Bio-based eugenol flame retardant for simultaneously enhancing fire safety and mechanical performance of epoxy resin

With the swift advancement of green sustainability, efficient bio-based flame retardant is imperative to be created for epoxy resin (EP) especially in construction materials. This article designed a bio-based flame retardant (EUSP) which contains epoxy groups through the synthesis between epoxidation of eugenol and Phenyl trichlorosilane. The obtained flame retardant was applied for conventional E51 EP. The resultant EP composites achieved the V-0 rating in accordance with UL-94 standards and demonstrated a high limiting oxygen index (LOI) value of 30.2 % when 30 wt% EUSP was introduced. Compared to pristine E51 EP, the peak heat release rate (PHRR) and the peak smoke release rate (PSPR) were reduced by 38 % and 35.2 %, respectively. The flame-retardant effect of EUSP is achieved through the condensed phase flame retardant of silicon element. The silicon oxygen bond in EUSP reacts at the initial stage of combustion to form silicon dioxide. After the formation of silicon dioxide, a layer of silicon dioxide is formed outside under the promotion of combustible gas, which can reduce the internal exchange of external heat and epoxy resin and prevent the release of combustible gas inside the sample. Under the protection of the silicon dioxide layer, a compact and complete carbon layer is formed inside, which can further absorb the external heat, stabilize the internal temperature of the epoxy resin and protect the matrix. In comparison to the pristine E51 EP, the incorporation of 30 wt% EUSP resulted in an increase in both tensile strength and flexural strength, with values rising from 55.16 MPa and 90.69 MPa to 85.05 MPa and 146.83 MPa, respectively, representing a rise of 54.1 % and 67.3 %. This study provides a simple pathway for the preparation of bio-based flame retardants aimed at enhancing both the flame retardancy and mechanical properties of epoxy resin (EP).