H-1-NMR STUDIES OF THE RADIATION-INDUCED CROSS-LINKING OF POLY(ETHYLENE)

The crosslinking of linear low density poly(ethylene) (LLDPE) by gamma irradiation has been studied using measurements of the decay of the t ransverse H-1 NMR magnetization. The T-2 decay of the molten polymers can be decomposed into three exponential processes, which are assigned to chains in bundles of incipient crystallites, chains in intermediat e regions, and chains in disordered regions, in order of increasing T? On irradiation, the proportion of the chains with the shortest T-2 in itially decreases. This is ascribed to the formation of defects in the crystallites, and is in agreement with the observed decrease in the h eat of fusion on irradiation. Irradiation to higher doses leads to fur ther crosslinking in all three domains of the polymer. Copyright (C) 1 996 Elsevier Science Ltd