bluuebunny/crossref_metadata_2025 huggingface dataset:
The spherulitic structure of crystalline polymers. Part III. Geometrical factors in spherulitic growth and the fine‐structure
Authors: Keller A. , Waring J. R. S.
Published: April 2003

The spherulites are built of distinct fibrillar units and their fine‐structure presents two problems: the arrangement of these units and their internal structure. In the present paper the first has been treated in greater detail. Based on direct observations, and on earlier works on nonpolymeric spherulites, a regular periodic branching mechanism of the fibrillar units is proposed, where, in the case of maximum regularity, the position of each branch with respect to the preceding one is defined by one constant branching period and one constant angle in the two‐dimensional case, and by one constant branching period, two constant angles, and a constant direction of rotation in the three‐dimensional case. The various stages of such a spherulitic growth were directly observed in suitable samples. It is shown that this mechanism can lead to helices, to be referred to as “large‐scale helices,” which produce the previously observed zigzag extinction effects. The effects of the thickness of the crystallizing layer is followed, and possible connections between these effects and more general problems of crystal growth are indicated. Investigations of the fine‐structure of the fibrils indicate a closely coiled rope‐like arrangement in samples suitable for these observations. These are on a size of 400 A. and upward, sometimes reaching the limit of the optical microscopic resolution dependent on the preparation. They will be referred to as “small‐scale helices.” These units appear to be built of and connected by much smaller fibrils which themselves possess a periodicity of 100–200 A. or less. The possible reasons for coiling and its relation to the perpendicular orientation found in Part II are discussed, and it is suggested that branching could be a possible consequence of the coiling structures. The conclusion is reached that, as far as the morphology is concerned, crystallization in polymers represents a special case of the formation of crystalline aggregates in viscous media.
The tensile strength of elastomers
Authors: Taylor G. R. , Darin S. R.
Published: April 2003

The tensile strength of decamethylene dismethylazodicarboxylate vulcanizates of GR‐S, 50°C. polybutadiene, 5°C. polybutadiene, and natural rubber has been determined as a function of temperature and/or the degree of crosslinking. A theory of tensile strength of amorphous polymers which adequately describes the effect of the degree of crosslinking on strength is proposed. The theoretical expression for the strength of amorphous materials is then modified to include the effect of crystallization. The complete expression for the tensile strength of crystallizable elastomers, which includes amorphous elastomers as a special case, is:

where ω0 = 1 − (1 + δ2λ3)−1/2, fc = volume fraction crystallinity, M = primary molecular weight, Mc = molecular weight per crosslink in the uncrystallized polymer, λ = extension ratio at break, and δ, K = parameters. The theory is shown to be good for GR‐S and semiquantitatively correct for a crystallizable polymer, 5°C. polybutadiene.
Determination of crystallinity in polyethylene by X‐ray diffractometer
Authors: Aggarwal S. L. , Tilley G. P.
Published: April 2003

A convenient and rapid x‐ray diffraction method is described for the determination of per cent crystallinity in polyethylene, using a scanning goniometer with Geiger tube and scaler counter. Results are presented on per cent crystallinities of a number of polyethylenes and on samples made by quenching polyethylene melt at different temperatures in the range of 20–102°C. The samples of polyethylene studied were found to have 65‐71% crystallinity. The temperature at which plyethylene melt is quenched has no appreciable effect on the crystalline content.
Contribution à l'étude de la cellulose sèche et mouillée à l'Aide de la diffraction des rayons X par la ramie
Authors: Antzenberger Paulette , Fournet Gérard , Rogué Jean
Published: April 2003

A partir du diagramme équatorial complet de diffusion des rayons X par la ramie sèche et mouillée, nous avons cherché non pas à préciser un modèle idéal de structure cristalline mais plutôt à obtenir des renseignements sur la structure réelle des fibres. Comme la cellulose contient plusieurs sortes d'atomes, nous avons considéré la fonction de répartition des densités électroniques et non celle des centres d'atomes. Cette fonction peut s'obtenir directement à partir des données de photométrie des diagrammes équatoriaux. Par ailleurs, G. Fournet a développé une méthode permettant d'obtenir cette fonction à partir du modèle de Meyer et Misch. Nous exposons la comparaison de la courbe synthétique avec les deux courbes expérimentales et montrons que l'accord est meilleur dans le cas de la ramie mouillée. Nous pensonsque dans le plan perpendiculaire à l'axe de fibre la cellulose sèche est assez homogène en densité électronique mais très perturbée à petite distance (distorsions locales de la maille) tandis que la ramie mouillée, plus hétérogène à cause des zones gonflées présente des zones cristallines presque parfaites de l'ordre de 100 Å.
Swelling and absorption by cellulose acetate in binary solvent‐hexane mixtures
Authors: Moore W. R. , Russell J.
Published: April 2003

