bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic properties of solutions of cellulose derivatives. I. Dilute solutions of secondary cellulose acetate
Authors: Moore W. R. , Tidswell B. M. 
Published: April 2003

AbstractOsmotic pressure of dilute solutions (c≤1.0 g./100 ml.) of a fraction from a secondary cellulose acetate in representative solvents have been measured at two or three temperatures. Number‐average molecular weights in acetone, aniline, methyl acetate, and pyridine do not vary with temperature but are significantly higher in methyl acetate in which association of polymer is possible. Molecular weights in acetic acid, nitromethane, and dioxane decrease with increase of temperature presumably because of degradation. Values of ΔF1, ΔH1, and ΔS1 have been estimated from temperature coefficients of osmotic pressure. All the systems are endothermal. It is suggested that the polymer is fully solvated and that solvated polymer and solvent mix with absorption of heat. With the exception of the aniline system, values for which are high, values of ΔH1 appear to be in the order to be expected from the solubility parameters of solvent and solvated polymer. ΔH1 and ΔS1 decrease with increase of temperature in all cases except that of acetic acid. ΔH1/ϕ, where ϕ2 is the volume fraction of polymer, seems to be effectively constant at each temperature. Values of ΔS1 are greater than “ideal” values but are less than those obtained for comparable systems containing more flexible and less polar polymers. ΔS1/ϕ decreases with increase of concentration but in some cases there is an increase at the highest concentration. ΔF1 becomes more negative with increase of temperature. It would seem that both entropy and heat terms contribute to the value of the interaction parameter χ1. It is possible, if solvation and the segment size and stiffness of chains are taken into account, that approximate lattice theories may apply to solutions of cellulose derivatives at lower concentrations than in cases of more flexible and less polar polymers.
The degradation of addition polymers by ultrasonic waves. II.
Authors: Mostafa M. A. K. 
Published: April 2003

AbstractAn accurate solution of the kinetics of degradation of addition polymers of known initial size distribution is given. This solution differs from an approximate solution given in a previous paper. The result obtained is applied to a sample of 1% polystyrene in benzene. The theoretical weight distribution curves at different stages of degradation, derived from the approximate and the accurate solutions, are given. The points of difference between the two resulting distributions are briefly discussed.
Polymerization of triallyl cyanurate
Authors: Clampitt Bert H. , German Dale E. , Galli Joseph R. 
Published: April 2003

AbstractDifferential thermal analysis (DTA) curves for the polymerization of triallyl cyanurate show two exothermic maxima. By integrating the area under the DTA curves the heats evolved during each exotherm are determined. Combination of these heat values with infrared spectral data indicates that the first step in the polymerization of TAC involves polymerization of two allyl groups, and the second step involves rearrangement to the polymerized triallyl isocyanurate form followed by polymerization of the remaining allyl group. Heats of combustion of TAC and TAIC indicate that the magnitude of the heat released during the second exotherm is reasonable and in line with the proposed mechanism.
Separation of amylose from amylopectin of starch by an extraction‐sedimentation procedure
Authors: Montgomery Edna M. , Senti F. R. 
Published: April 2003

AbstractCorn, wheat, and potato starch were fractionated into their amylose and amylopectin components by selective extraction of amylose in hot water after the starch had been pretreated by heating in aqueous mixtures of glycerol, n‐butanol, Pentasol, Cellosolve, or dioxane. About three‐fourths of the amylose was leached in relatively pure form from starch in the first extraction at 98°C. The granule residue, sedimented by centrifugation, was separated as relatively pure amylopectin after two or more additional extractions. Retention of the coherent structure of the granule in the extracted residue emphasizes the importance of amylopectin to granule properties. Amylose fractions isolated from successive extractions had progressively lower intrinsic viscosities and absorption coefficients of their iodine complexes indicating that this component was subfractionated according to molecular size and/or structure. X‐ray diffraction patterns of the pretreated starches indicated that a complex of amylose and organic solvent was formed which may account for the increased solubility of amylose after pretreatment. Evidence is presented which shows that little, if any, amylose occurs in the crystalline regions of granular starches.
The ultracentrifuge as an instrument for testing adhesion
Authors: Patrick R. L. , Vaughan W. A. , Doede C. M. 
Published: April 2003

