摘要:

AbstractRubber hydrocarbon irradiated in vacuo is decomposed by ultraviolet light of wave length less than 4000 Å. The rubber very rapidly becomes insoluble, and liberates a gaseous mixture which consists mainly of hydrogen when the irradiation temperature is less than 150°C. The reaction characteristics have been investigated and point to the occurrence of dissociation processes similar to those deduced for comparable simple olefins. When irradiated above 150°C., small but significant amounts of isoprene appear in the volatile product, thereby providing an experimental means of determining the activation energy for the separation of isoprene from a polyisoprene chain terminated by an allyl radic

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020101

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe refractive index‐temperature data for polyvinyl acetate show a second‐order phase transition temperature of 2

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020102

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe conductance in diphenyl ether at 35°C. and 60 cycles of the picrate of a 4‐vinylpyridine‐styrene copolymer (10:90) has been measured. The equivalent conductance, based on the nitrogen content, is of the same order as that of picoline picrate, and varies with concentration in accordance with the law of ion associa

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020103

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe addition of silver nitrate to polymerizable systems containing butadiene can result in increased over‐all rates of conversion. When butadiene is the only monomer and a cationic soap is used the addition of silver nitrate causes* a significant decrease in rate. The most active system studied was one which contained butadiene, styrene, a cationic soap, a peroxide, and silver nitrate. Comparison runs in a GR‐S type formulation with silver nitrate and potassium ferricyanide indicate that the silver salt is the more effective in producing higher over‐all rates of conve

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020104

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractA polyvinyl acetate polymer of medium viscosity was fractionated into sixteen fractions (first series) and three of the larger of these further separated into twenty subfractions (second series). The intrinsic viscosities and the osmotic pressure molecular weights were determined at 25°C. and the relation between them was found to be expressed by the equations: first series: [η] = (1.88 × 10−4) M0.69; second series: [η] = (1.76 × 10−4) M0.68. The data indicate that little, if any, increase in homogeneity is to be expected by further successive fractionations and that the equations applicable to the second fractionation series are representative of essentially homogeneous polyvinyl acetates in acetone. An equation applicable to fractionated and unfractionated vinyl acetate polymers is described that is useful in obtaining the intrinsic viscosity from a single viscosity measurement. Several unfractionated materials from different sources were also studied and the calculated ratios of the viscosity‐average to the number‐average molecular weight indicate that the degree of heterogeneity of chain‐length distribution increases with increasing average mo

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020105

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe usual occurrence of structural units of vinyl polymers in head‐to‐tail sequence is attributed to the stabilization of the free radical of the growing polymer chain by the monomer substituent(s). Addition at the unsubstituted carbon of the vinyl group reproduces a free radical of lower energy than does addition at the substituted carbon. In at least one instance (vinyl acetate polymerization) a very small percentage of head‐to‐head addition takes place in spite of this energy difference. These ideas can be extended to polymers of dienes. Here the problem is complicated by the simultaneous occurrence of 1,2 (or 3,4) as well as 1,4 addition. In the case of an unsymmetrical diene monomer such as isoprene it is possible, from detailed examination of the structure of the polymer, to distinguish between preferred addition at carbon atoms 1 and 4 of the

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020106

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe rate of emulsion copolymerization of butadiene and styrene, with soap as emulsifier and potassium persulfate as catalyst, is extremely small at 50°C. The presence of very small amounts of high‐molecular mercaptans promotes the copolymerization reaction. The promoting effect is at a maximum for primary, secondary, and tertiary dodecyl mercaptans and decreases for mercaptans of either higher or lower molecular weight. The promoting effect is independent within wide limits of the amount of mercaptan added after the minimum quantity has been exceeded. Mercaptans which are poor promoters may be so because they fail to bring about chain initiation or because they aid in chain termination. The low‐molecular mercaptans which are poor promoters prevent the high‐molecular mercaptans from exerting their good promoting effect when a mixture of both types of mercaptans is used. The mechanism of the promoting effect of mercaptans upon the emulsion copolymerization of butadiene (75 parts) and styrene (25 parts) or upon the polymerization of butadiene alone is not yet

