摘要:

AbstractThe effects of temperature on the radiation‐induced polymerization of ethylene in bulk and in the presence of ethyl alcohol,n‐butyl alcohol,tert‐butyl alcohol, cyclohexane, 2,2,4‐trimethylpentane, and 2,2,5‐trimethylhexane were studied. The changes of the amounts of polymerized monomer with the reaction temperature were different from each other in these reaction systems, especially in the range lower than 60–80°C. At temperatures lower than 60–80°C, as the reaction temperature increases, the amount of polymerized monomer decreased in bulk and in the presence oftert‐butyl alcohol. The amount was almost constant in the presence of ethyl alcohol and 2,2,4‐trimethylpentane, and it increased in the presence ofn‐butyl alcohol, cyclohexane, and 2,2,5‐trimethylhexane. However, in the temperature range higher than 60–80°C, the amount of polymerized monomer increased with increasing temperature in every reaction system except for bulk polymerization. The molecular weight of polymer decreased with increasing temperature in every reaction system except at temperatures lower than 25°C. The molecular weight of polymer formed in bulk, intert‐butyl alcohol, and also in 2,2,4‐trimethylpentane were relatively higher than that in other reaction systems. A bimodal molecular weight distribution was observed for the polymer formed in bulk and intert‐butyl alcohol at 40–60°C. These results are discussed in connection with the heterogeneity of the reaction system. The differences due to temperature in each reaction system are explained as due to the difference in affinity of the reaction system for the propagating chain and in the faci

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120801

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe radiation‐induced polymerization of ethylene in cyclohexane was carried out in a reactor of 100 ml capacity under a range of temperature of 25–150°C, dose rate of 4.1 × 104–2.9 × 105rad/hr, pressure of 200 kg/cm2, and amount of cyclohexane of 20–90 ml. The polymerization was found to proceed at a steady state from the beginning. The polymerization rate is maximum at ca. 50 ml of cyclohexane. The dose rate exponent of the polymerization rate was 0.6 at every temperature from 25 to 150°C. The polymer molecular weight is in the range of 103–104, independent of dose rate, and decreases with increasing amount of cyclohexane. The molecular weight distribution is unimodal and narrow. Kinetic analysis of these results indicates that the polymerization proceeds via a simple scheme of homogeneous polymerization and the polymer molecular weight was determined by the chain transfer reaction which takes place mostly with cyclohexane. The unimodal and narrow molecular weight distribution is also consistent with the homogeneous polymeri

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120802

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe heterogeneous polymerization of ethylene initiated by radiation intert‐butyl alcohol was studied. The polymerization was carried out in a 100‐ml reactor at 25–100°C and pressures of 200–300 kg/cm2in the presence of 50 ml oftert‐butyl alcohol containing 7 wt‐% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose a

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120803

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe radiation‐induced heterogeneous polymerization of methyl methacrylate in various precipitants, mainly methyl alcohol, was carried out, and the effects of reaction conditions on the polymerization behavior and the molecular weight distribution of polymer were studied. Bimodal molecular weight distributions were found for the polymer produced by the heterogeneous polymerizations in methyl alcohol and intert‐butyl alcohol. The apparent activation energy is 1.0 and 4.5 kcal/mole, respectively, for the polymerization at a monomer concentration of 10 vol‐% in methyl alcohol above and below 35°C. The polymerization at a monomer concentration lower than 40 vol‐% in methyl alcohol proceeded with the precipitation of polymer. The dose rate exponent of the mean rate of heterogeneous polymerization decreased from 0.5 to a smaller value as the polymerization progressed. The ratio of the two peaks in the bimodal molecular weight distributions of polymer produced in methyl alcohol was affected by the reaction conditions. These results show the coexistence in the polymerizations of two different physical states of propagating chain, a loose state and a rigid one. The reaction scheme is discussed in connection with the physical factors which affect the solubility or the mobility of propagating chains, and the rate of elementary reactions, which influences the degree of propagatin

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120804

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractPolyperfluorobut‐2‐yne is prepared by a fluoride ion‐induced polymerization of hexafluorobut‐2‐yne. The mass spectrum indicates a regular fragmentation pattern but the ESCA spectrum establishes the structure as a polyene, rather than a crosslinked system, and the occurrence of a shake‐up peak assists in this

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120805

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractHigh‐resolution proton magnetic resonance (PMR) spectroscopy was used to determine the chlorine distribution of chlorinated polypropylenes in 1,1,2,2,‐tetrachloroethane solution and suspension (5–25 wt % chlorine). The determination is based on measuring the relative amounts of methyl and methylene groups which are α, β, and γ to chlorinecontaining groups in chlorinated polypropylenes. The results obtained from the 100 MHz and 220 MHz PMR spectrometers were compared with the theoretical predictions provided by Frendsdorff and Ekiner, based on the statistics of substitution polymers. Furthermore, the PMR data were correlated with infrared and differential scanning calorimetry data to obtain the structural and crystalline properties. The comparison showed that the suspension‐chlorinated polypropylenes show structure heterogeneity and thermal instability, whereas polymers chlorinated in solution with gaseous chlorine show a random chlorine distribution and thermal stability compared with

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120806

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe behavior of trapped radicals in polyethylene which is irradiated in air at room temperature, under grafting of methylmechacrylate or butadiene has been studied by electron spin resonance. Part of the alkyl radicals are converted to allyl radicals by reaction with double bonds and the others disappear by recombination under vacuum. The active species of grafting are alkyl radicals when the vapor pressure of monomers is relatively high, while at low pressure allyl radicals also play a role as well as alkyl radicals. In the grafting at 20°C, the grafting yields depend mainly on the decay rate of alkyl radicals which come out of the crystalline regions of polyethylene. The decay rate of alkyl radicals and the rate of grafting at the initial stage increase with decreasing crystallite size of polyethylene

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120807

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractAn1H 300‐MHz NMR spectroscopic study of deuterated poly(propylene sulfide) shows that methylene protons are sensitive to triad effects. It was possible to distinguishi, hi, s, andhstriads. Experimental values found for different polymers are in good agreement with theoretical amounts obtained from statistical probability calculation. The methyl groups are also slightly stereosensitive. By using optically active deuterated monomers with different R/S ratios it was possible to confirm the assignment of peaks and the tacticity. Nondeuterated polymers give very complicated spectra, and only the highly stereoregular polymer could be analyzed through its ABCX3spin syste

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120808

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe copolymerization of the zinc chloride complex of acrylonitrile in excess acrylonitrile with α‐methylstyrene in the presence of lauroyl peroxide is described. Elemental and proton NMR analyses indicate the equimolar nature of the copolymer product.13C NMR examination shows that this copolymer is alternating in structure and suggests that the steric placements of the copolymer are random in nature; that complexation does not lead to a stereoselective enchainment mode is the implication of our results. A copolymer which appears to be similar to our product has been prepared by other workers using Al(C2H5)1.5Cl1.5complexation. Our conclusions regarding copolymer stereoregularity differ from thei

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120809

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractVinyl chloride has been polymerized by a modified Ziegler‐Natta type catalyst VOCl2· 2THF–Al(i‐Bu)3–THF, and the kinetics of the polymerization reaction have been investigated in some detail. The present kinetic analysis has demonstrated that the generation of active centers is directly proportional to the catalyst concentration, and that their depletion is by a second‐order decay process. Triisobutylaluminum has been found to contribute to the effective removal of active centers through complex

ISSN:0360-6376    

DOI:10.1002/pol.1974.170120810

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY