γ‐Radiation‐induced changes in the structure of polyethylenes

The concentrations of trans ‐vinylene groups in Marlex 50 and DYNH polyethylenes were determined from infrared spectra before and after irradiation of polyethylene films with gamma rays. Values of G for trans ‐vinylene growth were found to be 2.2 and 1.7 for Marlex 50 and DYNH polyethylenes, respectively. trans ‐Vinylene decay constants and concentrations at infinite dose were evaluated. The growth and decay of vinyl unsaturation and growth of vinylidene unsaturation in Marlex 50 are discussed. Assignment was made of polyethylene bands at 889 and 894 cm. −1 to vinylidene unsaturation and to ethyl groups in saturated paraffins, respectively, on the basis of different means of saturating the double bond. The frequencies of new bands produced in Marlex 50 and DYNH by irradiation were correlated with those of substituted cyclopentanes and cyclohexanes. It was concluded that a complex mixture of these cyclic compounds was formed in Marlex 50 and DYNH. There appeared to be no correlation between the frequencies of these irradiation‐induced bands and frequencies known to be characteristic of conjugated double bonds.