bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental analysis of the dynamics, mass transfer, and coagulation in wet spinning of fibers
Authors: White James L. , Hancock Tony A. 
Published: April 2003

AbstractNew models are developed to analyze the wet spinning process. These involve a formulation of simultaneous overall mass, force, and solvent mass transfer balances. In the first‐order model, internal concentration gradients and mass transfer resistance within the fiber are neglected. It is equivalent to the Kase–Matsuo melt spinning model. In the second‐order model, concentration gradients and diffusion within the fiber are included. Comparison is made with an experimental study of wet spinning nylon‐66 fibers. The first‐order model seriously underpredicts final fiber diameter under conditions of specified spinline tension and spinning efflux. The second‐order model gives better agreement between theory and experiment.
Stress relaxation behavior of biaxially oriented poly(ethylene terephthalate)
Authors: Hawthorne James M. 
Published: April 2003

AbstractThe stress relaxation behavior of biaxially oriented semicrystalline poly(ethylene terephthalate) was studied by thermomechanical analysis. Experimental techniques were developed for thin films. Relaxation moduli were measured as a function of stress, time, and temperature. The relaxation modulus was shown to be independent of stress over the range tested. Rate of loss of the relaxation modulus was found to be a nonlinear function of time and temperature up to about 100°C, encompassing the Tg for the polymer. Over the temperature range of 100–120°C it was primarily temperature‐dependent. An empirical time—temperature superposition showed that significant losses in modulus can occur at very short times. At temperatures above the Tg these losses can result in significantly reduced film physical properties.
Effect of tensile strain rate on the mechanical properties of constrained‐uniaxially and simultaneous‐biaxially drawn poly(ethylene terephthalate) sheets
Authors: Yokouchi Mitsuru , Mori Junichiro , Kobayashi Yasuji 
Published: April 2003

AbstractThe dependency of the mechanical properties (Young's modulus, yield strength, breaking strain, and breaking energy) of preoriented poly(ethylene terephthalate) (PET) sheets on the tensile deformation speeds was examined and discussed in relation to changes of density and birefringence. The procedures for preorientation were constrained‐uniaxially (CU) and simultaneous‐biaxially (SB) drawings at 65°C. The performance characteristics of the present tensile testing at room temperature were obtained over a wide range of extension rates (1.7 × 10−4−13.1 m/s = 0.29–2.3 × 104%/s) without changing the mode of deformation and the shape of the test pieces. The CU drawn PET is strain‐rate‐independent and mechanically superior in structure in the preextended direction with draw ratio λ > 2.5. In the SB drawn PET such a structure comes into existence at λ > 3, which has, furthermore, no dependency on draw direction (mechanically isotropic). The draw ratio of the latter case corresponded to the birefringence (−Δn/d) of about 5 × 10−2. These results imply a possibility of producing the strain rate (from low to impact speeds) independent, anisotropy‐free, and mechanically superior molded products of PET if adequate extrusion or blow molding methods which induce multiaxial orientation with −Δn/d > 5 × 10−2 are developed.
Chemistry of miscible polycarbonate–copolyester blends
Authors: Smith W. A. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractBlends of polycarbonate and the copolyester based on 1,4‐cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids are known to be completely miscible. This study was concerned with various chemical events which may occur in this system, particularly during melt processing. Degradation reactions were studied by both TGA and dilute viscometry techniques, and some indications of component interaction were noted. The residual titanium catalyst from the copolyester formation was found to produce color formation by interaction with phenolic end groups in the polycarbonate and to promote interchange reactions. Both events could be suppressed by deactivation of the residual catalyst with appropriate additives. An indication of the extent of interchange reactions was obtained by following the crystallizability of the copolyester component using differential scanning calorimetry.
The effect of moisture on the dielectric relaxations in wood
Authors: Handa Takashi , Fukuoka Masayoshi , Yoshizawa Shuji , Kanamoto Tetsuo 
Published: April 2003

