Synthesis of a triazine charring agent containing hydroxyl and triazine ring and its flame retardant application in thermoplastic polyolefin

The flame retardant work of polyolefin materials has always been a challenge in the industry. Herein, we report a triazine charring agent (TM) containing hydroxyl and triazine ring. Combined with ammonium polyphosphate (APP), TM was applied to prepare flame retardant thermoplastic polyolefin (TPO) composites. The results of thermogravimetric analysis (TGA) test show that TM has high initial pyrolysis temperature and retention rate of char residue at high temperature. The UL-94, limit oxygen index (LOI) and cone calorimetry tests (CCT) were used to characterize the flame retardancy of TPO composites. The UL-94 V-0 rating and LOI value of 29.2% are achieved with a loading of 9.17 wt% flame retardant (TPO-3). In particular, the fire performance index (FPI) associated with the flashover time also increases to 0.037 m 2 s/kW compared with TPO (0.030 m 2 s/kW). The synergistic effects of APP/TM were investigated in depth. The results show that APP/TM system forms a dense and continuous char layer on the surface of TPO during combustion, which effectively insulates the substrate from heat and oxygen erosion. Additionally, APP/TM system also plays a weak but important flame retardant role in the gas phase, including quenching effect of phosphorous compounds and dilution effect of non-combustible gases.