Synthesis of Halogen-free Phosphorus-nitrogen Flame Retardant and Its Flame Retardancy in PC

A novel halogen-free phosphaphenanthrene flame retardant DOPMI was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and N-phenyl maleimide (N-PMI). DOPMI was characterized by FT-IR,LC/MS,TG,and DSC. The effect of DOPMI in polycarbonate (PC) was compared with other flame retardants on flame-retardancy,mechanical properties,thermal degradation behavior,and char morphology. When 3 % DOPMI,2 % methyl phenyl silicone (MPS),and 24 % phosphorus-containing flame-retardant PET were blended with PC,limiting oxygen index of 30.4 % and UL94 V-0 rating were observed. Notched impact strength and tensile strength decreased after the flame retardants were added. DOPMI didn't improve the char yield of PC,but it accelerated crosslinking and char forming in PC. Additionally,SEM photos indicated that DOPMI could promote PC foaming,and MPS had a synergistic effect on PC.