bluuebunny/crossref_metadata_2025_split huggingface dataset:
Choice of solvent for the viscometric determination of molecular weights of high polymers
Authors: Cragg L. H. , Sones R. H. , Dumitru T. E. 
Published: April 2003

AbstractFor the viscometric determination of the molecular weight of a flexible linear high polymer, a very “poor” solvent in which the osmotic slope constant B is zero (i.e., a so‐called “ideal” solvent) has several advantages over the usually preferred good ones. For example, shear effects that are very troublesome with very high polymers in good solvents become negligible or easily manageable. Moreover, in an “ideal” solvent, the “contents” K and a in the equation relating [η] and M really are constant over a very wide range of molecular weights and, since a always has the value 0.50, are more easily determined. Because the advantages seem to outweigh considerably the disadvantages, the use of an “ideal” solvent should be given careful consideration, particularly when the molecular weights are very high or cover a wide range.
Elastic properties of polvinyl chloride gels
Authors: Walter A. T. 
Published: April 2003

AbstractYoung's moduli are measured by a simple compression method on plasticized polyvinyl chloride (Vinylite VYNW) compounds containing from 5 to 100% polymer covering a range of approximately seven orders of magnitude in modulus. By comparing values obtained at different temperatures, it is shown that the 60‐second modulus in the range of 25°C. is largely due to entropy changes occurring during deformation of compounds containing less than about 50% polymer, but upon internal energy changes in compounds containing higher concentrations of resin. A semiquantitative description of the three‐dimensional polyvinyl chloride network existing in the soft‐gel region is arrived at from the kinetic theory of elasticity, and a network structure is suggested for the region of high resin content. A method for comparing relative solvent power of various plasticizers is suggested based on moduli determined in the soft‐gel region. Effects of polymer composition on the network structure are also discussed.
On the kinetics of anomalous flow
Authors: Mack Charles 
Published: April 2003

AbstractAnomalous flow is considered to be associated with a transition of the particles, representing the units of flow from a state of greater order to a state of greater disorder or vice versa. The particles in the ordered state are, in general, understood to belong to regions where they are in positions of minimum potential energy. A change in the internal structure is accompanied by a variation in the number of vacancies or holes present. Expressing anomalous viscosity as a function of the fraction of the particles in the disordered state and of the fraction of holes present, it is shown that the rate of change in the concentration of these particles is the same as the rate of change in the concentration of the holes. The equilibrium constant is:

where η refers to a viscosity at a state near that of rest. ΔF is the change in the free energy of activation for a particle going from one state to another. This energy change is related to the change in kinetic energy, ΔEk, which permits the calculation of the mass of a particle. Experimental data are given for an asphalt whose shear rate is a power function of the shearing stress and for an asphalt whose shear rate is an exponential function of the shearing stress. It is shown that, in the first case, the degree of disorder increases with increasing stress, and that, in the second case, flow results in an orientation of the particles. In both cases the mass of a particle is considerably larger than that of a molecule. It would appear therefore that shear does not consist here in a shift of a particle from one position to another but is rather similar to slip in metals.
Second‐order transition temperature of butadiene copolymers
Authors: Gerke R. H. 
Published: April 2003

AbstractSecond‐order transition temperature of copolymers of butadiene and the following monomers, acrylonitrile, styrene, dimethylbutadiene, and methyl acrylate has been determined using the dilatometer method. That of polyacrylonitrile has been estimated by extrapolation of data. Mercury or 38% sulfuric acid was used as confining fluids. It has been found that the logarithm of the second‐order temperature in degrees Kelvin is a linear function of the weight fraction of monomer.
Effect of silicone coatings on denaturation of egg albumin
Authors: Kukin Ira , Rochow Eugene G. 
Published: April 2003