AbstractA technique was developed which allows the determination of essentially pure tensile strengths of single interface adhesive samples. Utilizing a suitably modified ultracentrifuge, model adhesive systems were ruptured in an attempt to obtain relative strengths of adhesive bonds in the interface.
The Flory constants for poly‐4‐vinylpyridine in ethanol
Authors: Berkowitz Joan B. , Yamin Michael , Fuoss Raymond M. 
Published: April 2003

AbstractVinylpyridine was polymerized in suspension, using azobis‐iso‐butyronitrile as initiator. The polymer was fractionated by partial precipitation from methanol solutions by addition of toluene to cloud point in chilled solution and then raising the temperature. Viscosities of four fractions were determined at 25, 50, and 70° in absolute ethanol. Rayleigh ratios and scattering asymmetry were determined for eight fractions; from the corresponding Zimm plots, molecular weights, coil diameters, and virial coefficients were determined. Addition of ammonia was found necessary at low concentrations to suppress ionization due to traces of acid impurities. Addition of water (a nonsolvent) lowers the second virial coefficient. Molecular weights were determined for two fractions by osmotic pressure. In absolute ethanol, the results are summarized by the equation [η] = 2.5 × 10−4M0.68; experimental range 0.102 ⩽ 106 M ⩽ 1.85. The second virial coefficient from light scattering was 4.2 ± 0.3 × 10−4, independent of molecular weight; the osmotic values agreed within experimental error. The Flory constant was found to be 2.1 ± 0.3 × 1021. Extrapolation for the θ‐point leads to the rough estimate θ ≈ −50°C. Evidence is presented which shows that polyvinylpyridine degrades slowly in solution.
Linear polyesters derived from protocatechuic acid
Authors: Bock Louis H. , Anderson James K. 
Published: April 2003

AbstractProtocatechuic acid which is available from tree sources was converted to a hydroxymethyl‐1,4‐benzodioxan carboxylic acid by reaction with epichlorohydrin. This hydroxy acid was condensed by heating under vacuum to from a linear polyester which was converted to fibers by melt spinning. By applying stretch during spinning a fiber with a tenacity of 4.4 g. per denier, a melting point of 210°C. and a softening point of 145°C. was obtained. Removal of one of the isomers formed in the preparation materially raised the softening point and raised the melting point above the decomposition temperature.
A diffusivity approach for studying polymer structure
Authors: Auerbach I. , Miller W. R. , Kuryla W. C. , Gehman S. D. 
Published: April 2003

AbstractStudy of the diffusion in polymers of molecules comparable in size and structure to the segments of the chain molecules is suggested as a means of securing information on structure and molecular friction forces in polymers. A convenient method for measuring the diffusivity in polymers of such compounds tagged with C‐14 was devised and used to study the diffusivity of octadecane, octadecanol, stearic acid, and octadecyl stearate for a range of temperatures in polymers including natural rubber, GR‐S, polybutadiene, polyisoprene, and polyisobutylene. Diffusivities were independent of concentration for the range used. The diffusivities of straight chain hydrocarbons in natural rubber appear to vary inversely as the molecular weight of the diffusing compound. Evidence was found for association effects in the diffusion of stearic acid in natural rubber. Activation energies for diffusion of the compounds were quite similar in any one polymer and of the same order as reported for low molecular weight hydrocarbons and for viscous flow. Larger differences in activation energies were observed for diffusion in the different polymers. Correlations were observed for the diffusivities of octadecane in a series of polymers with their densities and thermal expansivities, especially the latter. Some study was given to the effect on the diffusivity of octadecane of such parameters as polymer unsaturation, solution viscosity, molecular weight, and crosslink density. The diffusivity of octadecane in natural rubber had a pronounced maximum as a function of crosslink density, coinciding with the maximum in tensile strength. Possible implications of this are discussed. The diffusivities of octadecane in a series of elastomers were studied in relation to the internal frictional losses observed for 60 cps vibrations over a range of temperatures. It was concluded that frictional forces deduced from the diffusivity measurements have some correspondence to high frequency viscoelastic phenomena which involve small units of structure comparable in size to the segments of the polymer molecules.
Copolymers of butadiene and unsaturated acids: Crosslinking by metal oxides
Authors: Cooper W. 
Published: April 2003

