bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemorheological studies on polymer degradation
Authors: Murakami Kenkichi , Takasugi Sumio 
Published: April 2003

AbstractThe degradation of dicumyl peroxide‐cured natural rubber was studied by the stress relaxation method. Experiments were carried out in air, in nitrogen, and by irradiation of UV light in the temperature range of 30–200°C. We attempted to divide factors of the degradation into two parts: that caused by heat and that by light, and to study the respective degradation quantitatively. The degradation caused by UV light in nitrogen was almost independent of temperature. However, the degradation caused by UV light in air increased with temperature and the rate of degradation caused by the interaction between light and oxygen was greater at high temperature than at low temperature. It was found that scission along main chains occurs for dicumyl peroxide‐cured natural rubber by photo‐oxidation as well as thermal oxidation.
Gel permeation chromatography in the study of the molecular weight distribution of the copolymer vinyl chloride–vinyl acetate
Authors: Janča J. , Kolínský M. 
Published: April 2003

AbstractA sample of the commercial copolymer vinyl chloride–vinyl acetate was fractionated by the GPC method in the preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, GPC in the analytical scale, chemical analysis, and IR spectroscopy. They were compared with those obtained by precipitation fractionation. The M̄w and [η] values from the light scattering and viscometry of fractions of the commercial copolymer were employed for the calculation of the Mark‐Houwink equation valid in THF at 25°C for a copolymer with vinyl acetate content of 10–13%. Universal calibration of the [η]·M type was confirmed experimentally for the above polymer. Effects which could change the correct interpretation of the GPC data were discussed in detail. Correct interpretation of the GPC data showed an agreement between the GPC, light scattering, and viscometric data within 6–7%.
Cationic polymerization of β‐pinene and styrene
Authors: Snyder Charles , McIver William , Sheffer Howard 
Published: April 2003

AbstractThe yield, composition, and molecular weight of homopolymers and copolymers of β‐pinene and styrene are described as a function of the feed, temperature, and solvent. Fractionation, gel permeation chromatography, and nuclear magnetic resonance spectroscopy of GPC fractions are used as analytical tools to present evidence for copolymerization in methylene dichloride. Additional support for copolymerization is obtained from the relation of polymer composition to percent conversion. The reduction of molecular weights of homopolymers by aromatic solvents was investigated.
Filler structure and tensile properties of starch xanthide‐reinforced vulcanizates
Authors: Dennenberg R. J. , Buchanan R. A. , Bagley E. B. 
Published: April 2003

AbstractStress–strain behavior of some starch xanthide‐ and carbon black‐reinforced styrene–butadiene elastomers was investigated as a function of filler particle size and structure. In starch xanthide systems, low strain behavior is sensitive to particle structure; high strain behavior, to particle size. Electron photomicrographs of the several starch xanthide‐reinforced vulcanizates were analyzed with reference to filler particle size and structure. These parameters were then correlated with Mooney plots of [load/λ − λ−2] versus λ−1, where λ is the strain ratio. Plots of samples containing highly structured filler particles were highly nonlinear, rising steeply as λ−1 approached unity. Samples containing nonstructured filler particles were also highly nonlinear, rising steeply as λ−1 decreased to approximately 0.4. A preliminary study of the dynamic properties of these samples, as determined in an eccentric rotating‐disk rheometer, provided little additional information.
Effect of glass reinforcement on burning rates of poly(methyl methacrylate) composite candles
Authors: Barlow Joel W. 
Published: April 2003

AbstractBurning rates of glass‐reinforced poly(methyl methacrylate) candles were measured under limiting conditions using an oxygen index apparatus modified to allow weighing of the candle as it burns. The limiting oxygen index was found to increase slightly with increasing concentration of glass in the candle for all samples tested. Burning rates were found to be a function of both glass concentration and orientation with respect to the propagating flame front. The burning rates of candles constructed from randomly oriented glass mats were found to increase with mat concentration by a factor of nearly 3 as mat content was increased to 70% by volume. The burning rates of candles constructed with unidirectionally oriented fibers, parallel to the flame propagation direction, were found to decrease by a factor of 2 as the glass concentration increased to 40% by volume. Erratic burning rates were observed for candles constructed with oriented fibers perpendicular to the flame propagation direction. These results are correlated by extension of existing thermally thin flame spread theories through consideration of composite solid‐state energetics and the relative tendencies of the glass reinforcements to act as wicks for supplying the flame with degraded polymer liquid.
Graft polymerization of styrene onto starch by simultaneous cobalt‐60 irradiation
Authors: Fanta George F. , Burr Robert C. , Doane W. M. , Russell C. R. 
Published: April 2003

