Electron Trapping and Hydrogen-Atom Reactions in Irradiated Polyethylene

Abstract

The absorptionspectrum of electrons trapped in polyethylene during irradiation at low temperature is studied here, and an approximate G value for this of ∼0.8 at low doses is deduced. The spectrum stretches from the vacuum ultraviolet to the infrared (thus differing entirely from that in short‐chain branched alkanes) and changes somewhat with increasing irradiation dose. Another absorptionspectrum is found, which bleaches thermally but not optically, that is probably due to alkyl radicals. Thermal H atoms were studied at low temperature by adding benzene to the polyethylene and observing the ultraviolet absorptionspectrum of the resulting cyclohexadienyl radicals. The G value for thermal H‐atom production was found to be ∼1.8, similar to the value in short‐chain alkanes at room temperature, and the atoms apparently migrated considerable distances even at −170°C. Addition also of olefin with the benzene showed that olefin double bonds react ∼600 times more efficiently with thermal H atoms than do methylene groups, but despite this H‐atom capture is not an important mechanism for the destruction of these double bonds by radiation.