AbstractButadiene copolymers of low molecular weight containing combined acid groups react with metal oxides to give products with unusual properties. The salts, particularly the zinc and cadmium compounds, exhibit plastic flow under slowly applied stresses but are highly elastic on sharp impact; products closely resembling the silicone “bouncing putty” can be obtained. Although these salts contain many “crosslinks” per chain they are, within limits, soluble in solvents such as benzene or pyridine. The solubility is determined by the molecular weight of the copolymer, its acid content, and the nature of the metal ion. Their solutions are characterized by marked changes in viscosity on dilution and they develop osmotic pressures in dilute solution comparable to those from the unreacted acid copolymers. The high molecular weight polymers are strong elastomers which show marked creep under stress. The properties of salts of both high and low molecular weight copolymers are consistent with the view that exchange reactions can occur between ionic crosslinks on different chains when stressed or under the influence of solvents. This ability to relieve local stresses on stretching is thought to be of consequence when considering the tensile properties of these and other elastomers.
Estimating the unperturbed dimensions of polymer molecules
Authors: Krigbaum W. R. 
Published: April 2003

AbstractA procedure is described for estimating unperturbed molecular dimensions from data obtained in “nonideal” solvents. A knowledge of [η], M, and A2 is required. This should be particularly useful for high melting crystalline polymers, since for these polymers a direct determination by light scattering measurements performed under Flory θ conditions is complicated by the tendency of the polymer to crystallize from solution as the solvent becomes thermodynamically poorer. The intrinsic viscosity at θ, [η]θ, is calculated from the semi‐empirical relation:

where Γ2 = A2M. The unperturbed dimensions are then calculated through use of the relations appearing in Flory's treatment of intrinsic viscosity:

Unperturbed dimensions calculated in this manner for polyisobutylene and polystyrene compare favorably with values directly measured by light scattering. This procedure is used to estimate the unperturbed dimensions of polyethylene, 6,6‐nylon, polyethylene terephthalate, and polyacrylonitrile. A comparison of the relative chain stiffness of these polymers allows some interesting correlations with Flory's theoretical treatment of semi‐flexible chain molecules.
A study of the elastic modulus and extensibility of the crystalline regions in highly oriented polymers
Authors: Dulmage W. J. , Contois L. E. 
Published: April 2003

AbstractThe elastic modulus of highly oriented crystalline polymers is discussed in terms of a series model. As has been shown previously, if a polymer has fully extended chain configurations within the crystalline regions, the modulus of this phase may be expected to be high. In this case the macroscopic elastic modulus is limited primarily by the characteristics of the amorphous phase and the degree of crystallinity. Where the fiber identity period (FIP) indicates a contracted chain configuration, the crystalline regions, themselves, may be extensible and their modulus may not be much greater than that of the unoriented amorphous phase. In this case the macroscopic elastic modulus is much less dependent upon orientation and crystallinity. The elastic moduli of eight chemically different polymers have been determined from measurements of their macroscopic moduli and the extensions of their FIP when subjected to small strains. Where the degree of crystallinity could also be determined the modulus of the amorphous phases were also determined from these same measurements. The moduli of some of these systems are discussed in terms of their structure as deduced from birefringence measurements and x‐ray diffraction patterns.
Solution and fractionation properties of graft polymers
Authors: Kilb R. W. , Bueche A. M. 
Published: April 2003

AbstractThe lattice model is used to predict the solution properties of graft and block polymers. It is found that the solubility of a graft polymer is critically dependent on the heat of interaction of the various components of the polymers with the solvent. Furthermore, the precipitates from fractionations of graft polymer solutions are no longer simple functions of the over‐all molecular weight.
Formation of block polymers of butyl acrylate with styrene and vinyl pyridine
Authors: Funt B. Lionel , Collins Edward 
Published: April 2003

