Mechanical Property and Thermal Stability of Polyurethane/Epoxy Resin Composites With Fast Curing at Room Temperature

The epoxy resin (EP) was modified with polyurethane (PU), and the PU/EP material was cured by the curing agent to enhance its mechanical strength and toughness, compensating for the limitations of EP in pavement crack repair applications. To investigate the effect of PU on EPs, the PU‐modified EPs were prepared with the equivalent ratio of isocyanate group to hydroxyl group of 8 and a reaction temperature of 50°C. Then four different curing agents, triethylenetetramine, maleic anhydride, diethylenetriamine, and 1, 6‐hexamethylenediamine, were used to cure the PU/EP materials at room temperature. The mechanical results demonstrated that the addition of PU prepolymer significantly improved the tensile and flexural properties of the EP, especially triethylenetetramine‐cured and diethylenetriamine‐cured PU/EP materials, increased by 60.1%, 107% and 91.6%, 32.3% respectively. Thermogravimetric and differential scanning calorimetry analyses showed that the PU prepolymer enhanced the heat resistance of the EP material and there was outstanding compatibility between the PU prepolymer and the EP, with the PU component effectively reducing the agglomeration of the EPs during the curing process. The favorable mechanical properties and thermal stability of PU/EP materials benefit from the formation of an interpenetrating network structure and the addition of aliphatic amine curing agents.