bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscosity, sedimentation, and light‐scattering properties of fraction of an acid‐hydrolyzed dextran
Authors: Senti F. R. , Hellman N. N. , Ludwig N. H. , Babcock G. E. , Tobin R. , Glass C. A. , Lamberts B. L.
Published: April 2003

Dextran produced by Leuconostoc mesenteroides NRRL B‐512 was acid‐hydrolyzed and fractionated, yielding a series of fractions from which 24 were selected that ranged in molecular weight from 17,700 to 9.5 million. Light‐scattering and viscosity measurements were made on all fractions, and selected fractions were characterized by endgroup determinations and velocity ultracentrifuge measurements. Branching in these dextran fractions was evidenced by the progressively decreasing slope of the curve of logarithm of intrinsic viscosity plotted against logarithm of molecular weight, attaining a value of 0.11 at M = 107; by the upward curvature of the log‐log plot of sedimentation constant against molecular weight; and by the relatively large values of k′ in the Huggins specific‐viscosity equation for the high‐molecular fractions. Assuming Lansing‐Kraemer molecular‐weight distributions for the dextran fractions and using sedimentation data to furnish β, the measure of breadth of the distributions, physical characterizations were corrected for polydispersity. For molecular weights below 100,000, [η] = 1.0 × 10−3 Mv0.50. In the range 18,000 < M < 400,000 S200 = 0.0251 M00.44. The constant Φ′, of the Flory‐Fox theory, corrected for polydispersity of the fractions, was found to be 55.2 × 1021, which is larger than the value reported for linear polymers. It is concluded that the ratio of root‐mean‐square radius and hydrodynamic radius effective in viscosity differs for branched and linear molecules. The quotient (Φ′)1/2/P′ also appears to be significantly smaller for dextran than the value reported for linear molecules. Increase in Φ′, for dextran above the value previously assumed necessitates recalculation of data of Wales, Marshall, and Weissberg for g, the ratio of mean‐square radii of branched and unbranched dextran molecules.
Shear dependence of viscosity of alfin polyisoprene
Authors: Golub M. A.
Published: April 2003

The shear dependence of viscosity of alfin polyisoprene in dilute benzene solutions at 25°C. was studied over a wide range of molecular weights. The polyisoprene was prepared initially to amolecular weight of about 4,500,000, and a number of portions of the polymer were allowed to degrade to various intermediate molecular weights down to about 200,000 followed by stabilization at these particular molecular weight levels. This procedure provided a wide range of molecular weights without recourse to the usual fractionation. Inherent viscosities were measured in an Ostwald‐Fenske viscometer at rates of sher from about 1000 to 10,000 sec.−1 and at concentrations from about 0.05 down to 0.01 g./dl. Some data were also obtained in a series of similar viscometers of different radii. It was found that both the inherent and the intrinsic viscosities of the Alfin polyisoprene depend strongly on the rate of shear, the effect increasing with increasing molecular weight. Moreover, the shear dependence of the inherent viscosity is best expressed by an equation involving both a linear and a quadratic function of the gradient. The experimental data were examined from the standpoint of Katchalsky's proposed method for obtaining simply and rapidly the zero shear viscosity from measurements in an Ostwald‐type viscometer. According to this method, a plot of ts/t vs. P2R2, where ts and t are the flow times of the (Newtonian) solvent and (non‐Newtonian) solution, P the applied pressure, and R the radius of the capillary, should be linear, and the intercept of this line at P2 = 0 or R2 = 0 gives the reciprocal of the relative viscosity at zero shear. The agreement between the zero shear viscosities obtained by the Katchalsky method and from the conventional viscosity–shear curves was only fair. Above a molecular weight of about 280,000 the Katchalsky values are consistently smaller than the corresponding values obtained from the viscosity–shear curves, and furthermore this discrepancy increases with molecular weight. Because of this discrepancy, an attempt was made to modify the Katchalsky equation, so as to bring the respective zero shear viscosities in to better agreement. It was found that an anlogous equation, calling for a linear plot of ts/t vs. PR, provided a rather accurate measure of the zero shear viscosity.
Precipitation of polymer solutions
Authors: Colborne R. S.
Published: April 2003

A simple relationship between polymer concentration and precipitability in the system polymer‐solvent‐precipitant has been worked out. A relationship between precipitation methods of evaluating solvent power and other methods involving the coefficient μ has been traced.
Graft polymerization and branching
Authors: Voeks John. F.
Published: April 2003

An equation has been derived from a generalized set of polymerization reactions relating the branching fraction (ratio of new polymer bound to substrate to total new polymer) to various rate constants and reactant concentrations. Data from the literature are cited to illustrate various aspects of the equation. It is suggested that branching and grafting data can be correlated by a rather obvious extension of the Q and e systems.
Mastication of rubber. II. Interpolymerization of natural rubber and neoprene on cold milling
Authors: Angier D. J. , Watson W. F.
Published: April 2003

Graft copolymerization of rubber and neoprene has been effected by cold mastication. Experimental evidence is based on the properties of the gels produced, solubilities of the sol fractions, and vulcanization of the neoprene component by magnesium oxide. Mechanisms of branching and gelling of neoprene and rubber‐neoprene systems are discussed. The utility of selective precipitation for detection of graft polymers is outlined.
Rupture of rubber. II. The strain concentration at an incision
Authors: Thomas A. G.
Published: April 2003

The strain distribution around the tip of an incision in a thin test‐piece of highly elastic material is considered. Using the results of a previous paper, relations between this strain distribution and the over‐all forces or strains are derived for two particular types of test‐piece. Experiments designed to check the theory are described, and agreement is found to be satisfactory. The theory is extended qualitatively to the case where the test‐piece is taken to the point of rupture, and experiments are described which confirm the approximate relation derived. The relevance to tearing and to the previously proposed tear criterion is discussed.
Stress relaxation of peroxide and sulfur vulcanizates of natural rubber
Authors: Berry J. P. , Watson W. F.
Published: April 2003

The stress relaxation behavior of peroxide and sulphur vulcanized natural rubber has been investigated using a relaxometer of new design. The peroxide vulcanizates do not degrade significantly in vacuo and degrade by an exponential decrease in stress with time in oxygen. The vulcanizates from the two sulfur recipes used give stress relaxation in vacuo and more rapid relaxation in oxygen. A theoretical analysis provides the shape of stress–time curves anticipated for various modes of network degradation. The present data and other published results are consistent with a mechanism of scission at the crosslinks and not at random along the chains. The peroxide vulcanizates are interpreted as decaying by a first‐order scission of crosslinks and the sulfur vulcanizates by first‐order scission of two types of crosslink. The uncertainties still present in interpreting stress relaxation data are discussed.
Equilibrium distribution of molecular weights in noncyclic polymerizations
Authors: Harris Frank E.
Published: April 2003

The equilibrium molecular weight distribution in noncyclic condensation polymers depends upon the free energies of the various species in solution as well as upon the multiplicity of ways the polymerizable groups can be combined. It is shown that, although both the ideal solution theory and the Flory‐Huggins formula for the free energy of the solution lead to the well‐known molecular weight distribution obtained originally by Flory and by Stockmayer, only a restrictive group of deviations from ideality will lead to this distribution. Distributions were calculated using Guggenheim's expression for the free energy of mixing of the polymeric species, together with two alternative expressions for the free energy of the pure, separate, polymers, and in one case the distribution deviates markedly from the ideal solution result. It is concluded that reasonable deviations from ideality may significantly affect the equilibrium molecular weight distribution.
Vinyl polymerization. VI. Polymerization of acrylonitrile in the presence of substituted benzoyl peroxides and dimethylaniline
Authors: Imoto Minoru , Takemoto Kiichi
Published: April 2003

The solution polymerization of acrylonitrile was carried out by dilatometry at 40 ± 0.02°C. Using benzene as solvent, and various substituted benzoyl peroxide derivatives as initiator, experiments were made both in the presence and in the absence of dimethylaniline. It was found that the initial rate of polymerization. R0, could be expressed by:

The values of k0 were determined. The applicability of Hammett's rule are observed. In the presence of DMA the reaction constant ρ was positive, but in the absence of DMA ρ was negative. Molecular weights of polymers obtained were nearly reversely proportional to the initial rate of polymerization.
Polymer association. II. Osmotic pressure of an associating polymer in mixed solvents
Authors: Morawetz H. , Gobran R. H.
Published: April 2003

The osmotic molecular weight of a copolymer of 5 mole per cent methacrylic acid and 95 mole per cent methyl methacrylate in benzene at 29.8°C. indicates considerable molecular association, with the size of the molecular aggregate constant over a wide range of solution concentration. This behavior is consistent with a model in which the copolymer contains on the average less than two carboxyls free to participate in intermolecular association, which proceeds virtually to completion. It is shown that equilibrium constants for the association of the carboxyl groups of the polymer with cosolvents can be estimated from the dependence of the apparent molecular weight on cosolvent concentration.
A viscosity study of polyelectrolytes in the presence of added salts
Authors: Contois L. L. , Trementozzi Q. A.
Published: April 2003

The effect of various added simple electrolytes upon the solution viscosity of polymethacrylic acid and hydrolyzed polyacrylonitrile was studied. The viscosity behavior of these polymers in water and in the presence of added NaCl was typical of that of polyelectrolytes. The addition of multivalent anions (sulfate, diacid phosphate, oxalate, and succinate) to solutions of polymethacrylic acid decreasesd the viscosity at low added salt concentrations, but a reversal in the reduced viscosity–concentration curve was obtained as the ionic strength was increased. This increase in viscosity can be partly explained on the basis of increased ionization originating from the behavior of the added multivalent anions. However, this is not the complete explanation since the relative efficiency of these anions in increasing the viscosity is not consistent with the values of the dissociation constants. A possible alternative explanation involves the formation of associated complexes of the polyions. It is further demonstrated that the limiting intrinsic viscosities at infinite ionic strength is dependent upon the initial polymer charge.
Dynamic mechanical properties of polystyrene, polyethylene, and polytetrafluoroethylene at low temperatures
Authors: Sauer J. A. , Kline D. E.
Published: April 2003

