Co-MOF@MXene hybrids flame retardants for enhancing the fire safety of thermoplastic polyurethanes

Thermoplastic polyurethane (TPU) is the most used polyurethane, but its highly flammable characteristic restricts its extensive use. In this work, Co-MOF@MXene hybrids flame retardants were synthesized and incorporated into TPU . The flame-retardant characteristics of TPU composites were investigated by cone calorimeter test and thermogravimetric analyzer. Compared with TPU, the peak heat release rate and total heat release rate of TPU/Co-MOF@MXene composites were reduced by 28.3% and 14.5%, respectively; and the smoke production rate and total smoke production of the composites with only 2 wt% Co-MOF@MXene hybrids were also reduced by 58.8% and 47.5%, respectively. Furthermore, the char residues of TPU/Co-MOF@MXene composites were about 2 times that of pure TPU. Systematical characterizations were then carried out to investigate the flame retardant mechanism of Co-MOF@MXene hybrids, highlighting the barrier effects of MXene combined with the catalytic effect of Ti and Co. The hybrids flame retardants greatly benefit the further development of TPU nanocomposites.