Dynamical mechanical analysis of proton beam irradiated polyimide

The excellent mechanical properties, the outstanding thermal stability, and the lightweight of polyimide have a particular relevance to space missions. In order to assess the lifetime of polyimide subjected to ionizing radiation and extreme temperatures, a dynamic mechanical analysis of the effect of accelerated proton beams on polyimide films is reported. The temperature dependence of the loss factor proved the presence of two relaxations; a beta(2) relaxation located around 100 degrees C and a glass relaxation located around 400 degrees C. It is concluded that degradation of polyimide subjected to proton irradiation is controlled by chain scission reactions. The observed small shift of the glass transition temperatures due to proton irradiation encourages the use of polyimide in environments that combines radiation with extreme temperatures. Additional electron spin resonance data confirmed the generation of free radicals in proton-irradiated polyimide. (c) 2005 Elsevier B.V. All rights reserved.