Gel fractions and chain reactions in irradiated polyethylenes

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 prese nce of free radical mediated chain reactions, even during in vacuo irradiat ions. It is proposed that chain reactions, rather than polydispersity and s tructure, explain most of the deviation from ideal Charlesby-Pinner behavio ur of irradiated polymers. (C) 1999 Elsevier Science B.V. All rights reserv ed.