A Intumescent Flame-Retardant Polypropylene System and Its Burning Behaviors

A composite composed of polypropylene/intumescent flame retardant/montmorillonite(PP/IFR/MMT) was prepared.The effect of the content of various components on the flame retardancy of the composites was studied via limiting oxygen index(LOI) and vertical burning test(UL-94).The results show that when the total loading of flame retardants is 30% and the ratio of IFR to APP is 1 to 2,the LOI value of the composite reaches 29%.However,when 0.5%OMMT is added into the flame retardant system,the flame retardancy of the composites has a significant improvement: LOI value of 31% and UL-94 V-0 rating.Scanning electronic microscopy and Fourier transform infrared(FT-IR) were used to investigate the morphology and structure of char residues after burning.The results show that MMT can promote the PP/IFR system to form harder and more compact charring layers which reduces the transition speed of oxygen.A possible flame-retardant mechanism was explored.