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020107

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractA close correlation exists between the modifying effect of mercaptans in emulsion copolymerization of butadiene (75 parts) and styrene (25 parts) and mercaptan consumption during the polymerization. A procedure is described for the rapid amperometric titration of mercaptans in latices. Mercaptan disappearance curves (i.e., mercaptan used at various conversions) are given for a series of primary and tertiary mercaptans of widely varying molecular weight and of two secondary mercaptans. The consumption of (and modification by) primary mercaptans is affected to a much greater extent by the molecular weight of the mercaptan than that of tertiary mercaptans. The consumption of pure and of commercial n‐dodecyl mercaptan is greatly affected by the mode and rate of agitation during the polymerization, manner of preparation of the charge (preformed soap and soap “in situ,” separate emulsification of the modifier), dilution of the monomers with inert organic solvents, excess of free caustic in the charge, amount and kind of emulsifier, and the presence of substances which from complexes with the mercaptan. The consumption of tertiary dodecyl mercaptan is not affected by these variables. The difference in behavior between the two mercaptans is interpreted as a faster rate of solubilization into the locus of the reaction of tertiary mercaptans than of primary mercaptans of the same molecular weight. The disappearance curve of a mercaptan from a mixture of two mercaptans remains unaffected by the presence of the other mercaptan. At the same conversion the consumption of a mercaptan increases with decreasing temperature. Disappearance of mercaptan during the polymerization as a result of nonmodifying reactions is disc

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020108

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractAn empirical equation is described which predicts the intrinsic viscosities of 75:25 butadiene‐styrene emulsion copolymers from data on mercaptan consumption. The form of the equation is as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$\left[ \eta \right] = \left[ {\frac{{aP}}{{R_0 R}} + \frac{b}{{R_0 }}\int_0^P {\frac{{dP}}{{dR}}dP} } \right]^c $$\end{document}where [η] is the intrinsic viscosity, P is the conversion, R is the fraction of mercaptan consumed, R0is the mercaptan charged, and a, b, and c are constants equal to 0.22, 1.12, and 0.66, respectively. Evidence is given that the intrinsic viscosity of mutual‐recipe polymers can be described satisfactorily in terms of mercaptan consump

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020109

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe calculation of the “theoretical” minimum modifier requirement, TMMR, for butadiene‐styrene (75:25) copolymers of given intrinsic viscosities at various conversions is described. The TMMR of 75% conversion polymer of intrinsic viscosity 2.0 is R0= 0.28, which is only about 60% of the value of R0for commercial primary dodecyl mercaptan (C.M.) in large‐size reactors. The efficiency, E, of a modifier for 75:25 butadiene‐styrene copolymerization using soap as emulsifier and persulfate as catalyst has been defined by and calculated from the equation:\documentclass{article}\pagestyle{empty}\begin{document}$$E = \frac{{P\left( {0.2 + P} \right)}}{{R_0 \left( {M_v \times 10^{ - 5} } \right)}}$$\end{document}where Mvis the intrinsic viscosity molecular weight of the polymer at conversion, P, with an amount of mercaptan, R0, charged with the monomers. For all modifiers the efficiency is low at low conversions and gradually increases to a maximum with increasing conversion. For different modifiers this maximum may be as at low as 10% conversion or at higher than 80% conversion. After the maximum the efficiency decreases with further increase of conversion. The most efficient modifier for the production of polymers of intrinsic viscosity, [η], at conversion, P, will meet the following conditions, R = 1 at conversion, P, and dP/dR is constant. Inefficient modifiers may be made more efficient by changing the conditions or procedure of polymerization in such a way that the modifier more nearly complies with the above

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020110

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY