Novel high performances epoxy/anhydride formulations and their application in electrical insulation

Abstract

Epoxy/anhydride formulations are known for their excellent combination of thermo-mechanical properties combined with superior electrical insulation and are widely used in electrical insulation. Such formulations lead to thermosets which demonstrate superior chemical resistance even when exposed to harsh environments. The high cross-linking density combined with the inherent stability of the chemical bonds of the epoxy based network provides cured products with high thermal stability. The use of conventional epoxy/anhydride systems is potentially limited by their relative brittleness. The compositions are especially sensitive to thermal cycling or thermal shock that could result from inadequate processing conditions or in-use aging. The micro-cracks which may be formed during these thermal events drastically reduce the physical and electrical properties of the electrical components. The flexibilization of the epoxy/anhydride network has been used to remedy this issue. Better toughness is then achieved by scarifying the overall thermal stability of the product, i.e. by reducing the glass transition temperature. The objective of this work is to demonstrate that it is possible to greatly enhance the mechanical properties with minimal impact on thermal resistance by using separated toughening agents. After its fundamental evaluation, the new concept was applied to practical formulations used in electrical insulation.