bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical properties of natural rubber vulcanizates in finite deformation
Authors: Obata Yutaka , Kawabata Sueo , Kawai Hiromichi 
Published: April 2003

AbstractMechanical properties of four kinds of natural rubber vulcanizates differing in vulcanization conditions, and consequently in degree of crosslinking (having values of the Mooney‐Rivlin constant C1 ranging from 0.68 to 1.98) were observed under orthogonal biaxial stretching in a range of strain invariants Ii from 3.4 to 9.0 (extension ratios λi from 0.7 to 3.0). The results obtained were analyzed by two methods. One method employed the Valanis‐Landel postulate that the strain‐energy function W(λ1, λ2, λ3) is a separable symmetric function of the principal extension ratios, i.e., W(λ1,λ2,λ3) = w(λ1) + w(λ2) + w(λ3); the other utilized the contour plots of ∂W(I1, I2)/∂I1 and ∂W(I1, I2)/∂I2 surface within the (I1, I2) domain. The postulate for W was examined in detail with good agreement with experimental results. The dependences of ∂W(I1, I2)/∂I1 and ∂W(I1, I2)/∂I2 surfaces on the degree of crosslinking and temperature were further investigated, with the following conclusions. The surfaces have fairly steep slopes for the region of relatively small deformation (i.e., I1 < 5) and become flat with increasing Ii for all the test specimens. The slope becomes less steep with decreasing degree of crosslinking. The values of ∂W/∂I1 increase linearly and the ∂W(I1,I2)/∂I2 surface becomes flat, both with increasing temperature: i.e., the temperature dependence of ∂W/∂I1 further depends on Ii. The ∂W(I1,I2)/∂I2 surface has a maximum near 40°C.
Topologically interpenetrating elastomeric networks
Authors: Klempner Daniel , Frisch H. L. , Frisch K. C. 
Published: April 2003

AbstractSeveral partially interpenetrating polymeric networks (IPN) were made by combining chemically different linear elastomers. The polymer combinations were deposited as films from aqueous emulsions made by mixing the individual emulsions in equal proportions. The films were crosslinked to form two superimposed networks. In two cases, the networks were cleanly separated by hydrolysis of one of the component networks to demonstrate that there was no chemical interaction between the polymers. Measurement of crosslink density showed that, in most cases, partial interpenetration does occur as evidenced by an effective crosslink density of the IPN's greater than the arithmetic mean of the crosslink densities of the component networks. The swelling ratios, densities, and stress–strain properties were determined. For one of the network combinations, a poly(urethane–urea) and a poly(butadiene–acrylonitrile), a series of IPN's varying in polymer composition was made. The swelling ratios and densities are close to the arithmetic means; however, both the tensile strength and crosslink density exhibit a maximum at about 70% poly(butadiene‐acrylonitrile). The maximum tensile strength is actually significantly higher than that of either of the component polymers. The elongations all approach that of the poly(urethane–urea), the more extensible material, except for compositions approaching 100% poly(butadiene–acrylonitrile), which exhibit a very low extensibility.
Nucleation and growth of bubbles in elastomers
Authors: Stewart C. W. 
Published: April 2003

AbstractThe theory of homogeneous nucleation of bubbles is combined with an expression, for their rate of growth in elastomers to obtain approximate expressions for calculating the number of bubbles formed under a high degree of supersaturation. Experimental results are given for several elastomers with argon as the dissolved gas under a variety of foaming conditions. The theory adequately describes the manner in which the number of bubbles formed depends on the temperature, surface tension of the polymer, and permeability of the dissolved gas.
Fusion of homopolymers and ordered copolymers containing ethylene sebacate structural units
Authors: Theil M. H. , Mandelkern L. 
Published: April 2003

