bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of orientation and structure of crazed matter in polystyrene. I. Optical measurements
Authors: Brown H. R. 
Published: April 2003

AbstractThe optical birefringence and refractive index have been measured for crazes grown in specimens of varying thickness. The birefringence was found to consist of the sum of a small negative orientation term and a large positive form term. The latter term could be altered by filling the craze with liquids of various different refractive indexes. Two crazes, which showed a relatively constant width as the specimen thickness changed, could be described by a model with craze having a constant refractive index and birefringence but with impervious dense skins on either side. The numerical value of the form birefringence was approximately 0.6 of that predicted from a model of parallel rods which is not surprising as crazes have a networklike structure. The values of craze refractive index were in good agreement with other measurements. The existence of skins, of thickness approximately 300 nm, places some doubt on the relevance of thin‐film electron microscope observations to the situation in the bulk. Other crazes which tapered in width were found to show both varying skin thickness and refractive index along their length.
Effects of extension on the gas permeability of hard elastic polypropylene film
Authors: Shimizu Y. , Akabane H. , Tanioka A. , Miyasaka K. , Ishikawa K. 
Published: April 2003

AbstractPermeabilities of He, N2, O2, Ar, and CO2 in stretched hard‐elastic polypropylene film exhibiting extraordinarily high elasticity were measured as functions of temperature, pressure, and extension ratio. The permeability decreases slightly for strains of 10% or less, increases abruptly for strains from 15% to 30%, and then increases gradually for strains up to 100%. In recovery from extension, changes in permeability are similar to those in extension. The gas permeation mechanism is of the solution‐diffusion type for extensions less than 15%. Above 15% extension, the mechanism involves permeation through voids created during deformation. The apparent mean pore size, estimated from the gas permeation, is very large at comparatively small extensions, and decreases with increasing extension. The change in specific volume accompanying extension of the sample indicates that only a very small fraction of the voids are interconnected to form channels that traverse the thickness of the film.
Determination of crystallinity of swollen poly(vinyl alcohol) by laser Raman spectroscopy
Authors: Iwamoto Reikichi , Miya Masaru , Mima Seiichi 
Published: April 2003

AbstractLaser Raman spectra of atactic poly(vinyl alcohol) (PVA) after heat treatment and/or swelling in water have been obtained. An amorphous Raman band is observed at 1124 cm−1, while a crystalline Raman band is found at 1147 cm−1. A new method for crystallinity determination is proposed, in which the amorphous band is used instead of the crystalline band. The method is superior to others for water‐swollen PVA samples. Laser Raman spectra of swollen PVA revealed that swelling causes destruction of a major fraction of the crystalline regions and the remaining intact crystalline part increases with increasing temperature of heat treatment.
Thermal properties of polyamides containing 1,3–cyclohexane rings
Authors: Inoue Kazuo , Hoshino Sadao 
Published: April 2003

AbstractThe effect of the 1,3–cyclohexane rings in the chain backbone on thermal properties of polyamides, especially the glass‐transition temperature, has been studied using polyamides based on 1,3–cyclohexanebis(methylamine). The increase in glass‐transition temperature was far greater than that obtained with the analogous polymers containing m–benzene rings. However, the effects of 1,4–cyclohexane and p‐benzene rings are nearly equal. Several possible causes for this difference are examined. It is concluded that restricted chain mobility due to steric hindrance of the cis‐1,3–cyclohexane ring, the predominant isomer, is the most likely cause of the difference.
Optical rotatory dispersion and vacuum ultraviolet circular dichroism of poly[(R)‐oxypropylene]
Authors: Hirano Tsuneo , Sato Akira , Tsuruta Teiji , Johnson W. Curtis 
Published: April 2003

