bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pressure drop through a tapered die with optimized flow characteristics
Authors: Lenk R. S. , Slater G. 
Published: April 2003

AbstractThe flow of power‐law liquids through tapered dies has been analyzed in an earlier paper.1 We now consider a taper which is additionally streamlined so as to make the transition from a broad and sluggish flow to a flow which is narrow and fast and as smooth as possible. This involves (1) the rational selection of an appropriate taper function within the relevant flow geometry and (2) the integration, between limits, of that function.
Studies of liquid‐induced crystallization of bisphenol a polycarbonate
Authors: Turska E. , Benecki W. 
Published: April 2003

AbstractThe course of liquid‐induced crystallization of a bisphenol A‐derived polycarbonate was investigated using acetone, methyl propyl ketone, methyl isobutyl ketone, and xylene as swelling agents. It was found that above a certain temperature, characteristic of a given polycarbonate–swelling agent system, the diffusion process takes place with the formation of a sharp boundary. The velocity of motion of the diffusion front was determined at various temperatures, and these data were then used to calculate the apparent diffusion coefficients and diffusion activation energies for the different swelling liquids employed. Moreover, a distinct separation of the diffusion and crystallization fronts was observed in the systems investigated, changes in the distance between these two fronts having been determined for various swelling temperatures. The above phenomenon was used to determine the experimental conditions making possible the characterization of a crystallization process not controlled by the diffusion of the swelling agent into the sample. The dependence of half‐times of crystallization on temperature was determined based on crystallization kinetics studies performed by means of a light depolarization technique.
Room temperature‐vulcanized silicone elastomer: Effect of curing conditions and the nature of filler on mechanical and thermal properties
Authors: Bajaj P. , Babu G. N. , Khanna D. N. , Varshney S. K. 
Published: April 2003

AbstractLinear poly(dimethylsiloxane diol) of about 650 D.P. was synthesized by hydrolytic condensation of dimethyldichlorosilane in a saturated solution of sodium chloride. The polymer was then compounded with various fillers, Cab‐O‐Sil, Dicalite, and titanium dioxide, and cured at room temperature in the presence of tin salt and tri‐ or tetrafunctional silane. The tensile strength and elongation of the unfilled rubber were found to be 0.8 kg/cm2 and 320%, respectively. However, Dicalite White (100 phr)‐reinforced elastomer showed a tensile strength of 40 kg/cm2. Crosslink density was determined from the swelling studies. Thermal aging at 150, 200, and 250°C was also studied.
New attempt at flame‐retardation of polyester/cotton fabric blends
Authors: Inagaki Norihiro , Shintani Toshio , Kunisada Hideshi , Katsuura Kakuji 
Published: April 2003

AbstractTwo new flame‐retardation methods for polyester/cotton blend fabric were attempted with reference to thermal reactions of the blend fabric. One is the combination of phosphorylation of the cotton component and the addition of a phosphorus compound. The phosphorus compound must not interact with cotton component. The other involves the addition of a powerful flame retardant for the cotton component only. The flame retardant must induce only a small amount of carbonous products from the pyrolysis of the cotton component.
Mechanism and kinetics of grafting of macrodiisocyanate on to carboxyl‐containing acrylonitrile copolymers
Authors: Shalabi S. E. , Yan G. A. Gabriel , Rogovin Z. A. 
Published: April 2003

AbstractThe reaction of a carboxyl‐containing acrylonitrile copolymer with a macrodiisocyanate based on polypropylene oxide (Mn = 2000) in dimethylformamide (DMFA) and dimethylsulfoxide (DMSO) solutions was studied. The mechanism and main kinetic regularities of the grafting reaction were investigated. The reaction proceeds through formation of a mixed anhydride with its subsequent decomposition leading to liberation of CO2 and formation of graft copolymers. Carboxyl and nitrile groups of the copolymer take part in the reaction. A side reaction involving interaction of isocyanate groups of macrodiisocyanate with DMFA proceeds during synthesis of graft copolymers in DMFA solutions. The dependence of graft polymer yield on temperature, macrodiisocyanate concentration and on the catalyst/NCO ratio was determined. The activation energy of the grafting reaction is 22.9 kcal/mole. The specific viscosity of graft copolymers in DMFA solutions increases with the number of grafted chains.
Measurement of the rheological properties of thermoplastic elastomers
Authors: Han Chang Dae , Rao D. A. 
Published: April 2003