AbstractStarch‐g‐polystyrene copolymers have been prepared by the simultaneous 60Co‐irradiation of starch–styrene mixtures, and copolymers have been characterized with respect to weight per cent polystyrene (% add‐on) and also the molecular weight and molecular weight distribution of polystyrene grafts. In a typical polymerization, 4 g each of starch and styrene were blended with 1 ml water and 1.5 ml of an organic solvent; the resulting semisolid paste was irradiated to a total dose of 1 Mrad. With ethylene glycol, acetonitrile, ethanol, methanol, acetone, and dimethylformamide as the organic solvent, values for % add‐on ranged from 24% to 29%. The highest % add‐on (43%) and the highest conversion of styrene to grafted polymer (76%) were obtained when the organic solvent was omitted, and water alone was used. When water was also omitted, polymerization of styrene was negligible; however, graft copolymer was formed in the absence of water when either ethylene glycol or ethanol was added. Attempts were unsuccessful to achieve a % add‐on greater than 43% by doubling the amount of styrene in the polymerization recipe. Mixtures of equal weights of starch and styrene are relatively nonvicious, but these mixtures thicken when either water or ethylene glycol is blended in. Reasons for this thickening action and the possible influence of thickening on the graft polymerization reaction were explored.
Chemical modification of wool in aprotic swelling media
Authors: Koenig N. H. 
Published: April 2003

AbstractA limited number of polar, nonhydroxylic organic liquids are suitable swelling media for chemical modification of wool. An effective medium for acylating‐type internal modification should have low molecular weight, should lack active hydrogen atoms, be highly polar, swell wool fibers, have a high boiling point, and exert a catalytic effect. Rates of modification by phenyl isocyanate, myristoyl chloride, and dodecenylsuccinic anhydride in different media decrease in the order dimethyl sulfoxide > dimethylformamide > 1‐methyl‐2‐pyrrolidinone > 4‐butyrolactone. Nevertheless, equal maximum uptake of a given reagent in these varied media is evidence of internal chemical modification. Further examples of modifying reagents are phenyl isothiocyanate, benzyl chlorides, and α‐haloketones. Supercontraction and single‐fiber stress‐strain data indicate crosslinking by bifunctional isocyanates and acid chlorides.
Diffusion of radioactively tagged penetrants through random and block styrene–butadiene copolymers and filled cis‐polybutadiene
Authors: Rhee Chong‐Kon , Ferry John D. 
Published: April 2003

AbstractThe diffusion of radioactively tagged n‐hexadecane in trace amounts has been studied in 22 random styrene–butadiene (SBR) copolymers with different styrene contents and butadiene microstructures; in several SBR block copolymers with different average block lengths (also diffusion of tagged 1,1‐diphenyl ethane); in a triblock SBR copolymer cast from different solvents and also molded at elevated temperature; and in cis‐polybutadiene filled to different extents with carbon black, calcium carbonate, and microglass spheres. The diffusion coefficient in random SBR copolymers decreased with increasing content of styrene and/or vinyl configuration and could be correlated with fractional free volume on the basis of linear additivity of the cis, trans, vinyl, and styrene moieties. In SBR block copolymers, the diffusion coefficient increased with increasing average block sequence length. For the triblock copolymer, the diffusion coefficient was approximately the same for samples molded or cast from solvents which are good for polybutadiene, but was far smaller for a sample cast from ethyl acetate, in which the polystyrene domains are probably lamellar. The effect of fillers on diffusion in cis‐polybutadiene was compared with calculations on the basis of several theoretical models.
The xanthate method of grafting. V. Graftability of mechanical pulp
Authors: Hornof V. , Kokta B. V. , Valade J. L. 
Published: April 2003

