Below-Break Tensile Behavior of Irradiated Nylon

Abstract

The below-break tensile properties (tensile modulus, stress decay, and elastic recovery behavior) of carbon-are-irradiated nylon 66 and nylon 6 fibers were examined after extensions of 2 and 5% held for 0-15 min under both air-dry and wet conditions. In general, the moduli of fibers extended in air were increased in proportion to the exposure time. A non- ultraviolet-stabilized nylon 66 specimen, however, showed decreased moduli prior to the increases. In water, the modulus changes for the irradiated nylon 66 fibers were similar to, but smaller than those found in air; whereas those for the wet nylon 6 fibers were unchanged from the nonirradiated specimen. Changes in the stress decay of irradiated fibers extended in air were small and somewhat variable; whereas the stress decay of wet fibers increased as the radiation period was lengthened. After a 15-min holding period, the wet-fiber stress decay increases resulted in residual fiber-stress values similar to or marginally smaller than those inherent in the unmodified fiber. Elastic recovery behavior, exemplified by residual extension, was reduced after irradiation. The property changes were considered to be a manifestation of internal structure modifications resulting from interaction of the radiation with the fiber molecules.