In this paper

the damage to methyl silicone rubber induced by irradiation with protons of 150 keV energy wasstudied. The surface morphology

tensile strength

Shore hardness

cross-linking density and glass transition temperaturewere examined. Positron annihilation lifetime spectrum analysis (PALS) was perfomed to reveal the damage mechanisms ofthe rubber. The results showed that tensile strength and Shore hardness of the rubber increased first and then decreased withincreasing irradiation fluence. The PALS characteristics τ3 and i3

as well as the free volume Vf

decreased with increasing irradiation fluence up to 1015cm-2

and then increased slowly.It indicates that proton irradiation causes a decrease of free volume in the methyl silicone rubber when the fluence is less than 1015cm-2

while the free volume increases when the fluence is greater than 1015cm-2.The results on cross-linking density indicate that the cross-linking induced by proton irradiation is dominant at smaller proton fluences

increasing the tensile strength and Shore hardness of the rubber

while the degradation of rubber dominates at greater fluence

leading to a decrease of tensile strength and Shore hardness.