Preferential absorption and swelling by cellulose acetate in binary solvent‐type liquid/hexane mixtures has been studied at 25°C. Secondary cellulose acetate, of acetic acid yield 53.7%, was used in fibrous form and as film. Triacetate, prepared by nondegradative acetylation of the secondary, was also used. Factors affecting preferential absorption by the fibrous secondary acetate seem to include the activity of the solvent‐type liquid and its chemical type, the swelling power of the mixture, and steric effects. Preferential absorption of ketones and esters other than methyl formate appears to be independent of both acetyl content and structure. Absorption of methyl formate, acetic acid, and heterocyclic bases by the triacetate is less, at all concentrations, than by the secondary acetate. At low concentrations cresols and chlorinated hydrocarbons are absorbed to a smaller extent by the triacetate but at higher concentrations the reverse is the case, such variations in absorption being ascribed to steric effects and to the elimination of hydroxyl groups on complete esterification. Absorption by the secondary acetate films also suggests steric effects. Comparison of the measured weight of films with that estimated from the change in composition of the mixture following absorption, assuming no hexane to be absorbed, Suggests that this assumption is true at low concentrations. At higher concentrations, leading to high degrees of swelling or to gelatinization, the mixture seems to be imbided. There is no general relationship between swelling and the δ value of the solvent‐type liquid but δ values for the mixtures just causing complete solution of the acetates are not very different when the mixtures involve solvents of similar chemicals type.
Phase equilibria in ternary systems involving a polymer and two polar solvents
Authors: Newman S. , Krigbaum W. R.
Published: April 2003

A recent treatment of phase equilibria in nonpolar ternary systems is modified to permit application to the interesting case of a polymer and two polar liquids which may associate. The deviations from ideality exhibited by associated liquids are incorporated with the pair interaction free energy in the X parameter for the liquid pair. Hence, the expressions for the chemical potentials remain unaltered, but the X parameters for the polar liquid pair are concentration dependent; furthermore, the relation X12 = (V1/V2)X21, no longer applies. The equation deduced allows theoretical description of the phase equilibria in polar ternary systems provided sufficient information is available to characterize the binary polar liquid mixture. The predictions arising from the modified theory are tested using data obtained from phase composition analysis of the two ternary systems: nitrocellulose‐ethanol‐water and nitrocellulose‐diethylene glycol‐water. The isotherms obtained for the former system provide excellent confirmation of the theoretical predictions. Although for the second system studied the polymer‐solvent interaction parameters appear to be concentration dependent; nevertheless, application of theory yields values for the difference (lX − X) over the concentration range of interest. The (lX − X) differences deduced from the data for both ternary systems yield values for the nitrocellulose‐water interaction parameter which stand in good agreement with the value directly deduced from the sorption isotherm for that binary system, thus providing further confirmation of the theoretical treatment.
Rupture of rubber. III. Determination of tear properties
Authors: Greensmith H. W. , Thomas A. G.
Published: April 2003

A method of investigating the tear behavior of rubber vulcanizates is described. The method, based on the tear criterion of Rivlin and Thomas, involves the determination of the energy required to propagate a tear and its dependence on the rate of propagation. The type of test‐piece employed and the methods of measuring the energy and rate of tear propagation are described and discussed. Two principal types of tearing, indicative of different tear processes, are described. Experimental results for natural rubber and GR‐S gum vulcanizates, obtained over a wide range of temperature and rate of propagation, are given to illustrate the method. The results indicate that the nature of the tear process and the resistance to tearing, as represented by the energy required to propagate a tear, can change appreciably with the rate of propagation and the temperature. The significance of these changes is discussed.
The structure of neoprene. VIII. Effect of polymerization temperature on polymer properties
Authors: Maynard J. T. , Mochel W. E.
Published: April 2003

The chemical and physical properties of polychloroprenes made at temperatures ranging from −60 to +200°C. are discussed in the light of knowledge of structure gained from analysis of their crystallization behavior and infrared absorption spectra. The properties of polychloroprenes made below 0°C. are shown to be dominated by the preponderance of trans‐2‐chloro‐2‐butenylene units in their structure, e.g., they are highly crystalline and relatively unreactive. Polychloroprenes made at 10–90°C. show typical elastomeric properties and the chemical reactivity expected from the presence of a higher proportion of the allylic chloride units that result from 1,2‐polymerization. Polychloroprenes made at temperatures over 100°C. contain an even higher proportion of 1,2‐units and hence are unstable chemically. They are generally obtained as crosslinked gels. Chloroprene polymers made by ionic initiation are found to be chemically unstable, low molecular gums or resins. Their structure remains to be elucidated.
Polyvinyl alcohol gelling systems. I. Congo red and related dyes
Authors: Dittmar C. , Priest W. J.
Published: April 2003

Azo dyes of the Congo Red type are known to be amount the most effective gelling agents for polyvinyl alcohol. It has been shown by means of measurements of dilute solution viscosities that all of the dyes effective as gelling agents associate strongly with polyvinyl alcohol, as well as other hydroxylated water‐soluble polymers. This association is not, however, a sufficient condition for the promotion of gelation. Measurements of gel properties of aqueous systems consisting of polyvinyl alcohol and Congo Red or other related dyes have been made. From these measurements it has been possible to draw some conclusions pertaining to the nature of the crosslinks which contribute to the gel structure.
Crystallization in natural rubber. IV. Temperature dependence
Authors: Gent A. N.
Published: April 2003

