Cu₂P₂O₇ with great negative expansion properties simultaneously improves the flame retardant and mechanical properties of epoxy resin at cryogenics

The unmodified epoxy resin (EP) often faces limitations in extreme environments, such as cryogenics and fire hazards, due to its structural brittleness and flammability. In this study, first study on the potential of Cu₂P₂O₇, a material with unique negative expansion properties, is explored for its ability to improve both mechanical strength and flame-retardant capabilities of EP materials under cryogenics conditions. Cu₂P₂O₇ was synthesized through a simple ball-milling sintering method and demonstrates significant industrial application potential. Different filler contents of Cu₂P₂O₇ were incorporated into the EP matrix. The findings indicate that the incorporation of 6 wt% Cu₂P₂O₇ into the EP composites yields superior mechanical characteristics, specifically a tensile strength of 82.5 MPa and a fracture toughness of 1.49 MPa m¹/² at 77 K. These values signify enhancements of 37.0 % and 40.6 %, respectively, in comparison to those of pure EP. The enhancement can be attributed to Cu₂P₂O₇'s volume expansion, which effectively alleviates the thermal expansion mismatch between the filler and the EP matrix, thus improving toughness under low-temperature conditions. Moreover, Cu₂P₂O₇ significantly improves the flame resistance of the EP composites thanks to its outstanding thermal stability and capacity for catalytic carbonization ability. These findings suggest that Cu₂P₂O₇ is a promising, efficient, and multifunctional material for expanding the application of EP in extreme environments.