Rubber elasticity of branched polyethylenes

Two grades of ethylene/1‐hexene copolymer, containing about 0.4 and 1.3 butyl branches per 1000 carbons, were subjected to electron beam irradiation in vacuum and in an acetylene atmosphere. The resulting networks were characterized by gel fraction determination and melt elasticity behaviour. The rubber elastic force‐extension data were analysed in terms of the Edwards‐Vilgis slip‐link model. This theory provided good fits to the experimental data, and the calculated parameters agreed well with the gel fraction determinations. The results indicate that an increase in branch concentration causes an increased susceptibility to chain scission. Irradiation in acetylene is shown to enhance greatly the crosslinking process, without affecting the chain scission, leading to a more perfect network.