Ultraviolet stability of polyimides and polyamide–imides

Abstract

AbstractThe ultraviolet stability of polyimides and polyamide–imides was determined in both a wet and dry environment. Films have been exposed to these environments for 3000 and 6000 hr, respectively. The polymers are not stable to UV radiation (2900–4000 Å); serious deterioration of the mechanical properties occurs under both wet and dry conditions with the former giving rise to greater damage. The polyamide–imide polymer is more unstable to UV radiation than the two polyimides evaluated; however, it is more resistant to hydrolysis as indicated from rate data obtained from a kinetic analysis of the mechanical property degradation curves. The electrical properties of the polymers are relatively unaffected in the dry environment but begin to deteriorate as the polymer becomes brittle. In the wet environment these properties begin to deteriorate more rapidly. Dissipation factor and dielectric strength are the properties most affected.