bluuebunny/crossref_metadata_2025_split huggingface dataset:
Graphical representation of the state of orientation of polymer systems
Authors: Nomura Shunji , Nakamura Nobiru , Kawai Hiromichi 
Published: April 2003

AbstractThe orientation distribution function for noncrystalline structural units in polymer systems cannot be determined completely from any experimental source; only the second and/or fourth moments of the distribution function, i.e., the second and/or fourth orders of the generalized orientation factors Flmj, can be evaluated. It is there‐fore necessary to estimate the distribution function from F2mj and F4mj. In this paper, a graphical representation of the state of orientation is first discussed in terms of plots of F40j against F20j for several types of distribution functions for uniaxial orientation. These are three types of extreme concentration of the distribution at particular polar angles θ0 given by θ0 = 0, 0<θ0<π/2, and θ0 = π/2; five types of rather realistic distributions having single maxima at θj = 0, θ0, π/2 and double maxima at θj = 0, π/2, and a single minimum at θj = θ0; and four types of more realistic distributions including Kratky's floating rod model in an affine matrix. Second, estimation of the distribution function for uniaxial orientation from F40j and F20j is discussed quantitatively in terms of the mean‐square error by three approximation methods: (a) expansion of the distribution function in finite series of spherical harmonics through the fourth order, (b) approximation of the distribution function as a composite of two components, random orientation and a particular orientation distribution given by Na (cos2θj)a, Na being a constant, and (c) approximation of the distribution function by Na (cos2θj)a alone. It is concluded that when the orientation distribution is sharp, estimation by the second method of approximation gives a smaller error than the first.
Adhesion of viscoelastic materials to rigid substrates. III. Energy criterion for failure
Authors: Gent A. N. , Kinloch A. J. 
Published: April 2003

AbstractMeasurements are described of the strength of a model adhesive joint subjected to (1) tensile rupture, with the interface containing a small unbonded region of varying size, and (2) pure shear deformation, in the form of a partly unbonded sheet. These, and previous measurements of resistance to peeling separation, are all shown to be consistent with an energy criterion for adhesive failure. The characteristic failure energy per unit area of interface has been determined for the model adhesive material as a function of the effective rate of detachment, over a wide range covering almost the entire spectrum of viscoelastic response. The values obtained are found to increase from levels only slightly higher than thermodynamic considerations would predict, i.e., 102−103ergs/cm2, at low rates of crack propagation, up to a value of about 106ergs/cm2at high rates when the material responds in a glasslike manner. These results suggest that the failure energy has two components: the (reversible) work of adsorption and the (irreversible) work of deformation of the adhesive in effecting separation.
Laser‐Raman spectra of vinyl chloride‐vinylidene chloride copolymers
Authors: Meeks M. , Koenig J. L. 
Published: April 2003

AbstractSeveral copolymers as well as homopolymers of vinylidene chloride and vinyl chloride have been examined by Raman spectroscopy. Probabilities of concentrations of monomer sequences have been calculated from known reactivity ratios. Surface scattering intensities at some frequencies were found to be linearly proportional to specific microstructure concentrations. Normalization of scattering intensities was accomplished using the intensity of the CH2 asymmetric stretching mode at 2926 cm‐1, which is common to all samples examined. Good correlation was found for the concentrations of comonomer sequences {B}, {BB}, {BBB}, {AA} and {AAAA} in which A denotes vinylidene chloride and B vinyl chloride.
Determination of the pressure coefficient and pressure effects in capillary flow
Authors: Penwell Richard C. , Porter Roger S. , Middleman Stanley 
Published: April 2003

