Carbon 13 NMR of Gamma-Irradiated Polyethylenes

Abstract

Carbon 13 NMR has been used to investigate the structural changes occurring in polyethylene as induced by either 60Co or electron beam irradiations. In this brief review, NMR results are compared for solution and solid state NMR studies. There is a problem with the available sensitivity from both types of carbon 13 NMR techniques, although considerable information has become available from both the solution and solid state NMR studies. Chain scission, the formation of cis and trans double bonds in the amorphous phase, the formation of trans double bonds in the crystalline phase and the formation of “Y” types of long chain branches have been observed from these NMR studies. As background information for the quantitative carbon 13 NMR study of the radiation of polyethylene, a brief examination of polyethylene molecular weight measurements using carbon 13 NMR on NBS 1475 and a comparison of the structures of a medium density ethylene -1-hexene copolymer before and after severe melt processing are included.