AbstractSoftwood mechanical pulp was copolymerized with acrylonitrile using the xanthate redox grafting process. Experiments carried out under different reaction conditions (temperature, H2O2, concentration, pH, reaction time) showed that mechanical pulp is less apt to form graft copolymers than chemical pulps. In most cases, long inhibition periods were observed, and the product formed thereafter contained large quantities of homopolymer. It was not possible to raise grafting efficiency by increasing the concentration of hydrogen peroxide. A series of experiments with pulps having different particle size showed a moderate increase in total conversation to polymer with decreasing mean fiber length. The latter, however, produced little influence on the copolymer/homopolymer ratio.
Studies on melt spinning. VII. Elongational viscosity and fiber morphology of multiphase polymer systems
Authors: Kim Young Woo , Han Chang Dae 
Published: April 2003

AbstractMelt spinning experiments were carried out to investigate the elongational behavior and fiber morphology of multiphase polymer systems. Materials chosen for study were blends of calcium carbonate‐filled polypropylene with general‐purpose polystyrene and blends of calcium carbonate‐filled polypropylene with high‐impact polystyrene. The former is a three‐phase system in which the CaCO3 particles are dispersed, and the latter is a four‐phase system in which CaCO3 particles are dispersed, together with rubbery butadiene particles. Note that polypropylene is incompatible with the matrix of high‐impact polystyrene. The experimental technique described in part I of this series was used to determine the elongational viscosity. With the four‐phase system, the apparent elongational viscosity tends to increase as the stretch ratio is increased above a certain critical value which appears to be ca. 25. This transition does not occur with the three‐phase system and is attributable to elongation of the suspended rubber particles. The addition of small amounts of HIPS to PP‐CaCO3 increases spinnability in general, whereas larger amounts decrease spinnability.
Melting and glass transition of radiation‐induced graft polyethylene
Authors: Toi Keio , Kikuchi Midori , Tokuda Taneki 
Published: April 2003

AbstractMelting and glass transition data are reported employing DSC for styrene‐grafted high‐density polyethylene obtained by γ radiation. Judging from the data of the melting point and the heat of fusion, the grafted polystyrene had no effect on the polyethylene crystallites, but the half‐width of the thermogram was observed to increase slightly, showing an effect on the crystallite size distribution. As no effect was observed on the glass transition temperature by grafting, the amorphous region of the polyethylene apparently was not affected. It is suggested, therefore, that the free volume or segmental mobility will not be decreased by radiation‐induced grafting. Very few but long grafted chains had negligible effect on the average polyethylene chain length available for segmental motion, and grafted polystyrene should be expected to differ little from the styrene homopolymer in thermal motions.
Dynamic deposition of polyacids on porous membrane supports
Authors: Ozari Y. , Tanny G. , Jagur‐Grodzinski J. 
Published: April 2003

AbstractPoly(acrylic acids), poly(styrenesulfonic acid), and their block and random copolymers were tested for their ability to form dynamic membranes on partially cured asymmetric cellulose acetate. Chemically modified porous polypropylene (Celgard) was also used as a support for poly(acrylic acid). Salt rejections, water fluxes, and streaming potentials of membranes were tested under hyperfiltration conditions. Sorption of the polyelectrolytes by the cellulose acetate supports was studied using spectrophotometric, 22Na tracer, and electron microscopy techniques. The dynamic membrane formation was noted only for poly(acrylic acid) and for its 1:4:1 block copolymer with poly(styrenesulfonic acid). The uneffectiveness of other polyelectrolytes was discussed in terms of a negative zeta potential of cellulose acetate. The increase in salt rejection (R) due to the polyelectrolyte is strongly dependent on the initial Ri of the support. Sharp maxima in the ΔR ‐versus‐Ri curves have been noted for Ri in the range of 40–55%. The most significant improvement in the hyperfiltration characteristics of cellulose acetate was attained with the 1:4:1 block copolymer. Flux of 17 gfd at 350 psi and R = 93% was obtained in short‐term tests for a 0.1N feed solution. Long‐term tests did not reveal any flux or salt rejection decline for membranes in which poly(acrylic acid) was complexed with phosphoramidic groups grafted onto Celgard.
Carbon‐13 NMR of hydroxyethylcellulose: An accurate method for structural determination
Authors: DeMember John R. , Taylor Lloyd D. , Trummer Steven , Rubin Leon E. , Chiklis Charles K. 
Published: April 2003

