Thermal analysis and free volume study of polymeric supermolecular structures

Positron annihilation lifetime measurements were performed on samples cut down from commercially available polyethylene (PE) and poly(4-methyl-1-pentene) (PMP). The effect of a free volume on the segmental relaxation behaviour was examined. The samples were isothermally annealed at different temperatures. In order to study the effect of annealing on supermolecular structures of the polymers, the annealing temperatures were chosen between the transition temperatures of the polymers. All thermodynamic parameters varied as compared to the parameters of the samples which were not annealed. A slight change of the free volume was observed. The idea of two miscellaneous amorphous fractions in polymer was under consideration. Differential scanning calorimetry, dynamic mechanical thermal analysis were used to study the effect of specimen heat treatment on both glass transitions, too. The degree of crystallinity of the PE and PMP samples was determined. An attempt to estimate this parameter from positron annihilation data was undertaken.