Preparation of Flame-Retardant Glass Fiber-Reinforced Epoxy by Vacuum-Assisted Resin Infusion Process with Deep Eutectic Point Curing Agent

Enhancing the flame resistance of fiber-reinforced epoxy resins will broaden its potential applications. However, the inclusion of a flame retardant in epoxy resins with a curing agent shortens the process, posing a challenge for the production of flame-retardant composites. In this work, the process performance of flame-retardant epoxy resins was improved by using deep eutectic solvents (DES) as the curing agent. The gelation time and viscosity curves show that a flame-retardant epoxy with DES has excellent processability at 60 °C with a viscosity of 430 mPa∙s. Then, the manufacturing and experimental investigation of the flame-retardant epoxy (E-M) and composite (E-MC) were conducted. The fire retardancy of E-M is rated V0 according to the UL-94 test, and its limiting oxygen index (LOI) value is 36.8%. The mechanical performance of the epoxy resins is also slightly improved by the addition of the flame retardant. E-MC was successfully prepared by vacuum assisted resin infusion (VARI) with a V2 rating in the UL94 test, and extraordinary mechanical properties were achieved. The remarkable flame retardancy and mechanical properties of both the matrix and the composites demonstrate that the DES curing agent can homogenously disperse in and cure the epoxy resins. This work provides an inexpensive yet effective solution for manufacturing flame retardant composites by VARI, enabling the application of a range of flame retardants to composite materials.