AbstractThe high‐resolution carbon‐13 NMR spectrum of hydroxyethylcellulose (HEC) with about 2.5 moles of ethylene oxide (MS 2.5) average substitution per anhydroglucose ring (AHG) is presented. From models, the CMR chemical shifts for all of the different carbon atoms are assigned. Direct measurement of the relative intensities of the CMR signals for certain carbon atoms in HEC permits rapid and accurate computation of (1) the average chain length of poly(ethylene oxide); (2) the degree of substitution of ethylene oxide, and (3) the average relative degree of substitution of the alcohol groups on the AHG ring.
The influence of molecular weight on the large deformation behavior of SBS triblock copolymer elastomers
Authors: Chen Y.‐D. M. , Cohen R. E. 
Published: April 2003

AbstractEngineering stress–strain properties were determined for two polystyrene–polybutadiene–polystyrene (SBS) triblock copolymer elastomers, one consisting of blocks of molecular weight 7000/43000/7000 and the other, 16000/85000/17000. In addition, various blends of these two materials were prepared in order to vary the number‐average molecular weight of the blocks in a systematic way while maintaining polystyrene content in the range of 25–28 wt %. Samples were solvent cast from benzene or benzene/heptane mixtures and annealed before testing. Ring specimens were extended to rupture at varying strain rates on an Instron tensile tester. Results indicate that number‐average molecular weight has a marked influence on stress–strain behavior over the range of molecular weights and testing conditions employed. The observed behavior is consistent with a systematic increase in the proportion of a mixed interfacial region between the pure polystyrene and polybutadiene domain as molecular weight decreases. The interfacial region contributes to mechanical hystersis, rate sensitivity, and toughness in the SBS materials. Scanning electron photomicrographs of fracture surfaces also showed systematic changes with molecular weight.
Preparation of mercaptoethylated graft fibers for adsorption of heavy metal ions
Authors: Hayakawa Kiyoshi , Yamakita Hiromi 
Published: April 2003

AbstractVarious kinds of mercaptoethylated graft fibers were prepared and the abilities to adsorb the heavy metal ions were studied. 2‐Hydroxyethyl acrylate, 2‐hydroxyethyl methacrylate, and vinyl acetate were graft‐copolymerized by irradiation onto five kinds of synthetic fibers and two kinds of foam polymers. Preirradiation at low temperature was far more effective for grafting than simultaneous irradiation. The mercaptoethylation was carried out in the solution or in the vapor of ethylene sulfide onto the graft fibers treated with alkali. The mercaptoethylated graft fibers showed particular affinity for Hg and Ag ions. A few of the adsorption phenomena were pursued by flow experiment of the ionic solution through a column. The preliminary reduction of the mercaptoethylated graft fibers enhanced the capacity of adsorbing to three times that of the unreduced fibers. Effects of flow rate, pH, temperature, and concentration of Hg ion on the integrated adsorbed amount were also investigated.
The synthesis and evaluation of cyclic olefin sulfone copolymers and terpolymers as electron beam resists
Authors: Gipstein Edward , Moreau Wayne , Chiu George , Need Omar U. 
Published: April 2003

AbstractPoly(cyclopentene sulfone) (PCPS) and poly(bicycloheptene sulfone) (PBCHS) copolymers have been evaluated as potential positive electron beam resists which have good thermal properties and which show high sensitivity to ionizing radiation. It was found that thin copolymer films could be processed as resists but that films greater than 3000 Å thick cracked in the solvents used to dissolve the radiation‐exposed regions. Incorporation of plasticizing additives did not improve the film properties. Films from low molecular weight polymer fractions cracked less in solvents, but higher radiation doses were required to offset the reduced sensitivity. This resulted in the formation of intractable residues in the exposed regions which appear to be crosslinked polymer. Bicycloheptene monomers with specific functional groups did not improve the properties of the copolymer films. Terpolymerization with α‐olefins such as butene‐1 and cis‐2‐butene plasticized these films and reduced their tendency to crack in solvents. Poly(cyclopentene sulfone–co–butene‐1 sulfone) films were found to have the best properties, and 1.25‐μ resist images could be etched in SiO2 layers at an exposure dose of 4 × 10−6 C/cm2 at 25KV. However, one important limitation of this terpolymer was the low dissolution rate ratio between the exposed and unexposed regions. Since straight‐walled relief images are essential to the formation of high‐resolution patterns, the usefulness of this terpolymer as an electron beam resist appears to be hindered by the limited choice of good solvents to maximize the dissolution rate ratio. PBCHS block terpolymers containing methyl methacrylate (MMA) or methacrylic acid (MAA) were synthesized to improve the solubility in solvents and to incorporate the properties of methacrylates. PBCHS–MMA films cracked in solvents after irradiation; PBCHS–MAA polymers were too insoluble to form resist films.
Amylose graft polymers made by 60Co gamma‐irradiation
Authors: Hofreiter B. T. 
Published: April 2003