AbstractHuman blood is known to coagulate much more slowly in glass vessels lined with a very thin film of methyl silicone than in similar vessels with clean glass walls. In an attempt to explain this observation, the effect of various surfaces on the simpler system of egg albumin in aqueous buffer was studied. It was found that little or no denaturation of the albumin occurred when the solution of it was shaken for extended periods in either clean glass or silicone‐lined bottles in the absence of air. In the presence of a gas interface denaturation was fairly rapid, but proceeded at a somewhat lower rate in silicone‐treated bottles (coated by exposure to the vapor of mixed methylchlorosilanes) than in clean bottles. A relatively thick oily film of methyl silicone deposited by another method greatly increased the rate of denaturation, an effect due to a large degree to the increased oil‐water interface created by the dispersion of silicone oil droplets in the solution during shaking. Kinetic studies show that the over‐all denaturation is first‐order, regardless of the type of surface. A theoretical interpretation of these observations in terms of possible mechanisms is given.
The microstructure of diene polymers. II. Polyisoprenes and polybutadienes prepared at high pressures
Authors: Richardson W. S. 
Published: April 2003

AbstractPolyisoprenes and polybutadienes have been prepared by bulk polymerization at hydrostatic pressures of from 5,000 to 10,000 kg./cm.2. The microstructures of these polymers have been determined by infrared analysis. In general, the structures are not grossly different from bulk and emulsion polymers prepared at near atmospheric pressure.
Kinetics of alkaline hydrolysis of pectinic acids
Authors: Katchalsky A. , Feitelson J. 
Published: April 2003

AbstractThe second order rate constant of the alkaline hydrolysis of pectinic acid salts decreases rapidly with the progress of the reaction and shows a pronounced positive salt effect. This behavior is interpreted in terms of an electrostatic repulsion factor and an “intrinsic” rate constant characteristic of the hydrolyzable groups. It was found that the calculated potentials (ψ) of the charged pectinic acid molecules, based on potentiometric titrations, account for the kinetic behavior as determined experimentally under controlled conditions. The intrinsic rate constant is k = 23.8 1./m. min. at 4°C.
Effect of temperature and pH on the optical rotation of proteins
Authors: Golub Morton A. , Pickett Edward E. 
Published: April 2003

AbstractThe effect of temperature and pH on the optical rotation of a representative group of proteins was investigated. It was found that the proteins showed little or no effect of temperature on the optical activity whether in the native or denatured state. Where definite changes in rotation occurred among the native proteins, these were attributed to denaturation accompanying the change of temperature. Zein, casein, fibrin, erepsin, globin, native and denatured egg and serum albumins, edestin, and pepsin showed no temperature dependence of optical rotation, over the temperature range 20 to 60°C., although protamine sulfate and gliadin possessed small negative coefficients. Native chymotrypsin, trypsin and β‐lactoglobulin showed a marked increase in levorotation with increase of temperature, which was due to denaturation on heating. The denatured forms of the latter two proteins, however, showed no change of optical activity with temperature. The shapes of the optical rotation‐pH curves obtained for salmine, zein, gliadin, egg and serum albumins, casein, fibrin, and insulin were found to reflect the presence of free acid‐ and base‐combining groups in the proteins, with some uncertainty in the case of globin. Since native pepsin, trypsin, chymotrypsin, and β‐lactoglobulin were denatured at pH values not far from those of their normal aqueous solutions, the rotation‐pH curves for these proteins were not capable of similar analysis, but they could be used to follow polarimetrically the course of the denaturation.
Studies on light scattering by polymethyl methacrylate solutions
Authors: Bhatnagar H. L. , Biswas A. B. 
Published: April 2003

AbstractThe scattering of light by solutions of a well‐fractionated sample of polymethyl methacrylate in acetone, methyl ethyl ketone, and benzene, have been measured using 4358 and 5461 A. wave lengths as incident radiations. The average molecular weights of the polymer from turbidity measurements and lengths determined from angular dissymmetries of scattered light are 571,000 and 760 A. in acetone, 38,400,000 and 715 A. in methyl ethyl ketone, and 408,000 and 375 A. in benzene. The abnormal molecular weight observed in methyl ethyl ketone solution may be ascribed to low μ – μ0 value of the medium. The greater molecular extension in ketone than in benzene solutions is explained in terms of the relative magnitudes of solute‐solvent interaction. The depolarization ratios ρu, ρv and ρh have been measured and the decrease of ρv and ρh with increase in concentration of the polymer in ketonic solvents and little change under similar conditions in benzene, are discussed in the light of the “molecular field effect” of Gans.
Variation in the lattice spacing of cellulose
Authors: Wellard H. J. 
Published: April 2003