AbstractGeneral expressions for determining the pressure coefficient and axial distribution of the viscosity and pressure in capillary flow are derived for Newtonian and shear‐thinning fluids. The pressure‐dependent viscosity model is obtained from the WLF equation as derived from Doolittle's free volume theory. The model has also been derived from Eyring's hole theory for viscosity. Poiseuille's equation is modified to correct for the pressure effect on viscosity. A Newtonian, low‐molecular‐weight polystyrene and a shear‐thinning, high‐molecular‐weight polystyrene were tested in an Instron capillary rheometer. The axial velocity distribution was found to be negligibly affected by pressure whereas the viscosity was shown to increase markedly with a decrease in volume. The resulting pressure effects on the viscosity of both samples were analyzed by using the derived expressions.
Electronic states at defects in infinite polyenes
Authors: Begg A. H. , Pugh D. 
Published: April 2003

AbstractThe electronic states localized at defects in a polyene chain with alternating bond lengths have been investigated in the Hückel approximation by direct computation on large rings. The defects considered include substitutional impurities and bond distortions. None of the cases treated seem likely to be thermally activated donor or acceptor centers, but several examples of deep or shallow traps for electrons in the conduction band are found.
Nuclear magnetic resonance study of rubber–carbon black interactions
Authors: Kaufman Stanley , Slichter W. P. , Davis D. D. 
Published: April 2003

AbstractThe mobilities of polymer chain segments in mixtures of rubber and carbon black were investigated by nuclear magnetic resonance. Spin–spin relaxation time (T2) measurements on cis‐polybutadiene and ethylene–propylene–diene rubber (EPDM) bound rubbers detected at least two relaxing regions: an immobile region and a relatively free region. The molecular motions in the relatively free region are still constrained compared to those of the pure gum.
Mechanical relaxations in polyamides
Authors: Prevorsek D. C. , Butler R. H. , Reimschuessel H. K. 
Published: April 2003

AbstractDynamic mechanical measurements were carried out as a function of temperature (−100 to + 180°C) and frequency (3.5 to 110 cps) for a series of aliphatic terpolyamides, nylon 6 and nylon 12. Effect of crosslinking with toluene diisocyanate, of absorbed water, and of frequency are used to estimate the statistical segment length associated with the α′ relaxation. The effects of variations in the aliphatic chain length in the repeating unit on the temperature of the α′ relaxation are examined by means of copolymer rules with a view to explaining the reported insensitivity of the glass transition temperature of these polymers to changes in (CH2)/(amide) group ratio. From the estimated length of the segmental motion associated with the α′ relaxation it is inferred that in a series of polyamides of the type nylon X or nylon X,Y (where X or Y = 3, 4, 5, 6, etc.) there should be a relatively small change in the temperature of the α′ transition for those polyamides having X or Y less than about 45. Experiments which are intended to establish the position of the crystalline α–γ transition are discussed.
Contact angle of polyethylene on copper and its effect on adhesion
Authors: Sykes J. M. , Hoar T. P. 
Published: April 2003

AbstractTo determine whether the large differences in adhesion for polyethylene coatings applied to different types of copper surface could be attributed to changes in work of adhesion or wettability, the variations of contact angle with time has been measured for molten polyethylene droplets on these surfaces. It is concluded from these measurements that the low peel strengths obtained on certain substrates cannot be accounted for by a low work of adhesion of poor wetting of the surface.
Stress‐optical coefficients of swollen polymer networks
Authors: Gent A. N. , Kuan T. H. 
Published: April 2003

AbstractStress‐optical coefficients have been determined for crosslinked samples of polyethylen (PE) and polystyrene (PS) at high temperatures, i.e., in the rubberlike state, and when swollen in a variety of liquids. For PE, swelling liquids with long straight molecules gave large values of optical anisotropy whereas liquids with more symmetrical molecules gave minimum values, as found previously for cis‐ polyisoprene and trans‐polyisoprene. This solvent effect is attributed to short‐range orientational order in molecularly asymmetric media. Sizes of the equivalent random link for unperturbed molecules of these three polymers were deduced from the minimum values of optical anisotropy. Measures of shape asymmetry were also obtained by matching the optical anisotropy of samples when unswollen with that observed when swollen with a liquid of known molecular asymmetry. Reasonable agreement was found to hold between the two methods. In contrast, the optical anisotropy of swollen PS was found to be substantially independent of the swelling liquid. The apparent absence of a molecular ordering effect in this case is attributed to the bulky nature of the PS molecule. A marked reduction in optical anisotropy on swelling is ascribed to increased phenyl group motion.
New approach to the effects of pressure dependence on sedimentation velocity experiments
Authors: Dishon Menachem , Stroot Michael T. , Weiss George H. , Yphantis David A. 
Published: April 2003

