Flame-retardant effect of cross-linked phosphazene derivatives and pentaerythritol derivatives on polypropylene

A phosphazene-based flame retardant (PBFA) was synthesized by hexachlorocyclotriphosphazene andN-aminoethylpiperazine. To improve the flame retardancy of polypropylene (PP), PBFA and pentaerythritol derivatives (PEPA) were mechanically mixed to form a water resistance intumescent flame retardant (IFR). The flammability and thermal properties of the PP composites were analyzed by vertical burning test (UL-94), limit oxygen index, thermogravimetric analysis (TGA) and cone calorimeter test (CCT). The results indicate that there was a synergistic effect between PBFA and PEPA at a suitable mass ratio. When the mass ratio of PBFA/PEPA was 2:1, the PP composites can successfully achieve UL-94 V 0 rating. Compared with pure PP, the peak heat release rate and the total heat release were decreased by 75.40 and 15.38%, respectively; moreover, the total smoke production decreased by 22.11% during 0-465 s. The residual char after CCT was characterized by Fourier transform infrared spectrometer (FTIR). A strong pyrophosphate absorption peak was found in FTIR, indicating that the IFR mainly played a flame-retardant mechanism in the condensed phase.

Automated summary

A novel flame retardant PBFA was synthesized and mixed with PEPA to enhance the flame retardancy of polypropylene, achieving UL-94 V0 rating. The best performance was observed at a mass ratio of 2:1, significantly reducing heat release rate, total heat release, and smoke production. FTIR analysis showed that the IFR mechanism mainly operated in the condensed phase.