AbstractThe melting temperatures of homopolymers of poly(ethylene sebacate) possessing a most probable molecular weight distribution and ordered copolymers of ethylene sebacate/propylene adipate were studied by slow heating processes and by the analysis of the dependence of the melting temperature on the crystallization temperature utilizing rapid heating rates. For the ordered copolyesters, where the composition of the crystallizing co‐units ranged from 0.8 to 0.2 mole fraction the latter method gave results which were similar to those that have been obtained for the other polymer systems that have been studied. Extrapolated equilibrium melting temperatures could be obtained in a straightforward manner and were found to be independent of the copolymer composition in accord with theoretical expectations. On the other hand, a unique set of results were obtained for the homopolymers. A plot of the relationship between the melting temperature and the crystallization temperature for all the molecular weights studied gave a slope close to unity. This made it operationally impossible to extrapolate to the equilibrium melting temperature for this system.
Structure and properties of poly‐2,5‐distyrylpyrazine
Authors: Kanetsuna Hisaaki , Hasegawa Masaki , Mitsuhashi Shigenobu , Kurita Toshio , Sasaki Kanji , Maeda Katsuhiro , Obata Hiroko , Hatakeyama Tatsuko 
Published: April 2003

AbstractPoly‐2,5‐distyrylpyrazine (poly‐DSP) was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and measurements of dynamic viscoelastic and electrical properties. From DTA and TGA studies it was confirmed that poly‐DSP melts at 321°C and depolymerizes rapidly to the monomer at temperatures between 335°C and 345°C in helium. The polymer is affected by oxygen above 200°C. The E′ value from dynamic viscoelasticity measurements on amorphous film is 2 × 1011 dyne/cm2 at room temperature. It decrease abruptly in the temperature range 140–150°C; but the net decrease of E′ within this temperature range is relatively small. The electrical properties of amorphous poly‐DSP are characterized by a small temperature dependence of the dielectric constant between room temperature and 100°C. The dielectric loss tangent was observed to be small, and the dc conductivity was extremely small. It is concluded that rotation of the phenyl branches in the polymer occurs above −30°C and the glass transition occurs at about 150°C. These properties are discussed in some detail in relation to the polymer structure.
Dielectric relaxation and molecular motion in poly(vinylidene fluoride)
Authors: Yano Shinichi 
Published: April 2003

AbstractThe dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 10 Hz to 100 kHz at temperatures between −196 and 150°C. Three dielectric relaxations were observed: the α relaxation occurred near 130°C, the β near 0°C, and the γ near −30°C at 100 kHz. In the α relaxation the magnitude of loss peak and the relaxation times increased not only with increasing lamellar thickness, but also with decrease of crystal defects in the crystalline regions. In the light of the above results, the α relaxation was attributed to the molecular motion in the crystalline regions which was related to the lamellar thickness and crystal defects in the crystalline phase. In the β relaxation, the magnitude of the loss peak increased with the amount of amorphous material. The relaxation times were independent of the crystal structure and the degree of crystallinity, but increased slightly with orientation of the molecular chains by drawing. The β relaxation was ascribed to the micro‐Brownian motions of main chains in the amorphous regions. The Arrhenius plots were of the so‐called WLF type, and the “freezing point” of the molecular motion was about −80°C. The Cole‐Cole distribution parameter of the relaxation time α increased almost linearly with decreasing temperature in the temperature range of the experiment. The γ relaxation was attributed to local molecular motions in the amorphous regions.
Structural studies of pressure‐crystallized polymers. I. Heat treatment of oriented polymers under high pressure
Authors: Hasegawa Ryozo , Tanabe Yasuhiro , Kobayashi Masamichi , Tadokoro Hiroyuki , Sawaoka Akira , Kawai Naoto 
Published: April 2003

AbstractA convenient pressure apparatus was designed for crystallization of high polymers under hydrostatic pressure up to 5000 atm. Melt crystallization as well as heat treatment under various temperatures and pressures was carried out on several polymers, and the effects of pressure on the molecular and crystal structures of the samples are discussed. Heat treatment of syndiotactic polypropylene under high pressure yields a new crystal modification rather than the previously known helix and planar zigzag modifications. Of the three modifications of poly(vinylidene fluoride), modification III was found as a high‐pressure phase for specimens in the unoriented state, while modification I was obtained as the most stable one on heat treatment of oriented specimens under high pressure. Heat treatment under high pressure converts ordinary isotactic poly‐4‐methylpentene‐1 with a lower density than the noncrystalline value, to a new crystal modification with higher density. As is reasonable, the dense modification is stable in a high‐pressure range. For these three cases, the orientation of specimens was found to remain unchanged during the transitions, which must therefore occur in the solid state.
Study of reversible gelation of partially neutralized poly(methacrylic acid) by viscoelastic measurements
Authors: Silberberg A. , Mijnlieff P. F. 
Published: April 2003

AbstractThe gelation of poly(methacrylic acid) in water was studied as a function of degree of neutralization with NaOH. It was found that charging the molecular displaces the onset of gelation to higher concentrations but makes the transition occur over an even narrower concentration range. This extreme sensitivity of rheological properties to charge may play a role in biocolloidal systems. The phenomenon of reversible gelation is discussed in general and related to the properties of the particular system. The method of measurement, which involves the determination of the dynamic response in the 1 Hz region and the measurement of phase angle, is described in detail. A method of deriving the relaxation time spectrum from measurements of phase angle is given.
Scattering of light by films having nonrandom orientation fluctuations. II
Authors: Hashimoto T. , Stein R. S. 
Published: April 2003

AbstractThe theory for scattering of light from films in which the orientation correlation between two scattering elements depends upon the angle β between the optic axes and the vector connecting the two elements is extended. A delta‐function type dependence is assumed in which the correlation is strongest when β equals some preferred value β0. Calculated results of scattered intensities are shown to be similar to experimental observations.
Rheo‐optical studies of high polymers. XVIII. Significance of the vertical shift in the time‐temperature superposition of rheo‐optical and viscoelastic properties
Authors: Onogi S. , Sato T. , Asada T. , Fukui Y. 
Published: April 2003

AbstractTo determine the true reason for the increase in birefringence and the decrease in relaxation modulus for high‐density polyethylene with rising temperature, changes in crystalline structure as well as in thermal, viscoelastic, and rheo‐optical properties with temperature were measured, by several techniques, including DSC, DLI, infrared dichroism, x‐ray diffraction, and NMR. The values for degree of crystallinity obtained from the DSC fusion curve, density, and infrared absorbances coincide very well and show almost no divergence till about 80°C. The optical vertical shift factor pT can be related to the ratio of the orientation function for the crystal c axis at an arbitrary temperature to that at the references temperature, fε/fε0. The mechanical vertical shift factor bT, on the other hand, is associated with the temperature dependence of the mobile fraction, as determined by NMR measurements, but not with variations in degree of crystallinity.
Liquid–liquid phase separation in multicomponent polymer solutions. IX. Concentration‐dependent pair interaction parameter from critical miscibility data on the system polystyrene–cyclohexane
Authors: Koningsveld R. , Kleintjens L. A. , Shultz A. R. 
Published: April 2003

AbstractCritical miscibility data obtained from measurements of phase‐volume ratios have been used to calculate the concentration dependence of the pair interaction parameter for the system polystyrene–cyclohexane. The measured temperature and concentration ranges are 11–30°C and 4–18% polymer by weight, respectively. With the Gibbs free energy of mixing expressed in polymer segment mole fractions, x*, the pair interaction parameter is g(x*, T) = 0.4961 + 71.92/T + 0.2312x* + 0.0750x*2. In a polymer volume fraction formulation the parameter is g(φ, T) = 0.4099 + 90.65/T + 0.2064 φ + 0.0518 φ2, which approximates to χ(φ, T) = 0.2035 + 90.65/T + 0.3092 φ + 0.1554 φ2. Comparison of the temperature and concentration dependence with that obtained by other authors shows very good agreement, even when extensive extrapolations in temperature and concentration are applied. The present function is believed to be the most accurate. Solutions of mixtures of two narrow‐distribution polystyrenes in cyclohexane show separation into three liquid phases under the exact conditions predicted by theoretical calculation with the present pair‐interaction function.
Spectroscopic study of the formation and structure of polyselenacyclobutane
Authors: Cozzens R. F. , Harvey A. B. 
Published: April 2003

