Nylon 6.6 accelerated aging studies: thermal–oxidative degradation and its interaction with hydrolysis

Abstract

Accelerated aging of Nylon 6.6 fibers used in parachutes has been conducted by following the tensile strength loss under both thermal–oxidative and 100% relative humidity conditions. Thermal–oxidative studies (air circulating ovens) were performed for time periods of weeks to years at temperatures ranging from 37 °C to 138 °C. Accelerated aging humidity experiments (100% RH) were performed under both an argon atmosphere to examine the ‘pure’ hydrolysis pathway, and under an oxygen atmosphere (oxygen partial pressure close to that occurring in air) to mimic true aging conditions. As expected the results indicated that degradation caused by humidity is much more important than thermal–oxidative degradation. Surprisingly when both oxygen and humidity were present the rate of degradation was dramatically enhanced relative to humidity aging in the absence of oxygen. This significant and previously unknown phenomena underscores the importance of careful accelerated aging that truly mimics real world storage conditions.