摘要:

AbstractWhen subjected to the effect of ionizing radiation, such as atomic pile radiation or gamma radiation, cellulose is rapidly degraded into a powdery material. A theoretical treatment shows that if the effect of radiation is to cause fracture at random in the main chain, the relation between intrinsic viscosity [η] and radiation doseRshould be of the form:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log [\eta] = - \alpha \log (R + R_0) + {\rm constant} $$\end{document}whereR0is a “virtual” radiation dose needed to produce the initial number‐average molecular weight from a chain of infinite molecular weight. The published data of Saeman, Millett, and Lawton have been used to verify this formula, which leads to a relationship between [η] in cupriethylenediamine and viscosity‐average molecular weightMv:\documentclass{article}\pagestyle{empty}\begin{document}$$ [\eta] = KM_v^\alpha $$\end{document}with α = 0.71. The constantKhas been evaluated by comparison with data given by Gralen, but is less accurately known. It is deduced that one million roentgen results in fracture of 0.16% of the monomer units in the main chain. The decomposition of carbohydrates under radiation, which occurs at the same time as main chain fracture, can be explained on the assumption that approximately one monomer unit is decomposed per main chain fracture. The study of intrinsic viscosity of irradiated polymers appears to offer an accurate means of evaluating α in the usual formula for intrinsic viscosi

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157921

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractPolymerization of acenaphthylene by boron trifluoride‐ether complex as catalyst was carried out in benzene solution of various concentrations of the catalyst over a range of temperatures from 20 to 50°C. Over‐all rate of the polymerization was found to be of the first order both for the initial concentration of the monomer and for that of the catalyst:\documentclass{article}\pagestyle{empty}\begin{document}$$ - d[M]/dl = k[M][C] $$\end{document}Activation energy required in the reaction was calculated to be 12.5 kcal./mole, and the molecular weight of polymers measured by the Gee osmometer was shown to be of the same order as found by previous wor

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157922

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe reduced viscosityvs.concentration relation was measured for sodium chloride solutions of sodium carboxymethylcellulose (Na‐CMC ofDP≓ 400 andDE≓ 0.7) in a range of low concentrations (0.003 to 0.09 g./100 ml.), and the data obtained were analyzed following the procedure of Pals and Hermans. The results confirmed in many aspects findings which had previously been made in the literature, and supplied values of the necessary molecular quantities for our own sample. They indicated that our Na‐CMC molecule was relatively uncoiled even in solutions of high ionic strength. The Huggins slope constant was found to increase approximately linearly with increasing reciprocal of the ionic strength of the solution. Next, the shear dependence of reduced viscosity in dilute solutions of this polyelectrolyte was investigated by the use of a viscometric apparatus which was especially designed for accurate measurements at low shear rates. The shear rate region investigated was from about 50 to 1000 sec.−1. The measurements were made on salt‐free solutions and on solutions of constant ionic strength; in both cases only the regions of sufficiently low concentrations were treated. In the salt‐free solutions the ηsp/Cvs.q(qis shear rate) curves showed an upward curvature rather than a quadratic dependence at the limit of shear rate. In this case, the initial slope of each curve increased markedly with increasing dilution. The plots of ηsp/Cvs.qfor solutions of constant ionic strength (ca.0.0015 mole/l.) were approximately represented by straight lines within the concentration range investigated. The slope of the straight lines decreased regularly with increasing dilution. Some evidence that these plots have a horizontal initial tangent was observed, but this was never conclusive due to the paucity and inaccuracy of exprimental data at shear rates smaller than 100 sec.−1. The intrinsic viscosity obtained from ηsp/Cvs.Ccurves at constant shear rates for the isoionic system was independent ofq.From these findings it was realized how markedly the viscous behavior in dilute solutions of the polyelectrolyte studied was influenced by the addition of small amounts of neutral salt, not only in viscosity value itself but also in its shear rate dependence. Our data and results herein presented were concerned only with a sample of one (average) molecular weight and one degree of etherification. More data, therefore, are needed on samples of varying degrees of polymerization and etherification before a more definite understanding of the problem herein t

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157923

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractMethyl methacrylate, vinyl acetate, styrene and diethylene glycol‐bis(allyl carbonate) were subjected to irradiation by very intense microsecond pulses of electrons of 3 MeV energy. The methacrylate underwent a prolonged, slowly decaying polymerization beginning immediately after irradiation; in a typical run, a dose of 1.5 × 105rep delivered in 12 pulses resulted in 1% polymerization after six hours and 5% polymerization after 50 hours. The extent of polymerization was reduced by increasing the surface of glass in the reaction vessel. Freezing the monomer during irradiation reduced the extent of subsequent polymerization in the liquid state by approximately 40%. Evidence was obtained to show that the polymerizing radicals are of the normal type found in thermal and photochemical work, and their initiation is attributed to the formation of a catalyst during or immediately after irradiation. No significant amount of polymerization took place in the other monome

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157924

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractAbsorption of solvent and swelling by nitrocellulose fibers and films, in binary solventhexane mixtures of varying concentration and involving ketones, acetates, and phthalates, have been compared. Equilibrium is less rapidly attained with films. With solvents of smaller molecular size the equilibrium absorption of fibers and films, at a given concentration, is the same, suggesting that all regions of the nitrocellulose are accessible to such solvents. With solvents of larger molecular size lower equilibrium absorption values are obtained with films, suggesting that only certain regions are accessible to these solvents and such accessibility is less in films. Where absorption values are similar, swelling of films and fibers are comparable and similar modes of solution are observed. The assumption that no hexane is absorbed appears to be justified at lower solvent concentrations, but at higher concentrations the mixture in equilibrium with the nitrocellulose may be imbibed. Assuming such imbibition, the relationship between swelling or solvent power and cohesive energy density of solvent is interpreted in terms of interaction between solvated polymer and mixture.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120157925

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY