Dose rate effects of gamma irradiation on silicone foam

The dose rate effects of gamma irradiation on silicone foam were confirmed by investigating the relationships between the dose rate and the structures-property of the materials. With accumulation of the dose, the elongation at break (4) decreases significantly, while the creep ratio slightly decreases and gas yield increases after irradiation in air, especially at lower dose rate. However, the main gas yields, including H-2 and CH4, from samples irradiated in nitrogen do not increase linearly with reducing the dose rate. Furthermore, ESR spectra show that more radicals are generated at lower dose rate, indicating obvious dose rate effect. It is deduced that the dose rate effect is caused by the competition among the radical generation, reaction, and quenching rates.