bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steady‐flow viscous and elastic properties of polyisobutylene solutions in low molecular weight polybutene
Authors: Ueda Shigeyuki , Kataoka Tadao 
Published: April 2003

AbstractShear stress and first normal‐stress difference of polyisobutylene dissolved in low molecular weight polybutene (concentrations 0.7 to 19 wt‐%) were measured as a function of the shear rate. The dependence of viscosity η on shear rate \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document} was represented by the equation η = η∞ + (η0 − η∞)/(1 + α\documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document}n) proposed by Cross, where the subscripts (0 and ∞) denote values at infinitesimal and infinite rate of shear, α is a constant associated with rupture of entanglement linkages, and n is a constant. The empirical value of n is 10/13 for 19% solution and 2/3 for the other solutions. The concentration dependence of α was roughly expressed as α = 104 c2.7, where c is the concentration in grams polymer per milliliter solution. The first normal‐stress coefficient ψ12 can be represented by ψ12 = ψ12∞ + (ψ12∞ − ψ12∞)/(1 + β\documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma $\end{document}m). The analysis of data based on the equations shows that m = 2n and β ≈ α2. The steady‐state compliance Je was calculated from the relation Je = ψ120/2(η0 − ηs)2, where ηs is the solvent viscosity. Je shows a maximum at about c = 0.03 and is directly proportional to c−2 in the higher region of c.
Structural studies on polyformals. III. Poly‐1,3‐dioxocane and poly‐1,3‐dioxonane
Authors: Sasaki Shintaro , Tadokoro Hiroyuki 
Published: April 2003

AbstractMolecular and crystal structures of poly‐1,3‐dioxocane and poly‐1,3‐dioxonane, the polyformals [OCH2O(CH2)m]m with m = 5 and m = 6, respectively, are analyzed. Poly‐l13‐dioxocane is triclinic, space group with m = 5 and m = 6, respectively, are analyzed. Poly‐1,3‐dioxocane is triclinic, space group (fiber axis) and N (number of chains per unit cell) = 2. Poly‐1,3‐dioxonane is orthorhombic, (fiber axis) = 18.8 Å, and N = 2. The molecular conformations are roughly magnified image
where T, G, and G are the trans, and the two gauche forms, respectively.
Preferential uniplanar orientation mechanism of the (101) crystal plane of regenerated cellulose
Authors: Matsuo Masaru , Nomura Shunji , Kawai Hiromichi 
Published: April 2003

AbstractThe molecular orientation behavior of regenerated cellulose, in both crystalline and noncrystalline phases, was investigated quantitatively under various conditions during coagulation‐regeneration from viscose solution and during drying of the resulting gel film. It was concluded that the stronger the tensions which arise parallel to the film surface during coagulation‐regeneration and drying of the gel film, the more prominent become the uniplanar orientation of the (101) crystal plane and planar orientations of the crystal b axis and noncrystalline chain segments, all parallel to the film surface and associated with considerable distortion and disintegration of the regenerated crystal. This conclusion suggests an orientation mechanism of the cellulose II crystal, namely, rotation of the crystal around the U(101) axis associated with slippage of the (101) crystal plane, the most highly hydrated and most readily dislocated plane, in the direction of the tension, which is also parallel to the surface of the film. The behavior of this type of uniplanar orientation of the (101) crystal plane is characterized semiquantitatively by comparing observed distributions of the orientation of crystallographic axes with those calculated on the basis of a relatively simple model for crystal orientation.
Thermodynamic properties of some concentrated polymer solutions
Authors: Bonner D. C. , Prausnitz J. M. 
Published: April 2003

AbstractSolubilities of several solvents were measured in four molten polymers by using an isobaric vapor‐pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt‐%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.
Rotational isomeric‐state approximation for the unperturbed dimensions of a POLA polyester
Authors: Tan J. S. 
Published: April 2003

