Effect of Irradiation On Dynamic Mechanical Properties of 6–6 Nylon

Abstract

Measurements of elastic modulus and mechanical loss at audio‐frequencies have been obtained on irradiated and nonirradiated specimens of polyhexamethylene adipamide over a broad temperature range extending from 80°K to 600°K. The irradiations were carried out at the Brookhaven and Penn State Reactors. The internal friction spectrum of unirradiated nylon 6–6 contains at least four peaks corresponding to different mechanisms being invoked as the temperature is raised. With irradiation doses from 0.3×1018 nvt to 5.5×1018 nvt, significant changes in the dispersion regions occur. At temperatures above the main softening region, an increase in modulus with temperature is found. This is evidence of rubber‐like behavior and is accounted for by the introduction of cross‐links resulting from ionization and free radical formation produced by the irradiation. At high irradiation doses the percent cross‐linking appears to become independent of dose. The various effects found are discussed in terms of molecular forces and mobility of chain segments.