Synthesis of an integrated intumescent flame retardant and its flame retardancy properties for polypropylene

An integrated intumescent flame retardant (TPM) was prepared by using tris(2-hydroxyethyl) isocyanurate (THEIC), polyphosphoric acid and melamine as raw materials. The structure of TPM was characterized by FTIR, 1H NMR and 31P NMR spectra. The flame retardancy of PP/TPM composites were evaluated by limited oxygen index (LOI), UL-94 and cone calorimeter test (CCT), and compared with that of PP/(APP/PER) composite. The thermal degradation and swollen process of PP/TPM composite were studied by TGA, TG-FTIR, SEM and FTIR. It was found that PP/TPM composite could reach UL-94 V-0 rating and had a better mechanical property than PP/(APP/PER) at 20 wt% IFR loading. The mean heat release rate (HRR) and total smoke production (TSP) of PP/TPM decreased 65.6% and 17.7% in comparison with pure PP. TGA results showed that 20.7 wt% and 6.8 wt% chars remained in TPM and PP/TPM at 800 °C, respectively, showing a good char forming ability. Finally, the swollen process and flame retardant mechanism were studied through analysis of gaseous products, morphology and structure of residual char of PP/TPM composites.