AbstractRotational isomeric‐state theory has been applied to investigate chain configurations of a polyester prepared from 4′,5‐(1,1,3‐trimethyl‐3‐phenylindan) dicarboxylic acid and 2,2‐bis(4′‐hydroxyphenyl) propane (POLA polyester). Independent conformations for each repeat monomer unit of the chain have been assumed in the calculations of the unperturbed dimensions. Rotations about the oxygen‐phenylene‐carbon (OϕC) bonds are considered to be free with twofold symmetric potentials. The trans and cis conformations of the carbonyl‐phenylene‐carbon (OCϕC) and the indan‐carbonyl residues are assumed to have equal probability. Two rotational states, trans and cis, are assigned to the ester CO bonds. Calculation of the reduced unperturbed dimensions (〈r02〉/M)∞ with conformations thus assigned for the bonds in the repeat unit, and comparison with experiment (0.72 ± 0.02 Å2/g) indicate that the conformation in the ester CO bonds is predominantly trans. An equation for the conformational potential as a function of rotational angle about the ester CO bond has been formulated using data on potential barriers for low molecular weight compounds. This equation, yielding a potential difference between the cis the trans isomers of 2.5–3.0 kcal/mole, is in good agreement with the prediction made from the calculation of the unperturbed dimensions where a cis/trans ratio of 0.01 for the ester CO bonds was obtained.
Effect of temperature and physical state on the inhibition by additives of radiation‐induced degradation of poly(methyl methacrylate)
Authors: Wündrich Konrad 
Published: April 2003

AbstractIt has been reported in earlier papers that aromatic additives can reduce the rate of radiation‐induced degradation of poly(methyl methacrylate) (PMMA), depending on the concentration, the distribution, and the resonance of the aromatic system. In the present work, the temperature dependence is studied, together with the influence of molecular mobility, which is determined by the physical state of the system. For this purpose, PMMA containing benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, or benz[a]anthracene, was γ‐irradiated at room temperature and also, except with naphthalene and biphenyl, in the temperature range −80 to 160°C. The changes in degradation rate were related to the first excited singlet state and to the resonance energy of the additives. The results suggest that at low temperatures both electron scavenging and transfer of excitation energy occur. At temperatures between the γ transition and the glass transition, the significance of energy transfer compared with electron scavenging increases, whereas the inhibitory effect decreases. Above the glass transition temperature the inhibition decreases more rapidly. This is related to scavenging of radical chain fragments, due to increasing molecular mobility, which causes a decrease in recombination rate. This sensitization of degradation competes with the inhibition by energy transfer and electron scavening, and may prevail at temperatures above 185°C. The opposing effects of these mechanisms can be clearly shown with the system PMMA–benzene. In viscous mixtures, sensitization prevails even at room temperature.
Precipitation chromatography. III. Optimization of the experimental conditions and determination of the polydispersity of fractions
Authors: Böhm L. L. , Casper R. H. , Schulz G. V. 
Published: April 2003

AbstractThe influence of the solvent–nonsolvent gradient and the temperature gradient on the efficiency of the precipitation chromatography is investigated with radically and anionically prepared polystyrene samples. Only a combination of both gradients gives optimal effectiveness of the column. The separating power of the column was determined by using mixtures of well defined samples. From the elution curves of the mixtures the nonuniformity Ufr of fractions can be estimated. For fractions of anionically prepared polystyrenes Ufr is on the average 0.001; this value is of the same order of magnitude as the statistical error. These results show that with this chromatographic method it is possible to determine the narrow molecular weight distributions of anionically prepared polystyrenes (or other polymers) with an accuracy sufficient for kinetic studies.
Statistical thermodynamics of ABA block copolymers. III. Microstructural transitions and model verification
Authors: Leary David F. , Williams Michael C. 
Published: April 2003

AbstractThe predictions of a model presented previously are tested with data on five styrenebutadiene–styrene copolymers. Differential scanning calorimetry and laser light transmission are the primary tools, spanning 180–630°K, with some evidence supplied also by electron microscopy and mechanical properties. The existence of a first‐order phase transition, characterized by a separation temperatureTs, is verified and found to be predictable by the model. Details of morphology, including transitions in microstructure in certain temperature ranges, are also reported and shown to be consistent with the theory.
Effect of relaxation properties on the adhesion of rubber
Authors: Kendall K. 
Published: April 2003

