The effects of small doses of radiation on the flow and other properties of ziegler polyethylenes

Abstract

We have studied the effects of high energy radiation in doses of up to 1.0 Mrad on the properties of polyethylene. The interactions of some radiation variables and polymer variables have also been determined. The results obtained show that the main effects of radiation on polyethylene are to reduce its melt index and concomitantly to increase its flow parameter. The extent of these changes depends on several other factors. It is reduced by many common antioxidants (with the apparent exception of N-stearoyl-p-aminophenol). Under the conditions of our experiments it is not affected by the presence of air during irradiation, but it is reduced by post-irradiation milling. Our data also indicate that it increases with decreasing polymer melt index and with decreasing polymer density, but these apparent effects may be artifacts due to variations of antioxidant content. Radiation in small doses has little effect on any of the other properties of polyethylene, including high shear flow properties, softening point, tensile properties, impact strength, folding endurance, stress cracking resistance, thermal stability, and light stability.