Effect of ionizing radiation on the structure and properties of different polyethylenes

For isotropic and highly oriented samples of linear PE with low and medium molecular masses, the structural transformations induced by ionizing radiat ion were studied by the methods of X-ray diffraction and DSC. Radiation-ind uced changes in some structural and physical characteristics were found to be different for samples with different molecular masses and to be controll ed by competing radiation-induced chemical processes of crosslinking and sc ission of polymer chains. In oriented samples, different ratios between the products of crosslinking and scission of polymer chains may be explained b y the different content of intrafibrillar and interfibrillar amorphous regi ons in PE with different molecular masses. In the samples with medium molec ular masses, the fraction of interfibrillar amorphous regions is much highe r compared with that in a low-molecular-mass PE, and the contribution of ra diation-induced crosslinking is predominant. Upon radiation of low-molecula r-mass samples with a low content of interfibrillar amorphous phase, one ma y observe the well-pronounced phenomena related to the scission of tie macr omolecules within intrafibrillar amorphous regions.