Intumescent polybutylene succinate: Ethylenediamine phosphate and synergists

In this work, a series of intumescent flame retarded polybutylene succinate (PBS) formulations have been developed based on ethylenediamine phosphate (EDAP) and different co-additives, i.e ., zinc borate, melamine borate, zinc molybdate, and aminated multiwall carbon nanotubes, at relatively low loading (10 wt.%). Among them, zinc borate endows the best synergistic flame retardant effect with EDAP in PBS. Cone calorimetry shows that addition of EDAP and zinc borate with a ratio of 8:2 ( wt: wt ) dramatically reduces the peak heat release rate (pHRR) by 57% as compared to neat PBS, indicating the excellent flame retardant efficiency of this combination used at only 10wt.%. Beside, benefitting from the incorporation of zinc borate, PBS/EDAP/ZnB exhibits excellent smoke suppression and good mechanical properties. Solid state NMR ( 11 B, 13 C, and 31 P) gives information to determine the flame retardant mechanism of EDAP and ZnB in PBS. It was found that it involves the formation of a reinforced intumescent char with highly thermally stable inorganic species, which acts as a protective physical barrier increasing the char cohesion and limiting the formation of cracks.