Influence of the isothermal annealing on the free volume changes inthermo-shrunken polyethylene by positron annihilation

Abstract

Positron lifetime measurements in polyethylene have been performed. Samples of the polyethylene were isothermally annealed at three temperatures (373 K , 423 K , and 473 K ) for different time periods (from 5 min to 5 h). After cooling, the samples were used for the lifetime measurements in air at room temperature. A conventional fast-slow coincidence lifetime spectrometer with plastic scintillators has been used to perform the lifetime measurements. Mean free volumes radii and fractional free volume have been calculated from the lifetime data.