Tough epoxy resin systems for cryogenic applications
P. Studer, Alain Schwegler, Theo A. Tervoort
Abstract
This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures ( ) with a slow curing reaction (long pot life) and a glass transition temperature between and , ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to . It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis. The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature. • Design of epoxy resins with high cryogenic fracture toughness, long pot life and mechanical rigidity at room temperature. • High cryogenic fracture toughness due to incorporation of epoxide chain extenders consisting of flexible alkylamines. • Long processing lifetimes achieved by using sterically hindered alkylamines.