Experiments are described in which the temperature dependence of crystallization in natural rubber, unvulcanized and vulcanized by a peroxide, was investigated dilatometrically over the temperature range −37 to 0°C. Avrami type time functions describe the progress of crystallization to a first approximation. The numerical parameters indicate the growth of spherical crystal structures from nuclei which appear randomly at a constant rate in a purified rubber. It is shown that classical nucleation theory describes the temperature dependence to a first approximation. The retardation of crystallization caused by the introduction of crosslinks is ascribed partly to a reduction in chain segment mobility and partly to the prohibition of crystal nucleus formation around each crosslink. Crystal nucleation appears to be promoted in plantation smoked sheet rubber by the nonrubber constituents at temperatures below 0°C.
Studies on the mechanism of mastication of rubber. IX. Scission of squalene molecule with benzoate free radical
Authors: Imoto Minoru , Kiriyama Shigeru
Published: April 2003

Squalene was treated with benzoyl peroxide and isoprene‐dialcohol dibenzoate was isolated. It is now proved for the first time that the molecule of polyisoprene was decomposed by a free radical and the location of the scission was the CH2CH2 linkage.
Formation of spherulitic structure in polyhexamethylene adipamide (66 nylon). I. Structure and optical properties of spherulites at room temperature
Authors: Barriault R. J. , Gronholz L. F.
Published: April 2003

It is found in studies with the polarizing microscope that 66 nylon spherulites form readily at temperatures near the melting point and grow until they are stopped by the presence of other spherulites. They possess a radially positive birefringence of approximately 0.01. X‐ray diffraction studies confirm conclusions, drawn from the birefringence results, that the polymer chains are oriented approximately in the tangential plane and that the hydrogen bonds are oriented approximately along the radii. Spherulites are composed of the same type of crystallites as nonspherulitic, crystalline regions of the polymer. The formation of the “transcrystalline” region on the surface of the polymer in the temperature range where spherulites form has been observed at the interface between nylon and a wide variety of other substances. This is taken as evidence that spherulite nuclei form more readily on the surface than inside of the polymer. It is decided, on the basis of x‐ray melting point studies, that the true thermodynamic melting point of 66 nylon must be higher than the normally accepted fusion temperature. From the shapes of interfaces between spherulites, it is concluded that the radial growth rate is constant for any isotherm.
The relationship between the dielectric constant and water‐vapor accessibility of cellulose
Authors: Kane Daniel E.
Published: April 2003

The relationship between the water‐vapor accessibility of cellulose and its dielectric constant at 10,000 cycles per second and 30°C. has been examined. Six different celluloses were studied. These included a cotton linters, a hydrolyzed cellulose, two regenerated celluloses, and two bleached wood pulps. In the accessibility range between 35 and 85%, the relationship appears to be very nearly linear. The maximum deviation of the experimental dielectric constant values from the least squares regression line is 0.1. Extrapolation of this relationship indicates that the dielectric constant of accessible cellulose is about 9, while that of inaccessible cellulose is about 4. The dielectric constant of the cellulose can then be thought of as that of a two‐component system, one component the accessible fraction and the other the inaccessible fraction. A slight increase in the dielectric constant of cellulose was brought about by drying the cellulose by a solvent replacement method rather than from water. This increase could be explained by density changes in the cellulose.
Vinyl esters of perfluoro acids
Authors: Reid Thomas S. , Codding Donald W. , Bovey Frank A.
Published: April 2003

A series of seven vinyl esters of perfluoro acids has been prepared by the mercury catalyzed reaction of the acids with acetylene. Certain physical properties of the monomers are given. Homopolymers gave clear, flexible films with the exception of vinyl caprylate and caprate, which formed waxy films. Copolymerization of vinyl perfluorobutyrate proceeded readily with vinyl acetate and methyl methacrylate, but less readily with styrene, maleic anhydride, and acrylonitrile.
Base accelerated degradation of polyvinyl chloride
Authors: Campbell John E. , Rauscher William H.
Published: April 2003

The degradation at 150°C. of polyvinyl chloride in the presence of base is studied by means of ultraviolet, visible, and infrared spectra. The reaction of polyvinyl chloridebase systems at 150°C. is viewed as a base accelerated dehydrochlorination of polyvinyl chloride proceeding through initiation, propagation, and termination phases. Polyene units with sixteen double bonds in conjugation are considered to be the most probable component of polyene structures contributing to the longest wave length absorption maxima recorded at 550 mμu. Dichroism to polarized light is observed in a plasticized, oriented, base degraded polyvinyl chloride film. This dichroism is considered a confirmation of the assigned polyene structure. The infrared spectra obtained reveal the development, as the reaction progresses, of conjugated carbon‐carbon double bonds, conjugated carbonyl groups, bonded hydroxyl groups such as from hydroperoxides and/or alcohols, and the eventual formation of carboxyl groups. The mechanism of the oxidative degradation at 150°C. is attributed to the attack, after dehydrohalogenation, by molecular oxygen at the olefinic double bonds to form peroxide radicals which by radical chain transfer yield hydroperoxides that degrade to carbonyl containing products.
Monomer reactivity ratios in a model unsaturated polyester system
Authors: Gordon Manfred , Grieveson Brian M. , McMillan Ian D.
Published: April 2003

Monomer reactivity ratios for the system polyethylene fumarate/methyl methacrylate have been determined. The experimental methods used in measuring these ratios for simple linear systems had to be severely modified. While the technique evolved does not give results of great accuracy, the ratios obtained are in agreement with those expected from consideration of the radicals involved. Ethylene fumarate polymers have been characterized in several different ways, and it was shown that, although prepared from maleic anhydride, substantial conversion to the isomeric fumarate form had occurred.
Organopolysiloxanes containing group IV organometallic substituents in the side chains
Authors: Seyferth Dietmar , Rochow Eugene G.
Published: April 2003

In an attempt to increase the intermolecular attraction between polyorganosiloxane chains and rings, polar groups have been introduced into methyl groups attached to the silicon atoms. To avoid the usual weakening of the CSi bond by negative polar substituents, positive substituents of the type (CH3)3M (where M is Si, Ge, or Sn) were employed in this study. Cyclic trimers and extended linear polymers were prepared, both from the pure polar‐substituted monomers and from mixtures of these monomers with octamethyltetrasiloxane. Intermolecular attraction was estimated by measuring viscositities and activation energies of viscous flow. The preparations also were compared in these respects with pure dimethylsiloxanes and with neopentylsiloxanes. The results show that intermolecular attraction is increased by the positive polar substitutents, and that the CSi bond is rendered more stable toward OH− attack by such positive substituents than by negative. More detailed analysis indicates that the effects of the groups on the viscosity of the polymers depends on: (1) the dipole attraction of the polar groups, (2) the bulk or steric effect of the enlarged group, and (3) the effect of the metal M upon the ease of rotation of the methyl groups (the characteristically free intramolecular motion of silicon polymers). The trends of these effects oppose each other in the CSiGeSn series, and so limit the observed increase of viscosity.
Disulfide interchange in polysulfide polymers
Authors: Bertozzi E. R. , Davis F. O. , Fettes E. M.
Published: April 2003

A study has been made on the effect of thiols and disulfides on lowering the molecular weight of polysulfide polymers. It was shown that in the presence of aqueous sodium disulfide there is an interchange of chain segments. This effect is observable if a simple organic disulfide is present in the system, resulting in a lower molecular weight. Co‐polymers can be prepared by heating together in the presence of sodium disulfide, aqueous dispersions of two different polysulfide polymers. When thiols are present in the system, interchange of disulfide groups occurs in the absence of sodium disulfide. The results show that disulfide/disulfide redistribution and thiol/disulfide interchange take place in polysulfide polymers. The occurrence of these same reactions has recently been recognized by workers in the biochemical field. A literature survey of thiol/disulfide reactions showed that results formerly attributed to oxidation/reduction reactions could be also explained by an interchange mechanism.
The incorporation of aroyloxy radicals in polymer molecules
Authors: Dannley Ralph L. , Kay Edward L.
Published: April 2003

Initiation of the bulk polymerization of samples of 2‐vinylpyridine with N‐nitroso‐N‐phenyl‐m‐bromobenzamide and N‐nitroso‐p‐bromoacetanilide gave polymers containing 0.06% and 0.52% bromine, respectively. Therefore, the aroyloxy radical is only about one‐eight as reactive as the aryl radical for incorporation in a polymer molecule. This is a rough comparison, for there is no data upon which to base an estimate of the influence of the halogen substituent upon the reactivity of the parent free radicals. The purification of the polymers included an ether extraction of an acid solution of the substances to insure removal of all initiator fragments not attached to the polymer molecules. The presence of aroyloxy radicals in the polymers does not give assurance, however, that they were introduced in the step of chain initiation or even in the original polymerization process. For example, treatment of polystyrene with p‐chlorobenzoyl peroxide was found to introduce 0.60% chlorine which through saponification proved to be a minimum of 96% chlorobenzoyloxy groups. Therefore, it seems highly probable that, when nitrosoamides are used as catalysts, aryl radicals may serve exclusively as chain initiators while a much smaller quantity of aroyloxy groups are incorporated by other mechanisms.
A comparison of the propagation of longitudinal waves in rods of viscoelastic materials
Authors: Lee E. H. , Morrison J. A.
Published: April 2003

The stress and velocity distributions associated with the propagation of an impulsively applied velocity and stress along rods of viscoelastic materials are presented. Various viscoelastic materials are considered of complexity up to that represented by a four element model which exhibits a combination of instantaneous elastic response, delayed elastic response, and permanent viscous flow. The solutions are compared to determine under what circumstances the mathematically simpler solutions comprise an adequate approximation to the more complicated ones, to provide a guide to the choice of analysis in treating such dynamic stress analysis problems in viscoelastic bodies.
Lattice model calculation of the configurational entropy change for athermal mixtures
Authors: Krigbaum W. R.
Published: April 2003

