption of carbon tetrachloride in low‐density polyethylene pellets
Authors: Gupta J. P. , Sefton Michael V. 
Published: April 2003

AbstractUnsteady‐state conjugate sorption curves for carbon tetrachloride in low‐density polyethylene (LDPE) pellets at temperatures between 40 and 70°C suggested there was a maximum in the diffusivity‐concentration relationship at high values of concentration. The sorption curve at 70°C also displayed features characteristic of pseudofickian behavior, which was attributed to clustering of the penetrant at the high vapor acitivity corresponding to this temperature.
Polymerization of olefines through heterogeneous catalysis IV. Modeling of heat and mass transfer resistance in the polymer particle boundary layer
Authors: Floyd S. , Choi K. Y. , Taylor T. W. , Ray W. H. 
Published: April 2003

AbstractPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. External boundary layer heat and mass transfer effects are investigated for various catalysts and operating conditions. For high‐activity catalysts used in slurry, external film mass transfer effects may be significant. For gas‐phase polymerization of propylene or ethylene, the model predicts significant particle overheating at short times, which may explain the particle sticking and agglomeration problems sometimes observed in industrial reactors.
Optical recording by a 823‐nm GaAlAs laser, based on stretched‐polymer birefringence relaxation
Authors: Murthy Parvathi S. , Klingensmith Kenneth A. , Michl Josef 
Published: April 2003

AbstractA ∼5‐μm‐thick stretched sheet of a vinyl chloride–vinyldene chloride copolymer containing a suitable polymethine dye providing an optical density of 1–2 at 823 nm has been used to record ∼3μm‐diameter relaxed spots, produced with pulses of 250 μs or longer from a 5‐mW GaAlAs laser operating at 823 nm. The spots have been observed under polarizing microscope. It is proposed that this demonstrates a principle that could be used for recording and retrieval of information by a laser beam, using a stretched polymer as the storage medium.
Utilizing zero crossover points in the near infrared reflectance analysis of industrial polymers
Authors: Weyer Lois G. 
Published: April 2003

AbstractNear infrared reflectance methods were developed for the analysis of polymer pellets and films. Second derivative spectra were used to minimize the effects of scattering and to enhance spectral features. Zero crossover points, places in the derivative spectra where there is negligible response to concentration changes, were employed to minimize interferences at the measuring wavelengths. Two examples illustrate the utility of this technique for industrial quality assurance analyses. The examples include the measurement of three hydrocarbon polymers, directly in transparent pellets, and the determination of 0.1% MEK in an acrylic film. Precision and accuracy were found to be at least equal to that of other methods, and time savings were considerable.
Prediction of thermoset viscosity using a thermomechanical analyzer
Authors: Tong Ho‐Ming , Appleby‐Hougham Gareth 
Published: April 2003

AbstractA thermomechanical analyzer (TMA) in the parallel‐plate configuration was employed to study the viscosity behavior of an unfilled, FR‐4 type epoxy resin by monitoring its thickness change with time under a constant compressive force at various temperatures. With a dual‐Arrhenius reheology model, we were able to predict viscosities under nonisothermal conditions of high heating rate from more easily obtained isothermal viscosity data. Due to its simplicity and speed, this technique is well suited for investigating resin viscosity behavior during composite lamination in a manufacturing environment.
Reaction engineering aspects of suspension polymerization
Authors: Mikos Antonios G. , Takoudis Christos G. , Peppas Nikolaos A. 
Published: April 2003

AbstractSuspension polymerization is used for the production of polymer particles with diameter in the range of 50–750 μm. The particle size distribution of the particles produced in batch‐suspension polymerization is calculated using a population balance model. Power laws are derived for the average particle size and the standard deviation of the distribution. It is found that both quantities scale to the stable droplet mass of the initial dispersion of the organic phase into the aqueous one, which is a function of the agitation rate and the surface tension.
Kinetics of gelatinization of cornstarch adhesive
Authors: Inoue M. , Lepoutre P. 
Published: April 2003

AbstractIn the manufacture of corrugated board, thermal gelatinization of raw starch granules in the adhesive is essential for bonding setting. Kinetic studies of gelatinization of cornstarch adhesive under conditions simulating those at the corrugator revealed that the rate of advance of the gelatinization front in the starch film was linear with square root of time. A quasiactivation energy of 35.5 kJ/mol was found. The gelatinization process, above the gel point, was controlled by the rate of diffusion of water into the starch granules.
Modeling of melamine formaldehyde polymerization. II. Development of a simpler model
Authors: Gupta Santosh K. 
Published: April 2003

AbstractThe kinetic modeling of melamine–formaldehyde polymerization presents a relatively formidable mathematical challenge because of the simultaneous presence of several types of deviations from Flory's equal reactivity hypothesis. A molecule of melamine has six reactive amide hydrogens, which can react with the CH2OH groups of formaldehyde in solution. The reactivity of the secondary hydrogens on the melamine is about 61% of that of the primary hydrogens (induced asymmetry). There is a shielding effect present, i. e., the reactivity of the hydrogens near the outside of a multiringed polymer molecule is higher than that of the hydrogens inside the coiled molecules. Two bound CH2OH groups on the polymer molecules can self‐condense to give methylene linkages, the reactivity depending upon the location of the two groups. And, to confound modeling effort still further, all these reactions are reversible. An earlier attempt at molding this system considered the reactions between 36 “basic” species. This model was far too detailed and failed to acount for the reverse reactions. In the present study, a simpler model has been proposed which involves fewer “basic” species. An improved model for intramolecular reactions is also developed. Several important characteristics of the polymerization have been obtained as a function of time. Results from this model have been compared with those obtained from the earlier model, and also compared with the short‐time experimental results. The present model can be extended to account for the reverse reactions quite easily.
Compatibility studies of polystyrene–polybutadiene blends by thermal analysis
Authors: Kim Woo‐Nyon , Burns Charles M. 
Published: April 2003

AbstractIn order to examine the behavior of incompatible blends of polystyrene and polybutadiene, the glass transition temperature, the melting point, and the specific heat increment at the glass transition temperature for atactic polystyrene (a‐PS), isotactic polystyrene (i‐PS), polybutadiene (PBD), and blends of a‐PS/PBD and i‐PS/PBD were determined by use of a differential scanning calorimeter. Blends were prepared by solution casting, freeze‐drying, and milling. Weight fractions of polystyrene in the blends ranged from 0.95 to 0.05. The glass transition temperature of polystyrene changed with weight fraction in the blends, and with blending preparation methods; the glass transition temperature of polybutadiene remained essentially unchanged. The specific heat increment at the glass transition temperature of PBD decreases linearly with increasing proportions of PS in the PS/PBD blend for the broad and narrow molecular weight distribution polybutadience polymers, whereas the specific heat increment for PS did not decrease with increasing proportions of PBD in the PS/PBD blend. These results suggest that the polybutadiene dissolves more in the polystyrene phase than does the polystyrene in the polybutadiene phase.
Intrinsic birefringence of amorphous poly(bisphenol‐A carbonate)
Authors: Wu Maan‐Shii S. 
Published: April 2003

AbstractThe birefringence of uniaxially oriented poly(bisphenol‐A carbonate) (PC) samples stretched over a wide range of temperatures has been measured accurately with a combination of the compensator and the wedge methods. The Hermans' orientation function of anisotropic PC was calculated from the measured dichroic ratio of the infrared absorption band at 1364 cm‐1. Measurements using differential scanning calorimetry, X‐ray diffraction, or infrared spectroscopy indicated no stress‐induced crystallinity in stretched amorphous PC. At each state having a defined molecular orientation, samples stretched below the glass transition temperature (Tg) always exhibited excess birefringence and slightly higher density. This phenomenon is attributed to bond distortion during stretching, a result of the suppression of large‐scale segmental motions of polymer chains below the Tg. The birefringence of samples stretched above the Tg arises exclusively from the orientation effect as a result of greater chain mobility. These measured birefringence values are proportional to Hermans' orientation functions, yielding a linear relationship which allows precise determination of the intrinsic birefringence of amorphous PC as 0.192 ± 0.006.
Exposure of cross‐linked epoxy resins to the space environment
Authors: Garton A. , McLean P. D. , Wiebe W. , Densley R. J. 
Published: April 2003

AbstractTwo specimens of cross‐linked epoxy resins were attached to the Remote Manipulator Arm (“Canadarm”) of the space shuttle and exposed to the space environment (about 225 km altitude) experienced on the 41‐G shuttle mission. Portions of the specimens which had been coated with 10 nm of inconel, then gold, were relatively unaffected by space exposure, while the uncoated areas were eroded to a depth of about 5 μm. The eroded surfaces had a porous texture, consisting of tunnel‐like features extending a further 10 μm below the surface, with a hole density of 3 × 106 holes/mm2. Surface infrared (IR) spectroscopy showed that the first 1–2 μm of porous surface material was little affected chemically by the erosion process, indicating that any chemical erosion must have occurred progressively in a very thin surface layer, which then volatilized away, exposing fresh surface for attack. As a qualitative laboratory simulation, specimens of the same plastics were exposed to low‐pressure air and oxygen plasmas. Somewhat similar surface damage was observed, with no IR‐detectable change in surface chemistry. The criteria for selection of a satisfactory laboratory simulation of the space environment, and the factors responsible for the directionality of the erosion processes are discussed.
Tensile failure of γ‐ray irradiated blends of high‐density polyethylene and natural rubber
Authors: Akhtar Sania , De Prajna P. , De Sadhan K. 
Published: April 2003