AbstractA theory is developed for sedimentation velocity experiments when the sedimentation coefficient sp depends on pressure P as sp/so = (1 + γP)−1, where γ is a constant. In contrast to the more usually analyzed from sp/so = 1 − γP, this model does not lead, in extreme cases, to a negative sedimentation rate. A theory is presented for homogeneous macromolecules sedimenting with no diffusion. It leads to estimations of so and γ from a knowledge of the point of maximum concentration gradient as a function of time. Results of these calculations are compared with accurate numerical solutions of the Lamm equation with diffusion included.
ESR study of radiation damage in TPX polymer (poly‐4‐methylpentene‐1)
Authors: Goodhead D. T. 
Published: April 2003

AbstractElectron spin resonance spectroscopy has been used to study the effects of 15 MeV electrons, x‐rays, and ultraviolet radiation on poly‐4‐methylpentene‐1 (TPX) both at 77°K and at room temperature. At least seven identifiably different paramagnetic species are observable in unstabilized oxygen‐free TPX after irradiation, and additional species exist in the stabilized grades. The species which predominates under most conditions is interpreted as being due to the loss of hydrogen from a main‐chain tertiary carbon atom; interpretations of most of the other species are also given. Oxygen is found to diffuse rapidly into the polymer and to react with the free radicals to form peroxy species. In the absence of oxygen the radiation damage is expected to lead ultimately to crosslinking or double‐bond formation, or with oxygen to degradation. The general nature of the free radicals produced by electron or x‐ray irradiation is the same, but there are significant differences for ultraviolet irradiation. The observed spectra for irradiated TPX and their interpretations are in good agreement with the spectra and later interpretations for irradiated polypropylene, but are in less satisfactory agreement with the published papers on polybutene‐1 and poly‐3‐methylbutene‐1.
Redrawing of oriented polyethylene film
Authors: Yamada Mitsuo , Miyasaka Keizo , Ishikawa Kinzo 
Published: April 2003

AbstractDrawn and subsequently annealed polyethylene film was restretched along the original draw axis at various temperatures. The internal deformation was analyzed in terms of the structural parameters of a simplified model. The elementary deformations are the rotation of crystals around the b axis and shear at the crystal interface. The rigidity of the crystal plays an important role during extension; and as a result, disorientation of chains in the crystal occurs at high strain. At the same time, crystals deform in such a way that the crystalline chains tilt about the b axis along the (h00) plane. This deformation of the crystal is affected by temperature. The increase in long spacing with extension can be interpreted roughly by the changes in structural parameters. The strain in amorphous region in also discussed in relation to these parameters.
Morphological effects on formation and behavior of radicals in γ‐irradiated polyethylene single crystals
Authors: Kusumoto Naoshi , Yamamoto Tateo , Takayanagi Motowo 
Published: April 2003

