Synthesis of a Novel Triazine-Based Hyperbranched Char Foaming Agent and the Study of Its Enhancement on Flame Retardancy and Thermal Stability of Polypropylene

A novel hyperbranched char foaming agent (HCFA), successfully synthesized via the polycondensation of 2-chloro-4,6-di-(2-hydroxyethylamino)-s-triazine (CHT), was combined with ammonium polyphosphate (APP) to endow polypropylene (PP) with flame retardance. The study of thermal stability of various PP composites showed that HCFA/APP system could effectively improve the thermal degradation and thermal-oxidative stability of the char residues, and PP3 containing 30 wt % APP/HCFA with a 3/1 weight ratio left the highest amount of char residue at 700 °C. The results of flammability revealed that PP3 had the most effective flame retardancy and lowest fire hazards. The investigation of structure and morphology of char residues indicated that the compact and foaming char layer, as a good barrier against the transmission of heat and volatiles, was formed for PP3 during combustion.