AbstractThe dielectric constant ϵ′ and the loss factor ϵ″ of moistened wood were measured over a wide range of moisture content (MC), 0–40 wt% in the temperature range −196 to 0°C, and in the frequency range 30 Hz to 1 M Hz. Three relaxations were observed depending on the MC and frequency. The first ϵ″ peak at −103°C (30 Hz) in oven‐dried wood is known to be due to the methylol rotation in the amorphous regions. A new ϵ″ peak (second peak), which appeared for MC >0.6 wt% at −110 to −40°C (30Hz) depending on the MC, is assigned to the local mode motions of the complexes between moisture and polar groups in the wood system; it is enhanced as the overall loosening of the initial hydrogen bond network is promoted by the extended hydration due to further sorption of moisture. The peak temperatures and the activation energies for these relaxations changed complexly depending on the MC. At MC > 10 wt%, a novel ϵ″ peak (third peak) was disclosed around −40°C (30 Hz) as a shoulder of the ionic conduction. This novel peak may be attributed to the water frozen in wood on the basis of the peak temperature, relaxation strength vs. MC, the activation energy, and the fact that the peak is not observed for the sorption of various polar organic solvents. This suggests that some of the moisture sorbed by wood may probably exist in a frozen state at low temperatures, even at a MC well below the commonly accepted fiber saturation point.
High‐conversion diffusion‐controlled polymerization of styrene. I
Authors: Marten F. L. , Hamielec A. E. 
Published: April 2003

AbstractA kinetic model based on the free volume theory has been proposed for the polymerization of styrene. The model, which is capable of describing the course of polymerization in both bulk and solution, accounts for diffusion‐controlled termination and propagation and gives a limiting conversion.
Combustion and pyrolysis of poly(ethylene terephthalate). III. The effect of tris(2,3‐dibromopropyl) phosphate on the products of pyrolysis
Authors: Day M. , Parfenov V. , Wiles D. M. 
Published: April 2003

AbstractThe influence of the flame retardant chemical tris(2,3‐dibromopropyl) phosphate, and the related chemical species, tripropyl phosphate and 2,3‐dibromopropanol, on the products of pyrolysis of poly(ethylene terephthalate), has been examined as a function of chemical concentration. The species containing phosphourus only and bromine only had little effect on the composition and concentration of the pyrolysis products. The tris(2,3‐dibromopropyl) phosphate had a significant effect upon the pyrolysis product distribution, and is capable of influencing the decomposition reactions of poly(ethylene terephthalate).
Polyelectrolytes as secondary calibration standards for aqueous size‐exclusion chromatography
Authors: Bose A. , Rollings J. E. , Caruthers J. M. , Okos M. R. , Tsao G. T. 
Published: April 2003

AbstractThe effect of the ionic strength of the solvent on the size‐exclusion chromatography of narrow molecular weight dextrans and monodisperse sodium polystyrene sulfonates has been investigated. In both NaOH and NaCl solutions the elution volume of the sodium polystyrene sulfonates increased as the ionic strength was increased, while the elution volume of the dextrans decreased slightly as the ionic strength was increased. The elution data for various ionic strength solvents could not be described by the traditional universal calibration procedure of plotting the product of the intrinsic viscosity and the molecular weight vs. the elution volume. By using a modified calibration procedure which includes excluded volume effects, the elution data can be described for NaOH solution of moderate and high ionic strength. This modified calibration technique was unable to describe the elution data for very low ionic strength NaOH solutions and for the NaCl solutions. Possible explanations of the inability of straightforward size exclusion chromatographic calibration techniques to quantitatively described all the observed elution behavior are discussed.
Crystallization of crystalline/crystalline blends: Polypropylene/polybutene‐1
Authors: Siegmann Arnon 
Published: April 2003