AbstractPolyethylene single crystals differing in lamellar thickness, both as‐grown and annealed with different lamellar thickness, were irradiated by γ‐rays to a dose of about 107 rad at liquid nitrogen temperature in vacuo, and then ESR measurements were made. It was found for the as‐grown crystals that alkyl radicals were concentrated at the crystal surface. For the annealed crystals it was found that the radical concentration was greater than in the original crystals because of an increase in disorder with annealing. By assuming that the crystals form blocks upon annealing and that the surface and the interior of the blocks have the same trapping capacities for radicals as in the original crystals, the dependence of the size of the blocks upon variation in annealing temperature and the original lamellar thickness was estimated. This estimate is supported by the theory of the thickening process of single crystals. Two types of radical reactions with different reaction rates were found to occur simultaneously at room temperature. The rapid process was independent of lamellar thickness and was related to the reaction of radicals mainly in the surface region and the defects within the crystals. The slow process was strongly dependent on the lamellar thickness (i.e., the reaction rate was much depressed as the lamellar thickness was increased) and was inferred to be closely related to molecular motions manifested in viscoelastic measurements by the crystalline dispersion αc.
Infrared studies of drawn polyethylene. II. Orientation behavior of highly drawn linear and ethyl‐branched polyethylene
Authors: Glenz W. , Peterlin A. 
Published: April 2003

AbstractInfrared dichroism is employed to study the orientation of chain molecules in linear and ethyl‐branched polyethylene in the crystalline and noncrystalline regions during drawing and subsequent annealing. A crystalline (1894 cm−1) and a noncrystalline (1368 cm−1) band, as well as the bands at 909 cm−1 and 1375 cm−1 resulting from vinyl endgroups and methyl endgroups and sidegroups, are studied. For these bands relative orientation functions are derived and compared as a function of draw ratio and annealing temperature. It is shown that the relative orientation functions as derived from the dichroism of the noncrystalline, vinyl and methyl bands follow the same curve while the orientation function for the crystalline bands does not. These results support a two‐phase model for partially crystalline polyethylene and additionally favor segregation of the endgroups and sidegroups in the noncrystalline component during crystallization. It is further shown that shrinkage occurs at the temperature at which the noncrystalline chain molecules start to disorient. From the dichroism of the methyl groups in ethyl‐branched polyethylene, a value for the mean orientation of the noncrystalline chain molecules is calculated. We obtain for the orientation function of the noncrystalline regions at highest draw ratios (λ = 15–20), f = 0.35–0.57, while the chain molecules in the crystallites are nearly perfectly oriented (f ≈ 1.0). On the assumption that the noncrystalline component consists of folds, tie molecules, and chain ends, the different contributions of these components to the overall orientation are estimated. From these the relative number of CH2 groups incorporated into folds, tie molecules, and cilia can be derived. Further, on the basis of a simple structural model, the relative number of chains on the crystal surface contributing to the different noncrystalline components and their average length are estimated.
Properties of ethylene–propylene–vinyl chloride graft copolymers. I. Viscoelasticity of ethylene–propylene copolymers
Authors: Bares J. 
Published: April 2003

AbstractThe viscoelastic behavior of two different ethylene–propylene copolymers was studied as a function of the molar ratios of the components and the distribution of the lengths of the ethylene and propylene sequences. The glass transition temperatures Tg agree with the values calculated from relations between Tg and component ratio established by other authors. The copolymer with longer ethylene and propylene sequences was found to exhibit a relaxation spectrum with a slope less steep than −0.5. This broadening is explained by the broader distribution of friction factors of the statistical segments in this copolymer and by differences in crystallike nearest‐neighbor packing.
Glass transition in partially sulfonated polystyrene
Authors: Wallace Richard A. 
Published: April 2003

AbstractThe glass transition temperature Tg of partially sulfonated polystyrene has been measured dilatometrically as a function of degree of sulfonation. A semitheoretical relationship between Tg and degree of sulfonation has been derived by treating the strong‐acid polymer as a highly polar copolymer of styrene and styrenesulfonic acid. The Tg of copolymer has been found to increase linearly up to 0.15 weight fraction of styrene‐sulfonic acid wA as given by:

where TgB is the glass transition temperature of loosely crosslined (1%) polystyrene matrix. Our experimental results agree well with theoretical relations developed on the basis of the iso‐free‐volume state of glass transition applied to sulfonated polystyrene. The marked linear increase in copolymer Tg with the styrenesulfonic acid is accounted for by the effect of progressively higher intermolecular forces due to the highly polar sulfonic acid substituents.
A new relaxation process in the high‐elastic state at low temperatures
Authors: Bartenev G. M. 
Published: April 2003