AbstractSelenacyclobutane (trimethylene selenide) readily undergoes photochemical reaction to give polymeric products. Also, the material polymerizes rapidly when the polycrystalline solid film liquifies on a salt substrate in vacuum. Upon polymerization of the sample, infrared and Raman spectra exhibit profound changes which definitely establish ring cleavage. The Raman spectra of the polymer reveal strong C–Se stretching peaks but little or no scattering in the region of Se–Se stretching, strongly suggesting that the polymerization process proceeds in a regular head‐to‐tail fashion. An EPR study of the monomer exposed to ultraviolet radiation at −180°C supports this fact, since the resulting spectrum is indicative of an intermediate radical species, (CH2CH2‐CH2Se)n., where n is sufficiently large that the terminal electrons do not interact. No triplet spectra were observed. Molecular oxygen apparently plays an important role in the polymerization kinetics, since it is found that degassed samples of the substance, in contrast to those which have not been degassed, polymerize rapidly even under room illumination. Freezing‐point depression measurements fix a lower limit to the average molecular weight of the polymer at 2700 (n = 23 monomer units).
General description of mechanical anisotropy of semicrystalline polymers in relation to orientation of structural units composed of crystalline and noncrystalline materials
Authors: Maeda Matsuo , Hibi Sadao , Itoh Fumihiro , Nomura Shunji , Kawaguchi Tatsuro , Kawai Hiromichi 
Published: April 2003

AbstractA mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single‐phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two‐phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements.
Equation of state and the thermodynamic properties of liquid polymers: Application of the Hirai‐Eyring model
Authors: Smith Richard P. 
Published: April 2003

AbstractIt is shown that the Hirai‐Eyring model for the liquid state is capable of accurately describing the p, V, T behavior of liquid polymers in the temperature range over which measurements are now made, and below. Once the parameter choices necessary to accomplish the fit are made for a particular polymer, the excess thermodynamic functions (differences in properties, liquid less solid) are determined by the same parameters. Above the glass transition temperature Tg the volume, excess enthalpy, and square of the excess entropy are predicted by the model to be essentially linear with temperature, in agreement with experiment. Below Tg, these functions do not remain linear (as is usually assumed in extrapolating the equilibrium behavior to low temperatures), but instead they rapidly approach zero in a continuous way as the temperature is lowered. These remarks apply to glass‐forming materials composed of small molecules, as well as to polymers. The “paradox” raised by Kauzmann is thus resolved, and the Gibbs‐DiMarzio second‐order transition appears to be unnecessary.
Determination of polymer branching with gel‐permeation chromatography. I. Theory
Authors: Drott E. E. , Mendelson R. A. 
Published: April 2003

AbstractThe effect of long‐and short‐chain branching in polymer molecules on gel‐permeation chromatographic (GPC) separation is discussed. The calculation of calibration curves for branched polymers is developed from the universal calibration technique based on the hydrodynamic volume concept and previously established relationships for the effect of branching on molecular dimensions. Typical calibration curves are shown for different branching models and degrees of branching. As branching increases, the curves are shown to converge. Methods of characterizing branching and molecular weight distributions of franctions and whole polymers from GPC and intrinsic viscosity data are presented.
Self‐seeded crystallization and its potential for molecular weight characterization. II. Experiments on narrow fractions
Authors: Keller A. , Sadler D. M. 
Published: April 2003

