Effects of Gamma Irradiation in Semirigid Epoxies

The investigation of radiation-induced stress changes in two types of epoxies was discussed. A semirigid 3M-241 type of Scotchcast material which has low intrinsic internal stress was irradiated. The increase in stresses due to radiation is twofold. First the material seems to cure out completely. Further irradiation led to a linear pressure increase which was reversible once the material was removed from the gamma source. The Epocast type H2E-011 material, when completely cured, had high intrinsic stresses of 30,000 psi. When irradiated for an extensive period, the material changed color from a light yellow to brown, and internal stresses were reduced threefold. After the sample was removed, it regained the original high internal stress condition after two months on the shelf.