Study on positron annihilation lifetime spectrum of polysilicone rubber after proton radiation

The positron annihilation lifetime spectrum(PALS) method was employed to study the effect of proton radiation on microstructure of the space grade KH-L-Y polysilicone rubber. The results show that both τ 3 and I 3 of the longest lifetime component and the free volume V f decrease with the increase of the radiation fluence at the beginning and become level off after 10 15cm -2 radiation fluence. The proton radiation causes decrease in both the free volume of polysilicone rubber, and the distance between the molecules when the radiation fluence is less than 10 15cm -2. However, the proton radiation makes the free volume of silicon rubber increase when the radiation fluence is greater than 10 15cm -2. Both the experimental results of the cross-linking density and DMA indicate that the cross-linking effect due to the proton radiation is predominant in the range of small proton radiation fluence, while the radiation degradation become superior when the proton radiation fluence is larger.