AbstractThe adhesion to glass of rubbers with different relaxation properties but similar surface condition has been compared using the thin film peel test. At higher peeling stresses, the rubber–glass interface fractured at constant velocity and all rubbers gave the same adhesive energy values. However, at lower peel stresses, the lossy rubber appeared to adhere more strongly due to a crack‐slowing phenomenon at the rubber–glass interface.
Morphology of siloxane block copolymers: Tetramethyl‐p‐silphenylene siloxane–dimethylsiloxane
Authors: Kojima M. , Magill J. H. , Merker R. L. 
Published: April 2003

AbstractThe morphological features of random block copolymers of tetramethyl‐p‐silphenylene (TMPS) and dimethylsiloxane (DMS) have been studied as a function of copolymer composition. Wide‐angle and small‐angle x‐ray diffraction coupled with several electron diffraction and microscopy studies were used to investigate these materials. The results of this work clearly indicate that the amorphous segments do not enter into the crystalline lattice of the crystallizable component which is varied in content from 90% to 30%. Over the entire range of compositions the block copolymers are crystallizable. Spherulites can be grown from the melt, and single crystals and/or spherulites may be obtained from solution. Single crystals can be obtained over the entire range of compositions provided ample time is allowed for crystallization. The crystalline TMPS component exhibits tetragonal symmetry at all compositions. The amorphous phase manifests itself as a diffuse halo in patterns obtained by electron and x‐ray diffraction.
Relationship between structure and dielectric behavior of stereoregular poly(methyl methacrylate) in the glassy state
Authors: Tanaka Akira , Ishida Yoichi 
Published: April 2003

AbstractIn order to elucidate the relationship between dielectric behavior and structure in solid polymers, we studied the dielectric relaxation of stereoregular poly(methyl methacrylate) (PMMA) in the glassy state. Assuming that the extremes of molecular structure are attained in the crystal and in solution, the most probable conformation of the main chain in the glassy state is estimated for isotactic and syndiotactic PMMA in terms of conformational analysis, the unperturbed mean‐square end‐to‐end distance in solution, and the NMR second moment in the glassy state. Under the assumption that the molecular structure varies in a limited range near the most probable conformation and that the α‐methyl group rotates freely, the energy barrier for the rotation of the side group is calculated. With the calculated energy barrier, the dielectric relaxation due to the side group is interpreted fairly satisfactorily by the barrier theory of Hoffman and Lauritzen, although the width of the relaxation curve is not. The experimental result that the loss peak of syndiotactic PMMA is located at higher temperature than that of isotactic PMMA is interpreted qualitatively in terms of different conformations for the syndiotactic and isotactic chains.
Theory of phase transition kinetics with growth site impingement. I. Homogeneous nucleation
Authors: Tobin Marvin C. 
Published: April 2003

AbstractThe nonlinear integral equations governing phase transition kinetics with homogeneous nucleation and growth site impingement are developed and solved to the first order for the two‐dimensional case. It is shown that the fractional transformed area at time t is given approximately by a(t) = Kt3/(1 + Kt3). The iteration method used to get the solution is applicable to certain other nonlinear differential and integral equations. It is shown that the theory predicts the total number of growth sites formed, and that the nucleation rate and growth constants can be deduced from this and the gross kinetic data. The extension of the method of three‐dimensional growth is indicated.
Effect of temperature and molecular weight on the rate of spreading of polystyrene melts on plane soda lime glass surfaces
Authors: Lau Wayne W. Y. , Burns Charles M. 
Published: April 2003

