Flame retardancy and pyrolysis behavior of an epoxy resin composite flame‐retarded by diphenylphosphinyl‐POSS

Abstract

AbstractTo reduce the flammability of epoxy resin (EP), a flame retardant (designated as D‐POSS) containing diphenylphosphinyl and polyhedral oligomeric silsesquioxane (POSS) was constructed by aminopropyl‐isobutyl POSS and diphenylphosphinyl chloride. The chemical structure of D‐POSS was fully characterized, then it was used to enhance the flame retardancy of EP. When the flame‐retardant EP composite contained 4 wt% D‐POSS, its limiting oxygen index value was 29.0% and it achieved UL 94 V‐1 rating. Also, its peak of heat release rate (pk‐HRR), total heat release (THR) and total smoke production were decreased by 35.3%, 30.3%, and 38.3%, respectively. Moreover, the results from cone calorimeter disclosed that diphenylphosphinyl group and POSS group in D‐POSS showed a strong synergistic effect in inhibiting pk‐HRR, THR, and smoke production, promoting the charring formation of EP material, and forming an intumescent char layer. Additionally, the theoretical THR reduction of flame‐retardant EP composite was calculated by the equation deduced from the standard, and it was almost same with the practical THR reduction. Notably, some silicon oxide enriched on the residue's surface. The phenomenon led to form a double‐layer residue that consisted of white yarn‐like outer char and normal intumescent inner char. This double‐layer residue was contributed to enhance EP composite's flame retardancy.