The effect of methanethiol on the radiation chemistry of low-density polyethylene

The effect of methanethiol (CH₃SH) on the radiation chemistry of low-density polyethylene was examined by using intrinsic viscosity measurements, low-angle laser light scattering, and infrared spectrophotometry. Radiation-induced intermolecular linking was found to be almost completely inhibited in low-density polyethylene by the presence of less than one weight percent of CH₃SH during irradiation. The net yield of transvinylene was also reduced, probably by reaction of transvinylenes with methylthiyl radicals (CH₃S). The inhibition of radiation-induced intermolecular linking by CH₃SH demonstrates that linking is a relatively slow process involving reactions of alkyl free radicals, and that prompt intermolecular links caused by rapid ionic, ion–molecule, or “hot hydrogen” processes are not significant in the radiation chemistry of low-density polyethylene.