Adhesion behaviour of polyamic acid cured epoxy

The adhesion behaviour or lack thereof, of polyimides is well known. The inherent brittleness of epoxy resins has also led to a search for additives to improve the physical properties of epoxy. In order to improve both of these properties, we utilized a unique strategy to cue a diepoxy (diglycidyl ether of bisphenol A) with a polyamic acid derived from oxydianiline and pyromellitic dianhydride. The polyamic acid synthesis was conducted in a low boiling point solvent consisting of tetrahydrofuran and methanol (80/20) and nor traditional high boiling point aprotic solvents such as dimethylacetamide. This resulted in a material that had adhesion superior to both the pure epoxy and the pure polyimide. The state of cure was also seen to have an effect of the adhesion strengths. (C) 1997 Elsevier Science Ltd.