Abstract:

The effect of the mass ratio and composition of melamine polyphosphate(MPP)/pentaerythritol(PER) in intumescent flame retardants(IFRs), synergist group MgO/EG/SiO₂ of which composition with m(MgO):m(expandable graphite, EG):m(SiO₂)=1:5:5, and the silane coupling agent KH550 on the flame retardancy of polypropylene-based wood-plastic composites(WPC) were studied by means of limiting oxygen index(LOI), linear burning rate(LBR), thermogravimetric analysis and cone calorimetry. The results show that when m(MPP):m(PER)=23:2 in IFRs(code IFRs-M1) and its mass fraction is 25%, the flame retardant performance is the best, and LOI and LBR of the intumescent flame retardant composite WPC/IFRs-M1 are 27.1% and 3.89 mm/min, respectively, which are 48.1% higher and 89.79% lower than those of the unadded WPC. Compared with the unadded WPC, the heat release rate and total heat release during combustion decrease by 76.2% and 50.1%, the carbon residue rate at 600 ℃ increases by 498.3%, the total smoke emission reduces by 6.9%, and the release of CO₂ drops by 65.4%. It also indicates that both the synergist group and KH550 surface treatment can further improve the flame retardant properties of WPC/IFRs-M1, and both have good flame retardant synergistic effect on IFRs-M1. Compared with WPC/IFRs-M1, LOI of WPC/IFRs-M1/MgO/EG/SiO₂/KH550 with both flame retardant means mentioned above is enhanced by 3.7%, and its LBR declines by 20.3%. At the same time, its thermal stability significantly improves, the thermal weight loss goes down, and its heat release rate and total heat release during combustion reduce by 36.5% and 37.6%, respectively. Its carbon residue rate at 600 ℃ increases by 84.02%, the total smoke release reduces by 57.5%, and the amount of CO₂ release reduces by 33.33%, indicating a better synergistic effect.

Key words: melamine polyphosphate, pentaerythritol, synergist group, wood plastic composite, flame retardant