AbstractThe effect of temperature T and weight‐average molecular weight M̄w on the rate of spreading of polystyrene melts on plane solid surfaces has been examined. The activation energy E of spreading was estimated to be 25.2 ± 3 kcal/mole, which is of the same magnitude as the activation energy for flow of polystyrene melts. The rate of spreading was found to be inversely proportional to M̄w raised to the 1.5 power. This rate of spreading, measured as the time rate of increase in the liquid–solid contact area, dA/dt, could be expressed as

where γ1v is the melt surface tension and θd and θs are the dynamic and static contact angles, respectively. The numerical value of K has been calculated to be (6.025 ± 3.693) × 10−14 in the temperature range of 110–260°C and for the values of M̄w from 2000 to 37000.
Normal coordinate analysis of cis‐1,4‐polybutadiene
Authors: Coleman M. M. , Tabb D. L. , Farmer B. L. , Koenig J. L. 
Published: April 2003

AbstractThe fundamental vibrational frequencies of an isolated chain of cis‐1,4‐polybutadiene have been calculated. Infrared and polarized Raman data are used in the force constant refinement routine. The assignments of the vibrational frequencies are discussed in terms of the potential energy distribution.
Small‐angle light scattering from hedrites, ovoids, and spiral ovoids. II. Experimental
Authors: Gałȩski A. , Kryszewski M. 
Published: April 2003

AbstractProcedures for obtaining hedrites, ovoids, and spiral ovoids in polyoxymethylene are described. Results of morphological studies on these structures by optical and electron microscopy are presented. Small‐angle light scattering studies on single isolated supermolecular structures are described. The Vv and Hv diffraction patterns obtained experimentally are discussed in the light of theoretical results of Part I of this study.
Edge yielding in poly(vinyl chloride) films
Authors: Martin John R. , Johnson Julian F. 
Published: April 2003

AbstractSamples of thin, unplasticized PVC films were fatigued to rupture in nitrogen and ethanol vapor. Examination of the fracture surface edges showed unusual yielding due to the proximity of an unconstrained surface. The scanning electron microscope (SEM) photomicrographs show several indications of supermolecular order in these highly oriented edges and possibly in the relatively unoriented bulk material.
Effect of morphology on the dynamic mechanical properties of a semicrystalline polysiloxane
Authors: Murray A. D. , Markovitz Hershel 
Published: April 2003

AbstractThe dynamic mechanical properties of semicrystalline poly(tetramethyl‐p‐silphenylene siloxane) in three morphological preparations were measured over the wide frequency range of about 0.002 Hz to 500 Hz and the temperature range of about − 190°C to 100°C. The three samples were all isothermally crystallized at 125°C. Two samples had a spherulite size of 25 μ diameter but differed in the time allowed for secondary crystallization. The other sample had a smaller spherulite size. By assuming compliance additivity, the viscoelastic behavior could be separated into five relaxation processes with an indication that a sixth existed at low temperature. Two processes called γ1 and γ2 could be resolved at low temperatures. The γ1 process was associated with the amorphous region since the peak strength was affected by the rate of cooling through the glass transition region; the γ2 peak, unaffected by cooling rate, is attributed to the crystalline part. In the high‐temperature region, the β peak is associated with the glass transition and has a shape and location that is essentially independent of the morphology. The highest temperature α2 process, whose maximum was not observed in the experimental range covered, is attributed to the crystalline region and is sensitive to changes in crystallization history. The strength of the α1 process unlike that of the other processes was found to be a function of temperature; it was associated with the noncrystalline region.
Modified graessley theory for non‐newtonian viscosities of polydimethylsiloxanes and their solutions
Authors: Ito Yoshio , Shishido Shunsuke 
Published: April 2003