A study of the dynamic mechanical properties of several high polymers has been made over a temperature range from 80°K. to above room temperatures and at frequencies in the range from 200 to 4000 cps. For amorphous polymers such as polystyrene the mechanicalloss rises sharply in the neighborhood of 80°C. but over the rest of the temperature range studied exhibits no relaxation peaks. For partly crystalline polymers such as polymethylene, polytetrafluoroethylene, and nylon the loss curve exhibits one or more definite internal friction peaks in the temperature range studied. The observed relaxation behavior is discussed in terms of possible molecular mechanisms and the results correlated with specific heat measurements and other mechanical loss measurements where such data are available.
Viscometric behavior of polyacrylate ion in concentrated salt solutions
Authors: Kagawa Ikumi , Fuoss Raymond M.
Published: April 2003

Viscosities of polyacrylate ion in the presence of potassium bromide, sodium bromide, lithium bromide, sodium iodide, sodium hydroxide, and hydrochloride acid in aqueous solution were measured over the approximate ranges 0.0–0.6% polymer and salt up to saturation with respect to polyacrylate or to salt. The general initial effect of added electrolyte is to reduce the ratio ηsp/c and to convert the curve characteristic of polyelectrolytes into a straight line, which can be extrapolated to zero polymer concentration to given [η], the intrinsic viscosity of the polymer in the presence of excess salt. Sodium hydroxide and sodium bromide produce minima in plots of [η] against salt concentration. Sodium iodide precipitates polyacrylate at 1.5 N iodide as a translucent gel, which redissolves at 3.0 N and finally reprecipitates at 6 N. In the latter range of concentration, [η] exhibits a maximum. Both by‐ions and counter‐ions have specific effects on the viscosity of the polyion.
Alkyl thiolacrylates: Their preparation and polymerization
Authors: Marvel C. S. , Jacobs S. L. , Taft W. K. , Labbe B. G.
Published: April 2003

A convenient synthesis of alkyl thiolacrylates has been described and a number of the intermediates, as well as the esters, have been characterized. These esters have been found to homopolymerize readily under free radical conditions to give clear plastics which have higher softening points than the corresponding acrylate ester polymers. In general the thiolacrylates copolymerize readily with common vinyl monomers. The reactivity ratios for copolymerization with butadiene have been found to be r1 (butadiene) = 0.35 ± 0.01 and r2 (methyl thiolacrylate) = 0.20 ± 0.05. The butadienemethyl thiolacrylate copolymer prepared from a 90/10 charge ratio to a 45% conversion contained 18.1% of combined methyl thiolacrylate. Tests on the compounded and cured polymer indicate that it has properties very close to those of standard GR‐S, except for its higher temperature rise.
The melting behavior of polybutadienes
Authors: Mandelkern L. , Tryon M. , Quinn F. A.
Published: April 2003

The melting temperatures of five emulsion polymerized polybutadienes containing varying amounts of trans‐1,4 units were determined. Since slow heating rates were used subsequent to the initial crystallization, melting temperatures were observed that were appreciably higher than previously indicated. The data were analyzed according to the theory of the melting point depression of copolymers, and a lower limit for the heat of fusion per 1,4‐trans unit of 18.5 cal./g. was obtained. This value is larger than that for natural rubber and explains why calorimetric measurements of the heat of fusion apparently give abnormally high values. The index of refraction and densities of the amorphous polymers were determined at 25°C. and the specific refractivities found to be constant and independent of polymer constitution in the composition range studied.
The ultimate properties of simple elastomers
Authors: Bueche A. M.
Published: April 2003

A criterion for the rupture of simple elastomers is postulated and its consequences examined. The criterion assumes that the sample will break when the rate of increase of tension due to further elongation is equal to the decrease due to bond rupture. The former is computed from the rate of strain and the form of the stress‐strain curve. An expression for the latter is found using reaction rate considerations. The resulting expression represent the experimental data on the rupture of polydimethylsiloxanes within the limits of experimental error. The free energy of activation for bond rupture obtained from the tensile data, by use of the theory, at one temperature is in approximate agreement with the activation energy obtained from stress relaxation measurements at several temperatures.
Electron exchange‐polymers. V. Hydroquinone‐formaldehyde polymers
Authors: Verplanck Vincent , Cassidy Harold G.
Published: April 2003

Hydroquinone‐formaldehyde and related polymers were prepared and examined for oxidation‐reduction properties in a preliminary way. Instability toward oxidizing agents and alkali was shown by the polymers, and further study of them was suspended. Where this work is related to that of G. Manecke, the two are in general agreement. Instability toward an oxidizing agent (iodine in KI at pH 8) was shown also by the products resulting from the treatment of several commercial sulfonated phenol‐formaldehyde ion exchange resins, and a 7:6 phenol‐formaldehyde novilac with Fremy's salt, or with diazotized sulfanilic acid, followed by reduction with sodium hydrosulfite, to produce catechol‐ or hydroquinone‐type residues.
Sulfinic acid derivatives as accelerators in the polymerization of methyl methacrylate
Authors: Brauer G. M. , Burns F. R.
Published: April 2003

A study was made of the efficiency of amine salts of p‐toluenesulfinic acid as accelerators in the polymerization of methyl methacrylate. These compounds are readily synthesized by addition of amine to the ether solution of the sulfinic acid. Most of the salts are stable in air. Salts of secondary and tertiary aromatic amines, such as the methylaniline or dimethyl‐p‐ toluidine salts, are very efficient accelerators in the benzoyl peroxide‐initiated polymerization. However, colored products are formed. Aliphatic amine salts as well as the free acid give colorless polymers, but the setting time is increased considerably. Heterocyclic amines show reduced activity as polymerization accelerators. The setting times of monomer–polymer mixtures containing some of these accelerators have been determined. Physical properties of the polymers have been evaluated by measuring their resistance to indentation and recovery.
Infrared studies on chlorinated rubbers
Authors: Ramakrishnan C. S. , Dasgupta Sharda , Pande J. B.
Published: April 2003

The changes in the infrared absorption spectra accompanying the chlorination of unmasticated deproteinized natural rubber dissolved in carbon tetrachloride, with phenyl iododichloride, are reported. The 6% chlorine content product shows, in general, decreased absorption in the 8–11 μ region. The spectrum of 6% chlorine content product is markedly different from that of fully chlorinated rubber. The 19% chlorine content product is intermediate to that of 6–51% and shows some of the characteristics of fully chlorinated rubber, while retaining part of the characteristic absorption of natural rubber. The spectrum of the fully chlorinated product is similar to that of hydrochlorinated rubber and chlorinated rubber obtained by the gaseous chlorine reaction.
Chain scissions in a polymer network
Authors: Horikx M. M.
Published: April 2003

Relations between the soluble fraction and the number of effective chains between crosslinks in a three‐dimensional network undergoing a scission reaction have been derived. Three limiting cases have been considered: (a) random scission in the chains, (b) scission in the chains directed by the crosslinks, and (c) scission of the crosslinks. The number of scissions can be computed from the fraction of soluble material in a degraded network, as determined experimentally. This procedure has been applied to the oxidation of a natural rubber vulcanizate. In a natural rubber sulfur‐Santocure vulcanizate, the scission reaction accompanying the oxygen absorption at 100°C. does not involve opening of the crosslinks, but it remains undecided whether the scission in the chains is directed or at random. At each chain scission about 5–10 molecules of oxygen are taken up by the rubber at 100°C. under various conditions, this number being apparently independent of the rate of oxidation, the absence or presence of antioxidants and metal stearates as catalysts, and the oxygen pressure.
Determination of the second virial coefficient in dilute polymer solutions from light scattering data
Authors: Fleming P. , Peacocke A. R. , Wallis R. G.
Published: April 2003

Various methods are discussed of utilizing light scattering data obtained at only one angle (other than measurements to determine the intrinsic dissymmetry), in order to obtain values for the second virial coefficient. Illustrative data from light scattering measurements at two wave lengths using a sample of sodium polyglutamate from Bacillus anthracis are presented.
Reaction of ozone with natural hevea and acrylonitrile‐butadiene rubbers
Authors: Kendall F. H. , Mann J.
Published: April 2003

The physical changes that occur when ozone reacts with unvulcanized rubber or unstretched vulcanizates have been studied. The speed of reaction is controlled by diffusion of gas into the rubber; as a consequence, initial products formed near the surface are subjected to further action by ozone. To minimize this possibility experiments have been carried out with thin films of Hevea rubber and monolayers of Hycar OR‐15, and the products have been characterized by infrared spectroscopy. The results are considered in relation to observations on the ozonization of simpler compounds recorded in the literature. It is concluded that, during ozonization there is a spontaneous scission at the carbon‐carbon double band with the production of aldehyde and/or ketone and a peroxy biradical. The measurements show the presence of a reaction which is inhibited by 1% phenyl‐β‐naphthalamine and which is presumably a chain reaction. The nature of this chain reaction is discussed and it is shown that suppression of this reaction does not prevent the cracking of stretched vulcanizates. The suggestion is made that the characteristic feature of cracking is a reaction which takes place in a thin layer at the surface of the rubber.
Methanolysis and hydrolysis of cotton cellulose III
Authors: Nelson Mary L. , Segal Leon , Mares Trinidad , Creely Joseph J.
Published: April 2003

Well‐decrystallized cotton yarn, the remaining organized regions of which consisted predominantly of crystalline cellulose III, was subjected to partial solvolysis in aqueous and methanolic hydrochloric acid. From x‐ray examination of the residues a hypothesis is advanced regarding the reversion of cellulose III to cellulose I. The viscometric data indicated identical values of leveling‐off degree of polymerization by hydrolysis and by methanolysis, which is at variance with certain published data showing lower values for methanolysis. The data therefore neither support nor disprove the idea of recrystallization during hydrolysis, but indicate the need for further work along these lines.
Crosslinking of polyethylene‐type polymers by high‐energy irradiation
Authors: Okamoto H. , Isihara A.
Published: April 2003

Effects of high‐energy radiation on polyethylene‐type polymers were considered. At the initial stage of irradiation, crosslinking, double bond formation, and hydrogen evolution are proportional to the radiation dose. The efficiency of irradiation in forming an infinite network was estimated. It depends on the mobility of decomposed atoms or radicals in the solid polymers.
Decomposition of benzoyl peroxide in dilute solutions
Authors: Barson C. A. , Bevington J. C.
Published: April 2003

A study of the decomposition of benzoyl peroxide in very dilute solutions is reported. This work is preliminary to a detailed investigation of the mechanism by which the peroxide initiates radical polymerizations; 14C‐benzoyl peroxide has been used. In dilute solutions in benzene, almost all the benzoate radicals generated from benzoyl peroxide lose carbon dioxide before they can enter into other reactions; various substance e.g., diphenylpicrylhydrazyl, styrene, and cumene, which can react with free radicals, decrease the yield of carbon dioxide.
Preparation and properties of fibers containing mixed polymers. I. Polyacrylonitrile‐cellulose acetate fibers
Authors: Cates David M. , White Howard J.
Published: April 2003

Fibers containing both polyacrylonitrile and cellulose acetate were spun using dimethyl formamide as a solvent. The relative polymer proportions ranged from 100% polyacrylonitrile to 20% polyacrylonitrile. The x‐ray diffraction patterns, optical appearance, solubility, density, absorptive capacity for water and dyes, electrical resistivity and mechanical properties of the fibers were studied, and experimental results are given. In addition several experiments bearing on the structure of the fibers and the compatibility of the spinning solutions are reported. The results indicate that the fibers contain discrete regions of each polymer. It is probable that, for most of the relative concentration range, continuous networks of each polymer extend throughout the fiber. In addition void spaces, probably resulting from the drawing of the fibers, appear to be present.
Tensile stress in jets of viscoelastic fluids. I
Authors: Gill Stanley Jensen , Gavis Jerome
Published: April 2003

Experimental observations have been made on jets of a viscoelastic fluid (carboxy‐methylcellulose–water solutions). The jet was subjected to transverse vibrations by the nozzle. The resulting wave pattern of the jet was compared to the theoretical results of three mechanisms of wave propagation: tension, rigidity, and elastic stretching. The results conform to the case of tension, and thus demonstrate the existence of a tensile stress in jets of viscoelastic fluids.
Characterization of graft polymers
Authors: Blanchette Joseph A. , Nielsen Lawrence E.
Published: April 2003

Two styrene‐rubber polymers were prepared by mass polymerization and fractionated to isolate the insoluble graft portions of each. These graft fractions were analyzed by two methods (titration and infrared) for unsaturation. Cleavage at the hydroxylated double bonds was carried out and the polystyrene chains were isolated. A diagrammatic structure for the insoluble graft material has been calculated from the length and number of the polystyrene chains isolated by the cleavage technique. The physical and mechanical properties of the gel fractions are reported.
Application of the theory of absolute reaction rates to the creep failure of polymeric filaments
Authors: Coleman Bernard D.
Published: April 2003

A discussion is given of the creep failure of partially oriented polymeric filaments. The theory of absolute reaction rates is used to obtain differential equations which permit the calculation of the lifetime of a single filament when it is subjected to different uniaxial loading histories. Explicit expressions are obtained for the lifetime of a filament for three special cases: dead loads, increasing linearly with time, and sinusoidal loads. Results of lifetime under dead load measurements are presented for drawn 66 nylon yarns. The treatment of the data by the theory yields plausible values for the molecular parameters involved. It is shown that the parameters which are calculated from the dead loading experiments may be used to calculate the dependence of the tensile strength on the speed of measurement (when obtained using a constant rate of loading tester). Tensile strength values were measured at rates of loading in the range between 0.14 × 109 and 4.8 × 109 dynes cm.−2 sec.−1 and found to be in satisfactory, agreement with those predicated by the theory.
Poly‐α,β,β‐trifluorostyrene
Authors: Livingston Daniel I. , Kamath Pandurang M. , Corley Richard S.
Published: April 2003

An improved preparation and handling procedure for the monomer is described. The polymer was prepared best by emulsion polymerization, although anionic polymerization was also found to be operable. A number of properties of the polymer are described, including solubility, the infrared absorption spectrum, x‐ray diffusion (amorphous scattering), dielectric constant (2.56 ± 0.05), and dielectric loss tangent (0.0006 to 0.0035 over the range 102 to 1011 c.p.s.). Copolymerization with trifluorochloroethylene gave a copolymer containing 0.096 mole fraction of trifluorochloroethylene, and with styrene a copolymer containing 0.397 mole fraction. The copolymerization curve and constants for copolymerization with styrene are presented and discussed.
The tensile rupture of hard plastics
Authors: Gruntfest I. J.
Published: April 2003

The tensile strength of polymethyl methacrylate is calculated from “modulus” data applying a criterion for mechanical stability and assuming that the failure process is adiabatic. Reasonable agreement with observed values is obtained. Application to the tensile strength of glass and of nylon is also considered.
Fractionation of polyethylene
Authors: Tung L. H.
Published: April 2003

Commercial polyethylenes were fractionated at 130°C., 15 degrees above the crystalline melting point of the polymer. Both extraction and precipation techniques were used. The solvent was xylene, and the nonsolvent was triethylene glycol. The inherent viscosities of the fractions were measured and the differential and integral distribution curves were presented. A method of constructing the differential and integral distribution curves was discussed. Using this method, fractionation data can be smoothed out from a linear plot, and the graphic differentiation step in constructing differential distribution curves can be eliminated.
The effects of crystallization and drawing on the viscoelastic properties of fibers
Authors: Tokita Noboru
Published: April 2003

The viscoelastic properties of four kinds of nylon‐6 and viscoses rayon having various degrees of crystallinity and of drawing are studied. The crystallinity is estimated from the density measurement for nylon‐6, while for viscose rayon it is determined by the acid hydrolysis method of Nickerson. The various kinds of measuring instruments are described by which the complex Young's modulus of fiber monofilament is measured over a wide range of frequency. The dynamical measurements for both materials are made over the frequency range from 0.047 c./sec. to 100 kc./sec. at 20°C. and 66% RH, and then the spectra of relaxation times and the distribution function of retardation times for each sample are obtained. From the experimental results, it is concluded that the mechanical dispersion found in the audio‐frequency range for partially crystallized nylon‐6 is due to the motion of segments in strained amorphous parts. The distribution function of retardation times for the heat conditioned nylon‐6 is well represented by a Cole‐Cole's distribution function with β = 0.29. On the other hand, the shock‐cooled nylon‐6 shows distinctively a non‐linear property at the strain of order of 10−3. Besides, it is found that the increase of the degree of crystallinity and drawing results in shifting the dispersion regions, as a whole, to longer time regions, and that the shapes of spectra of relaxation times are almost independent of the degree of crystallinity, while the shapes of spectra corresponding to wedge‐type spectra become less steep with increase of the degree of mechanical drawing. These facts are attributed to the sterile hindrance against the segmental motion. As regards viscose rayon, the mechanical dispersion represents itself at about 65°C. in 65% RH, and the activation energy for the segmental motion in amorphous parts is about 190 Kcal/mole. The water molecules adsorbed in fibrous structure are supposed to be playing the role of a plasticizer. The degree of crystallinity (70–75%) does not affect the mechanical behaviours of viscose rayon so much.
Molecular orbital theory of reactivity in radical polymerization. Part II
Authors: Hayashi K. , Yonezawa T. , Nagata C. , Okamura S. , Fukui K.
Published: April 2003

Several problems in the process of radical polymerization, e.g., the relation between the chemical structure of vinyl monomer and its chemical reactivity, the prevalence of head‐to‐tail configuration, the reactivity of initiator radicals, the alternation tendency in heteropolymerization, and the relative ease of coupling in several cases of homopolymerization, are treated by the theory previously proposed by the present authors, in which reactivity is represented by the magnitude of stabilization energy due to π conjugation between a monomer and a radical in the transition state. In addition, a brief discussion on the existing theories of reactivity and some applications of Hush's method to the problem of termination are presented. The agreement between results of calculation and experiment is shown to be almost statisfactory.
Sorption of water by wool
Authors: Windle J. J.
Published: April 2003

A model for the system of wool plus sorbed water is proposed in which the sorbed water consists of three distinct molecular species: localized water irrotationally bound to localized sites in the fiber, mobile water with properties identical to bulk water, and intermediate water with a potential energy of sorption between that of the localized and mobile water. The theoretical isotherm for this system has been determined from statistical considerations and compared with the experimental isotherm for wool reduced to one hydrostatic pressure. The statistical parameters of the model have been evaluated thereby and the distribution of the sorbed water among the three energy states inferred. The nature of the localized sites and the properties of the sorbed water are discussed. The model is applied to the interpretation of data on the microwave dielectric behavior of wool–water systems, the heat of wetting of wool, and the effects of sorbed water upon the elastic properties of the fiber.
Oxidative degradation of polyethylene
Authors: Beachell Harold C. , Nemphos Spero P.
Published: April 2003

The degradation of polyethylene in molecular oxygen between 150 and 250°C., in ozone‐enriched O2 between 20 and 109°C. and in fuming HNO3 between 25 and 83°C. has been studied. The solid, liquid, and vapor products have been analyzed by means of their infrared spectra. Kinetically, the O2 oxidation reaction appears to be second order. The Elovich chemisorption equation dq/dt = ae−αq was applied to the data and yielded comparable results. The kinetics were followed by pressure change and constant pressure measurements of oxygen uptake, and by the rate of increase of bands in the infrared spectra. The activation energy of the process was found to be 8–9 kcal./mole for the volumetric and manometric studies as well as for the ozone‐catalyzed reaction, while the HNO3 oxidation gave a 35.6 kcal. value.
Rupture of rubber. IV. Tear properties of vulcanizates containing carbon black
Authors: Greensmith H. W.
Published: April 2003

