Gel fractions and chain reactions in irradiated polyethylenes

Abstract Atomistic computation, Flory–Stockmayer theory and rheological measurements have been applied to the analysis of gel-fraction data from two linear low density poly(ethylene)'s (LLDPE's) irradiated and annealed either in vacuo or in the presence of acetylene. Good agreement between the three methods, as the extent of crosslinking at any given gel-fraction, confirm the presence of free radical mediated chain reactions, even during in vacuo irradiations. It is proposed that chain reactions, rather than polydispersity and structure, explain most of the deviation from ideal Charlesby–Pinner behaviour of irradiated polymers.