Study on novel boron-containing triazine flame retarded thermoplastic polyester elastomer composites and the flame retardant mechanism

A triazine‑boron non-halogenated flame retardant (CPB) was synthesized. The chemical structure of CPB was confirmed by Fourier Transform Infrared Spectrometer (FT-IR) and Nuclear Magnetic Resonance (NMR), and the thermal, flame retardant and combustion properties of Thermoplastic Polyester Elastomer (TPEE) composites with CPB addition were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test (CCT). The results showed that the LOI of the TPEE/20CPB composite increased to 30.2% with the addition of 20 wt% CPB and was able to pass the UL-94 V-0 rating. At the same time, the total heat release(THR) as well as peak heat release(pHRR)of TPEE/20CPB relative to TPEE was reduced from 129.3 MJ/m2 and 1234.1 kW/m2 to 63.7 MJ/m2 and 329.8 kW/m2 respectively, and the total smoke production (TSP) and smoke production rate (SPR) was also found to be reduced. This indicates that CPB can exert flame retardant properties as well as smoke suppressing properties. Finally, the structure and morphology of the residual char were investigated by Laser-Raman Spectroscopy (LRS), Scanning Electronic Microscopy (SEM) and FT-IR. The results showed that CPB could promote the formation of carbon in the condensed phase as well as the formation of a glassy cover layer to act as a thermal insulation and oxygen barrier, which can be highly effective in flame retardation.