The Influence of Crystallization Conditions on Radiation Effects in Polyethylene - I. Crystallization from Dilute Solution and from the Melt

Samples of Marlex 50 crystallized from dilute solution (yielding single crystals) and in the bullfc form were irradiated by high-energy electrons and. the solubilities compared. The single-crystal specimens remained fully soluble after a dose of 20 megarads, which rendered the bulk two-thirds to three-quarters insoluble. Since the initial free-radical concentration was identical and the chemical changes induced were not widely different in the two kinds of specimens, it is suggested that intramolecular crosslinks, occurring in a larger number in the single crystals, are responsible for this behavior. high doses the same solubility limit is approached by both specimens, which is ascribed to the possibility of chain cutting becoming increasingly ineffective in the single crystal. In the light of these findings, the limitations of the conventional treatment of radiation effects are discussed and the possible significance of (he present results for morphological problems is pointed out. A number of further ejfects are reported in connection with melting behavior and spin resonance spectra that are at variance with results in the literature. I. INTRODUCTION* The effect of ionizing radiation on polyethylene has been extensively studied in the past 1,2 but no investigation has been reported concerning the irradiation of polyethylene single crystals. 3 We have examined the influence of morphology on the irradiation behavior of polyethylene. These studies are purely exploratory and many of the physical tools involved were used only in "key" tests.