AbstractThe circular dichroism (CD) spectrum of poly[(R)‐oxypropylene] in a number of solvents has been measured in the vacuum ultraviolet region. Two CD bands were measured for cyclohexane, acetonitrile, and trifluoroethanol solutions. The CD spectrum was extended to 140 nm and three bands were measured in a 1,1,1,3,3,3‐hexafluoro‐2‐propanol solution. The similarity of these four CD spectra in sign, shape, and intensity confirm that poly[(R)‐oxypropylene] has similar conformations in all solvents studied, even though the optical rotatory dispersion (ORD) in the visible region is positive for the cyclohexane solution but negative for the alcohol solutions. A Kronig–Kramers transform of the two CD bands observed for the cyclohexane solution accounts for the observed positive ORD spectrum. In contrast, a third large and negative CD band centered below 160 nm is necessary to account for the negative ORD spectra observed for the alcohol solutions. Apparently the anomalous sign variation of the ORD curves observed in the visible region is due to subtle changes in the interplay of a large number of CD bands. Solvent interaction, observed as a blue shift of the first two CD bands for the alcohol solutions, could produce the subtle changes necessary to change the sign of the ORD curve in the visible region. The first two CD bands of poly[(R)‐oxypropylene] are tentatively assigned as nσ* and the third as an n3s.
Dielectric evidence for thermal creation of defects in polyethylene crystals
Authors: Boyd Richard H. , Sayre John A. 
Published: April 2003

AbstractA recent study of the effect of pressure on the dielectric α process in slightly oxidized linear polyethylene showed that the intensity of the process decreases with increasing temperature. This phenomenon was attributed to thermal generation of conformational defects. In the present work a quantitative interpretation of that data is carried out to arrive at defect creation energy parameters. It is found that the creation energy lies in the range of 3–6 kcal/mole and that it has a high degeneracy or statistical weight (in the range 40–800). The statistical weight is interpreted as largely arising from the number of sites in a given crystalline chain for a defect to occur, that is, the number of CH2 units spanning the crystal. It is speculated that kinks are the likely conformational defect.
Oriented polymers from solution. I. A novel method for producing polyethylene films
Authors: Coombes A. , Keller A. 
Published: April 2003

AbstractA novel method for the production of uniaxially oriented polyethylene film is demonstrated, it being an extension of the “surface growth” method for obtaining polyethylene fibers from solution using a Couette apparatus. The film growth is found to be affected by temperature, rotor speed, rotor material, and surface roughness. Together with its possible practical importance, film growth is presented as a useful means of sample preparation and as a way to increased linear fiber growth rates. In addition, its use for studies on solution grown polypropylene fibers is indicated as well as its implications for “surface growth” of polymer crystals in general.
Total integrated light‐scattering intensity from polymeric solids
Authors: Koberstein J. , Russell T. P. , Stein R. S. 
Published: April 2003

AbstractPresently existing theories of small‐angle light scattering by polymeric materials are extended by consideration of the total integrated scattering intensity. It is shown how this quantity, known as the total integral or Porod invariant in small‐angle x‐ray scattering, may be used to calculate the average square of the fluctuations in refractive index and orientation. Calculations are presented using both statistical and model approaches.
Molecular architecture and physicochemical properties of some vinyl alcohol‐vinyl acetate copolymers
Authors: Scholtens B. J. R. , Bijsterbosch B. H. 
Published: April 2003

AbstractTwo series of vinyl alcohol‐vinyl acetate copolymers were prepared by homogeneous and heterogeneous acetylation of the same precursor poly(vinyl alcohol). Their intramolecular monomer distributions were analyzed by IR spectrometry, calorimetry, and differential thermal analysis. The results show a more blocky distribution for the heterogeneously prepared copolymers. The properties of these (co)polymers in dilute aqueous solution were determined by means of viscometry. Whereas the copolymer‐solvent interaction parameter of the homogeneously acetylated, random copolymers hardly varied with acetate content, a definite minimum was found for the blocky copolymers at about 7 mole% vinyl acetate. These findings were attributed to the incompatibility of dissimilar sequences, which sharply decreases with decreasing vinyl acetate sequence length. Up to about 17 mole% vinyl acetate content, the solvent quality for the copolymers is at least as good as for poly(vinyl alcohol). In addition, the dilute solution properties of the samples were established in water saturated with 1‐butanol. For copolymers with up to about 17 mole% vinyl acetate, at 25°C this mixture is a better solvent than water. The highest increase in solvent quality was found for the homopolymer, whereas the increase diminished with acetate content, irrespective of the intramolecular vinyl acetate distribution. These findings are explained in terms of preferential adsorption of 1‐butanol onto the (co)polymer backbone due to hydrophobic interactions and prevention of this process by the bulky acetate groups.
Viscosity of poly(vinyl acetate) and its concentrated solutions
Authors: Berry G. C. , Nakayasu H. , Fox T. G. 
Published: April 2003

AbstractData on the viscosity of poly(vinyl acetate) (PVOAc) and its concentrated solutions in diethyl phthalate (DEP) and cetyl alcohol (CeOH) are examined over the molecular weight range 8 × 103 < M < 1.3 × 106, the range 0.15 < φ < 1.0 of the volume fraction φ of polymer, the temperature range 308 to 430°K for PVOAc and its solutions in DEP, and at 396°K in CeOH. The latter is the θ temperature for dilute solutions of PVOAc in CeOH. The data are analyzed with the relation η = KXc(αφM/Mc)a exp[1/β(T – T0)], where a is 1 or 3.4 for αφM less than or greater than a constant Mc, respectively, and XC, is a constant. The expansion factor αφ of the chain dimension is found to be essentially unity for φ > ca. 0.25, increasing with decreasing φ for smaller φ. Both β and T0 depend on φ, and T0 also depends on M at low M.
Relationship of stress to uniaxial strain in crosslinked poly(dimethylsiloxane) over the full range from large compressions to high elongations
Authors: Pak Hyungsuk , Flory Paul J. 
Published: April 2003

AbstractExperiments on inflated sheets of crosslinked poly(dimethylsiloxane) covering a sixfold range of compression are combined with measurements in elongation conducted on specimens from the same sample to obtain the relationship of stress to strain over a 24‐fold range in the extension ratio λ1. With increase in λ the reduced force [f] ≡ f(λ1 – λ)−1 rises to a maximum near λ = 1.2–1.4, then decreases very slowly with further increase in λ. The form of the relationship of [f] to λ confirms recent theory.
Entanglement networks of 1,2‐polybutadiene crosslinked in states of strain. VII. Stress‐birefringence relations
Authors: Carpenter Rick L. , Ferry John D. 
Published: April 2003

AbstractCrosslinks are introduced by γ irradiation into 1,2‐polybutadiene while strained in uniaxial extension near Tg with stretch ratio λ0, thereby trapping a proportion of the entanglements originally present. The stress at any subsequent strain λ is accurately given by the sum σN + σx, where σN is the stress contributed by a trapped entanglement network with λ = 1 as reference and a Mooney–Rivlin stress‐strain relation, and σx is that contributed by a crosslink network with λ = λ0 as reference and neo‐Hookean stress‐strain relation. The birefringence is accurately given as δn = ℯNσN + ℯxσx, where the ℯ's are the respective stress‐optical coefficients. From measurements at λ = λ0 where σx = 0, ℯN can be determined separately. For polymer with 88% 1,2 microstructure, ℯN and ℯx are nearly equal and independent of irradiation dose, though strongly dependent on temperature. For polymer with (95–96)% 1,2, ℯN and ℯx are different (even opposite in sign) and dependent on dose. This behavior is associated with a side reaction of cyclization by the γ irradiation, which is inhibited by the 1,4 moiety in the polymer with lesser 1,2 content. It is responsible for residual birefringence in the state of ease (λ = λs) where σN = –σx and the stress is zero.
Bulk properties of synthetic polymer‐inorganic salt systems. V. Mechanical properties of oriented poly(caproamide)
Authors: Acierno D. , La Mantia F. P. , Polizzotti G. , Ciferri A. 
Published: April 2003

AbstractSingle filaments of nylon‐6 and of its mixtures with KCl, LiCl, and LiBr (salt content up to 5% w/w) were prepared by extrusion at 265°C. As‐spun filaments with a varying degree of orientation were obtained by altering the take‐up velocity a t constant outflow velocity. These as‐spun filaments were further subjected to controlled thermal and mechanical treatments. Determinations of the elastic modulus, of birefringence, of wide‐angle x‐ray scattering, and of shrinkage were carried out for the as‐spun and for the treated filaments. While KCl caused no detectable alteration of the properties of nylon‐6, lithium halides caused a considerable increase of the elastic modulus of the polymer. Under the conditions adopted, moduli up to 14 GPa were obtained. The birefringence of as‐spun fibers was, however, lower when lithium salt was present. Greater shrinkage a t 170°C was exhibited by the salted than by the pure polymer. The body of results has been interpreted in terms of a more efficient orientation of the extruded polymer when lithium salt is present. The latter effect is associated with the role of these salts in reducing the crystallization rate and in increasing the melt viscosity of the polyamide as characterized in preceding papers of this series. Lithium salts also favor the α → γ transformation between the two crystalline forms of nylon‐6. The transformation was, however, reversed under sufficiently high applied stress.
Oriented polymers from solution. II. Fibers and films of polyethylene/polypropylene blends
Authors: Coombes A. , Cannon C. G. , Keller A. 
Published: April 2003

AbstractA version of the surface growth method by Zwijnenburg and Pennings is being used to produce blended fibers of polyethylene and polypropylene under conditions where polypropylene does not yield to this fiber growth technique but would grow films. The blended fiber contains intimately mixed crystalline regions of each pure component and combines thermal and mechanical properties of both. The growth method itself underlines the part played by adsorbed surface layers and entanglements within such layers which can involve the entanglement of chemically different species. This feature suggests a potentially new method for blend production.
Molecular characterization and glassy‐state properties of poly(spiro[2,4]hepta‐4,6‐diene)
Authors: Hayashi Seiji , Ikuma Sadao , Okuyama Kenji , Kajiyama Tisato , Takayanagi Motowo 
Published: April 2003

AbstractPoly(spiro[2,4]hepta‐4,6‐diene) (PSHD) is a random copolymer composed of 1,2 and 1,4 units. Although PSHD has been reported to have a very large Sakurada–Mark–Houwink exponent (a = 1.71) characteristic of rigid rods, a new determination of the intrinsic viscosity–molecular‐weight relation for fractionated samples with known copolymer composition gives a smaller value (0.81). The rigidity of the PSHD molecule was also investigated by calculations of the conformational energy associated with the main chain and the dynamic viscoelasticity associated with the molecular motion in a solid state. A sharp potential energy minimum occurs at a dihedral angle χ1 = 260° in polymer composed of all trans 1,4 units. The dynamic loss tangent for the primary absorption decreases with increasing fraction of the 1,4 unit. These properties result from the characteristics of the stiff 1,4 unit sequences in the molecular chain. The density of PSHD decreases with increasing content of 1,4 units and was found to be considerably smaller than values for typical polymers, in relation to the occupied volume of the repeat unit. This fact can be explained by the peculiar aggregation state of molecular chains composed of rigid and flexible units.
Second virial coefficients of homopolymers and copolymers of butadiene and styrene in tetrahydrofuran
Authors: Stacy C. J. , Kraus Gerard 
Published: April 2003

AbstractSecond virial coefficients have been measured in tetrahydrofuran for a series of anionically polymerized narrow distribution homopolymers and copolymers of butadiene and styrene. The results fit the general empirical equation A2 = M−1/4(0.0216wB + 0.00995wS + CwBwS), where M is the polymer molecular weight, wB and ws are the weight fractions of butadiene and styrene, and C is a constant which is zero for block polymers and equal to 7.9 × 10—3 for random copolymers. The equation is independent of the degree of 1,2 addition of butadiene and fits data on both linear and tetrachain star‐branched polymers within experimental error.
Cellulose acetate butyrate in solution. I. Hydrodynamic behavior
Authors: Vyas N. G. , Shashikant S. , Patel C. K. , Patel R. D. 
Published: April 2003

AbstractCellulose acetate butyrate has been studied in regard to its hydrodynamic properties in several solvents. The polymer was fractionated by precipitation, and the molecular weight distribution of the polymer fractions was determined by gel permeation chromatography. The number‐average molecular weight was estimated by osmometry. The Mark–Houwink–Kuhn–Sakurada relations between viscosity and molecular weights were established, and the unperturbed dimensions of the polymer chains were evaluated. In light of these data, current theories of polymer solutions are discussed. A new method of estimating unperturbed dimensions is proposed for semiflexible linear polymers.
A calorimetric study of acrylate photopolymerization
Authors: Tryson G. R. , Shultz A. R. 
Published: April 2003