AbstractUsing the Han slit/capillary rheometer, measurements were taken of the rheological properties of commercially available thermoplastic elastomers, namely, styrene–butadiene–styrene (SBS) block copolymer (Shell, Kraton), ethylene–propylene copolymer (Exxon, Vista), olefinic‐type thermoplastic rubbers (UniRoyal, TPR 1600, TPR 1900, and TPR 2800), and urethane thermoplastic elastomers (UniRoyal, Roylar A863 and Roylar E9). The rheological properties determined were shear viscosity and first normal stress difference at various melt temperatures. Depending on the material and the melt temperature tested, the range of shear rates tested was 50 to 700 sec−1, and the range of shear stresses tested was 105 to 106 dyn/cm2. For comparison purposes, rheological measurements were also taken for a few materials using the Weissenberg rheogoniometer although its use was limited to low shear rates (or shear stresses). It was demonstrated clearly that the Han slit/capillary rheometer is a unique instrument for determining the rheological properties of thermoplastic elastomers in the range of high shear rates (or high shear stresses) often encountered in various polymer processing operations.
Photochemical behavior of poly(organophosphazenes). I. Poly[bis(p‐tolylamino)]phosphazene
Authors: Bortolus Pietro , Minto Francesco , Beggiato Giancarlo , Lora Silvano 
Published: April 2003

AbstractThe photolysis of poly[bis(p‐tolylamino)]phosphazene has been studied in methylene chloride solution. The main reactions observed were chain scission and crosslinking. The dissociation into radicals of polyphosphazene is proposed as the primary act of the photolysis. This has been substantiated by the results of the photolysis carried out in the presence of both radical scavengers and some benzophenones as sensitizers.
Wool shrinkage control and surface modification by ozone
Authors: Thorsen W. J. , Ward W. H. , Millard M. M. 
Published: April 2003

AbstractIn treating fine wool top, more ozone is needed to achieve a given level of felting shrinkage control than with coarse wool. Treatment that allows no more than about 20% top shrinkage in three successive washes is usually satisfactory for controlling fabric shrinkage. A detergent rinse after treatment markedly decreases top and fabric shrinkage. Ozonization decreases fiber strength and wet friction against glass but increases fiber‐to‐fiber adhesion enough to increase yarn strength. Scanning electron microscopy (SEM) of fibers before and after treatment and laundering indicates that ozone makes the fiber surface more plastic (presumably when wet) but more liable to mechanical damage and erosion, which increase with the severity of treatment and with laundering. However, treatments most effective for shrinkage control are not distinguished from less effective treatments by the degree and character of surface changes shown by SEM. Ring dyeing of fiber cross sections shows that effects of ozone are greatest near the surface. X‐ray photoelectron spectroscopy (XPS) and amino acid analysis show that cystine is oxidized to cysteic acid and that carbon is also oxidized at the surface. The increased dyeability (rate and uptake) is attributed to increased wettability, changed ionic balance, and crosslink scission, which, with cuticle damage, allow greater swelling and easier penetration. As found earlier with coarse wools, acid milling (leveling) dyestuffs further decrease shrinkage of treated fine wool. The position of wool in the triboelectric series is shifted toward the negative end by ozone treatment, expressing the higher electron work function of the added sulfonic acid groups. This shift is not simply related to shrinkage. Decreased feltability is attributed to softening of the wet cuticle layer and to increased surface charge, but the mechanism needs further study.
Preparation of ultrahigh modulus isotactic polypropylene by means of zone drawing
Authors: Kamezawa Mitsuhiro , Yamada Kenji , Takayanagi Motowo 
Published: April 2003

AbstractHighly oriented isotactic polypropylene with ultrahigh modulus was prepared by means of the zone drawing method proposed by Kiho and Asai. This method features heating a limited portion of the sample. The maximum value of modulus attained was 15 GPa, which corresponds to about half the crystal modulus along the molecular axis evaluated by the x‐ray method. Such an ultrahigh modulus was obtained for a sample of medium molecular weight by inducing necking in the heater and subsequently cooling the sample at lower temperature. The loss tangent peak with the initiation of micro‐Brownian motion of amorphous chains became progressively smaller and broadened more at higher temperatures with increasing draw ratio. Orientation function of the crystal c‐axis increased with draw ratio λ in the region below λ = 9, but reached a constant value, 0.995, in the region above λ = 9. The modulus increased with draw ratio in all ranges of the draw ratio.
Flame‐retardant thermoplastics. I. Polyethylene–red phosphorus
Authors: Peters Edward N. 
Published: April 2003

AbstractRed phosphorus is a highly effective flame retardant for polyolefins. The low additive levels of red phosphorus in polyethylene make it an attractive route to nonhalogen flame‐retardant systems. The mode of action of the red phosphorus has been investigated. Results indicate that the red phosphorus is effective both in the vapor and condensed phase. In the gas phase, PO species produced from the combustion of red phosphorus quench radical processes. In the condensed phase, the red phosphorus substantially lowers the heat of oxidation and traps radicals. This improved thermal stability results in a decrease in fuel production during burning.
Mechanochemical aspects of repetitive impacts and sliding on polymers
Authors: Sacher E. , Engel P. A. , Bayer R. G. 
Published: April 2003

AbstractScattered data exist in the literature on the chemical reactions which occur during mechanical contact. It is our contention that these reactions occur as a direct result of the high temperatures generated at the contact interface, due to the dissipation of mechanical energy. A theoretical analysis is used to identify and rank the various sources of heat generation during repetitive impact or sliding. New data, on both filled and unfilled polymers and elastomers, supported by data from the literature, are used to show that the resultant temperature rise causes reactions at the interface; the extents of these reactions depend on the polymer structure and the magnitude of the temperature rise. Several ways of reducing the magnitude of this temperature rise are discussed.
Influence of history on the gas sorption, thermal, and mechanical properties of glassy polycarbonate
Authors: Chan A. H. , Paul D. R. 
Published: April 2003

AbstractGlassy polycarbonate has been subjected to sub‐glass‐transition annealing and exposure to high‐pressure CO2. The subsequently measured solubilities of nitrogen, argon, and CO2 in these specimens were found to be decreased by the former and increased by the latter. Annealing decreases the enthalpy of polycarbonate and mechanically embrittles it, whereas subsequent exposure to CO2 erases these effects of annealing, can make the polymer even more ductile than the untreated material, and can apparently give it a higher enthalpy. Annealing densifies the glass, whereas the CO2 treatment dilates it. The gas sorption observations are in accord with the dual‐sorption model, and the effects of prior history are apparently the result of changes in the Langmuir capacity, which evidently is a sorption mechanism that exists as a result of the nonequilibrium nature, or excess volume, of the glassy state.
Spectroscopic evidence for mechanochemical effects of moisture in epoxy resins
Authors: Levy R. L. , Fanter D. L. , Summers C. J. 
Published: April 2003

AbstractInternal reflectance Fourier transform infrared (FT‐IR) spectra of tetraglycidyl diaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulfone (DDS) obtained before and after exposure to the combined effect of stress, elevated temperature, and moisture (STM), elevated temperature and moisture (TM), or stress and elevated temperature (ST) environments were used to search for evidence of irreversible chemical changes in epoxy resins. These changes were compared with the infrared changes observed during the late stages of curing. The infrared intensities of the bands attributed to the sulfone group are sensitive to chemical changes and moisture content, which suggests their potential use as molecular monitors within the epoxy network. The results of eight experimental series provide spectroscopic evidence indicating that exposure of epoxy specimens to STM and TM environments that greatly exceed anticipated service conditions results in detectable rupture of chemical bonds in the polymer network. The extent of bond rupture is independent of the applied stress in the 0–90 kg/cm2 range. Internal swelling stresses are therefore believed responsible for the observed bond cleavages. Spectral evidence indicates that postcure reactions are the most prominent chemical changes induced by exposure of epoxy specimens to the ST, SM, M, and T environments.
Mechanics of the extension of cotton fibers. II. Theoretical modeling
Authors: Hearle J. W. S. , Sparrow J. T. 
Published: April 2003

AbstractA preliminary analysis of deconvolution of a nylon model is given. This is then developed to give the available deconvolution strain in cotton. The total extension is then given by adding the fibrillar strain and is compared with experimental values of breaking extension. The relation between convolution extension and stress is calculated in terms of structural and mechanical parameters. An earlier analysis derived cotton fiber modulus in terms of fibril extension and volume change. A new analysis shows that the introduction of shear resistance does not have a significant effect when rotation is prevented. However, false untwisting can occur at the helix reversal in cotton fibers. An analysis which allows for this rotation shows a strong dependence on shear modulus as well as fibril extension and helix angle. There is no volume change.
Interaction mechanisms between poly(methyl methacrylate) and tricalcium silicate (C3S)
Authors: Sugama T. , Kukacka L. E. , Horn W. 
Published: April 2003

AbstractInteraction mechanisms between poly(methyl methacrylate) (PMMA) molecules and tricalcium silicate (C3S) occurring in a C3S‐filled PMMA molecular structure before and after exposure to a simulated 25% geothermal brine solution at 240°C have been investigated by use of thermal analysis, infrared spectroscopy analysis, scanning electron microscopy, and compressive strength tests. For C3S‐filled PMMA samples before exposure to hot brine, it was observed that an interaction between the C3S filler and the CH2 groups in the main chain of the PMMA occurred. After exposure to the hydrothermal environment, indications were that the brine solution induced ionic bonding between the carboxylate anion (COO−) groups in the PMMA and the Ca2+ ions from the C3S. The reaction contributed to improvements in the thermal stability of the PMMA.
Ultradrawing of amorphous polymers by coextrusion illustrated with atactic polystyrene
Authors: Zachariades Anagnostis E. , Sherman Edward S. , Porter Roger S. 
Published: April 2003

AbstractFilms of pure and high‐impact atactic polystyrene were prepared by the recently developed technique of solid‐state coextrusion. The films were produced at extrusion rates ≥4 cm/min at 126°C with a maximum extrusion draw ratio (EDR) of 11.6. These ultradrawn films are fibrous, have a high birefringence of −2.24 × 10−2, and exhibit a 72% elastic recovery. The material has a tensile modulus of ∼4–5 GPa and a tensile strength to break of 85 MPa. Thermal analysis suggests a constant Tg.
Properties of some cast polyurethane rubbers prepared from poly‐ε‐caprolactone polyols and diisocyanates
Authors: Guise G. Bruce , Smith Geoffrey C. 
Published: April 2003

AbstractPolyurethanes were prepared by a one‐step method from poly‐ε‐caprolactone (PCL) diols, diisocyanates, and a triol crosslinking agent (either PCL triol or trimethylolpropane). The influence of composition on mechanical properties was examined. In some formulations the elastomeric properties were lost by crystallization of the PCL segments. The occurrence and rate of crystallization were influenced by the composition and factors such as hydrolytic degradation and oil swelling. In one series of polymers the susceptibility to crystallization could be predicted from the composition. These materials showed melting and glass transitions when examined by differential scanning calorimetry and thermomechanical analysis. The molecular weight of the PCL diol had a greater influence on the glass transition temperature than the diol concentration.
Bonding elastomer layers together by a surface oxidation reaction
Authors: Chang R. J. , Gent A. N. , Hsu C. C. , Sehgal K. C. 
Published: April 2003

