Biobased itaconic anhydride (ITA), combined with DOPO, generated a polymeric P FR showed to be effective in epoxy. ITA is a dicarboxylic acid, derived from citric acid, which can be produced from renewable sources. It was here combined with DOPO* to generate a hyperbranched polymer (ITA-HBP), which was then dispersed in DGEBA and then cured into epoxy resin at 0 – 20% loading (0 – 0.93% P in final epoxy). 20% loading of ITA-HBP in exoxy increased LOI by nearly 60%, reduced peak heat release by over 30% and reduced total smoke release by nearly 25%. Just 5% ITA-BHP was sufficient to achieve UL 94 V-0 (3 mm). Also, impact strength, fracture toughness and fracture energy were significantly improved.
“A bio-based hyperbranched flame retardant for epoxy resins”, J. Zhang et al., Chemical Engineering Journal 381 (2020) 122719 https://doi.org/10.1016/j.cej.2019.122719