AbstractThe effect upon seeding behavior of adding well characterized fractions has been studied, so as to assess the technique as a measure of small amounts of high molecular weight. The material available to us restricted the study to fractions with comparatively low average molecular weights. Self‐seeding is shown to be an extremely sensitive measure of high molecular weight tails. Knowledge of the molecular weights concerned enabled estimates to be made of the weight of molecules involved in seeding. Instability of seeds has been observed, and is explained in terms of a particular amorphous crystalline “equilibrium” within the seeds.
Effect of optical rotation on low‐angle light‐scattering patterns
Authors: Picot C. , Stein R. S. 
Published: April 2003

AbstractThe effect of optical rotation of the environment is calculated for the Hv and Vv low‐angle light‐scattering patterns of two‐dimensional spherulites. As with the effect or birefringence, the change in the Hv pattern is greater than that of the Vv pattern. With increasing optical rotation, the patterns lose their characteristic shape and become more circular.
Dielectric absorption in polyoxymethylene obtained from tetraoxymethylene crystal by radiation induced polymerization
Authors: Tanaka Akira , Uemura Shinsaku , Ishida Yōichi 
Published: April 2003

AbstractIn order to study the dielectric behavior of polyoxymethylene prepared by radiation‐induced solid‐state polymerization, large crystals of tetraoxymethylene (2 cm in diameter) were prepared by Bridgman's method and polymerized by γ‐rays. The x‐ray diffraction pattern of the polymer did not reveal the existence of a so‐called amorphous region. In dielectric measurements, only one dielectric absorption was observed in the low‐temperature region, while in the high‐temperature region ε″ did not change up to about 120°C, where thermal decomposition started. When the specimen was stabilized by acetylating the endgroups in the solid state, ε″ did not change up to about 150°C. This dielectric absorption showed a significant anisotropy for the direction of an applied field. The dielectric absorption was much larger when the electric field was perpendicular to the fiber axis than when the field was parallel. The dielectric absorption was larger in a specimen which was estimated to be more imperfect according to DSC analysis. This leads to the conclusion that the dielectric absorption is attributable to defect regions. On the other hand, the dielectric absorption became larger with increasing numbers of terminal OH groups, and hence it is attributable to the response of the terminal OH groups. Moreover, the dielectric absorption was depressed by the acetylation of the OH groups in the solid state. It is, therefore, concluded that the dielectric absorption observed in polyoxymethylene prepared by solid‐state polymerization of tetraoxymethylene is due to the response of terminal OH groups localized in defect regions. Polyoxymethylene crystallized from the melt gives an asymmetric low‐temperature absorption. This asymmetry can be ascribed to the superposition of two relaxation processes. When its absorption curve is compared with that of the solid‐state polymerized polymer, the low‐temperature component can be assigned to crystal defects and the high temperature one to amorphous regions.
Swelling of thin films. I. Acrylamide–N‐isopropylacrylamide copolymers in water
Authors: Chiklis Charles K. , Grasshoff J. Michael 
Published: April 2003

AbstractThe swelling curves of 6μ films of low conversion homopolymers and copolymers of acrylamide (AM) and N‐isopropylacrylamide (NIPAM) were obtained in water by an optical microscope technique. Poly(AM) swelled appreciably faster than poly(NIPAM) but there was no apparent correlation between overall swelling rate and copolymer composition. A 57/43 (mole %) AM–NIPAM copolymer swelled fastest. Sequence distribution calculations indicated that its backbone structure tended toward comonomer alternation, which might reduce the extent of hydrogen bonding in the film. The amount of water sorbed during swelling, as approximated from increasing film thickness, was proportional to the square root of time and agreed well with previous work in the literature. Homopolymer films from runs of ca. 50% conversion consistently swelled slower than their low conversion counterparts, probably due to branching and increased entanglements. Heating also promoted slower film swelling due to a tightening of the film structure and/or a low degree of imidization. Monomer reactivity ratios and Alfrey‐Price Q and e values for NIPAM were calculated. Cloud points of 5% aqueous solutions of the copolymers were measured and found to decrease with increasing NIPAM content.