(3-DOPO-propyl)-triazine trione (TAD) achieved UL 94 V-1 and one third reduction in peak heat release in PET at 5% loading. The experimental PIN FR contains three phosphorus atoms (10.3% P w/w) and three nitrogen atoms. It was blended into PET (polyethylene terephthalate) by extrusion at 1 – 5 % w/w, with 0.6% antioxidants and 0.4% anti-drip PTFE (a fluorinated PFAS). At 5% loading, UL 94 v-1 (3.2 mm) was achieved, peak heat release rate was reduced by a third (compared to neat PET) and LOI was increased to 30.2 (from 23.8 neat PET). Mechanical properties of the PET were generally deteriorated by the TAD addition at 5%, but at 1 – 3 % loading were in some cases improved. The fire safety action of TAD was considered to be a combination of gas phase, with phosphorus radicals inhibiting burning, and protective char production.
“The behavior and mechanism of tris-(3-dopo-propyl)-triazine trione flame retardant polyethylene terephthalate”, H-Y. Liu et al., J Appl Polym Sci. 2023;140:e54069, https://doi.org/10.1002/app.54069