Mechanical properties of cryogenic epoxy adhesives: Effects of mixed curing agent content

Phenyl glycidyl ether was used to react with solid metaphenylene diamine (MPDA) to produce N-(3-phenoxy-2-hydroxypropyl)-1,3-benzenediamine (NPHB). MPDA was intentionally formulated to have an excessive amount to obtain a new liquid MPDA–NPHB mixture. The mixed curing agent was indicated to have a few advantages over MPDA. The mixed curing agent was then used to cure diglycidyl ether of bisphenol A as cryogenic epoxy adhesive. The effects of the MPDA–NPHB content were systematically studied on the impact strength and shear strength at both room temperature and cryogenic nitrogen temperature of the epoxy adhesive. Moreover, two coupling agents with various contents were used to further enhance the shear strength of the optimal cryogenic epoxy adhesive. Finally, differential scanning calorimetry analysis showed that the modified adhesive showed a higher glass transition temperature than the unmodified adhesive.