Effect of Red Phosphorus Masterbatch on Flame Retardancy and Thermal Stability of Polypropylene/Thermoplastic Polyurethane Blends

In this work, red phosphorus masterbatch (RPM) was filled into polypropylene/thermoplastic polyurethanes (PP/TPU) blends as a halogen-free flame retardant. The flammability behaviour, thermal stability and mechanical properties were investigated by limit oxygen index (LOI), UL-94 vertical burning, cone calorimeter tests (CCT), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the addition of RPM improved the flame retardant performance of PP/TPU blends. The LOI values of the composites with RPM were higher than that of the PP/TPU blends, and the UL-94 V-2 rating was achieved for PP/TPU/RPM composites. The CCT results further indicated that the heat release rates (HRR), total heat release (THR), and the CO ₂ production rate (CO ₂ P) decreased in comparison with the PP/TPU blends. TGA data indicated that RPM greatly enhanced the thermal stability and char residues of PP/TPU blends. The addition of RPM deteriorated the tensile strength of the PP/TPU/RPM composites. However, the impact strength of the composites was improved.