Isomer yields for butanes and butanes from the radiation degradation of polyolefins

γ-Irradiation of high and low density polyethylenes and ethylene-α-olefin copolymers at temperatures from 30 to 175° produces butane, and above 100°, butene, in addition to hydrogen and other volatile hydrocarbons. The butane has been shown to be mainly isobutane at 30°, except for polymers with butyl branches; the isobutane/n-butane ratio decreases with increasing temperature. The butene is mainly isobutene, with a lesser amount of 1-butene and only a trace of 2-butene. Scavenger studies indicate that both free radical and ionic intermediates are involved in the formation of the isomers. Irradiation of samples containing added n-butane show that only a portion of the isobutane can be formed by radiation-induced isomerization of primary product n-butane. Similarly, it is shown that 1-butene is an effective scavenger of H atoms to form n-butane, but is not significantly isomerized to isobutene