FREE-VOLUME RELATED STRUCTURAL-CHANGES IN THE EPOXY POLYMER TGDDM

Positron lifetime measurements have been carried out in an amine-cured epoxy polymer TGDDM/DDS/BFE as a function of annealing temperature. T he measured spectra are best fitted to three component analysis. From the measured long lifetime component the average size of the free volu me holes has been calculated following Nakanishi et al.'s treatment. V ariation of lifetime parameters with temperature indicates the prefere ntial trapping of positronium atoms in the regions of increased free v olume hole sizes. On the other hand, positrons are being trapped at mi cro-voids in the ordered regions. The slow increase of free volume upt o 170-degrees-C may be due to the thermal expansion and we measure 170 -degrees-C as the T(g) 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.