EFFECTS OF GAMMA-IRRADIATION, IRRADIATION ENVIRONMENT, AND POSTIRRADIATION AGING ON THERMAL AND TENSILE PROPERTIES OF ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE FIBERS

The effects of gamma irradiation in four types of irradiation environm ent on the thermal and tensile properties of gel-spun, ultrahigh molec ular weight polyethylene fibers (Spectra(TM) 1000) have been investiga ted. The gamma irradiation was conducted at 2.5 Mrad and in air, nitro gen, acetylene, and vacuum to study the effects of irradiation media o n the aforementioned properties. Thermal and tensile properties of vir gin and irradiated fiber samples were examined using differential scan ning calorimetry and an Instron tensile tester, respectively. The resu lts indicate that both gamma irradiation and irradiation environment a ffected the properties of the polyethylene fibers, and substantial cha nges were observed for the oxygen-containing environment. The tensile- fractured surfaces of the fibers were examined by scanning electron mi croscopy. The properties of irradiated fibers were further evaluated a t 160 days postirradiation and found to be affected, substantially. Th e postirradiation aging significantly decreased the tensile strength a nd elongation of the irradiated fibers, indicating that polyethylene f ibers should not be exposed to gamma irradiation. (C) 1996 John Wiley & Sons, Inc.