Mechanism Investigation and Safety Evaluation towards Flame-retardant Structural Thermoplastic Polyurethane Composites Inspired via Interfacial Synergy Strategy

Thermoplastic polyurethane (TPU) is widely applied in many fields including construction, cables, automobiles, and aerospace. However, TPU is extremely flammable, endangering people's lives and property. Boron nitride (BN) nanosheets are highly thermally stable, and nano-metal oxides (CoMoO₄) are great for catalytic carbonization. Therefore, in this work, CoMoO₄ is facilely assembled on the surface of BN, to design three types of BN-CoMo fillers (namely, BN-CoMo-1, BN-CoMo-2, BN-CoMo-3). These fillers are further utilized as flame retardants for TPU, with composites containing 6.0 wt% BN-CoMo-1 being the most effective. Compared with pure TPU, the peak heat release rate (PHRR) is decreased by 51.6%. Meanwhile, BN-CoMo-1 shows substantial benefits in suppressing smoke and CO production. In specific, the peak smoke production rate (PSPR) and peak CO production rate (PCOP) of TPU/6.0 BN-CoMo-1 are decreased by 64.8% and 62.2%. Through a comprehensive assessment, it is further verified that BN-CoMo-1 has outstanding advantages in enhancing the flame retardancy of TPU. Due to the excellent flame retardant and thermal insulation properties of TPU/6.0 BN-CoMo-1, it can be used as the barrier material to inhibit the thermal runaway propagation of batteries.