Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE A bio-based flame retardant, DPO-ITA, was synthesized via a facile one-step reaction, and its incorporation markedly enhanced the initial thermal decomposition temperature, glass transition temperature, and flame retardancy of the epoxy resin.


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-ITA2.3 achieved a UL-94 V-0 rating and a limiting oxygen index of 39.5%. Cone calorimetry results showed that EP/DPO-ITA2.3 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-ITA2.3 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.