The lattice model treatment of athermal mixtures is reexamined by considering a two step process in which a growing chain forms an interference with a completed molecule. The expectancy, f, that an interference will arise is given by the product of the respective probabilities, P, and Q, that each step will occur. For low solute concentrations, the result is nearly the same as a revised form of the equation derived in various ways by Huggins, Miller, Orr, and Guggenheim. The same result is obtained for linear, bent, or branched molecules, but only so long as no ring‐forming intramolecular contacts exist. Dilute solutions of coiling polymer molecules require special treatment, due to a variable number of intramolecular 2‐2 contacts that depends upon the average molecular configuration. Branching, through its effect on molecular configuration, will after the dilute solution properties. The effect of branching and intramolecular contacts should become less important as the polymer concentration is increased. As the volume fraction of solute is increased, both of the probabilities, P and Q, become rapidly varying functions of this variable. An approximate calculation based on the two‐step encounter process yields values for f nearly equal to the average expectancy f̄ that a randomly selected site will be occupied. The latter was empolyed in the treatment of Flory. Thus, the refinements introduced by Huggins and others are only applicable to dilute solutions of noncoiling molecules. This furnishes an explanation for the observation that the proposed refinements do not improve the agreement with experiment shown by the simpler expression due to Flory.
Kinetics and heats of copolymerization of acrylonitrile and methyl methacrylate
Authors: Baxendale J. H. , Madaras G. W.
Published: April 2003

Methyl methacrylate and acrylonitrile monomers have been copolymerized in aqueous solution and at room temperature, in the presence of an emulsifying agent, using the redox catalyst, ferrous ions, and hydrogen peroxide. The copolymer latex resembles that of polymethyl methacrylate similarly prepared. The rate and extent of conversion of monomers to copolymer were obtained by independent estimations of both monomers in the reaction mixture. Heats of copolymerization have been measured using a wide ratio of initial methyl methacrylate and acrylonitrile concentrations. The values lie between those of the respective homopolymerizations. The results are discussed in terms of the steric hindrances in a polymer composed entirely of a 1,1‐disubstituted monomer being reduced by the incorporation of a monosubstituted monomer into the chain.
Determination of degree of crosslinking in natural rubber vulcanizates. Part I
Authors: Mullins L.
Published: April 2003

This paper examines the relationship between the stress–strain properties of highly swollen natural rubber vulcanizates and their equilibrium volume swelling. It is shown that the empirical relationship obtained can be described equally well by either the Flory‐Huggins equation or the Flory modification of this equation, and values of the interaction constant μ for natural rubber in decane are determined. Observed differences in the values of μ obtained for sulfur and peroxide vulcanizates are interpreted in terms of the diluent effect of nonrubber constituents in the former. The effect of the initial molecular weight of the unmasticated rubber on these physical properties is examined and an empirical correction making allowance for chain segments terminated by a crosslink at only one end is obtained. The correction is larger than that derived by previous workers and possible sources of the observed differences are discussed. It is considered that internally self‐consistent estimates of the degree of crosslinking of natural rubber vulcanizates may be obtained using the methods developed.
An investigation of the theory of rubber elasticity using irradiated polydimethylsiloxanes
Authors: Bueche A. M.
Published: April 2003

High‐energy electrons were used to crosslink a series of polydimethylsiloxanes. Equilibrium tension measurements at low elongations were used to determine the number of chains between crosslinks as given by the kinetic theory of elasticity. After a rapid increase at low radiation doses the number of chains was found to be proportional to the dose. The linear relationship between number of chains and dose, found at higher doses, extrapolated to zero dose, has a positive intercept. This intercept was independent of the initial molecular weight of the polymer and was taken to be a measure of the effect of the maximum number of permanent entanglements in this polymer. The dependence of the number‐average molecular weight of irradiated polydimethylsiloxane fluids on radiation dose was determined. The data were analyzed to find the efficiency of crosslink formation in this polymer. The number of chains between crosslinks produced by a given dose and determined by the kinetic theory was found to be only one‐half the number to be expected from the measurement of the molecular weights of the irradiated fluids.
Diffusion in concentrated polymer solutions. I. A. An interferometric micromethod for diffusion measurements. B. Diffusion of sucrose in solutions of polyvinylpyrrolidone
Authors: Nishijima Yasunori , Oster Gerald
Published: April 2003

A simple micromethod for the measurement of diffusion coefficients has been developed. The diffusion cell is a wedge of two partially reflecting microscope slides and the liquids to be examined are placed in the wedge. Typical results for the diffusion of glycerol against water and 10% sucrose against water are shown. The method is applied to the measurement of the diffusion of sucrose in various concentrations of polyvinylpyrrolidone using samples of three different molecular weights. The local relative viscosity, as given by the ratio of the diffusion constant in water to that in the polymer solution, is nearly unity for low concentrations of polymer but above a critical concentration rises to a value that is independent of molecular weight of the sample. The lower the molecular weight, the higher is the critical concentration and the more abruptly is the rise in local viscosity with polymer concentration. These results are explainable in terms of a random coil model if it is assumed that the critical concentration is reached when the molecules overlap to a small extent. The rise in local viscosity is attributed to an entanglement of the chain segments resulting finally in a loss of identity of the individual polymer molecules. Applications of these results to a theory of wet spinning of fibers are indicated.
Variation of photoelastic behavior with temperature for some polymers
Authors: Kawata Kozo
Published: April 2003

