Effects of a semi-bio-based triazine derivative on intumescent flame-retardant polypropylene

A semi-bio-based synergist ( N , N ′, N ″-1, 3, 5-triazine-2, 4, 6-triyltris-glycine [TTG]) was prepared by using glycine and cyanuric chloride. The structure of TTG was characterized by 1 H NMR and Fourier transform infrared spectroscopy. The TTG was applied in polypropylene (PP)/intumescent flame-retardant compounds to improve its flame retardancy. The flame-retardant properties of PP compounds were evaluated by limiting oxygen index and vertical burning tests (UL-94). The results showed that 17 wt% intumescent flame-retardant and 1 wt% TTG makes PP achieve the UL-94 V-0 rating without drippings, and the limiting oxygen index value is increased to 29.5 vol%. The thermal degradation behavior and char morphology of PP compounds were investigated by thermogravimetric analysis and scanning electron microscopy. The results indicated that TTG accelerates the formation of char layer, regulates the porous structure of char layer, and enhances its barrier property. Therefore, the temperatures of PP compound after two ignitions during the UL-94 test are decreased significantly as shown in infrared thermal imaging. In addition, the combustion characteristics of PP compounds were investigated by cone calorimeter. The peak of heat release rate (PHRR) of PP compound is 67% reduced, and the t PHRR is delayed from 223 to 430 seconds, indicates that the combustion risk of PP compound is reduced.