Evaluation of residual lifetime of LDPE degraded radiation by time-temperature superposition method

A novel method has been proposed to determine the residual lifetime of low density polyethylene (LDPE) by time-temperature superposition (TTS) using a dynamic mechanical analyzer (DMA). The principle of this new method is to detect the change in response of polymeric materials to multi-frequency dynamic loading over a glass transition interval. LDPE was irradiated with gamma rays up to 1000 kGy at a dose rate of 5 kGy/hr in the presence of air at room temperature. The glass transition temperatures of irradiated samples were tested and compared with TGA and DMA methods. The inter-relationship between TGA and TTS methods for lifetime prediction was investigated. For radiation degradation of polymeric materials, TTS method can be a useful tool to predict the residual lifetime.