Isomer yields for butanes and butenes 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 deg produces butane, and above 100 deg, butene, in addition to hydrogen and other volatile hydrocarbons. The butane has been shown to be mainly isobutane at 30 deg, 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. (author)