bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of γ‐radiation on the dynamic mechanical properties of silicone rubbers
Authors: Traeger R. K. , Castonguay T. T. 
Published: April 2003

AbstractDimethyl‐, trifluoropropyl‐, and high phenyl content polysiloxanes were irradiated in a 60Co source to doses of 100 Mrad. The hardness of the specimens increased with dose. Crosslink density changes did not directly reflect the hardness changes. The crosslink density of the dimethyl polymer increased significantly and that of the trifluoropropyl polymer increased only slightly. There was a slight decrease in the crosslink density of the aromatic material. The storage moduli reflected the changes in crosslink density. Loss moduli of the dimethyl‐ and trifluoropropylpolysiloxanes initially decreased and then increased on continuing irradiation. Dynamic moduli of the high aromatic content polymer were essentially unchanged by the radiation. All the dynamic data were correlated by the WLF time–temperature relationship.
Effect of crosslinking on flatspotting of nylon 6 tire yarn
Authors: Cipriani C. , Papero P. V. , Moore M. S. , Menkart J. 
Published: April 2003

AbstractTires containing nylon tire cord exhibit a temporary deformation upon standing under load. The delayed recovery from this deformation, due to the fact that the yield point of nylon is exceeded under normal inflation pressures, results in the phenomenon of “flatspotting.” Previous attempts to improve the viscoelastic characteristics of nylon by crosslinking have been discouraging on account of the general degradation of properties caused by the treatment. It has now been found that short, vapor‐phase treatments with diisocyanates, particularly tolylene diisocyanate, produce nylon 6 of greatly improved flatspotting resistance, without undersirable side effects. The development of this procedure, the evaluation methods employed, and the proposed mechanism are discussed.
Properties and structure of nylon fibers in relation to drawing and aqueous phenol treatments
Authors: Sakuma Yasuhiko , Rebenfeld Ludwig 
Published: April 2003

AbstractThe changes in nylon 66 fiber structure and properties which take place during drawing and aqueous phenol treatments were studied by means of measurements of length, birefringence, density, moisture regain, x‐ray diffraction, stress–strain behavior, and sound velocity. Drawing was found to establish molecular orientation along the fiber axis predominantly in the early stages, whereas the development of lateral order occured primarily after a certain level of orientation had been achieved. Treatments in aqueous phenol solutions caused longitudinal contractions which depended on phenol concentration (1‐5%), draw ratio (1‐6), and the tension on the fiber during the treatment. The treatments resulted in an increase in the lateral order, decrease in orientation and corresponding changes in mechanical properties. Moisture regain was inversely related with density for the untreated fibers of various draw ratios, but the relationship became complex after treatments in phenol. The data are interpreted in terms of changes in the lateral order distributions, which permits an increase in the fibers' sorptive capacity despite an increase in the mean lateral order.
Tensile properties of TiO2‐filled poly(vinyl acetate) in the transition region
Authors: Galperin I. , Kwei T. K. 
Published: April 2003

AbstractThe stress–strain properties of TiO2‐filled poly(vinyl acetate) have been studied at filler percentages of 0, 10, 20, 30, and 40% TiO2 over a strain‐rate range of 100–5000%/ min at 24°C. Tensile strength, Young's modulus, and offset yield strengths all were found to increase with higher strain rates and higher TiO2 contents. Ultimate elongations decreased with greater TiO2 content and higher strain rates. Shift factors for volume fraction of filler were estimated for tensile properties as function of test rate. Stress relaxation studies have shown a reduction in relaxation times with increasing TiO2 content. Calculations of the out‐of‐phase Young's modulus were made as a function of filler content employing a box‐type of distribution of relaxation times. A possible explanation for the stress–strain behavior observed is that introduction of TiO2 changes the internal viscosity of the system, similar to the effect of temperature. This would also mean that the ultimate properties would be dependent on filler content and strain rate because viscous resistance to chain deformation would be altered. The effect of filler on stress relaxation could be thought of being due to an increase in short‐range chain motion.
Equilibrium of water between gelatin solution and ice
Authors: Tanner J. E. 
Published: April 2003

AbstractThe equilibration of water between aqueous gelatin solution and physically separate cakes of ice was observed. Typically, the water content of the solutions reached a nearly steady value several times before final equilibrium, reasons for which are discussed. The equilibrium gelation concentrations were found to be 72 ± 1%, 77 ± 2%, and 80 ± 3% at −10, −21, and −33°C., respectively, in moderately good agreement with predictions based on the vapor pressure measurements of Bull at higher temperatures.
Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. III. Rigid epoxy foam
Authors: Asay James R. , Guenther Arthur H. 
Published: April 2003

AbstractThe velocity and attenuation of longitudinal bulk waves in a solid epoxy foam were measured by an acoustic pulse technique in the frequency range of 0.667–4.0 Mc./sec. and in the temperature range from ambient to 150°C. The measurements are reported with the density of the solid epoxy and with aluminum impurity loading as parameters. Over the indicated temperature and frequency ranges, complete attenuation and velocity measurements are reported for one foam corresponding to a density of 0.325 g./cc. In the density range of 0.088–0.325 g./cc. for the unloaded foams, attenuation is reported at room temperature. It is observed that the longitudinal velocities for all the densities decrease with temperature by about 40% in a span of 100°C. and that an approximately linear relation exists with temperature. The velocities in the foams loaded with small percentages of aluminum and heat‐treated at 250°C. exhibit temperature behavior which is dependent upon the combined effects of loading, density change, and epoxy properties. For the loaded foam with the highest density (1.068 g./cc.), velocity is reported to a temperature of about 250°C. The velocities of all the various density samples with the exception of the loaded foams exhibit inflections at a temperature of about 110°C. The attenuation–temperature measurements on the 0.325 g./cc. sample show similar behavior at this temperature except that the effect is much more pronounced than the velocity inflection, hence a better indication of the transition. The precision of the measurement is about 2% for the relative longitudinal velocities and about 20% for the attenuation.
Universality of the temperature‐independent viscosity characteristic of polymer melts and some of its consequences
Authors: Malkin A. Ya. , Vinogradov G. V. 
Published: April 2003

AbstractIt is shown that some results of recent publications (of Longworth and Piesky and of Bartoš) can be treated as particular consequences of the principle of universality of temperature‐independent viscosity characteristics of polymer melts, earlier found by these authors. This concerns the method of determination of molecular weight by means of melt index measuring and supposition that the definite value of apparent viscosity to initial Newtonian viscosity ratio can be considered to be a criterion of elastic turbulent flow emerging.
Isothermal permeabilities from thermo‐osmosis experiments
Authors: Bearman Mirion Y. , Bearman Richard J. 
Published: April 2003

AbstractWith the use of strain‐gauge pressure transducers, an improved constant volume apparatus has been constructed for the measurement of isothermal permeabilities of gases from thermo‐osmosis experiments. Permeabilities are reporducible to about ±5% accuracy and compare favorably with those obtained by alternative techniques. Revised values are presented for the permeability coefficients of the noble gases in rubber.
Chloride‐sulfate equilibria and transport processes in benzidine‐formaldehyde and other anion‐permeable membranes
Authors: Gregor Harry P. , Bruins Paul F. , Kramer Richard M. 
Published: April 2003

AbstractExchange equilibria, ohmic resistances, concentration and bi‐ionic potentials, diffusion coefficients, and transport numbers were measured for the chloride–sulfate–oxalate system in anion‐permeable membranes with quaternary ammonium and benzidine exchange sites. The benzidine membranes showed a greater selectivity for sulfate than chloride as compared with the quaternary ammonium membranes, but a lower transport number. These phenomena were interpreted in terms of an ion‐binding mechanism. Fair agreement was observed between measured transport numbers and those calculated from selectivity coefficients, diffusion coefficients, and equivalent conductances.
Application of DTA traces to polymer pyrolyses
Authors: Reich Leo 
Published: April 2003

AbstractVarious expressions are presented for the estimation of kinetic parameters during pyrolysis from DTA traces. These expressions are applied to polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, isotactic poly(propylene oxide), and poly(methyl methacrylate). The results obtained are compared with reported values, and advantages and disadvantages of the various methods are given.
Thermal oxidation of thermoplastics
Authors: Kelleher P. G. 
Published: April 2003

AbstractCommercial thermoplastics may be classified by the types of rate curves obtained on thermal oxidation. The rate of oxidation of an acrylonitrile‐butadiene‐styrene plastic is affected by sample thickness and appears to be diffusion‐controlled. Pigmentation increases the reaction rate of this compound in all the cases studied because of the catalytic effect of the metals present. Carbon black adversely affects the oxidation rate of stabilized polypropylene. The acetal plastics decompose under oxidative condition at 140°C. Of the thermoplastics examined, polytetrafluoroethylene, fluorinated ethyleneproplyne copolymer, poly(vinylidene fluoride), poly(ethylene terephthalate), and polysulfone are the most resistant to thermal oxidation at 140°C.
Water–formaldehyde–hydrogen sulfide system. II. Formation and growth of thiomethylenic chains.
Authors: Credali Lino , Mortillaro Luigi , Russo Mario , De Checchi Carlo 
Published: April 2003

AbstractA linear polymer with a high melting point is obtained from the water–formaldehyde–hydrogen sulfide system in the presence of sulfuric acid. This polymer is substantially formed by a polythiomethylene chain with a few oxymethylene units. Its formation involves a topochemical reaction of the mercaptomethanol present in solution on the first separation solid of the system. On heating, the polymer loses oxymethylene units; in the same way, the first solid product separated from the system loses formaldehyde and undergoes a morphological and chemical transformation to polythiomethylene.
Effect of processing conditions on the gloss of polypropylene films
Authors: Schael G. W. 
Published: April 2003

AbstractA study of the effect of three processing variables, melt temperature, quench temperature, and air pressure, on the gloss of polypropylene films shows that although these processing parameters are used to control this property they do not constitute the primary cause of gloss variations. The main causes of gloss variations were found to be changes in the polymer melt index, i.e., melt roughness, and film crystallinity, both of which can be controlled by changing the processing conditions.
A study of the morphology and physical properties of polypropylene films
Authors: Schael George W. 
Published: April 2003

AbstractData are presented showing that rapidly quenched polypropylene films contain a paracrystalline phase in addition to crystalline and amorphous phases. The density of the paracrystalline phase was found to vary between 0.8890 and 0.9080 g./cm.3. Other data show that the density of quenched polypropylene films increases during aging, the increase being a linear function of the logarithm of the film age. The physical properties of the films, secant modulus, impact strength, and coefficient of friction, were found to vary not only with crystallinity, i.e., composition‐dependent density, but also to vary during aging when the density was increasing with little change in crystallinity. An example of this dependence is the increase in secant modulus of 10.9 × 106 psi/g./cm.3 during aging and only 3.7 × 106 psi/g./cm.3 as the crystallinity increased. Because of the three phases and the density–time change, it is possible to have films with the same density and different physical properties and, conversely, films with the same physical properties and different densities.
Graft copolymers of starch. I. Copolymerization of gelatinized wheat starch with acrylonitrile. Fractionation of copolymer and effect of solvent on copolymer composition
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E. 
Published: April 2003

AbstractThe starch–polyacrylonitrile graft copolymer prepared from gelatinized wheat starch with ceric ammoninm nitrate as the initiator has been freed of ungrafted polyacrylonitrile and separated into fractions by extraction with dimethylformamide, γ‐butyrolactone, and dimethyl sulfoxide. The copolymer fractions obtained differed appreciably in level of add‐on, molecular weights of grafted chains, and grafting frequency. To determiue the molecular weights of grafted chains, the starch part of the copolymer was effectively removed by hydrolysis with α‐amylase. It was necessary to dissolve or swell the polymer in dimethyl sulfoxide and freshly precipitate it by addition to water before enzymatic hydrolysis. In studying the effect of reaction medium on copolymer composition, there was less ungrafted homopolymer formed and a higher yield of graft copolymer possessing more frequent grafts with water than with aqueous dimethylformamide or aqueous ethylene glycol. Polymer solubility, the results of control polymerizations of acrylonitrile in the absence of starch, and the detection of glucose endgroups on the polyacrylonitrile liberated from the fractionated polymer by hydrolysis are presented as evidence that the copolymers obtained are true grafts rather thau intimate mixtures.
Hyperfiltration studies. III. Effect of certain metal ions on the salt filtration properties of cellophanes
Authors: Kuppers J. R. , Harrison Neva , Johnson James S. 
Published: April 2003