AbstractA new relaxation process, explaining the change of elasticity in rubberlike polymers at critical stress (0.1−0.5 kgf/cm2) has been discovered. This process is characterized by the low value of activation energy (weak temperature dependence of relaxation times) and large sizes of kinetic units (strong dependence of relaxation time on stress). Critical stress depend on temperature and for rubberlike polymers turns to zero at 40°−60°C. Mechanism of the phenomena can be explained by the existence of the ordered molecular microregions, creating additional crosslinking points of nonchemical nature with free chains of the network, breaking up at critical stress. Observed phenomena is analogous to the process of forced rubber elasticity of those polymers in glassy state. Critical stress is analogous to the limit of forced rubber elasticity below glass transition temperature.
Sedimentation equilibrium in nonideal heterogeneous systems. I. Fundamental equations for heterogeneous solute systems and some preliminary results
Authors: Kotaka Tadao , Donkai Nobuo , Inagaki Hiroshi 
Published: April 2003

AbstractThe sedimentation‐equilibrium method is extended to treat nonideal solutions of heterogeneous macromolecules. The solute is assumed to be heterogeneous not only in molecular weight but also in other quantities such as partial specific volume, second virial coefficient and specific refractive increment. General expressions for various observable molecular weights, especially for weight‐average, z‐average, and number‐average molecular weights, are derived. Their dependences on sedimentation parameter and solute concentration are discussed in detail. For the extrapolation of observable molecular weights, giving a type of weight‐average, and z‐average, to infinite dilution to estimate the molecular weight and the second virial coefficient, average concentration is superior as a concentration variable to original concentration. The plots of observable molecular weight versus average concentration are usually less influenced by the choice of the sedimentation parameter, especially of rotor speed. The general expressions are applied to a few special cases; monodisperse polymer, polydisperse homologous polymer, and polymer blend. The results are compared with experiments on a monodisperse, polystyrene, a polydisperse poly(methyl methacrylate), and a mixture of the two polymers, all in 2‐butanone at 25°C. The agreement between the theory and experiments is satisfactory.
Theory of deformation and strain‐induced crystallization of an elastomeric network polymer
Authors: Yamamoto Misazo , White James L. 
Published: April 2003

AbstractA new theory of deformation and strain induced crystallization of network polymers has been developed. The effects of lattice vacancies, variation in distribution of trans and gauche bond conformations in stretched amorphous polymers, and the crystallite orientation in the partially crystalline stretched vulcanizate were considered in the evaluation of their partition functions. Stress‐extension ratio relationships were evaluated for the amorphous and semicrystalline polymers. The rise in melting temperature due to strain induced crystallization is discussed. The new theory seems to be in closer agreement with the actual strain‐induced crystallization process than earlier research.
Stress‐optical coefficient of poly‐1,4‐butadienes
Authors: Fukuda M. , Wilkes G. L. , Stein R. S. 
Published: April 2003

AbstractThe stress‐optical coefficient of poly‐1,4‐butadiene is measured as a function of strain, cis/trans ratio, and degree of swelling. Deviations from the Kuhn‐Grün theory are found which are reduced upon swelling. Results are interpreted in terms of the Shindo‐Stein theory of birefringence of polymers containing statistical segments of different sizes. This interpretation for the unswollen polymer leads to the unreasonable conclusion that the cis segment is considerably longer than the trans. Reinterpretation for the swollen polymer leads to the more reasonable conclusion that the trans segment is slightly longer than the cis. The dependence of the stress‐optical coefficient on the nature of the swelling solvent is similar to the observations of Gent and Nagai and is believed to result from the effect of internal field from anisotropic solvent molecules. It is felt that the value of the stress‐optical coefficient for the dry rubber is modified by the internal field from somewhat locally ordered neighboring polymer molecules.