AbstractAn experimental study has been carried out of the self‐adhesion of thin layes of three crosslinked elastomers: cis‐polyisoprene (natural rubber) and two polybutadienes. For the polybutadiene materials, the strength of self‐adhesion was found to be strongly dependent upon the time of exposure of the two surfaces to air before they were brought into contact. The strength rose dramatically after the first hour or so of exposure so that in some instances the layers could not be forcibly separated later. When the surfaces were exposed to air for longer periods before joining them, the strength of self‐adhesion fell to low levels again. This remarkable enhancement in self‐adhesion, caused by prior exposure to air for short periods, did not take place on exposure to nitrogen or for samples of cis‐polyisoprene, and it was reduced or delayed in samples containing antioxidant. It is therefore attributed to surface oxidation reactions that can lead to the formation of interfacial covalent bonds with polybutadiene but not with polyisoprene. Some possible reaction schemes are discussed.
A VSE equation of state for liquids. VI. Polymethylene 450–650 K
Authors: Doolittle Arthur K. 
Published: April 2003

AbstractThis is the sixth and final paper in the series under the above title. In prior papers, a VSE equation of state was proposed and applied to a variety of liquids at ambient pressure, but over broad ranges of temperature. Comparisons of thermodynamic quantities calculated from the equation were made with published measured values. In the present paper v, α, s, γ, cv, and cp are calculated for polymethylene from our equations between 450 and 650 K, but extensive corresponding values have not been measured on polymethylene at these temperatures. One approximate value of cp and one value of γ, measured on high‐density polyethylene, show that our predicted values for polymethylene must be of the correct order of magnitude. Several characteristics of the liquid state, observed during the progress of this study (1954–1979), are listed and discussed.
Effect of nitrogen‐donor ligands on the stability of the photolysis products of Mn2(CO)10
Authors: Busetto C. , Mattucci A. M. , Cernia E. 
Published: April 2003

AbstractThe photolysis of Mn2(CO)10 in the presence of nitrogen donor ligands has been investigated in various solvents. The disproportionation reaction has been found to be strongly dependent on the solvent and on the temperature. The substitution of CO with the nitrogen donor ligand takes place on the anion Mn(CO)−5. The polymeric ligand poly(4‐vinylpyridine) manifests a stabilizing effect on the substitution product.
Fire‐retarding polypropylene with magnesium hydroxide
Authors: Miyata Shigeo , Imahashi Takeshi , Anabuki Hitoshi 
Published: April 2003

AbstractFour types of magnesium hydroxide with different particle and crystallite sizes and different degrees of agglomeration were added at amounts up to 60% by weight to polypropylene to obtain a series of composites. The burning characteristics, tensile yield strength, flexural modulus, notched Izod impact strength, and melt flow index of the resulting composites were measured. Magnesium hydroxide coated with sodium stearate was found to give an increased melt flow index and impact strength to the composites as compared to values obtained with uncoated magnesium hydroxide. Incorporation of not less than about 57% by weight of magnesium hydroxide made the composite nonflammable, but at the same time considerably reduced its impact, flexural, and tensile yield strengths. As the amount of magnesium hydroxide filler was increased, the tensile yield strength and flexural strength of the composite proportionally decreased while the flexural modulus increased. The impact strength reached a maximum value when the amount of incorporation was 30% by weight. The lower the degree of agglomeration of the magnesium hydroxide filler and the greater the crystallite size within the range to about 2μm, the better were the mechanical properties of the composite.
Polymerization mechanisms and molecular weight distributions. III. Gamma‐radiation‐initiated polymerization of methyl methacrylate
Authors: Braks Jorma G. , Mayer Gunter , Huang Robert Y. M. 
Published: April 2003

AbstractThe termination mechanism in gamma‐radiation‐initiated polymerization of methyl methacrylate was investigated. The termination mechanism and the associated rate constants were determined by comparing the theoretical molecular weight distribution (MWD) and the experimental MWD, which was determined by gel permeation chromatography. Disproportionation occurs 1.2 times as frequently as combination at 30°C and 0.5 times as frequently at 0°C. The activation energy for disproportionation is 5.5 kcal/mole greater than that for combination. The rates of initiation were determined by a new method and were found to compare well with those reported in the literature. It is also suggested that it is necessary for the theoretical MWD to have the same shape as the experimental MWD before a mechanism can be authenticated.