Investigations on the Low-Temperature Transitions and Time Effects of Branched Polyethylene by the Positron Lifetime Technique

Positron lifetime measurements are performed in branched polyethylene in the temperature range between −195 and +40 °C. The lifetime spectra are resolved into four components, and corresponding annihilation mechanisms are discussed. Within the temperature range mentioned above four different transitions at −145, −95, −58, and −13 °C can be observed. From the behaviour of the lifetime parameters of the longest-lived component it is possible to deduce a criterion for the glass transition, which is situated at −13 °C. Additionally, time effects of the lifetime parameters are detected.