Evaluation of intumescent fire retardants and synergistic agents for use in wood flour/recycled polypropylene composites

• Low cost WPC was prepared with recycled PP nonwoven and wood flour.
• Fire retardant synergistic agents enhanced the fire retarded performance of WPC.
• The mechanical property was increased by adding fire retardant synergistic agent.
• The synergy between IFR and ZB or MnO2 was greater than that of MMT or SnO2.
• 5 wt% of ZB or MnO2, MMT and SnO2 addition made WPC with a V0 rating.

The effects of fire retardant synergistic agents zinc borate (ZB), montmorillonite (MMT), manganese dioxide (MnO2) and stannic oxide (SnO2) on the mechanical properties, thermal degradation and flame retardant performance of wood flour–recycled polypropylene composites (WPC) comprised of intumescent flame retardants (IFR) were studied. The species were characterized by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 tests, and cone calorimeter measurements. The results showed that the synergistic effect between IFR and ZB or MnO2 was greater than that of MMT or SnO2. The addition of 5 wt% of ZB or MnO2, MMT and SnO2 created fire retardant WPC with a V0 rating, exhibiting excellent fire retardancy.