Design, synthesis and application of a highly efficient mono-component intumescent flame retardant for non-charring polyethylene composites

A novel hyperbranched mono-component intumescent flame retardant poly(piperazine methylphosphonic acid pentaerythritol ester) defined as PPMPPE was synthesized, and its chemical structure was characterized. The individual PPMPPE was incorporated into polyethylene (PE), and the fire resistance, thermal properties and flame retardant mechanism of PE composites were investigated in detail. The 1.6-mm PE/PPMPPE sheets fulfilled UL-94 V-0 level during vertical burning tests, and the limiting oxygen index was 25.3% when the loading amount of PPMPPE was 22 wt%. PPMPPE was completely melted, and the expanded char layer was generated on heating. The addition of PPMPPE stimulated the degradation and charring of PE composites in advance and improved the residual mass and thermal stability of FR-PE at high temperature. The cone calorimeter tests verified that the heat release rate and total heat release of PE/PPMPPE composites were obviously declined. PPMPPE exerted shielding effect in condensed phased and quenching active free radicals in the gas phase. The flame was constrained and even extinguished. Thus, PE composites fulfilled superior flame retardant properties. Graphic abstract

Automated summary

The novel hyperbranched mono-component intumescent flame retardant PPMPPE significantly enhanced the fire resistance and thermal stability of PE composites, reducing heat release rate and total heat release. The addition of PPMPPE exhibited superior flame retardant properties by shielding effect in condensed phase and quenching active free radicals in the gas phase, ultimately constraining and extinguishing the flame.