Synergistic of ammonium polyphosphate and alumina trihydrate as fire retardants for natural fiber reinforced epoxy composite

Abstract Various compositions of epoxy/hardener with flame retardant (FR) as additives were used to produce natural fiber composite through the resin infusion technique. The effects of natural fiber (NF), ammonium polyphosphate (APP), alumina trihydrate (ATH) and ATH/APP hybrid on flammability, thermal and mechanical properties of the composites were investigated. Incorporation of NF into neat epoxy matrix reduced the gross heat of combustion with improved thermal degradation properties. Addition of APP enhanced the flame resistant properties of the composite with a much reduced total flame time and zero drip. The 10 wt·% ATH and 5 wt·% APP hybrid showed the most promising flame retardancy with a self-extinguishing property as well as the lowest gross heat and greatest char residue amongst the various formulations investigated. In general, the formulations containing only ATH couldn't provide the effective flame resistivity as compared to that of the APP-filled composites. The ATH-filled formulations reduced the tensile strength, elongation at break and flexural properties while an increase in the flexural strength of APP-loaded formulations was observed. An increase in moduli of the FR-filled composites was measured as compared to that of the NF/epoxy composite, owing to a more brittle characteristic.