AbstractThe salt rejection properties of cellophanes are substantially increased, and permeation rates decreased, by pretreatment with certain metal ions or presence of these ions at low concentration in feed solutions. In a typical case, a cellophane which initially rejected about 20% of salt from a 0.05M NaCl solution rejected over 70% in Presence of 10−3M ThCl4. Permeation rates were decreased, usually be a factior of 2 or 3. Additives found to have a marked effect were Fe(III), Th(IV), U(VI), Cu(II), and hydrolyzed pb(II). Mg(II), Ba(II), La(III), and unhdrolyzed Pb(II) had little effect. The mechanism by which the additives affect the cellophane is not clear.
Molecular weight distribution in alkyd resins. Part II. Castor oil and hydrogenated castor oil alkyds
Authors: Solomon D. H. , Hopwood J. J. 
Published: April 2003

AbstractAlkyds prepared from castor and hydrogenated castor oils have been prepared direct from the oil and by first subjecting the oil to a glycerolysis reaction. The molecular weight distributions of the alkyds have been measured in solvent systems designed to separate predominantly on polarity and molecular weight. The properties of the alkyds in stoving enamels have been evaluated. The results are discussed in relation to existing theories relating processing conditions to molecular weight distribution in alkyd resins. Previous suggestions regarding the reactivity of the hydroxyl groups in the oil molecules are not consistent with the results obtained in this study.
Milling behavior of gum elastomers: Experiment and theory
Authors: Tokita Noboru , White James L. 
Published: April 2003

AbstractWhen an uncompounded elastomer is processed on a two‐roll mill, four different regions of mechanical behavior are observed, depending upon the temperature and the severity of the nip deformation. this behavior is observed on materials with a wide variety in chemical composition, through the severity varies. The flow at high temperatures is typical of melt or polymer solution behavior. At lower temperatures unstable flow and elastic solidike regions are observed. By presuming the elastomer to be an isotropicviscoelastic medium, the stress and velocity fields were computed in the polymer melt region. The unstable regime was found to correspond to a critical value of the ratio of viscoelastic to viscous forces. The mathematical analysis, done interms of the Green‐Rivlin‐Noll theory of viscoelastic media, extends earlier studies of deformation in this geometry by Gaskell and Bergen.
Ultrasonic degradation of macromolecules in solution. Study of degradation kinetics by estimation of free‐radical scavenger DPPH and solution viscosity measurements
Authors: Chandra (Mrs.) Sarswati , Roy‐Chowdhury Phanibhusan , Biswas A. B. 
Published: April 2003

AbstractThe kinetics of degradation of butyl rubber in two solvents, cyclohexane and toluene, was studied by two independent techniques: viscosity measurements and free‐radical estimation as a function of DPPH consumed. The general shape of the rate curves in the two cases is similar, but not identical. The rate given by estimation of DPPH is faster than that obtained from solution viscosity data. This has been attributed to the inherent limitations of the two methods for the quantitative determination of the number of breaks occurring in the polymer molecules. The rate is also reduced as the viscosity of the solution medium is increased, which may be correlated with the reduction of the cavitation effect responsible for degradation. The degradation rates in two solvent media initially having the same viscosity were unequal. This may be due to different solvent–solute characteristics, which means that the viscosity and cavitation change to different extents in the two cases throughout the course of degradation. The limiting degree of Polymerization (DP)∞ obtained after prolonged irradiation has been found to be dependent on parameters such as intensity of irradiation, solution viscosity, and initial DP of the molecules.
Cold flow in high‐impact polystyrene
Authors: Arends C. B. 
Published: April 2003

