Flame-retardant wood polymer composites (WPCs) as potential fire safe bio-based materials for building products: Preparation, flammability and mechanical properties

Improving the efficiency of traditional flame retardant additives is a challenging task in the field of wood polymer composites (WPCs). In this work, novel flame retardant system for WPCs was developed based on the combination of ammonium polyphosphate (APP) with physic acid modified layered double hydroxide (Ph-LDH). Thermogravimetric analysis illustrated that the incorporation of Ph-LDH resulted in earlier thermal degradation of the WPCs with more thermally stable products during degradation, giving improved char formation. Limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimetry tests were used to study the flammability of WPCs and the results showed that the addition of Ph-LDH had a synergistic effect on their fire performance. The char residues of the WPCs after the cone calorimetry tests were characterised by scanning electron microscopy (SEM). Mechanical properties of the flame retardant WPCs were analysed using impact and tensile tests. Partial substitution of APP with polypropylene (PP) resulted in a deterioration in the tensile and impact properties, while co-incorporation of nano-fillers led to an enhancement of the mechanical performances of the flame retardant WPCs. This WPC with good flame retardant and mechanical properties could potentially be used in the fields of building or furniture which require high flame retardancy.