AbstractModel products were needed to elucidate structure–property relationships in a starch graft polymer research program. Simultaneous irradiation of amylose and acrylamide in oxygen‐free, dilute aqueous solutions gave graft polymers with maximum add‐on of about 16%. The graft polymers were separated from homopolymer and subfractionated by incremental additions of nonsolvent (methyl or ethyl alcohol) to irradiated aqueous reaction media. The graft polymers were fairly homogeneous in graft content. Effects were determined of ratios of monomer to substrate, dose rate, and total dose on yield, graft content, intrinsic viscosity, and homopolymer characteristics. Under some conditions, crosslinks probably formed between graft side chains. Large differences in solution properties of a synthetic mixture of separately irradiated amylose and acrylamide and an irradiated solution of amylose and acrylamide indicated that grafting had occurred. Further evidence for true grafting was based on the action of a selective precipitant, n‐butyl alcohol, on graft polymer solutions.
A new method for torsional pendulum analysis of polymers through the glass transition region
Authors: Fava R. A. , Chaney C. E. 
Published: April 2003

AbstractA freely oscillating torsional pendulum has been used to measure the dynamic‐mechanical loss of polymers through the softening temperature by encapsulating the polymer in a rigid matrix of cured phenolic resin. The method is illustrated with loss curves through the glass transition region of poly(vinyl chloride), polystyrene, a styrene–maleic anhydride copolymer, poly(phenylene oxide), and two binary alloys involving these polymers. The advantages and simplicity of the technique are emphasized.
Fatigue crack retardation in polycarbonate
Authors: Banasiak D. H. , Grandt A. F. , Montulli L. T. 
Published: April 2003

AbstractResults are presented from a recent study of the influence of tensile overloads on fatigue crack growth in polycarbonate. Fatigue cracks were grown under conditions of constant range in stress intensity factor in four‐point bend specimens. The data presented here indicate that tensile overloads may significantly retard subsequent fatigue crack growth in polycarbonate. The period of delay in crack growth was shown to increase with the magnitude of the overload. Recovery of stable crack extension following the overload appeared to involve reinitiation of separate crack growth sites at the tip of the blunted crack tip, similar to the original crack initiation at sharp V‐notches.
Vena contracta suppression in dilute polymer solutions
Authors: Chiou C. S. , Gordon R. J. 
Published: April 2003

AbstractVery small amounts of high molecular weight polymers were found to eliminate vena contracta formation in flow through a circular orifice. This effect was reflected in the decreased efflux time for drainage between two fixed levels in a tank, reductions up to 30% being obtained. Aqueous solutions of seven commercially available polymers were studied, consisting of a poly(acrylic acid), two polyacrylamides of different degrees of hydrolysis, and four poly(ethylene oxides) of widely differing molecular weights. The poly(acrylic acid) and two highest molecular weight poly(ethylene oxides) each caused a sudden drop in efflux time at a “critical concentration”, which was 2, 50, and 90 wppm, respectively, for these three polymers. An explanation of this phenomenon in terms of the high Deborah number flow field existing near the orifice edge is advanced. In the case of the polyacrylamide solutions, a very gradual reduction in efflux time with increasing polymer concentration was observed, beginning at about 3 wppm. Coincident with this was the formation of a wine‐glass stem or converging flow field upstream of the orifice. Such a flow field was not observed for the other solutions. It is suggested that vena contracta inhibition with polyacrylamide is simply a manifestation of solution die swell. The reason for the differing efflux time behavior between the various polymers is not known and represents a challenging problem for further study.