AbstractBlock copolymers of butyl acrylate–styrene and butyl acrylate–2‐vinyl pyridine were prepared in a flow system. An intense ultraviolet source was focussed on a stream of monomer falling into a second monomer. The period between photochemical initiation in the stream and block polymer formation was controlled by varying the flow rate and distance of fall. By application of nonstationary state kinetics the yield of polymer in the stream was calculated and compared with the experimental yield determined spectrophotometrically. A comparison was made of the composition of random copolymer based on the copolymerization equation and that determined experimentally. The yields and compositions of the products showed that the desired block copolymers had been formed.
Graft copolymers: Synthesis and characterization
Authors: Shashoua V. E. , Van Holde K. E. 
Published: April 2003

AbstractTrue 100% grafted polymers were prepared in a two‐stage emulsion polymerization process. Microgels of styrene crosslinked with divinylbenzene, methyl acrylate crosslinked with divinylbenzene, and acrylonitrile crosslinked with methylene‐bisacrylamide were used as first stage polymers, and the grafting of styrene and acrylonitrile were studied. The polymers were analyzed as microsols by limiting viscosity number and by ultracentrifuge measurements. In the ultracentrifuge the quantitative separation of crosslinked particles from linear polymers was demonstrated. From a study of the polymerization conditions which result in a single sedimenting component in the ultracentrifuge, 100% grafted polymers were synthesized. The results indicated that in order to obtain 100% grafting initiation must be by free radicals present in the polymer particles with none from residual catalyst or by thermal initiation. The existence of polymeric free radicals of lives greater than 100 days is demonstrated.
Further study of the decomposition of benzoyl peroxide in the presence of styrene
Authors: Bevington J. C. , Toole J. 
Published: April 2003

AbstractStyrene has been polymerized at 80°C. using as sensitizer benzoyl peroxide labeled with carbon‐14 in the benzene rings. From the specific activities of the polymers before and after hydrolysis, it has been possible to compare the velocity constants for the alternative reactions of the benzoyloxy radical, viz., addition to monomer or decomposition into a phenyl radical and carbon dioxide. By combining these results with those obtained at 60°C., the difference between the activation energies for the two reactions of the benzoyloxy radical has been calculated. Assuming normal values for the activation energy of the addition reaction and for the frequency factor of the decomposition reaction, the rate constant for the latter has been calculated.
Rebound relaxation spectra and principle of constant isoelastic curing rates
Authors: Gordon Manfred , Grieveson Brian M. 
Published: April 2003

AbstractAn apparatus has been constructed for measuring rapidly the coefficient of restitution by impact of a steel ball on samples of polymers as a function of temperature. Such measurements are described as rebound relaxation “spectra,” the energyEabsorbed on impact being plotted against temperatureT. The main absorption peak corresponds to the dynamic second order transition. First‐order transitions give anS‐shapedE–Tplot. The validity and sensitivity of the technique are illustrated with rebound spectra of amorphous and crystalline linear polymers as well as crosslinked resins. The kinetics of various “curing” (crosslinking) reactions are followed in terms of the displacement of the second order transition peak towards higher temperatures. Where such a curing reaction approaches an equilibrium (or pseudo‐equilibrium), the observed kinetics are interpretable on the theory of relaxation processes. For this purpose, the displacement of the peak may be charted fromisothermalmeasurements ofE. A more significant technique usesisoelasticmeasurements of the peak displacement,i.e., measurements of the change with time of the temperature required to keep the rebound height constant. The isothermal approach of the peak to its equilibrium value is a typical Maxwellian (first order) rate process. The isoelastic approach to equilibrium atconstantrebound producesconstantrates of peak displacement over big temperature ranges. This is explained qualitatively because elastic rebound and chemical crosslinking are both dependent on the molecular relaxation rate of chain segments. The theory is illustrated with the curring reactions of expoxide, polyester, urea‐formaldehyde, and phenol‐formaldehyde resins. The epoxide system studied behaves as a “conservative” system, in which the rate of cure is dependent on the state of cure and the temperature, but not on the curing schedule by which that state of cure has been achieved.
The phenomenon of “inversion” in thermal diffusion of high polymer solutions
Authors: Kossler I. , Krejsa J. 
Published: April 2003

