Enhanced Flame Retardancy in Epoxy Resins bu ZnAl-LDH/Ammonium Polyphosphate Synergism: Impact of Alkali Source Variation

Abstract

The application of ammonium polyphosphate (APP) as an additive flame retardant to epoxy resin (EP) flame retardant is common, while, APP is poorly dispersed and easily agglomerated in EP. For solving the problem, in this paper, three kinds of ZnAl-layered double hydroxides (ZnAl-LDH1, ZnAl-LDH2 and ZnAl-LDH3) were successfully prepared by using sodium hydroxide, urea and triethanolamine as differences alkali source, respectively, which were used to strengthen the flame retardant performance of EP with APP. The results showed that the heat release peak and the smoke production rate peak were decreased by 58.2% and 44.2% after the addition of APP (5 wt%) and ZnAl-LDH3 (5 wt%) which is prepared with triethanolamine as the alkali source compared with that of Pure-EP.The addition of ZnAl-LDH3 will contribute to the dispersion of APP and the increase of the most C element in this process by SEM and XPS. The metal oxides were uniformly distributed on the surface of the carbon layer after combustion. The residual carbon value of ZnAl-LDH3 was smaller than that of ZnAl-LDH1-APP-EP and ZnAl-LDH2-APP-EP by the raman pattern. The heat release profile of APP-EP was better than that of ZnAl-LDH3-APP-EP, however, the tensile property and elongation at break of ZnAl-LDH3-APP-EP are better than that of APP-EP.