AbstractA deviation from Graessley's theory of entanglement viscosity appears at very high shear rates when the flow of polydimethylsiloxanes of various molecular weights and their solutions with various concentrations is measured by the capillary method. In order to explain this deviation, a modified Graessley theory is proposed according to the previously reported suggestion that frictional viscosity appears not to be negligible at high shear rates. A reducing procedure taking a frictional viscosity parameter into account was performed. All of the reduced data are combined to give a master curve in spite of a wide range of molecular weight, concentration, and shear rate (from the lower Newtonian to very highest non‐Newtonian flow region). The findings from the reducing procedure completely explain the mechanism of non‐Newtonian flow for the bulk polymers with various molecular weights, including those below the critical molecular weight for entanglement, and for polymer solutions at any concentration. The viscosity of the linear polymer system consists of the shear‐dependent entanglement term ηent proposed by Graessley and the shear‐independent frictional term ηfric. The non‐Newtonian behavior depends on the ratio of ηent/ηfric at the shear rate of measurement. The ratio of zero‐shear entanglement viscosity ηent,0 to ηfric and the critical shear rate for onset of the non‐Newtonian flow may be used as a measure of the non‐Newtonian behavior of the system and a measure of capability for its rising, respectively. The Graessley theory is to be included in the present modified theory and is applicable to the case of ηentηfric ≫ 1.
Effects of peroxide bonds and their degradation products on the dielectric relaxations of polystyrene
Authors: Yano Okimichi , Wada Yasaku 
Published: April 2003

AbstractPolystyrene radically polymerized in atmosphere of air is composed of bisegment (C‐A) or trisegment (C‐A‐C) block copolymers consisting of styrene segment (A) and styrene peroxide segment (C). Dielectric measurements of a system of copolymers of styrene and oxygen were obtained above the glass temperature. Three primary relaxations, a, b, and c, in order of descending temperature, were found corresponding to three microphases: styrene phase (phase a), styrene peroxide phase (phase c), and an intermediate phase (phase b) which contains a low concentration of peroxide bonds. An alternating copolymer of styrene and oxygen exhibits the relaxation c alone. With heat treatment above the glass temperature, relaxation c and subsequently relaxation b vanish with thermal degradation of peroxide bonds. The sum of relaxation strengths is linearly related to the content of peroxide bonds which was evaluated by the elementary analysis and DTA. Below the glass temperature, the temperature dependence of dielectric loss of carefully purified polystyrene without peroxide bonds shows very weak peaks which correspond to γ (200°K at 10 kHz) and δ (50°K at 10 kHz) peaks, respectively, in the activation plot. When low molecular degradation products of peroxide bonds are occluded or impurities such as benzaldehyde are added into the specimen, the height of the γ peak is appreciably enhanced, indicating that the reorientation of small polar molecules in polystyrene accompanies the vibration of the phenyl group about the CC6H5 bond which gives rise to the γ relaxation.
Distribution of monomer configurations in polypropylene as determined with 13C NMR
Authors: Randall J. C. 
Published: April 2003

AbstractAn amorphous polypropylene sample was examined by using 13C NMR at 25.2 MHz and all ten possible methyl resonances from monomer pentads were observed. Assignments were made through a consideration of an additivity relationship among the methyl resonances. Confirmation for the assignments was obtained through observed conformity of the methyl resonance intensity distribution with second‐order Markov statistics. The relative intensity distribution of the methyl resonances can be used to characterize the structure of polypropylenes with confidence, since experimentally it is shown that an equal nuclear Overhauser effect exists for each of the methyl resonances.
Brillouin scattering in amorphous polymeric solids
Authors: Mitchell R. S. , Guillet J. E. 
Published: April 2003

AbstractBrillouin scattering of laser light has been used to study the temperature dependence of phonon velocity in a variety of amorphous polymeric systems, particularly internally and externally plasticized methacrylates. Discontinuities in the temperature coefficient of the hypersound velocities are observed at the glass transition temperatures (Tg). This phenomenon is related to changes in the temperature behavior of the specific volume accompanied by corresponding discontinuities in certain second‐order thermodynamic quantities. This method was also used to examine the temperature dependence of the Landau‐Placzek ratio.This ratio is relatively large in polymer systems and appears to be independent of temperature in the region of the glass transition, provided that there are no internal strains in the sample at the temperature of measurement. Evidence is presented which suggests that the abrupt changes in this ratio at Tg reported by earlier workers were due to kinetic effects related to the relaxation of internal strains above Tg, and the results of recent studies by other investigators, both corroborating and supplementing the present work, are reviewed.