The tear properties of natural rubber and GR‐S vulcanizates containing carbon black are compared with those of gum vulcanizates, using a method developed in a previous paper. The distinctive features in the tear behavior of the filed vulcanizates are noted and discussed. The results indicate that there are two types of tear process, which vary in importance according to the tearing conditions, and the influences of carbon black on these processes is discussed.
Viscosity measurements on molten polyethylene
Authors: Philippoff W. , Gaskins F. H.
Published: April 2003

The flow curves for two samples of molten polyethylene and one of plasticized polyvinylbutyral were measured in a large range of rates of shear and shearing stresses. Two conicylindrical viscometers of greatly different dimensions were used to obtain the wide ranges; the data from these viscometers coincided in the region of overlapping. The behavior of the molten plastics is essentially parallel to the one for solutions of high polymers. Absolute values of the initial viscosity of these polyethylenes at different temperatures were close to those obtained by Dexter on other polyethylenes. The apparent activation energy for viscous flow calculated from these experiments was very similar to the ones reported in the literature.
Studies on carbon black. III. Theory of bound rubber
Authors: Villars D. S.
Published: April 2003

On the hypothesis that “bound rubber” is a gel of carbon black particles, the bonding agent of which consists of the longer polymer molecules, a statistical theory is developed. The probability is first computed that a rubber molecule of i segments will be attached to j carbon black particles. By means of this probability the number and weight of molecules connecting carbon black particles are calculated. The theory predicts loadings below which bound rubber may not be expected (carbon black runs through into extract), and relates amount of bound rubber to total surface area of the black and the molecular weight of the remaining dissolved rubber to that of the rubber originally present. The theory gives a logical explanation of the often observed preferential adsorption by carbon black of polymer molecules of higher molecular weights.
Infrared spectra of the crystalline modifications of cellulose
Authors: Marrinan H. J. , Mann J.
Published: April 2003

The bands due to stretching of OH groups of all four crystalline modifications of cellulose have been measured using a deuteration technique which enables crystalline regions to be studied independently of amorphous regions. Cellulose III prepared from cellulose I (IIII) was found to be different from cellulose III prepared from cellulose II (IIIII). Similarly different cellulose IV's were obtained from celluloses I and II (IVI and IVII). However, the infrared spectra suggest that only one of these, namely, IIII should be regarded as having a crystal structure distinctively different from those of cellulose I and II. Thus IVI and IIIII closely resemble celluloses I and II, respectively, while IVII shows a diffuse absorption and may well possess a disordered lattice. The bearing of these results on the crystal structures of celluloses I and II is discussed.

The unit cells of celluloses IIIII and II are different, although their infrared spectra are very similar. These facts suggest that hydrogen bonding in these two forms is of the layer type in the (101) plane, though the possibility of hydrogen bonding in the (101) plane cannot be entirely eliminated.
Tensile stress in jets of viscoelastic fluids. II
Authors: Gavis Jerome , Gill Stanley Jensen
Published: April 2003

A viscoelastic fluid jet is treated as a moving infinite string under slowly varying tension. When the system is subjected to a sinusoidal point vibration, the resulting wave form enables the tension to be determined along the jet. The total tension is composed of a surface reaction and an internal, decaying tension. The surface reaction may be calculated from the surface tension of the jet fluid and the radius of the jet. Data for 1.4 and 1.7% carboxymethylcellulose water solutions are presented for three different jet radii and for solution temperatures of 5, 25, and 35°C. It is found that the observed tensions approach the calculated surface reaction far from the nozzle. The rate of decay is a function of concentration and temperature. The internal tension for a 1.7% solution at 25°C. was observed to decay from about 8000 to 500 dynes/cm.2 in 200 milliseconds. Relaxation times of 0.27 sec. for 1.4% and 0.32 sec. for 1.7% solutions at 25°C. describe the internal tensile properties between 40 and 200 milliseconds after ejection.
Hydrodynamic properties of polyelectrolytes. Part III. Sodium alginate
Authors: Mathieson A. R. , Porter M. R.
Published: April 2003

The viscosity and streaming birefringence of fractionated and unfractionated samples of sodium alginate have been measured at various concentrations, and rates of shear, and in the presence and absence of added salt. The viscosity data show the concave upward curve typical of polyelectrolytes at low concentrations, but pass through a minimum at higher concentrations. The influence of shear is least at this minimum. The initial slope of the orientation angle versus velocity gradient curves increases with concentration, but Δn/c is independent of concentration. The semiempirical theory of Peterlin for concentrated solutions is obeyed by the data for Δn, but not by that for the orientation angle. Molecular weights have been calculated from the hydrodynamic parameters. The viscosity behavior is interpreted in terms of the rigidity of the molecule.
Degradation of long‐chain molecules by ultrasonic waves. Part VI. Effect of pressure
Authors: Brett H. W. W. , Jellinek H. H. G.
Published: April 2003

