Scission Efficiencies of Short Chain Branches in the γ-Radiolysis of Ethylene-α-Olefin Copolymers

Abstract

Abstract γ-Irradiation of copolymers of ethylene with propene, 1-butene, and 1-hexene, containing from 1 to 6 alkyl short chain branches per 1000 carbon atoms, at 25°C in vacuum, produced small amounts of n-alkanes with a maximum yield for the alkane corresponding to the alkyl branch of the α-olefin unit. A multilinear regression analysis showed a highly significant dependence of G(Cn alkane) on the frequency of alkyl branches containing n carbon atoms, determined by 13C-NMR. The corrections to the G(Cn alkane) yields from other fragmentation processes were substantial but no dependence for G(Cn alkane) on fragmentation of chain ends or fragmentation of the chain following branch elimination could be deduced from the data. The scission efficiencies = G(alkane) divided by the branch frequency per 1000 carbon atoms ± 95% confidence limits were (0.7 ± 0.7) × 10−3, (2.7 ± 0.8) × 10−3, and (1.5 ± 0.3) × 10−3, for methyl, ethyl, and butyl branches, respectively. These factors can be used to determine the short-...