Environmental Effects on Polymer-Matrix Composites.

A variety of environmental factors can influence the performance of advanced polymers and composites. In particular, exposure to a combination of moisture and elevated temperature can significantly alter properties. The extent of chemical and physical changes is a function of exposure time and the temperature and humidity of the environment. This work discusses the effects of chemical and physical aging of AFR700B, a high-temperature addition polyimide resin. Neat resin samples were isothermally aged for 500 and 1000 hours at 250 deg C in dry air, humid air, and dry nitrogen. Changes in the dynamic mechanical properties and weight of the resin samples after these different exposures are discussed. An accelerated aging process was developed to facilitate the study of hydrolytic degradation. The effect of degradation on the Tg, weight, and mechanical behavior is discussed. The use of a silicon-nitride moisture barrier proved ineffective.