AbstractThe kinetics of the photoinitiated polymerization of lauryl acrylate (LA), 1,6‐hexanedioldiacrylate (HDDA) and pentaerythritol tetraacrylate (PET4A) have been investigated using differential scanning calorimetry (DSC). An autoacceleration phenomenon is observed with the multifunctional acrylates, but not with lauryl acrylate. The empirical dependences of reaction rate on such parameters as incident light intensity, initiator concentration, and temperature have been established and are in general found to vary with monomer conversion. Apparent activation energies for the photopolymerizations have been determined from rate versus temperature data. The multifunctional acrylates show an increasing activation energy with monomer conversion, whereas the apparent activation energy for lauryl acrylate not only decreases with conversion, but becomes negative at conversions greater than about 30%. The ratio kp/k is calculated from rate versus conversion data under constant illumination and the (independently determined) initiation rate. Analysis of rate versus time data under nonsteady‐state conditions (light turned off) yields the ratio kt/kp. With these two ratios the rate constants for propagation (kp) and termination (kt) may be separated and their respective values calculated. Both kp and kt are found to decrease substantially with monomer conversion, indicating a significant change in the rates of both the propagation and termination steps as the polymerization advances. These observations are explained in terms of a radical isolation phenomenon and diffusion control of the propagation step.
Light scattering study of an aromatic polyamide‐hydrazide polymer
Authors: Bianchi E. , Ciferri A. , Tealdi A. , Krigbaum W. R. 
Published: April 2003

AbstractThe aromatic Polyamide‐hydrazide, Monsanto X‐500, has been studied by light scattering in dimethyl sulfoxide, a thermodynamically good solvent. The unperturbed dimensions, (〈r〉av/M)1/2 = 1.93 × 10−8 at 25°C., indicate a rather highly extended chain. The persistence length falls in the range 35–63 Å, which corresponds to a length of between two and four formula units. This is considerably smaller than the values which have been reported for the aromatic polyamides, poly(p‐benzamide) and poly(p‐phenylene terephthalamide). X‐500 appears to approximate coil‐like behavior at a molecular weight of 45,000. Theoretical predictions, based upon the 〈r〉av/bL ratio, are compared with the observation that no evidence for an anisotropic phase has been found in X‐500 solutions in dimethyl sulfoxide at polymer volume ranging from 0.12 to 0.19 (depending upon the concentration of added LiCl).
Intrinsic viscosity of polystyrene
Authors: Einaga Y. , Miyaki Y. , Fujita H. 
Published: April 2003

AbstractZero‐shear‐rate intrinsic viscosities [η]0 in benzene at 25°C and in cyclohexane at 34.5°C were measured for two series of polystyrene samples: six fractions ranging in Mw(weight‐average molecular weight) from 8.8 × 106 to 5.7 × 107 and 11 “monodisperse” samples ranging in Mw from 4 × 103 to 4.8 × 106. The results, combined with typical literature data, yielded

These relations cover the broadest range of molecular weights reported so far in the literature on synthetic polymers. In contrast to Slagowski et al., we observe no “anomaly” in the molecular weight dependence of [η]0 for benzene solutions of very high molecular weight samples (>107).
Melting and crystallization of a polyphosphate
Authors: Benkhoucha Rachid , Wunderlich Caryn C. , Wunderlich Bernhard 
Published: April 2003

AbstractLithium polyphosphate crystals produced by crystallization during polymerization and crystallization from the polymer melt were analyzed by thermal analysis. The glass‐transition and melting temperature, heat of fusion, and entropy of fusion were found to be 336°C, 651.5°C, 21 kJ/mole, and 23 J/deg mole, respectively. Crystallization from the macromolecular melt was followed by thermal analysis, x‐ray diffraction, and electron and optical microscopy. It could be shown that chain folding may be the first step to crystallization from the macromolecular melt. Oligomers could not effectively nucleate crystallization. Lithium polyphosphate is shown to present a prime example of the processes involved in crystallization during polymerization and macromolecular melt crystallization.