Enhancing the flame retardancy of thermoplastic polyurethane by introducing montmorillonite nanosheets modified with phosphorylated chitosan

Abstract Phosphorylated chitosan (PCS) was applied to decorate montmorillonite under ultrasonic catalysis to prepare organically modified exfoliated montmorillonite (PMT). It was demonstrated that PMT had better synergism with aluminum hypophosphite (AHP) than MMT in improving the fire resistance of thermoplastic polyurethane (TPU) composites. By the presence of 9% AHP and 1% PMT, the limiting oxygen index of TPU composites was increased to 28.4%, the UL-94 rating was achieved to V-0. The peak heat release rate and total smoke release were reduced from 1090 kW/m 2 and 831 m 2 /m 2 of control TPU sample to 195 kW/m 2 and 91 m 2 /m 2 of the TPU/AHP/PMT sample respectively. The char residue after cone calorimetry demonstrated PMT nanoplatelets were well dispersed in the polymer matrix, which served as the thermal insulation layer to shield the underlying matrix from the exterior heat irradiation.