AbstractThe crystallization, from molten blends, of polypropylene (PP) and polybutene‐1 (PB), two highly crystallizable, polymers, their interaction in the amorphous phase, and the resulting tensile mechanical properties were studied. The crystallization was followed by DSC, showing two separate PP and PB crystallization processes which are affected each by the presence of the other component. The crystallization temperature of PP is significantly affected only in PB rich blends whereas that of PB is affected in the whole composition range. The PP crystalline phase, acting as a nucleating agent, increases the PB crystallization temperature whereas the PP amorphous phase, acting as a high viscosity polymeric diluent, reduces the PB crystallization temperature. The first effect is dominant at low PP content, and the second one becomes increasingly effective with increasing PP content in the blend. The interaction between the two polymers in the amorphous phase was studied by applying dynamic mechanical analysis, in which a single glass transition was observed for the blends and its temperature was found to vary with the blends' composition. Tensile mechanical properties of blends were found to be more sensitive to thermal treatments, such as isothermal crystallization or annealing at elevated temperatures, than single component systems. Such thermal treatments enable better structured blends to be formed, resulting in mechanical properties with no abrupt changes in the whole composition range.
Grafting onto wool. XX. Graft copolymerization of vinyl monomers by use of redox initiators. Comparison of monomer reactivities
Authors: Misra B. N. , Singha A. S. , Sharma R. K. 
Published: April 2003

AbstractMethyl methacrylate (MMA) and ethylacrylate (EA) have been graft copolymerized onto Himachali wool in aqueous medium by using a ferrous ammonium sulfate–hydrogen peroxide (FASH2O2) system as redox initiator. Percentage of grafting has been determined as functions of concentration of monomer, molar ratio of [FAS]/[H2O2], time and temperature. Percentage of grafting is found to depend upon the molar ratio of [FAS]/[H2O2]. An attempt has been made to compare the reactivities of the acceptor monomer (MMA and EA) with that of the donor monomer (VAc) toward grafting onto wool.
Rheological properties of polyethylenes modified with dicumyl peroxide
Authors: Lem Kwok‐Wai , Han Chang Dae 
Published: April 2003

AbstractLow‐ and high‐density polyethylenes were modified using dicumyl peroxide. The modified polyethylenes were subjected to steady and oscillatory shearing flows. The viscous and elastic properties determined with a cone‐and‐plate rheometer are correlated to the molecular weight of the materials, which was determined with the aid of size exclusion chromatographic analysis. It was found that both the melt viscosity and elasticity increase with the amount of dicumyl peroxide used, and shear‐thinning behavior becomes more intense. The Bueche master curve of viscosity is constructed by using a relaxation time based on the weight‐average molecular weight for both virgin and modified resins.
Environmental degradation of some polymer blends. Blends of polystyrene with acrylonitrile butadiene styrene, poly(vinyl chloride), and polybutadiene and blends of polybutadiene with poly(vinyl chloride)
Authors: Kolawole E. G. , Agboola M. O. 
Published: April 2003

AbstractOne class of polymer/additive which has become increasingly important is polymer blends. In this study the ultimate tensile strength, elongation at break, and the modulus of acrylonitrile–butadiene–styrene, poly(vinyl chloride), polybutadiene and polystyrene and their blends have been studied over an entire binary composition range. We have correlated these mechanical properties to their degradation behavior under natural and accelerated weathering by measurement of various indices during thermal and natural weathering. It was found that during natural weathering the presence of polystyrene in acrylonitrile–butadiene–styrene (ABS) improved the weatherability of ABS; the converse was true when the blends were heated in an air oven at 100°C. It was also found that the weatherability of PB was improved in the presence of polystyrene and large improvement in the rigidity was observed. Similarly, from a measurement of carbonyl index, it was found that PVC has a stabilizing effect on PB. In many cases, the 50:50 composition of the polymers gave the best compromise of good mechanical properties, heat stability, and outdoor weathering. The mechanisms of possible interactions between the degrading polymers are discussed.
Mechanical properties of blends containing HDPE and PP
Authors: Bartlett D. W. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractThe mechanical properties of binary blends of high‐density polyethylene and polypropylene are quite good compared to those for blends of some other immiscible pairs. The property relationships observed depend strongly on the process used to fabricate the blends as shown by comparisons of specimens made by injection and compression molding with widely varied cooling rates in the latter. Strength and modulus may show additive behavior or have positive or negative deviations, depending on the process conditions; however, measures of ductility like impact strength or elongation at break always show negative departures from additivity and exhibit minima in some cases. Addition of an appropriate ethylene–propylene elastomer greatly improves the ductility of these blends but with a corresponding decrease in strength and modulus. The presence of weld lines has a serious detrimental effect on mechanical properties of these blends.
Kinetics of emulsion copolymerization. II. Effect of free radical desorption on the rate of emulsion copolymerization of styrene and methyl methacrylate
Authors: Nomura M. , Yamamoto K. , Horie I. , Fujita K. , Harada M. 
Published: April 2003

