Influence of TiO2 particles and APP on combustion behavior and mechanical properties of flame-retardant thermoplastic polyurethane

The experimental investigation on combustion behavior and mechanical properties of flame-retardant thermoplastic polyurethane were performed in the article. By the masterbatch-melt blending technique, the TiO2 particles were well dispersed in TPU/APP composites. The microscopic morphology structure was observed by TEM and SEM. TEM images of TPU-TiO2 masterbatch material showed that the grain sizes of TiO2 particles were 200-400 nm. The SEM result indicated that the TiO2 particles could enhance compatibility and dispersion of APP in TPU. The mechanical properties of TPU composites were characterized by dynamic mechanical analysis (DMA) and tensile tests, respectively. The DMA results indicated that TiO2 particles could improve the viscoelastic property of the TPU/APP composites. The tensile strength achieved a significant improvement with addition of TiO2 particles. APP/TiO2-5 obtains a better value of 344% than APP-1 (277%). Also, the flame-retardant property and thermal stability of the TPU composites were characterized using cone calorimeter test (CCT) and thermogravimetric analysis (TGA), respectively. The CCT results revealed that TiO2 particles could enhance the flame-retardant property of APP in TPU. The peak heat release rate of APP/TiO2-4 containing 0.5% TiO2 decreased to 157.27 kW m(-2) from 225.5 kW m(-2) of APP-1 sample without any TiO2. The TiO2 particles could promote the formation of carbon layers which restrict the diffusion of fuels into combustion zone and access of oxygen to the underlying materials. The TGA results indicated that TiO2 can improve the thermal stability of TPU/APP composites.