Synthesis of a novel hyperbranched and phosphorus-containing charring-foaming agent and its application in polypropylene

In this work, a novel hyperbranched and phosphorus-containing triazine derivative (HPCFA) is synthesized. HPCFA is used as charring-foaming agent and combined with ammonium polyphosphate (APP) as intumescent flame retardant to flame retard polypropylene (PP). PP/HPCFA/APP composite can achieve limited oxygen index value of 31% and pass UL 94V-0 rating by addition of 20wt% HPCFA/APP (1/2, w/w). Besides, HPCFA is compared with another hyperbranched charring-foaming agent (HCFA). HPCFA and HCFA have similar chemical structure, and their only difference is that HPCFA has phosphorus-containing unit in the main chain compared with HCFA. HPCFA/APP system exhibits superior flame retardancy compared with HCFA/APP system. Char residue analysis demonstrates that HPCFA/APP system can form denser and more compact char layer in comparison with that of HCFA/APP system.