DAMAGE OF SILICONE RUBBER INDUCED BY PROTON IRRADIATION

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 τ_3 and I_3, as well as the free volume V_f, decreased with increasingirradiation fluence up to 10~(15) cm~(-2), and then increased slowly. It indicates that proton irradiation causes a decrease of freevolume in the methyl silicone rubber when the fluence is less than 10~(15)cm~(-2), while the free volume increases when thefluence is greater than 10~(15)cm~(-2). The results on cross-linking density indicate that the cross-linking induced by protonirradiation is dominant at smaller proton fluences, increasing the tensile strength and Shore hardness of the rubber, while thedegradation of rubber dominates at greater fluence, leading to a decrease of tensile strength and Shore hardness.

DAMAGE OF SILICONE RUBBER INDUCED BY PROTON IRRADIATION

 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 V_f,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.