Synergistic Enhancement of Toughness and Strength in Cryogenic Epoxy Adhesives Through Cyclohexane–Tetrahydrofuran Copolyether Modification

Epoxy adhesives with high toughness offer significant potential for service under extreme working conditions. However, their inherent brittleness at cryogenic temperatures significantly hinders their broad application. Thus, it remains a pressing challenge to develop epoxy adhesives with high toughness while maintaining mechanical strength at low temperatures. Herein, epoxy-terminated cyclohexane–tetrahydrofuran copolyethers (CTEs) were synthesized by combining rigid cyclohexane segments with flexible polytetrahydrofuran chains. Subsequently, the as-synthesized CTEs were used as toughening agents to participate in cross-linking reactions with E51 and E44 under a modified aromatic amine curing agent (590) for preparing E51(E44)-CTE–590 adhesives. E51–10 wt % CTE31–590 shows a remarkable enhancement in mechanical performance at 77 K, with a tensile strength of 86.52 MPa and a fracture elongation of 1.52%. More importantly, E51–10 wt % CTE11–590 exhibits a high shear strength of 29.8 MPa at 77 K. This work provides a promising route to developing high-performance epoxy adhesives that are suitable for cryogenic engineering applications.