Effect of a biomass based waterborne fire retardant coating on the flame retardancy for wood

The biomass based flame retardant additive was prepared derived from renewable chitosan, melamine formaldehyde resin coated ammonium polyphosphate and organic montmorillonite and then incorporated into waterborne epoxy resin (WBEP) to produce waterborne fire‐retardant coatings. Finally, the coating was used to prepare flame retardant wood composites by spraying the mixture on wood surface. The coated wood composites passed UL‐94 V‐0 rating during vertical burning tests and its limiting oxygen index value reached 31.8% when the loading amount of flame retardant additive was 18 wt% in coating and the coating thickness was 3 mm. After water resistance tests, the wood composites remained excellent flame retarded performance. The introduction of biomass based flame retardant enhanced the carbonization capability of coating, and the residual char reached 23.9 wt% at 800°C. The cone calorimeter tests revealed that the release of heat and smoke of the coated wood composites were obviously decreased and the expanded, integrated and sealed char layer was generated at the end of combustion. The formed char layer exhibited excellent isolation effect and the wood substrate was effectively protected from combustion, and the flame retardant performance of the coated wood composites was enhanced. Thus, the prepared flame retardant WBEP coating possessed good water resistance and flame retardant efficiency for wood substrate, and it had excellent application aspect for preparing flame retardant wood composites with good comprehensive performance.