AbstractA comparative study of the unit cell parameters a, c, and β of a considerable number of cellulose specimens including samples of the four structure types cellulose I, II, III, and IV has been carried out using an evacuated camera. Small variations were observed as between samples of different origin for cellulose I and cellulose II and were most marked in the monoclinic angle parameter β and in the case of cellulose I (bacterial cellulose β = 98.25°, ramie β = 96.5°). No unit cell parameter differences greater than the experimental error were found for cellulose III, but the intensity of the (020) reflection showed large variations.
Qualitative infrared analysis of polyphenylbutadienes
Authors: De Radzitzki P. , De Wilde M. C. , Smets G. 
Published: April 2003

AbstractThe infrared spectra of synthetic poly‐1‐phenyl‐ and poly‐2‐phenylbutadienes have been examined, principally in the region from 9 to 15 μ. The different intramolecular structures of these polymers, corresponding to the different types of monomer additions (1,4, 1,2, and 3,4) were examined by this method; the data are in complete agreement with the chemical results as reported previously. The influence of the method of polymerization on the internal structures of the polymers is taken in evidence; the presence of the aromatic substituent in position 1 or 2 in the monomer molecule exerts a large influence on the position and the intensity of the characteristic absorption bands, if they are compared with the results for synthetic polyisoprenes.
Chemistry in carbon black dispersion
Authors: Barton Bernard C. , Smallwood Hugh M. , Ganzhorn George H. 
Published: April 2003

AbstractHeating rubber‐carbon black mixtures at elevated temperatures results in vulcanizates with lower electrical conductivity, lower hysteresis, lower Durometer hardness, and increased abrasion resistance. These changes are apparently the result of chemical reactions between carbon black and rubber which alter the dispersion of the carbon black. Data are presented which show that the basic factors effecting these changes are the chemical reactivities of the carbon black and the polymer and the time and temperature of treatment.
Investigations of crosslinking in the emulsion polymerization of butadiene
Authors: Drysdale J. J. , Marvel C. S. 
Published: April 2003

AbstractA study of the dilution effect of four hydrocarbons (biallyl, hexane, 3‐methyl‐1‐butene, and isopentane) on the rate of polymerization of butadiene and on the characteristics of the resulting polymer has shown that chain transfer of the following type is an unimportant reaction in butadiene polymerization:
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The above result is consistent with the kinetic treatment of crosslinking as developed by Flory. The results of a comparison of the emulsion polymerization of 2,2′‐azobisisobutyronitrile‐ and of persulfate‐catalyzed butadiene are adequately accounted for without considering the effect of the catalysts on branching or crosslinking. As previously suggested, the differences noted between 2,2′‐azobisisobutyronitrile‐ and persulfate‐catalyzed polybutadienes are probably due to a different molecular‐weight distribution. This difference in molecular‐weight distribution is partly produced by a large difference in r values for the two systems. The unmodified emulsion polymerization of butadiene with 2,2,‐azobisisobutyronitrile in an oxygen‐and peroxide‐free system produces a highly crosslinked polymer.
Viscosities of extremely dilute polystyrene solutions
Authors: Streeter D. J. , Boyer R. F. 
Published: April 2003

AbstractIt is shown that ηsp/c for a polystyrene fraction (M̄v = 250,000) in toluene decreases approximately linearly as the concentration is lowered from 1.0 to 0.1 g./100 ml. and then increases to a maximum at 0.001 g./100 ml. as the concentration is lowered still further. This increase in ηsp/c with dilution is a new effect which we ascribe to the expansion of polymer coils as well as to the disentangling of entire polymer molecules once the concentration is lowered to where there is ample room in the solution for each polymer molecule. The new techniques employ a viscometer with a flow time of 3893 seconds for toluene, special filtering of the solutions, and prolonged agitation of the solutions after each dilution. We present data to show that ηsp/c is time dependent at concentrations below 0.1 g./100 ml.
Calibration of light scattering photometers with Ludox
Authors: Maron Samuel H. , Lou Richard L. H. 
Published: April 2003

AbstractA simple and exact method is presented for the calibration of light scattering photometers in absolute turbidity units employing du Pont Ludox as the calibration medium. It is shown that previous attempts to employ Ludox as a standard took no cognizance of the relatively high scattering power of this substance in relating τ to I90, and hence results considerably in error were obtained. To check the validity of the calibration, molecular weights were run on the standard Cornell polystyrene in toluene and MEK, and on the I. U. C. sample III polymer in MEK at both 4358 and 5461 A. The results obtained show excellent internal consistency as well as agreement with published data.
The hydrolysis of cellulose part II. Acid sensitive linkages in egyptian cotton
Authors: Sharples A. 
Published: April 2003

AbstractIt has been shown that a hydrolytic study of the kinetics of chain degradation can be used to detect the presence of acid‐labile linkages in cellulose, provided that the amount of ordered or crystalline material in the sample is first reduced by a treatment involving regeneration from alkaline solutions. The results for Egyptian cotton regenerated from benzyl trimethyl ammonium hydroxide in the absence of oxygen show that only a very small fraction of acid‐labile linkages—less than one per 2900 glucose residues—can be present in the original chain molecules. It is possible that even this small amount is produced during the alkali treatment. Thus weak bonds of the types proposed by Schulz and Pacsu are definitely absent. Cotton regenerated from cuprammonium and cupriethylenediamine solutions, however, does contain randomly distributed linkages which are approximately 10,000 times more sensitive to acids than the normal glycosidic type. These appear to be formed from a limited number of special sites in the chain molecules, by oxidation in alkaline solution. Assuming the value of P̄n for undegraded cotton to be 2900, the amount of these extranormal linkages is one per 660 glucose residues.
A viscometer for solutions of high polymers
Authors: Keeling C. D. , Dole Malcolm 
Published: April 2003

AbstractA viscometer for solutions of high polymers having the following features is described: (1) The lower level of the capillary viscometer is determined by an overflow into an auxiliary reservoir. (2) The solutions are prepared, insoluble gel filtered, and dilutions carried out in the auxiliary reservoir. (3) Because of the fact that the viscometer is a closed system it can be rotated through 360° within the constant temperature bath, automatically filling the upper reservoir and allowing repetitive measurements to be carried out. (4) As constructed, the viscometer can only be used for solutions of low surface tension.
Solvation of cellulose nitrate in acetone‐water mixtures
Authors: Scherer Philip C. , Crookston Norbert J. 
Published: April 2003

AbstractThe sorption of acetone and water by cellulose nitrate from mixtures of the two solvents was studied by allowing the solid cellulose nitrate to come to equilibrium with aqueous solutions of acetone and measuring the change in concentration of the liquid phase. Changes in concentration were determined by measuring the index of refraction using a dipping refractometer. The values calculated for acetone sorbed per (C6) mole of cellulose nitrate are a function of the acetone concentration of the equilibrium solvent. Moles of water sorbed by one (C6) mole of cellulose nitrate depend inversely on the equilibrium acetone concentration of solvent.
Infrared analysis of isomerized, vulcanized and oxidized natural rubber
Authors: Salomon G. , Van Der Schee A. Chr. 
Published: April 2003

AbstractThe purpose of this study was to follow by i.r. analysis double bond shifts and chemical modification of natural rubber. Accurate determination of the original rubber spectrum is facilitated by the use of an internal standard. Isorubber, prepared by thermal dissociation of rubber hydrochloride, contains about 50% of double bonds in the side groups. Although a similar double bond shift is observed in the cyclization of rubber, part of the absorption, in the 11 μ region, may here be due to ring formation. Vulcanization with accelerated sulfur mixtures does not produce changes in the i.r. spectrum, unless the rubber is transformed into a derivative by overcuring with S2Cl2 or during hard rubber formation. At least three types of oxidation reactions can be distinguished spectroscopically: (1 ) degradation of the rubber (by oxidation of a rubber solution with air) with the ultimate formation of only volatile oxidation products; (2 ) gradual formation of oxygenated derivatives (oxidation with ozone), with a distinguishable structure in the spectrum; (3 ) gradual formation of an oxidized and more saturated rubber (oxidation of solid rubber with air), with less characteristic broad absorption bands.
Improved relationships for diffusion and sedimentation constants and for viscosity and streaming birefringence of solutions of polymers
Authors: Kuhn H. , Kuhn W. , Silberberg A. 
Published: April 2003