AbstractIn the study of thermal diffusion of high polymers in a solvent, instruments are commonly used which have a lower and upper chamber. The thermal diffusion effect causes an increase of concentration in the lower chamber and, conversely, a decrease in the upper one. Simultaneous changes in the average molecular weights occur in both chambers, and, in agreement with theory, the average molecular weight in the lower chamber increases. In our experiments we found that the average molecular weight first increases in the upper chamber, reaches a maximum, and then decreases to values even below the initial value. The opposite occurs in the lower chamber. This phenomenon of “inversion” must be taken into account in studying the applicability of thermal diffusion for obtaining distribution curves. We are also attempting to use it directly for separating fractions of lower molecular weight.
Détermination de la fonction de distribution d'un polymère en solution. Etude et comparison de deux méthodes
Authors: Freund L. , Daune M. 
Published: April 2003

AbstractOn considère les fonctions de distribution g(S) et f(D) d'un polymère, relatives aux deux paramètres: constante de sédimentation S et constante de diffusion D. La distribution g(S) est obtenue à partir des mesures de vitesse de sédimentation par la méthode de Baldwin et Williams. Pour obtenir la distribution f(D) on applique la méthode que nous avons précédemment décrite et qui consiste à effectuer une double transformation de Fourier sur la courbe expérimentale. Après avoir établi les deux courbes de distribution dans le cas d'un alcool polyvinylique, nous avons comparé les résultats des deux méthodes et essayé de déterminer la courbe de distribution des masses moléculaires.
Aromatic polyanhydrides, a new class of high melting fiber‐forming polymers
Authors: Conix Andre 
Published: April 2003

AbstractContrary to the aliphatic polyanhydrides prepared by Carothers, polyanhydrides containing aromatic nuclei in the main chain possess high melting points and good hydrolytic stability. A number of different aromatic polyanhydrides were prepared. Their preparation and properties, such as fiber‐forming properties, melting points, glass transition temperatures, and crystallinity, are described. An effort has been made to correlate some selected physical properties, such as melting points and crystallizability, with the chemical structure of the particular polyanhydride. The influence of p‐phenylene, m‐phenylene, carbonyl, ether, thioether groups, etc. on the properties of the polymers is discussed.
Synthèse de copolymères greffés par action des rayonnements ionisants sur des solutions de polyisobutylène dans le styrolène
Authors: Sebban‐Danon Jeanne 
Published: April 2003

AbstractOn étudie la polymérisation radiochimique du styrolène en présence de polyisobutylène. La polymérisation du styrolène est amorcée par les radicaux provenant du styrokléne et les radicaux provenant du polyisobutyléne, ces deux sortes d'amorcage conduisant respectivement à la formation de polystyroléne et de copolymère greffé, polystyroléne sur polyisobytyléne. On édie l'influence de l'intensité du rayonnement et de la concentration initiale en polyisobutylène sur la cinétique de la réaction.
Etude de la polarisation de fluorescence de la polyéthylène imine conjuguee
Authors: Wahl Ph. 
Published: April 2003

AbstractUn appareil de mesiire oculaire de la polarisation de fluorescence a été construit. Avec cet appareil nous avons étudié la polarisation de la lumière fluorescente émise par des polymères possédrtnt des groupes NH ou NH2, et sur lesquels a été fixé le chlorure de l'acidc 1‐diméthylaminonaphtalène‐5 sulfonicque. De la variation de la polarisation avec la température on déduit le temps de relaxation de l'unité rotetionnelle de ces polymères. Ceci renseigne sur leur rigiditè. Des résultats sont présentés pour la polyéthylène‐imine.