AbstractThe rate coefficient for radical desorption from the polymer particles is derived for an emulsion copolymerization system, assuming, for simplicity, that only monomer radicals can desorb from the particles. The effect of free radical desorption on the rate of emulsion copolymerization and the copolymer composition is theoretically analyzed, using the rate coefficient for radical desorption developed in this paper and a mathematical reaction model proposed earlier by the present authors for an emulsion copolymerization system where the average number of total radicals per particle does not exceed 0.5. The validity of the analysis is demonstrated experimentally using the seeded emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA). Radical desorption from the particles does not affect the copolymer composition, but the desorption of MMA—monomer radicals plays an important role in determining the rate of emulsion copolymerization, while the desorption of ST—monomer radicals from the particles can be neglected from a kinetic point of view.
Use of polyelectrolyte complex for immobilization of microorganisms
Authors: Kokufuta Etsuo , Matsumoto Wataru , Nakamura Isei 
Published: April 2003

AbstractCells from Escherichia coli (IAM 12119) were immobilized with the polyion complex of trimethylammonium glycol chitosan iodide (TGCI) and potassium poly(vinyl alcohol) sulfate (KPVS). The immobilization was carried out at pH 8 by mixing TGCI with the cell suspension, followed by addition of KPVS. The immobilized cells were characterized by investigating the glucose oxidizing activity. The results obtained indicated that the glucose consumption with immobilized cells is due not only to the cells released from the complex support but also to the entrapped cells which are grown in the complex; therefore, the cells entrapped in the complex have the glucose oxidizing activity. The physicochemical studies on the immobilization mechanism showed that cells are immobilized via two stages: the aggregation of cells with TGCI and the entrapment of the aggregates in the TGCI–KPVS complex. In the aggregation process, a part of TGCI which is added to cell suspension adsorbs on the cells and the other remains in the suspension. In the entrapment process, the remainder forms the polyion complex with KPVS added and the aggregated cells are coprecipitated with the complex.
Calibration of size‐exclusion chromatography columns with polydisperse polymer standards. I. Theory
Authors: Kubín M. 
Published: April 2003

AbstractRelationships have been derived between the spreading factor and the respective slopes of actual and effective linear calibrations in size‐exclusion chromatography. On this basis a new calibration procedure has been developed for determining simultaneously the dependences of sample molecular weight and of the spreading factor on elution volume from chromatograms of polydisperse polymer samples with known values of number‐and weight‐average molecular weight. No assumptions about the shape of sample molecular weight distribution are required. If necessary, the calibration dependences may be further improved by an iteration procedure described.
Exactly alternating silarylene–siloxane polymers. V. Evaluation of the mechanical properties of crosslinked elastomers
Authors: Livingston Mary E. , Dvornic Peter R. , Lenz Robert W. 
Published: April 2003

AbstractThe search for technologically useful elastomers with good thermal stability at elevated temperatures combined with low temperature flexibility has led us and others to the preparation of a series of linear alternating silarylene–siloxane polymers. Because of the very favorable thermal stabilities of these polymers, a detailed study was made of methods for their vulcanization and for the evaluation of their mechanical properties. The results of these investigations are described, including mechanical properties of the vulcanizates both before and after heat aging and before and after immersion in different solvents, as well as their characteristics after prolonged and repeated extension.
Kinetic model of cure reaction and filler effect
Authors: Hsich Henry S.‐Y. 
Published: April 2003

