Facile Synthesis of Eugenol-Based Phosphorus/Silicon-Containing Flame Retardant and Its Performance on Fire Retardancy of Epoxy Resin

The fire resistance property of epoxy resin is crucial for its engineering applications. In this work, a eugenol-based flame retardant containing phosphorus (P) and silicon (Si) groups (EGN-Si/P) was synthesized via the Williamson etherification and subsequent hydrosilylation reaction. The resulting EGN-Si/P was used as a flame retardant for bisphenol A epoxy resin (DGEBA). The resulting epoxy resin passed the UL-94 V-0 rating and had a high limiting oxygen index (LOI) value of 28% when only 0.5 wt % Si/P content was introduced into the hybrid system. The results of cone calorimetry tests demonstrated that compared to those of DGEBA, the peak heat release rate and the total heat release of EGN-Si/P reduced by 49.6 and 46.8%, respectively, when 2 wt % Si/P was loaded into the hybrid system. The Si and P synergistically promote the formation of a stable carbon residue, which served as an effective thermal insulation layer to shield the underlying matrix from the exterior heat irradiation. This eugenol-based P and Si synergistic flame retardant opens a pathway to develop sustainable high-performance flame-retardant biobased polymer materials for practical application.