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EFFECTS OF COMBINED GAMMA RADIATION AND THERMAL EXPOSURE ON SOME MECHANICAL PROPERTIES OF THREE POLYAROMATIC YARNS.
Technical rept. Jan-Nov 65,
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
Three experimental polymeric yarns, a polyimide, an aromatic polyamide, and a polybenzimidazole were exposed to various gamma dosages up to 1.4 x 10 to the 9th power ergs per gram carbon and exposure times up to 18.2 hours. Specimens were 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. A portion of the irradiated yarn specimens were subsequently aged, at 400, 600, and 800 F for periods of 1 to 18.2 hours. All specimens were evaluated for mechanical properties, i.e., tenacity, elongation, and work-to-rupture. The results obtained showed that each polymeric yarn had higher strength, greater elongation, and better energy absorbing capability after thermal-gamma exposure. Exposure at 600 F and all radiation dosages gave the best results for the polybenzimidazole PBI yarn while exposure at 400 F and radiation dosages of 1.9 x 10 to the 8th power and 7.3 x 10 to the 8th power ergs per gram carbon gave the best results for the polyimide and aromatic polyamide yarns. It can be concluded that the elevated temperature stability of these yarns can be improved by thermal gamma treatment. Author
APPROVED FOR PUBLIC RELEASE