ABSTRACT In this study, a bio‐based flame retardant, DPO‐ITA, was efficiently synthesized from diphenylphosphine oxide (DPO) and itaconic acid (ITA) via a facile one‐step reaction. The incorporation of DPO‐ITA increased the initial thermal decomposition temperature and glass transition temperature compared with those of the unmodified epoxy resin (EP‐0). At a phosphorus content of 2.3 wt%, EP/DPO‐ITA 2.3 achieved a UL‐94 V‐0 rating and a limiting oxygen index of 39.5%. Cone calorimetry results showed that EP/DPO‐ITA 2.3 exhibited significantly reduced peak heat release rate, total heat release, average effective heat of combustion, and fire growth rate, with reductions of 65.1%, 25.7%, 16.1%, and 74.5%, respectively, compared with EP‐0. The enhanced flame retardancy arises from the synergistic action of DPO‐ITA in both condensed and gas phases, including the formation of a dense, highly graphitized char layer, quenching of reactive radicals by phosphorus‐containing species, and dilution of flammable volatiles by nonflammable gases released during decomposition. Meanwhile, EP/DPO‐ITA 2.3 exhibited tensile strength comparable to EP‐0, while its flexural strength was significantly enhanced by 47.03%. This work demonstrates that DPO‐ITA is an effective bio‐based flame retardant for epoxy resins and provides insights into the development of high‐efficiency flame‐retardant materials.
Hao et al. (Mon,) studied this question.
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