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 (B-11, C-13, and P-31) 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. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this study, intumescent flame retarded polybutylene succinate (PBS) formulations were developed using ethylenediamine phosphate (EDAP) and different co-additives. Among them, zinc borate showed the best synergistic flame retardant effect with EDAP in PBS. Analysis using solid state NMR and cone calorimetry revealed the formation of a highly thermally stable inorganic char by EDAP and zinc borate in PBS, acting as an effective flame retardant mechanism.