The variations of photoelastic behavior for styrenedivinylbenzene copolymers and a diallyl phthalate polymer were studied between 20 and about 190°C. The birefringences for constant stresses were measured. With suitably crosslinked polymers the transition from the glassy state to the rubber‐like state was observed distincitly. In the higher temperature region the photoelastic behavior was in agreement with the statistical theory for ideal rubbers. The photoelastic coefficient in the entropy elasticity range varied linearly with increasing degree of crosslinkage. The extrapolated value of Δn/σ for styrene copolymers to zero content of the crosslinking agent coincides with the value for polystyrene itself. With the very highly crosslinked polymer the transition was observed not to be distinct.
The dipole moments and the structure of polyoxymethylene dimethyl ethers
Authors: Uchida Tadashi , Kurita Yukio , Kubo Masaji
Published: April 2003

The dipole moments of monoxymethylene dimethyl ether and dioxymethylene dimethyl ether were measured in hexane solution. From the dependence of the moments of these compounds on the number of oxygen atoms as well as from the temperature dependence of the moments of monoxymethylene dimethyl ether, it was concluded that these compounds are mixtures of rotational isomers, the predominant ones of which assume helical or almost helical structures arising from the gauche minima in the internal rotation about single bonds. The trans minimum, which is 1.74 kcal./mole higher than the gauche minima, is also significant and gives rise to rotational isomers having configurations deviating from the simple helical structure.
Über naturliche und synthetische amylose. V. Über oxyäthylamylosen1
Authors: Husemann E. , Resz R.
Published: April 2003

Da die Untersuchung von Amylosen durch einige Faktoren wie z.B. variable Molekülgestalt und schwierige Löslichkeitsverhältnisse erschwert ist, wurden wasserlösliche Oxyäthylamylosen verschiedenen Substitutionsgrades hergestellt und auf ihre Eignung geprüft, als Modellsubstanzen für Amylose zu dienen, insbesondere bei fermentativem Abbau und zur Feststellung etwaigen Abbaues bei verschiedenen Reaktionen.
Crystallinity studies of polyamides by infrared, specific volume and X‐ray methods
Authors: Sandeman I. , Keller A.
Published: April 2003

Examination of the infrared absorption of three nylons, polyhexamethylene sebacamide, polyhexamethylene adipamide, and polycaproamide (nylon 6,10, 6,6, and 6, respectively) revealed the existence of bands associated with crystalline order. These discoveries were utilized in the study of crystallinity of nylon 6,10 and nylon 6 in conjunction with x‐ray and specific volume methods. The work falls into three parts. Part I deals with elementary consideration of dichroism and deduces a method of comparing the intensity of an infrared band in a drawn sample of polymer with that of a disoriented sample. A theory of dichroism in materials that have rotational symmetry about one direction is formulated. The question of measuring the absolute intensity of an infrared band is briefly considered. In Part II the crystallinity content of nylon 6,10 (a polymer chosen for its suitability for testing the method) is determined by using the 940 cm.−1 band and specific volume measurements. The effects of annealing and drawing are studied. Proportionality between change in specific volume and change in infrared absorption is confirmed by experiment up to an annealing temperature of 180°C. Above this temperature specific volume measurements give too high a crystallinity figure. Cold‐drawing is found to be connected with a reduction of crystallinity, and can produce voids. The crystallinity of our samples varied between 20 and 55%. The significance of these figures—absolute and relative—is discussed. An absolute figure of 1.052 for the amorphous density of nylon 6,10 is deduced. Part III deals with nylon 6. The infrared spectrum in the 7.5–12.5 μ region is examined and several of the bands are classified as crystalline or noncrystalline. Variation of these bands is studied when the polymer is annealed, drawn, and melted. Both annealing and cold‐drawing increase crystallinity content. In the drawn samples the crystallites are found to be better oriented than the noncrystalline parts. The direction of the transition moment of the 935 cm.−1 band is determined. X‐ray results reveal a new type of ordering corresponding to a state of packing intermediate between randomness and full crystalline order. Infrared bands at 990 and 720 cm.−1 are found to be connected with this state of order. Direct evidence is obtained that the molecules possess an order in the quenched amorphous state. The density of amorphous nylon 6,10 calculated from this ordering is in complete agreement with the figure deduced in Part II.
Neue ergebnisse über das grenzflächenverhalten von carboxymethylcellulose
Authors: Stüpel H.
Published: April 2003

Carboxymethylcellulose ist ein wichtiger Aufbaustoff für Waschmittel, der von allem die Resorptionstendenz des Schmutzes hemmt. Der Wirkungsmechanismus von CMC als Schmutzträger beim Waschvorgang wurde bisher auf die Absorption durch das Textil zurückgeführt. In der Fluoreszenzmikroskopie wurde eine einfache und elegante Methode gefunden, den Adsorptionsort von CMC zu bestimmen. Es wurde gefunden, dass CMC im Waschvorgang nicht an der Faser adsorbiert wird, sondern am Schmutz haftend sichtbar gemacht werden kann. Bei hoher Konzentration im neutralen Bereich, abver vor allem im sauren Millieu gelangt CMC an die Fasern.
Molecular weight distribution of a low conversion polystyrene sample
Authors: Guzmán G. M.
Published: April 2003

