摘要:

AbstractA series of polyethylene resins made by making progressive changes in temperature, pressure, and catalyst content has been studied by infrared absorption spectroscopy. From the methyl content and the number‐averages molecular weight of each resin, it was found that as molecular weight increases degree of branching decreases. Also revealed was the fact that each of the three types of double bond groups present,i. e., RHCCH2, RHCCHR, and RRCCH2, decreases in concentration with increasing molecular weight. Using polarized radiation, high resolution grating spectra were obtained on polyethylene films which had been highly oriented by cold drawing 500%. The results show that the CH3terminated branches are not predominantly oriented either parallel or perpendicular to the direction of stretch. It is the authors' view that the chain branches vary in length with a considerable fraction short enough to be essentially at right angles to the long chain axis while others are sufficiently long to be parallel to the long chain axis in stretched polyethylene. When a stretched polyethylene film is heat relaxed (110–115°C.), its spectra using polarized radiation reveal the presence of crystallites in which the long carbon‐to‐carbon chain axes are predominantly oriented at right angles to the dire

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110101

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractIsobutylene and styrene were copolymerized at low temperatures, in methyl chloride solution, in the presence of aluminum chloride. The temperature was varied from −30 to −94°C., and the monomer/solvent ratio, the ratio of monomers, and the catalyst concentration were varied over a considerable range. The copolymerization equation was found to be applicable to the data, and the reactivity ratios were determined for various experimental conditions. For an “open” system in which the volume steadily increases during the course of polymerization, it is shown that the copolymerization equation is formally identical to that of Mayo and Lewis, except that concentrations are replaced by amounts of the reacting species. The temperature coefficients of the reactivity ratios in the present system are compared with those for free‐radical systems; some important differences are noted. The reactivity ratios of isobutylene and styrene in the present system are greatly increased under conditions of turbulent agitation. A procedure for the compositional fractionation of the copolymers is described. The results are interpreted in terms of the copolymer chain structure; they appear to admit the postulate that the reactivity ratios and corresponding propagation rate constants are functions of ch

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110102

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractIntrinsic viscosities of polystyrene and polyisobutylene fractions in good and in “ideal” solvents have been examined from the point of view of their dependence on molecular weight. A compilation of results is presented which covers exceptionally wide ranges, from several thousand to several to million, in molecular weight. The intrinsic viscosity in an “ideal” solvent (i.e., cyclohexane at 34°C. for polystyrene, or benzene at 24° for polyisobutylene) is remarkably well fitted over the molecular weight range cited above by the relation:\documentclass{article}\pagestyle{empty}\begin{document}$$ [\eta]\Theta = KM^{1/2} $$\end{document}whereKis a constant, independent of molecular weight, for a particular polymer at a given temperature. The molecular expansion factor α3which applies in good solvents (e.g., toluene for polystyrene and cyclohexane and diisobutylene for polyisobutylene) as calculated from:\documentclass{article}\pagestyle{empty}\begin{document}$$ [\eta] = KM^{1/2} \alpha^3 $$\end{document}increases with molecular weight approximately in accordance with the relationship:\documentclass{article}\pagestyle{empty}\begin{document}$$ \alpha^5 - \alpha^3 = 2C_{M\psi 1} (1 - \Theta /T)M^{1/2} $$\end{document}However, the quantity (α5− α3)/M1/2changes appreciably withMin some cases. This is particularly true for molecular weights below 50,000. Results of an examination of the effect of rate of shear on the viscosity of polystyrene in benzene at 25° and in cyclohexane at 34°, and of the intrinsic viscosity‐molecular weight relation for polystyrene in benzene at

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110103

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110104

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

Abstract1A viscometer to which variable pressures may be applied is shown to be convenient for measuring viscosities of sodium thymonucleate (NaTN).2The viscosities of solutions of NaTN investigated vary with velocity gradient. All of the solutions obey the empirical equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ 1/pt = A + Bp $$\end{document}wherepis the average pressure on the solutions during the outflow time,t.Ais used to calculate what are believed to be characteristic relative viscosities.3The viscosity of solutions of alcohol precipitable NaTN is found to depend on the concentration according to the equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ \eta _{{\rm sp}} /c = [\eta] + k''[\eta]\eta _{{\rm sp}} $$\end{document}Our preparation of NaTN gives values of 11.1 dl./g. and 0.24 for [η] andk″, respectively.4The viscosity of NaTN solutions not easily precipitable depends on the concentration according to the equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ \eta_{{\rm sp}} /c = [\eta] + k'[\eta]^3 c $$\end{document}Our values for [η] andk′ are 21.8 dl./g. and 0.26, respectively.5The viscous behavior of NaTN is discussed in the light of modernP polymer t

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110105

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractVinyl acetate has been copolymerized with small amounts of the diallyl ester of dithiodiglycolic acid (DADT). A method has been devised for the reduction of the disulfide crosslinks to sulfhydryl groups by means of thioglycolic acid under mild conditions, thereby enabling the recovery of the primary molecules of the original polymers. The method has been applied both to soluble copolymers (made with the lowest concentrations of DADT) and to insoluble space‐network copolymers (made with slightly higher concentrations of DADT). The polymers have been characterized before and after reduction by viscosity determinations. The reduction process had only a negligible effect on the viscosity of poly(vinyl acetate). The rate of reduction was diffusion controlled not only in the case of the gels, but apparently also in cases where soluble polymers were made with amounts of DADT less than necessary for gelation at high conversion. The DADT acted not only as a crosslinking agent, but also as a chain transfer agent. The method is suggested as potentially useful in developing the theory of three dimensional polymerization, and in studying the properties of space‐network polym

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110106

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractRedox recipes containing nitroprusside are described for the emulsion copolymerization of butadiene (75)‐styrene(25). Approximately 65% conversion is reached in 8 hours at 25° with a recipe containing 5 parts of fatty acid soap, 0.3 part of sodium nitroprusside dihydrate, 0.1 part of hydroxylamine hydrochloride, 0.1 part of diisopropylbenzene hydroperoxide, 0.5 part ofn‐dodecyl mercaptan, and 0.5 part of potassium chloride per 180 parts of water and 100 parts of monomers. If alkali is added to the polymerization system the polymerization is accelerated markedly and the addition of 0.1 part of hydroxylamine does not affect the rate. Approximately 60% conversion is reached in 12 hours at 5°C. with a recipe similar to that given above, but without hydroxylamine, provided that the aqueous phase is 0.01Min trisodium phosphate or alkali hydroxide. From the effect of various factors upon the rate of conversion it is postulated that in the low temperature recipe (with added alkali) the initiation occurs by RO · radicals:In the recipe without added alkali but with hydroxylamine hydrochloride the initiation apparently occurs by RS · radicals (RSH is mercaptan) formed by interaction of the oxidation product of nitroprusside with primary me

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110107

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractNatural rubber has been vulcanized to varying degrees of crosslinkage through the use of decamethylene dismethyl azodicarboxylate. The effect of degree of crosslinkage on extent of heat deterioration is demonstrated. Studies are also presented on the beneficial or deleterious action on heat deterioration of various chemical agents incorporated in the free state into natural rubber vulcanizate.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110108

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110109

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY