Temperature effects on radiation induced phenomena in polytetrafluoroetylene (PTFE)-change of G-value

Temperature dependencies on the radiation induced phenomena and G-value of polytetrafluoroethylene (PTFE) have been studied in a temperature range 77-653 K. It is well known that main chain scission occurs very;effectively below the melting temperature of PTFE (600 K). We have found in our experiments that G-value of chain scission increases significantly with increasing irradiation temperature, until 600 K. In addition to that, we have realized that crosslinking occurs by irradiation in the molten state at 613 K (Tabata, 1992; Oshima et al., 1995; Tabata et al., 1996). In the molten state, G-value of crosslinking was found to be 0.35 (number of crosslinking/100 eV absorption), as a lower limit, and the apparent G-value of chain scission is drastically reduced. Above 633 K, radiation induced crosslinking mainly occurs, however parallel thermal depolymerization or decomposition takes place to some extent. (C) 1997 Elsevier Science Ltd.