The fractionation of a low conversion polystyrene sample has been carried out using the precipitation technique in the system methyl ethyl ketone–methanol. Six fractions were isolated and the cumulative and differential curves plotted according to the customary assumptions. Statistical analysis has also been applied on the basis of a Bernouillian distribution for the fractions. The parameters of the binomial have been calculated by means of Beall's method. The results show a considerable divergence with regard to the usual ones. The accumulation of the MW by the classicial procedure is too rapid from a DP of 5600, and is slightly lower than the binomial from zero to 5600. In addition, the classical procedure does not supply any information with regard to the high MW range of the distribution (DP up to 34,000), which amounts to nearly 18% of the whole sample. The distribution has been reproduced, using Bruns' series, from the successive MW averages, and the result agrees with that of the binomial distribution. On the other hand, the distribution has been worked out kinetically, assuming that combination and disproportionation are both the main mechanisms of termination. The results show that disproportionation occurred about twice as frequently as combination.
On the viscosity of polymer solutions in fine capillaries
Authors: Lifson Shneior
Published: April 2003

When a polymer solution flows through fine capillaries there should be an increase of the apparent viscosity as a result of the inhomogeneity of the flow. This increase is dependent on the ratio between the dimensions of the macromolecules and the capillary. It is independent of the rate of flow as long as the assumed spherical symmetry of the macromolecule is not disturbed by the hydrodynamic forces. The change in the apparent specific and intrinsic viscosities of such solutions is calculated for two forms of capillaries, i.e., parallel planes and cylinders.
A statistical model for amylopectin and glycogen. The condensation of A‐R‐Bf−1 units
Authors: Erlander Stig , French Dexter
Published: April 2003

The authors have developed a statistical model for a branched polymer built from a monomeric unit (such as glucose) which has two types of reactive groups (aldehydic and alcoholic). The treatment differs from that of Flory's in that the different B groups in the A‐R‐Bf‐1 monomer have differing reactivities instead of equal reactivities. The mole fraction of a particular x‐mer having b1, b2,…bf‐1 linkages at their respective B1, B2,…Bf−1 functional groups is:

where \documentclass{article}\pagestyle{empty}\begin{document}$ x = 1 + \sum\limits_{i = 1}^{f - 1} {b_i}$\end{document} is the total number of monomer units per molecule and p1,p2,…pf‐1 are the probabilities that any monomer unit is linked at the B1, B2,…Bf‐1 functional group. From the above, x̄n, the number‐average DP, x̄w, the weight‐average DP, x̄z, the Z‐average DP, and wx, the weight fraction of an x‐mer, have been obtained. It is shown that the limit of x̄z/x̄w is 3 and the limit of x̄w/x̄n is infinity as the degree of polymerization increases for all cases where “f” is greater than two. These results were used for the randomly branched polymers, amylopectin and glycogen, where the functionality of the monomer in both cases is three. p4 and p6 were used to represent the probabilities that any glucose unit is linked at the 4 or 6 position. Using values of p6 = 0.05 and p4 = 0.94933, x̄n = 1500, M̄n = 243,000, M̄w=35,100,000, and M̄z = 104,500,000, giving M̄w/M̄n = 140 and M̄z/M̄w = 2.99. Literature values for molecular weights of amylopectin and glycogen are compared with the above statistical model and with less random statistical models.
Specific heat of synthetic high polymers. VII. Polyethylene terephthalate
Authors: Smith Carl W. , Dole Malcolm
Published: April 2003

From specific heat measurements on drawn, undrawn, and annealed polyethylene terephthalate over the temperature range – 10 to 280° it has been possible to observe the magnitude of: (a) the glass transition, (b) recrystallization effects, and (c) the change of crystallinity with temperature. The change in the function cp/T at Tg is shown to be roughly proportional to the fraction of amorphous polymer present. Drawing the fiber reduces Δcp/T, but increases the rate of recrystallization so that, on the unannealed drawn samples, recrystallization occurs over a range of temperatures such that the glass transition cannot be observed. Good agreement is obtained between the crystallinity estimated from enthalpies and that calculated from density data except in the case of the samples that recrystallized during the calorimetric measurements. The estimated heat of fusion is in agreement with that calculated from the statistical thermodynamic theory of the effect of copolymers on the melting point. The influence of the surface free energy of the crystallites on their melting point. The influence of the surface free energy of the crystallites on their melting range is discussed.
Flow birefringence behavior of some amylopectins and limit dextrins
Authors: Stacy Carl J. , Foster Joseph F.
Published: April 2003

The flow birefringence behavior of some amylopectins and their limit dextrins are reported. Though no quantitative interpretation is possible due to the great heterogeneity and their probable deformation in the flow gradient, several characteristics seem quite general. The extinction angle is relatively independent of the flow gradient. The gradient range over which observations could be made was limited at the lower end by lack of precision and at the higher end by precipitation which invariably occured. The birefringence curves characteristically showed a saturation behavior. Possible qualitative explanations for the observed behavior are discussed.
Ladder structures for representation of viscoelastic systems. II
Authors: Gross Bernhard
Published: April 2003

