Development of Intrinsically Flame-Retardant and Bio-Based Fiber-Reinforced Polymer Composite Using a Furan-Based Epoxy and Flax Fibers

Fiber-reinforced polymer composites (FRPCs) are commonly derived from petroleum-derived feedstocks and are highly flammable, necessitating flame-retardant chemicals that adversely affect both polymer properties and the environment. In this work, the flammability and sustainability of each component in the composite (polymer matrix and fiber reinforcement) were evaluated. Three polymer matrices were utilized: (1) a furan-based epoxy resin, PolyFDE, (2) the diglycidyl ether of bisphenol A (DGEBA), and (3) a commercially available flame-retardant epoxy resin (Intumax EP102), while two fiber reinforcements were utilized: (1) glass fiber and (2) flax fiber. The thermal stability, thermomechanical properties, and flammability of the three polymer matrices were evaluated utilizing thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and micro-combustion calorimetry (MCC). FRPCs were fabricated using two fiber reinforcements, PolyFDE and DGEBA, and their flammability was tested using cone calorimetry and UL-94 vertical testing. Furthermore, the mechanical properties were measured using a three-point bend flexural test. Among the polymer matrices, PolyFDE had an increased storage modulus (E′) at 25 °C of 3.1 ± 0.2 GPa, a glass transition temperature (Tg) of 100 ± 1 °C, and a char yield at 1000 °C in nitrogen of 39.3 ± 0.1%, compared with the other two systems. Using PolyFDE as the polymer matrix in FRPCs, regardless of the fiber used, improved flammability. Furthermore, the flax fibers provided a plant-derived alternative that helped reduce the composite’s overall flammability. However, due to sample arrangement and replication limitations in cone calorimetry, further evaluations are necessary to fully elucidate the role of flax fibers in FRPCs. Utilizing PolyFDE as an intrinsically flame-retardant polymer matrix demonstrated the successful reduction in the overall flammability of FRPCs without flame-retardant chemicals. Additionally, a fully sustainably sourced FRPC was fabricated using PolyFDE and flax fibers.