摘要:

AbstractVapor pressures of solutions of nitrocellulose in acetone were measured in all‐glass systems over the complete range of concentration, at temperatures from 20 to 60°C. Applying Flory's theory, the interaction parameter, χ1, was calculated. From its temperature‐dependence, the free energy of interaction between polymer and solvent was separated into interaction heat and interaction entropy components. A graph in which the heat terms are plotted against the corresponding entropy terms shows a straightline relation, with the line going through the o

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410701

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractMolecular weights of low pressure polyethylene fractions were measured by an ebulliometric method and an osmotic pressure method. The results can be correlated by an equation, [η] = 5.10 × 10−4M0.725, with the intrinsic viscosity measured at 130°C. in Tetralin, for a molecular weight greater than 3750. All three types of polymer fractions, Ziegler‐type low pressure polyethylene, Phillips low pressure polyethylene, and polymethylene from the decomposition of diazomethane, conform to the above correlation. The molecular weight distributions of two samples of Ziegler type polyethylene and one sample of Phillips' Marlex 50 were determined. All three distributions were found to be very broad and contained large amounts of low molecular weight mat

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410702

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractCopolymerization data involving a wide variety of monomers containing methylenic double bonds led to the conclusion that only acrylonitrile exhibited repulsive effects between adding monomer and copolymer containing higher proportions of the same monomer. Employing a modified procedure based on the Barb equationr1andr1′ values were determined for the following systems: methyl α‐chloroacrylate‐vinylidene cyanide, methyl methacrylate‐vinylidene cyanide, acrylic acid‐vinylidene cyanide, 2,5‐dichlorostyrene‐vinylidene cyanide, vinylidene chloride‐vinylidene cyanide, and 2‐chlorobutadiene‐vinylidene cyanide. These results confirm the predicted diversions from normal copolymerization behavior of vinyli

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410703

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractOsmotic determinations of the degree of polymerization of cellulose nitrate have been performed using different types of cellulosic membranes. For unfractionated samples the results were dependent upon the type of membrane, whereas for fractionated samples good agreement was obtained for different membranes. The leakage of nitrocellulose through the membrane has been determined. In separate experiments the solution used for measurements in osmometers with coarse membranes were transferred to osmometers with tighter membranes. A considerable increase in osmotic pressure was observed in the latter case; this shows that the lower osmotic pressure obtained in osmometers with nonselective membranes cannot be ascribed solely to a lowering in the molar concentration because of leakage. The results are in agreement with the theory postulated by Staverman. Plots of osmotic pressure against time as well as direct determinations of the leakage give insufficient information about the error obtained when using nonselective membranes.

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410704

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractA variety of polymers containing pendant isocyanate groups was prepared by the copolymerization of small amounts of β‐isocyanatoethyl methacrylate. Polystyrenes prepared by sodium amide initiation in liquid ammonia at −33°C. were characterized and shown to contain one terminal primary amine group per polymer chain. Approximately equivalent amounts (by functional group) were reacted in a dry inert solvent, generally at room temperature for one to two days. Graft copolymers were formed in high efficiency; this was conclusively shown for graft copolymers of poly(methyl methacrylate)‐polystyrene by disappearance of titratable amine groups, extraction of the graft copolymer with diethyl ether, ultraviolet analysis of the product, and agreement between calculated and actual number‐average molecular weight. The preparative method allows control of the length of the backbone and number of attached polystyrene side chains; the complete structure of the graft copolymer is known, including the number and length of si

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410705

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractA technique for characterizing the optical properties of biaxially oriented films is described. This involves measuring the optical retardation as a function of the tilt angle of the film. The method is illustrated for a film of biaxially oriented polystyrene.

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410706

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractPermeability constants at four temperatures for twelve organic solvents in three polyethylenes and one electron‐irradiated polyethylene are reported, together with some swelling data, and compared with data on N2, O2, CO2, and CH3Br. Irradiation appears to increase permeability and solubility coefficients for large penetrants at low temperatures, decreases the permeability coefficients of small penetrants at all temperatures, has little effect on the solubility coefficients of small penetrants, and tends to decrease both permeability and solubility coefficients of large penetrants at high temperatures. In almost every case irradiation decreased bothEpandP0\documentclass{article}\pagestyle{empty}\begin{document}$ (P = P_0 e^{ - E_p /RT} ); $\end{document}and there exists a temperature,T(inversion) = ΔEp/R(Δ lnP0) at which the permeability constants of a penetrant in polyethylene and irradiated polyethylene are equal. These inversion temperatures tend to increase with increasing polarity of the penetrant. To account for these observations, it seems sufficient to assume that irradiation decreases crystallinity and increases crosslinking, that an increase in polymer crystallinity is accompanied by an increase in the quasicrystalline‐like character of amorphous regions, and that small penetrants may dissolve, and diffuse, through the crystalline regions of polyethylene. It is postulated that activated diffusion in polyethylene induces structural changes in the polymer not unlike local melting. An explanation is given for the observation that flexible molecules tend to have small frequency factors compared to rigid molecules of similar activation energy. And a simple, particle‐in‐a‐box model is proposed for diffusion of small penetrants in a crosslinked polymer. This model predicts that irradiation should leaveEpunchanged, and should decreaseP0, by nearly the same factor for all penetrants at all temperatures, very much as observed for N2,

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410707

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe initial growth rate of a particle in a polymerizing emulsion is constant with respect to time and also with respect to the aqueous concentration of the initiator. However, as a particle becomes larger, a size is reached where positive deviations from this constant rate are observed. It is shown that the kinetic analysis of Ewart and Smith qualitatively implies this type of behavior. In order to obtain quantitative agreement between theory and experiment, It is necessary to assume that free radicals entering a particle are generated at the particle‐water interface. When this restriction is imposed on the kinetic analysis, the latter gives a highly satisfactory account of the experimental results throughout the region in which the approximation employed in the analysis is valid. The results of the analysis indicate specifically a nontrivial dependence of the kinetics of emulsion polymerization on particle size and initiator concentratio

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410708

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractThe creep of a highly nitrated cellulose under constant tensile load has been investigated. Over a wide time range, the strain–time curves were found to obey an equation frequently used to describe the creep of metals. This analysis separates the creep into two components, a rapid elastic deformation and a deformation increasing with the 1/3 power of the time. The first of these components was found to be directly proportional to the applied stress, while the second increased very rapidly with increasing stress, again in accord with observations on metallic creep. The recovery following short creep experiments was found to be complete and accurately predictable from the creep curves and a modified form of the Boltzmann superposition principle. This was not true of the recovery following a very long creep experiment. The superposition principle was also used to calculate a “stress–strain” curve from creep data. This curve was found to be qualitatively similar to curves which have been reported for nitroce

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410709

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY

摘要:

AbstractTwo viscometric methods have been developed for detecting the “critical concentration” (the concentration at which individual polymer molecules interfere with each other) of a dilute solution of a high polymer, B. In the first of these, the intrinsic viscosity, [η], of another polymer, A, is measured in a series of mixed solvents, each consisting of a solution of Polymer B in the solvent S, and each differing from the others only in the concentration of B (CB). For a number of polymer‐polymer‐solvent systems, data are presented which show that [η] is essentially independent ofCB, except over a small range where its value changes fairly abruptly. This change marks the critical concentration. The second method is much faster but probably less reliable than the first. Nevertheless, the two gave values in good agreement. A method of calculating the critical concentration, based on the Flory‐Fox theory of intrinsic viscosity, is described. Critical concentrations calculated for the several systems investigated agreed well with those obtained experimentally. The critical concentration was shown to be inversely proportional to the intrinsic viscosity of the Polymer B in experiments in which [η]Bwas varied by changing the molecular weight of the polymer and by changing the solvent. The effects observed are explained as resulting from interactions of the two polymer species in t

ISSN:0022-3832    

DOI:10.1002/pol.1957.1202410710

出版商:Interscience Publishers, Inc.    

年代:1957

数据来源: WILEY