Flame retardant thermoplastic polyurethane based on a combination of chitosan and phosphotungstic acid

Thermoplastic polyurethane was increasingly used in many applications, and reducing its fire hazard was a very important research direction. In this paper, CS and PWA and their combinations were added to TPU as flame restardants. The flame restardant and smoke suppression performance of the samples after adding CS/PWA combination was investigated by CCT, SDT, LOI, and TG-IR. The CCT results showed that the combination of CS/PWA could effectively reduce the heat release rate of TPU, and the pHRR value could be reduced by 76%; the TSR value would be reduced by 50%. Moreover, the THR value could be reduced by 35.4%. The combustion time could be prolonged, and the LOI value could be increased from 21% to 24.8%. The SDT results showed that CS/PWA combination could effectively reduce the smoke production in the test. The structure of the char residue layer of TPU composites became more dense and continuous. The reduction of MDI generation from TPU thermal decomposition was demonstrated by GC–MS, and it was further demonstrated that CS/PWA could promote the formation of the dense char layer and protected the matrix material. The mechanical performance tests proved that the CS/PWA combination had little effect on the structure of the TPU material. The above results indicate that the CS/PWA combination had a good prospect in reducing the fire hazard of TPU.