Synthesis of a novel mono-component intumescent flame retardant and its high efficiency for flame retardant polyethylene

A novel polymeric mono-component intumescent flame retardant poly(piperazine methylphosphonic acid neopentylglycol ester) (PPMPNG) was synthesized from methylphosphonic acid, piperazine and neopentyl glycol. Its chemical structure was detailed characterized by Fourier transform infrared spectroscopy (FTIR), C-13 and P-31 solid-state nuclear magnetic resonance. PPMPNG was incorporated into polyethylene (PE) and the flame retardancy, thermal properties and flame retardant mechanism of materials were investigated. The samples with the thickness of 1.6 mm passed UL-94 V-0 rating during vertical burning tests and the limiting oxygen index was 25.6% when 23 wt% PPMPNG was introduced. The results of thermogravimetric analysis (TGA) showed that the addition of PPMPNG promoted the degradation and carbonization of materials at the beginning and improved the char residue amount and thermal stability of FR-PE at high temperature. Cone calorimeter tests indicated that the peak value of heat release rate was considerably reduced with the incorporation of PPMPNG. The flame retardant mechanism showed PPMPNG exerted isolation effect in condensed phased and quenched active free radical effect in gas phase. The combustion intensity was reduced and the flame was suppressed and even extinguished, thus a high efficiency for PE matrix was achieved.