Ultrasonic degradation of polystyrene in benzene solutions has been studied as a function of pressure exerted on the solutions. Appreciable differences in the rate and extent of degradation have been found if the pressure was exerted via a mercury column, the solutions being saturated with gas at one atmosphere or if the pressure of nitrogen over the solutions was increased, the solution being saturated with nitrogen at each respective pressure.
Oxidation of polybutadiene. I. Rate of oxidation
Authors: Bauman Richard G. , Maron Samuel H.
Published: April 2003

The rate of oxidation of thin films of polybutadiene have been studied between 50 and 90°C. The films were prepared directly from latex by dipping, and thoroughly purified. The oxidation rates were found to go through an induction period, to accelerate rapidly to a maximum, and then to decrease to low values. The decrease in rate past the maximum may be due to consumption of polymer, or diffusion control of the rate. Test of the latter possibility showed the oxidation process to be diffusion limited at 90°, but not at 50°C. These results show that change of temperature leads here actually to a change in the mechanism of the oxidation process.
The structure of polysiloxanes: Solvent swelling of soluble polymethylsiloxanes
Authors: Price Fraser P. , Martin Sylvia G. , Bianchi Joseph P.
Published: April 2003

Viscosity–molecular weight relationships for polymethylsiloxanes of Me/Si from 2.0 to 1.5 have been determined in a variety of solvents. It has been found that, at Mw = 106, in going from an ideal solvent to the best solvent used, 2.0, 1.8, and 1.5 Me/Si polymers expand volumetrically by factors of 3.8, 2.0, and 1.15, respectively. This is consistent with the hypothesis that the 1.8 and 1.5 Me/Si materials are internally crosslinked to a high degree, and are probably spherical in shape. The solvent‐polymer interaction parameters for the linear polymer in several solvents are calculated, and estimates of the solubility parameters of the various polysiloxanes are obtained.
Equal reactivity of amide groups in acid hydrolysis of polyamides from ϵ‐aminocaproic acid
Authors: Heikens D.
Published: April 2003

Samples of the linear dimer and trimer and of a mixture of linear oligomers of ϵ‐aminocaproic acid with a mean degree of polymerization of 15, being free of lower oligomers up to the pentamer, were hydrolyzed in aqueous 7.72 N HCl at 110°C. for chosen time intervals. It is shown that the rate constant pertaining to the hydrolysis of the amide groups is independent of chain length and has the value of 0.24 hr.−1, proving that in the system investigated the principle of equal reactivity holds.
Allyl polymerization. IV. Effective chain transfer in polymerization of allylic monomers
Authors: Gaylord Norman G.
Published: April 2003

In addition to degradative chain transfer, effective chain transfer is characteristic of the polymerization of allylic monomers. The order of increasing effective chain transfer in a series of allyl compounds is ethyl ether < ethyl carbonate < acetate < propionate < trimethylacetate < chloride < laurate < benzoate < chloroacetate, and varies from 3% in allyl ethyl ether to 85% in allyl chloroacetate. A constant value of dM/dC is obtained in all of these cases. The decreasing order of [dM/dC]cat←0 is chloroacetate > benzoate > laurate > chloride > propionate > acetate > ethyl carbonate > trimethylacetate > ethyl ether and ranges from 108 for the chloroacetate to 6.3 for the ether. The decreasing order of DP is ethyl carbonate > acetate > propionate > benzoate > chloride > chloroacetate > laurate > trimethylacetate > ethyl ether and ranges from 14 for the carbonate to 4 for the ether. A radical displacement reaction may be operative in the polymerization of the trimethylacetate and benzoate and possibly in the case of the ethyl carbonate and ethyl ether. Considerable effective chain transfer occurs in the polymerization of allyl chloride and allyl chloroacetate as the result of hydrogen abstraction to yield halogen‐containing radicals. Effective chain transfer is predominant in the polymerization of allyll laurate, possibly through the operation of an intramolecular hydrogen transfer.
Infrared spectra of high polymers. IV. Polyvinyl chloride, polyvinylidene chloride, and copolymers
Authors: Krimm S. , Liang C. Y.
Published: April 2003

The infrared spectra of polyvinyl chloride, polyvinylidene chloride, and their copolymers have been analyzed with the help of group theory and of spectra in the extended range of 70 to 3000 cm.−1. The assignments of the bands have been made with the help of polarized spectra of oriented samples. For both polyvinyl chloride and polyvinylidene chloride the tentative structure suggested by x‐ray diffraction studies has been used as a basis for predicting the infrared spectrum of the polymer. In both cases a quite satisfactory interpretation of the spectrum has resulted, thus lending further support to the postulated structures. For each polymer, the group theory analysis is used to obtain selction rules and the distribution of normal modes among the symmetry species. On the basis of approximate separability of group modes, it is possible to analyze in detail the expected hydrogen, chlorine, and skeletal normal modes. Assignments of these frequencies are inferred from this information, knowledge of the region in which the normal frequency is expected to occur, and the polarization properties of the bands. In the case of the skeletal modes, the assignments are based upon recent calculations of the skeletal frequencies expected in long chain molecules.