Development of fire retardancy of natural fiber composite encouraged by a synergy between zinc borate and ammonium polyphosphate

The current work investigated the effects of zinc borate (ZB), ammonium polyphosphate (APP)/ZB and alumina trihydrate (ATH)/ZB hybrids as flame retardants on the flammability, calorimetric, thermal and mechanical performances of empty fruit bunch (EFB) fiber reinforced epoxy composites. The formulations with concentration of 5, 10, 15 wt·% ZB and 15 wt·% APP/ZB, 15 wt·% ATH/ZB hybrids and the Control composite (EFB reinforced epoxy) were fabricated using resin infusion method. The composite containing 10 wt·% APP and 5 wt·% ZB was found to produce the highest flame retardancy in 12 s vertical Bunsen burner test and show promising results in terms of burn length, drip flame time and total flame time as obtained from 60 s vertical Bunsen burner. This could be attributed to the synergism that was created at this mass fraction between the hybrid of APP and ZB. Flexural properties did not change significantly with the inclusion of APP and ZB hybrid whereas tensile strength and elongation at break experienced an obvious reduction.