Determination of Fire Resistance, Mechanical Property and Physical Stability of Boron Phosphate Containing Wood Polymer Composites

This study presents the improvement in flame retardancy of wood polymer composites (WPCs) by boron phosphate (BPO4) additive. The WPCs were manufactured by phenol formaldehyde and wood flour of Oriental beech (Fagus orientalis L.) using compression molding. Polydiphenylmethane-4,4’-diisocyanate (PMDI) was also added to enhance the compatibility of hydrophilic wood flour and hydrophobic polymer resin. The strengthening of interfacial adhesion by PMDI incorporation resulted in better mechanical (flexural) and physical (water absorption, thickness swelling) properties. The BPO4 flame-retardant additive in WPCs formulation was first reported and thermal behaviors of composites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 tests. The BPO4 compound promoted the char formation of WPCs, and the LOI values of composites were increased from 28.7 to 35.6. The UL-94 tests also showed that the flame retardancy of composites were improved by changing the V-2 rating to V-0 with the addition of 5 wt.% BPO4.