Changes in the various elements of the structure of polyethylene induced by ionizing radiations (as revealed by differential scanning calorimetry)

The DSC method has been used to measure the heat capacity at 100–430 K of linear and branched PE exposed to irradiation with fast electrons (5–700 Mrad). The changes in the various elements of the unordered regions (four regions of relaxation) and the radiation stability of the PE crystallites have been investigated. The authors demonstrate the specific influence of irradiation in each case due to the prevalence of crosslinking of portions of the chains with sufficient segmental mobility and the prevalence of the processes of degradation in conditions of “suppressed” mobility. Sharply marked dependence of the radiation stability of the crystallites of PE on its prehistory was found. On recrystallization of PE amorphized by irradiation, the formation of crystallites of the smallest possible size was observed close to the length of the Kuhn statistical segment.