AbstractThe effect of 60Co γ‐radiation on the tensile properties of thermoplastic elastomer blends of natural rubber (NR) and high‐density polyethylene (HDPE) has been investigated. The samples were irradiated to absorbed doses ranging from 0.1 to 100 Mrad in air at room temperature (25°C) at a dose rate of 0.21 Mrad/hr. The effect of blend ratio and addition of carbon black (N 330) dicumyl peroxide (DCP) on the radiation resistance of the blends has also been studied. High energy radiation at a high dose rate was found to cause extensive crosslinking in the bulk, which in effect, caused a minima in the ultimate tensile strength in the range of 10–25 Mrad and a continuous decline in the elongation at break in all the blends. Chain scission, on the other hand, was restricted to the surface under the above‐mentioned experimental conditions. This contention was substantiated by the results of irradiation of the samples in a nitrogen environment. Scanning electron microscopy (SEM) studies on the tensile fracture surface morphology of the blends have also been undertaken in order to gain insight to the mechanism of failure.
Transport of direct dye into cellulose membrane
Authors: Yoshida Hiroyuki , Kataoka Takeshi , Nango Mamoru , Ohta Shozo , Kuroki Nobuhiko , Maekawa Masako 
Published: April 2003

AbstractThe dyeing process for a cellulose membrane–direct dye system is analyzed based on a parallel transport mechanism of surface and pore diffusion with Freundlich isotherm. Numerical solutions were obtained in order to clarify how the surface and pore diffusion resistances affect the uptake curve. The numerical solutions were also compared with an analytical solution for surface diffusion control to establish the range where the analytical solution can be considered as an acceptable approximation. The uptake curves in the cellulose membrane‐chromophore (C.I. Direct Yellow 12) system in the presence of inorganic electrolyte were measured. The rate of adsorption and the maximum amount of adsorption increased with an increase in the concentration of those electrolytes. The rate of adsorption was approximately controlled by the surface diffusion rather than by pore diffusion. The surface diffusivities of the dye were little affected by either the concentration and or nature of the electrolyte.
Sorption and transport of inert gases in PVF2/PMMA blends
Authors: Chiou J. S. , Paul D. R. 
Published: April 2003

AbstractSorption and transport of several inert gases (He, Ar, N2, and CH4) in miscible blends of PMMA and PVF2 are reported as a function of pressure at 35°C. For each gas, the permeabilities are independent of pressure for all blend compositions. Sorption isotherms are linear for rubbery compositions (PVF2‐rich) and nonlinear for glassy compositions (PMMA‐rich) as expected. In contrast to CO2, these gases do not plasticize any of these materials. The data are analyzed using appropriate models for sorption and transport, and the parameters are correlated in terms of blend composition and molecular characteristics of the gases. Effects of crystallinity are discussed. Sorption behavior is compared with poly(methyl acrylate) and poly(vinyl acetate).
Short fiber formation during extrusion of polyethylene–sodium lignosulfonate blends
Authors: Albihn P. , Franzén B. , Kubát J. , Rigdahl M. 
Published: April 2003

AbstractWhen extruding a blend of low density polyethylene (LDPE) and a technical grade of sodium lignosulfonate through a capillary it was observed that LDPE formed fibers in a matrix of the lignosulfonate. With short capillaries and low shear rates, short fibers of LDPE with lengths between 0.5 and 5 mm and with diameters in the range 2–20 μm can be produced. Since sodium lignosulphonate is water‐soluble, the LDPE fibers can easily be isolated. Such fibers can be used for synthetic wood pulp or in nonwoven types of applications.
Internal stress of epoxy resin modified with acrylic core‐shell particles prepared by seeded emulsion polymerization
Authors: Nakamura Yoshinobu , Tabata Haruo , Suzuki Hideto , Iko Kazuo , Okubo Masayoshi , Matsumoto Tsunetaka 
Published: April 2003

AbstractIn order to reduce the internal stress in a cured epoxy resin, the submicron polymer particles were dispersed therein prior to curing. For this purpose, four kinds of poly(butyl acrylate), poly(methyl methacrylate) core‐shell particles were prepared by seeded emulsion polymerization for methyl methacrylate with poly(butyl acrylate) seed particles having different particle diameter, and subsequently were powdered by drying at room temperature. It was observed by SEM that poly(butyl acrylate) particles as core were dispersed in the cured epoxy matrix. Poly(methyl methacrylate) as shell seems to dissolve in the matrix. The internal stress of cured epoxy resin decreased with the modification of the particles and the tendency was enhanced with a decreasing in the particle diameter.