Flame-retarded poly(propylene) with melamine phosphate and pentaerythritol/polyurethane composite charring agent

In this paper, a novel intumescent system including MP as well as PER/TPU which acts as composite charring agent, is adopted to flame-retarded PP. The encapsulation of charring agent PER by TPI effectively avoids the reaction of PER with MP during the compounding with PP at high temperature and also prevents the leaching out of polar PER from nonpolar PP matrix, thus remarkably enhancing the stability and water-resistance of the intumescent system. PER and TPU have different but complementary charring mechanisms. So flame-retarded PP with MP/composite charring agent shows a much better charring performance and flame-retardancy than MP/PER flame-retarded PP. The experimental results show that the former can reach UL-94 V-0 rating at 1.6 mm thickness at 25 wt.-% flame retardant loading.