MOLECULAR DESIGN OF AN EPOXY FOR CRYOGENIC TEMPERATURES

The mechanical and thermal properties of several epoxy resins were mea sured to obtain guidelines for the molecular design of an epoxy resin for cryogenic temperatures. Two types of epoxy resin with different nu mbers of epoxy groups were mixed (with different mixing ratios) and cu red. Fracture toughness, flexural strength and thermal contraction of the hybrid epoxy resins were measured down to cryogenic temperatures. The results suggest that epoxies with larger molecular weights between crosslinkings relaxed stress at the crack tip, even at cryogenic temp eratures. Intermolecular forces and stress relaxation at the crack tip were found to be important for high fracture toughness.