AbstractA new kinetic model for cure reactios has been developed from the concept of nonequilibrium thermodynamic fluctuation theory in which a distribution function relaxation spectrum is used for explaining cure kinetics of polymer–filler systems. It is found that an increase in filler loading reduces the relaxation time but broadens the relaxation spectrum of the cure reaction. The model is used to explain the cure curves which are obtained both from the Monsanto Rheometer 100 and the Rheometric Mechanical Spectrometer. Not only can the model predict scorch time, cure time, and activation energy of the cure reaction, but it can also take into account polymer–filler interaction and predict physical and mechanical properties of polymer systems during cure.
A comparative study of semi‐2 and full interpenetrating polymer networks based on poly(n‐butyl acrylate)/polystyrene
Authors: Widmaier J. M. , Sperling L. H. 
Published: April 2003

AbstractSequential poly(n‐butyl acrylate)/polystyrene (PnBA/PS) semi‐2 and full IPN's of various compositions were made by UV photopolymerization. Acrylic acid anhydride and divinylbenzene were used as labile and permanent crosslinkers, respectively, for the rubbery phase and the plastic phase. After IPN formation, network I was selectively decrosslinked. After extracton of polymer I, the remaining PS network II was characterized by swelling measurements and examined by scanning electron microscopy. It was found that crosslinked PnBA affects the formation of the second network more than uncrosslinked PnBA does. A porous phase formed by an aggregate of spherical polystyrene domains was observed. The experimental domain diameter was in good agreement with previous theoretical values. The dynamic mechanical properties of full IPN's, decrosslinked IPN's, and semi‐2 IPN's were also studied. A significant level of molecular mixing was found for full IPN's of midrange compositions. The major difference between the full IPN's and the decrosslinked IPN's is that the glass transitions of the respective polymers become more pronounced in the latter case, with a deeper valley between them. With the destruction of the crosslink sites, there is no longer a forced miscibility of the interlocked phases, which are, in fact, thermodynamically incompatible.
Fractography of human hair
Authors: Kamath Y. K. , Weigmann H.‐D. 
Published: April 2003

AbstractThe fracture behavior of human hair has been investigated with a view toward delineating fracture mechanisms that lead to different types of fracture under tensile loading. Principally, three types of fracture are encountered—smooth fractures, step fractures, and fractures involving undefined fibrillated ends. The moisture content of the fiber plays an important role in determining the type of fracture that occurs. Fiber conditioned at either low (∼0%) or high (90%) relative humidity give predominantly smooth fractures, whereas those conditioned at intermediate relative humidities given predominantly step fractures. Surface treatments with polymers or surfactants do not seem to have any effect on the strength or the fracture behavior of fibers. At low moisture contents, fracture initiation occurs more often in the cortex, whereas, at high moisture contents, fracture almost always initiates at the surface of the fiber, suggesting that the swelling pressure of the cortex plays a significant role in fracture initiation. Fibers with larger cross‐sectional areas tend to split along the axis because of the higher probability of encountering flaws or medullary cells which direct cracks along the fiber axis. Unlike synthetic polymeric fibers, hair fibers seem to follow the Griffith criterion of brittle fracture. This may be coincidental since electron microscopic evidence suggests that fracture propagation occurs by secondary cracks generated as a result of stress concentrations building up at the periphery of the primary crack. The rate of stress transfer to adjacent cortical cells via intercellular cement probably plays an important role in the fracture mechanism.
Diffusion of cyclic hydrocarbons in benzene‐swollen, divinylbenzene‐crosslinked polystyrene beads
Authors: Roucis John B. , Ekerdt John G. 
Published: April 2003

AbstractDiffusion of cyclic hydrocarbons within benzene‐swollen, polystyrene‐divinylbenzene gel‐type beads were studied at 25°C. Solute concentrations less than 6.3 × 10−2M and volume fractions of polymer less than 0.6 were used. Diffusion coefficients were calculated assuming Fick's law diffusion, and were found to depend upon the volume fraction of polymer. The dependence suggests that the swollen polymer network acts as a physical obstruction to diffusion. Studies indicated that the solute–solvent interactions affecting diffusion were the same in the solvent‐swollen polymer as in the pure benzene solvent.