AbstractFor the description of the practical properties of a large number of linear polymer molecules as well as for the discussion of the various mean parameters of the individual chain molecule, the model usually employed to represent the molecule consists of N m straight line chain elements of length A m statistically joined to each other (straight element model). For the construction of large‐scale wire models of polymer molecules to be used in model experiments on the hydrodynamic behavior of chain molecules, a somewhat different model (circular segment model) was employed in previous papers. In these papers the relationships connecting the parameters which characterize these two models respectively have been determined on the basis of certain assumptions. These assumptions, as has recently been shown, were however partly in error and certain corrections have now to be applied to the numerical constants which appear in previously published formulas for the diffusion and sedimentation constants and for the intrinsic viscosity and streaming birefringence. The formulas, resulting after these corrections have been incorporated, are compiled in the present paper and the effect of these corrections on the interpretation of both new and old experimental results is discussed. It is found that agreement between theory and experiment is improved by the use of the corrected expressions and that in particular certain discrepancies which had previously existed between the lengths A m of the statistical chain element as calculated from sedimentation and diffusion experiments, on the one hand, and viscosity determinations on the other, disappear after these corrections are applied (see Table I).
Vulcanization of crepe rubber by sulfur monochloride. Part II. The dilatometric method
Authors: Glazer J. 
Published: April 2003

AbstractThe kinetics of the reaction between natural rubber hydrocarbon and sulfur monochloride is investigated in dilute hydrocarbon solution by the dilatometric technique. Control experiments with trilaurin and triolein show that the reaction requires unsaturated linkages in the compound to be cold‐vulcanized. The extent and rate of the nonaccelerated reaction with rubber is shown to depend strongly on the nature of the solvent. Moreover, the nonaccelerated reaction is autocatalytic in nature, and exhibits kinetics that are first order with respect to sulfur monochloride. The accelerating effects, on the reaction, of Butyl 8, mercaptobenzothiazole, dibutylammonium dibutyl‐dithiocarbamate (DBA), and methanol are investigated and it is shown that, in the presence of sufficient Butyl 8 or DBA, the autocatalytic nature of the reaction is changed to one that is kinetically of pure first order. The accelerated (Butyl 8) reaction is found to be first order with respect to sulfur monochloride. The accelerated reaction is further shown to be first order with respect to DBA and second order with respect to methanol. A free radical mechanism is proposed for the nonaccelerated reaction, involving attack by the intermediate $ \mathop {\rm S}\limits^ * {\rm \bond S \bond Cl} $ at the double bonds of the rubber molecule. It is suggested that accelerators function by reacting with sulfur monochloride to produce the active intermediate $ \mathop {\rm S}\limits^ * {\rm \bond S \bond Cl} $.
Phase equilibria in polymer–liquid 1–liquid 2 systems
Authors: Krigbaum W. R. , Carpenter D. K. 
Published: April 2003

AbstractThere are investigated the relations between the liquid compositions in the two phases formed when a polymer equilibrates in a mixed solvent. By imposing the simplifyng constraint that all of the polymer be located in one of the two phases, an expression for the equilibrium composition ratio, R = (φ1/φ2)/(v1/v2), is obtained through use of the customary expressions for the free energy of polymer solutions:

Here subscripts 1, 2, and 3 refer to the two liquids and the polymer, respectively, χ is a free energy parameter, l is the ratio V1/V2 of the molar volumes of the two liquids, φ and v represent the volume fraction in the ternary and binary phases, respectively, and ϵ is an auxiliary variable relating φ and v for the two liquid components. Certain consequences of the equilibrium composition relationship are examined, and there are suggested possible applications to diffusion, light scattering, and solubility. The results of analysis of the two phases formed when crosslinked natural rubber equilibrates with the mixed solvent pairs: benzene–nitromethane and m‐xylene–nitromethane confirm the form of the equilibrium composition relationship, and the values for the free energy parameters required to represent the data for these ternary systems appear to be reasonable.