The effect of crystallization conditions on radiation-induced crosslink formation in polyethylene part VI. Some effects in the bulk material

Abstract

It is found that insolubility induced by a given radiation dose can be variable also in melt crystallized material depending on pre-history. In analogy to solution crystallized material this is attributed to the differences in the effectiveness of crosslinks in samples of differing morphologies reflecting variations in molecular coordination. It follows that solubility methods are insufficient to define the crosslink content even in the bulk. In particular the effects of primary crystallization and annealing treatments were followed as regards radiation induced insolubility, long spacings and density. A resemblance in trend was noticed between the long time end of the primary crystallization and heat annealing as regards all three properties. This trend is consistent with expectations of isothermal lamellar thickening and for molecular fractionation during primary crystallization. The details, however, raise new unanswered problems.