Thermoplastic Polyurethanes as Carbonization Agents in Intumescent Blends. Part 2: Thermal Behavior of Polypropylene/Thermoplastic Polyurethane/Ammonium Polyphosphate Blends

Melt blending of thermoplastic polyurethane (TPU)/ammonium polyphosphate (APP) additives in a polypropylene matrix improves fire proper ties of the polypropylene-based materials via an intumescence process. In this study, the protective effect of intumescence is studied considering the thermal stability of a particular FR PP/TPU/APP blend in the conditions of its thermo-oxidative degradation. Thermogravimetric analysis allows the computation of the degradation rate of a particular system using the Invariant Kinetic Parameters method. The study shows that a reaction between APP and TPU leads to the formation of the intumescent shield and gives a material with improved thermal stability. Finally, we present the computed temperature of the degradation front of the blend that is proposed as a probe for the estimation of the fire retardancy.