This paper presents the theory of a model that consists of identical springs and dashpots arranged in the form of a ladder network. The expressions for complex compliance and complex modulus function are given in closed form; creep and relaxation function are given by series expressions. Comparison of the relaxation spectrum derived from this model with that of Rouse's theory shows both expressions to be identical. Therefore all other expressions obtained with the aid of the model apply equally to Rouse's theory and the model represents a convenient working scheme for the completion of the latter. A discussion of the temperature effect is given.
Light scattering by solutions of polyethylene in 1‐chloronaphthalene
Authors: Moore Louis D.
Published: April 2003

A Brice‐Phoenix light‐scattering photometer was modified for use at elevated temperatures by enclosing the cylindrical cell filled with solvent in a tightly fitting copper block wrapped with heating wire. Heat input was controlled by a regulated Powerstat. Temperature was measured by a copper‐Constantan thermocouple and maintained at 125 ± 2°C. This regulation was considered adequate for use with solutions of polyethykene in 1‐chloronaphthalene. Solutions were placed in scattering cells which were shaped like Erlenmeyer flasks and could be easily removed and replaced in the bath of 1‐chloronaphthalene. Commercial polyethylenes from four sources were studied with this instrument and surprisingly large dissymmetries in scattering were encountered in these samples. These dissymmetries sometimes led to correction factors greater than 6 on molecular weights measured at 90° [P−1 (90°) > 6]. Another surprising and significant finding was that polyethylenes from different sources has strikingly different light‐scattering properties. In general, the results obtained lend support to the recent theories of Roedel and Beasley on the mechanism of “long‐chain” branching and its influence on molecular‐weight distribution. Samples were found to vary in their distribution ratio (weight‐average molecular weight/apparent number‐average molecular weight) from 2.5 to 70. According to the Beasley theory this last figure would indicate as many as 140 “long‐chain” branches per weight‐average molecule.
Preparation and properties of fibers containing mixed polymers. II. Polyacrylonitrile‐cellulose fibers
Authors: Cates David M. , White Howard J.
Published: April 2003

In the previous paper the preparation and properties of fibers containing both polyacrylonitrile and cellulose acetate were discussed. It has proved possible to hydrolyze the cellulose acetate without extensive side reactions to produce fibers containing both cellulose and polyacrylonitrile. The properties of such fibers are discussed in this paper. The fibers have been examined optically and using x‐ray diffraction techniques. The absorptive capacity for water and direct dyes, the density, the electrical resistivity, and the mechanical properties of the fibers have been measured. The results are compatible with a structure consisting of submicroscopic regions of each polymer throughout the fiber interspersed with void spaces that are probably produced during drawing.
The structure of crystalline 1,2‐polybutadiene and of other “syndyotactic polymers”
Authors: Natta G. , Corradini P.
Published: April 2003

With the aid of anionic polymerization catalysts, 1,2‐polybutadiene of high molecular weight has been synthesized. It is a crystalline material with a melting point above 150°C. Electron and x‐ray diffraction studies with oriented films permitted determination of the elementary cell, the space group, and the coordinates of the individual carbon atoms in the cell. The chains deviate slightly from the conventional planar zig‐zag structure, the vinyl group substituents are arranged in the 1–3 sequence with alternating D and L configurations. It is proposed to call this type of spatial arrangement in head‐to‐tail vinyl polymers a syndyotactic arrangement. Also polyvinyl chloride, obtained with free radical catalysts, contains small ordered regions, with a structure similar to syndyotactic 1,2‐polybutadiene.
Dilaminar elastomeric films
Authors: Defries Myron G. , Schneider Louis , Fram Paul , Leonard Fred
Published: April 2003

Many applications of rubberlike materials require a combination of bulk and surface properties which may not be attained with a specific elastomeric composition regardless of vulcanization, reinforcement, or other modification by compounding, but may be achieved by combining two materials in a laminated structure. This paper describes a technique for casting hollow laminated elastomeric structures from aqueous dispersions in molds of plaster of Paris. An elastomeric composition which has the properties required of the surface is deposited first, and a second composition having the properties required of the bulk is then cast against original film before the latter dries in the mold. This process, termed “dilaminar” film casting, yields laminated films having resistant surface layers of uniform, controllable thickness that are inherently bound to the substrate. The properties of a series of butyl acrylate‐acrylonitrile copolymers of varying monomer ratios and amounts of organic reinforcing agents were studied. It was found that unreinforced copolymers of approximately 27–30% acrylonitrile had suitable resistance to staining and abrasion, while reinforced compositions of an elastomer copolymer having an acrylonitrile content of about 10% displayed optimum bulk but poor surface properties. Dilaminar films were cast of two compositions having optimum properties for surface and substrate layers. The laminated films retained the surface resistance of the outer laminare and exhibited mechanical properties intermediate between the properties of the two components. Equations relating tensile and flexural properties of laminated elastomeric films to those of the single homogeneous compositions were derived, and calculated tensile and flexural values were found to agree with the experimental data.