FREE VOLUME RELATED STRUCTURAL CHANGES IN THE EPOXY POLYMER TGDDM

Abstract

Positron lifetime measurements have been carried out in an amine-cured epoxy polymer TGDDM/DDS/BFE as a function of annealing temperature. The measured spectra are best fitted to three component analysis. From the measured long lifetime component the average size of the free volume holes has been calculated following Nakanishi et al.’s treatment. Variation of lifetime parameters with temperature indicates the preferential trapping of positronium atoms in the regions of increased free volume hole sizes. On the other hand, positrons are being trapped at micro-voids in the ordered regions. The slow increase of free volume upto 170°C may be due to the thermal expansion and we measure 170° C as the Tg for this epoxy. Lifetime data are also used to calculate the trapping rates in the ordered and disordered regions of the epoxy based on Goldanskii’s kinetic relations.