The Production of Modulus Gradients at Interfaces

Abstract

AbstractWe have developed a range of “antiplasticizing” additives for epoxy and polyimide resins which can increase the modulus of the cured polymers by > 40%, increase their tensile and shear strengths, modify their fracture behavior, and decrease their water uptake. These additives may be used alone or in conjunction with rubber modifiers. The optimum additive formulations are complex mixtures, but we describe here two relatively pure model systems. The epoxy additive is the reaction product of 4-hydroxyacetanilide (HAA) and vinylcyclohexene dioxide (VCD), while the polyimide additive is the reaction product of epoxyphenoxypropane (EPP) and HAA. These additives are mixed with the epoxy resin and curing agent (or polyamic acid solution in the case of polyimides), before curing, and the mixture is then cured in the conventional fashion. We describe here some physical properties of the modified epoxies and polyimides and their use in adhesive formulations. These materials offer the potential for constructing modulus gradients at interfaces through their use as primers, so as to allow testing of the many hypotheses concerning desirable interphase properties. Some initial experiments in this area are described.