Functionalizing MXenes with molybdenum trioxide towards reducing fire hazards of thermoplastic polyurethane

Abstract

The development of high-efficiency flame-retardant polymers with low toxic fumes during combustion remains a great challenge. In this work, molybdenum trioxide (MoO₃) was loaded on titanium carbide (Ti₃C₂T_x) nanosheets through electrostatic interactions for preparing a Ti₃C₂T_x–MoO₃ hybrid. Then solvent mixing and melt blending methods were conducted to prepare flame-retardant thermoplastic polyurethane (TPU) nanocomposites. The scanning electron microscopy (SEM) result showed that the uniformly distributed Ti₃C₂T_x–MoO₃ hybrid had a strong adhesion and good compatibility with the TPU matrix. The thermal stability of TPU was significantly improved upon the introduction of Ti₃C₂T_x–MoO₃. The cone results revealed that the peak of heat release rate and the peak of smoke production rate of TPU nanocomposites containing 2.0 wt% Ti₃C₂T_x–MoO₃ were significantly reduced by 26.2% and 42.9%, respectively, as compared to those of pure TPU. Besides, the peak of the carbon monoxide production rate and the total carbon monoxide yield of Ti₃C₂T_x–MoO₃-2.0 were reduced by 44.7% and 44.7%, respectively. The distinguished fire resistance of the TPU/Ti₃C₂T_x–MoO₃ system is principally attributed to the physical barrier effect and the catalytic carbonization of Ti₃C₂T_x–MoO₃ hybrids together with the chemical conversion of Ti₃C₂T_x.