AbstractEyring's theory of viscous flow has been applied to some mechanical properties of rubber‐modified polystyrenes. Yield strength as a function of orientation, temperature, of transition from ductile to strain have been shown to be consistent with the theory. The temperature of transition from ductile to brittle fracture as a function of orientation has also been measured and found to be consistent with theoretical predictions.
Heptane‐soluble material from atactic polypropylene. II. Interaction with liquids
Authors: Moore W. R. , Boden G. F. 
Published: April 2003

AbstractReduced melting point and swelling measurements, involving heptane‐soluble material from atactic polypropylene and over thirty liquids of differing chemical type, are reported. A value of 578 ± 40 cal. is obtained for the molar heat of fusion of a crystalline repeat unit which is much lower than values given for isotactic polypropylene. Some reasons for the low value are considered. Values of the polymer‐solvent interaction parameter χ1 for systems involving alkylbenzenes and n‐alkanes suggest a solubility parameter of 7.9 ± 0.1 (cal./cc)1/2 for the polymer. These values of χ1 decrease with increasing molar volume of liquid. Polar liquids of comparable solubility parameter or molar volume are associated with higher values of χ1. Intrinsic viscosities and values of the slope constant k′ are given for fractions in the molecular weight range 3,000–25,000 and six solvents at 25°C. The results suggest the following order of solvent power: cyclohexane ≈ cyclohexene > methylcyclohexane > trichloroethylene > decalin > carbon tetrachloride. Intrinsic viscosities are higher than those generally obtained for flexible polymers of comparable molecular weight, and the values of the Mark‐Houwink exponent appear to be high. Some reasons for these high values are considered.
On the complex poisson's ratio of a urethane rubber compound
Authors: Thomson Ker. C. 
Published: April 2003

AbstractThe complex Poisson's ratio of a urethane rubber compound was determined for frequencies up to 700 cps. It is shown that the assumption made by earlier workers using this material, that Poisson's ratio is a numerical constant slightly less than 1/2, while approximately correct at low (creep) frequencies is definitely invalid in certain more elevated frequency bands.
Accuracy of approximations in kinetic data circulation
Authors: Haber Václav 
Published: April 2003

AbstractKinetic data can be determined from the relation of two kinetic equations in their integrated form. For the calculation of the exponential integral, approximations are generally used, which allow a simple calculation of the activation energy. With respect of the most frequently used approximations, an evaluation of error produced by their application has been calculated. The best results can be achieved by using the equation

equation image

which permits determination of E to within 1% accuracy.
Absorption of water by proteins and related compounds
Authors: Ramsden D. K. , Wood F. , King G. 
Published: April 2003

AbstractIsotherms have been obtained for the absorption of water by proteins and polyamides and by simple amides closely related to the repeat chemical unit of the polymers. The differential heat of absorption of water at zero water content has also been determined for these substances, from isosteres and from heats of mixing. In addition the nature of the hydrogen bonding of water to these compounds has been investigated by infrared spectroscopic methods. The large differences found between the heats of absorption by the polymers and the simple model compounds are discussed.
Stress softening in natural rubber vulcanizates. Part IV. Unfilled vulcanizates
Authors: Harwood J. A. C. , Payne A. R. 
Published: April 2003

AbstractStress softening (Mullins effect) is observed in gum natural rubber vulcanizates. The magnitude of this softening is similar to that in carbon black‐filled vulcanizates. The amount of stress softening is slightly greater in vulcanizates cured to produce predominantly polysulfide crosslinks than in those containing monosulfide or carbon–carbon crosslinks. The total recovery of stress softening in the vulcanizates containing monosulfide or carbon–carbon crosslinks suggests that the phenomenon is attributable to a quasi‐irreversible rearrangement of molecular networks due to localized nonaffine deformation resulting from short chains reaching the limit of their extensibility. This non‐affine deformation results in a displacement of the network junctions from their initial random state.