Phosphorus-containing resveratrol-based flame retardants derived from esterification reactions for flame-retardant epoxy resins

With an increasing focus worldwide on protecting the environment and developing in a sustainable way. Developing halogen-free, environmentally benign flame retardants is of critical relevance. To enhance the fire-safety performance of epoxy resins while simultaneously mitigating their environmental impacts. The bio-derived flame retardant DOPR was prepared in a single-step, one-pot process using resveratrol and DOPO as the key starting materials. The resulting product was subsequently incorporated into an epoxy matrix to obtain EP/DOPR composites. Despite encompassing only 0.35 wt% phosphorus, the EP/5DOPR composite exhibited an increased LOI of 28.19% and secured the top-tier V-0 grade in the UL-94 flammability evaluation. Compared with neat EP, its pHRR, THR and TSP were lowered by nearly 15.65%, 33.13% and 9.62%, respectively. Furthermore, the residual char yield of the composite was improved from 14.78% to 17.88%. The mechanical properties of the composite material were enhanced following the addition of 3wt% and 5wt% flame retardant, indicating a more favourable balance between flame retardancy efficiency and additive loading. The relevant research findings may provide a potential fundamental approach for the application of bio-based flame retardants to enhance the high performance of epoxy resins.