Effects of Combined Gamma Radiation and Thermal Exposure on Some Mechanical Properties of Three Polyaromatic Yarns

Abstract

Three experimental polymeric yarns, a polyimide, an aromatic polyamide, and a polybenzimidazole, were exposed to various gamma dosages up to 1.4 × 109 ergs/g carbon and exposure times up to 18.2 hr. Specimens ere exposed to the gamma radiation alone and also in combination with elevated temperatures. Temperatures of 400°, 600°, and 800°F were used in conjunction with the gamma radiation. All speci mens were evaluated for mechanical properties, i.e., tenacity, elongation, and work-to- rupture. Each polymeric yarn had higher strength, greater elongation, and better energy absorbing capability after thermal-gamma exposure. Exposure at 600°F and all radia tion dosages gave the best results for the polybenzimidazole (PBI) yarn, while exposure at 400°F and radiation dosages of 1.9 × 108 and 7.3 × 108 ergs/g carbon gave the best results for the polyimide and aromatic polyamide yarns. It can be concluded that the thermal stability of these yarns can be improved by thermal gamma treatment.