The novel application of chitosan: Effects of cross-linked chitosan on the fire performance of thermoplastic polyurethane

In this paper, a novel flame retardant (ACS) was prepared by crosslinking chitosan with bis-(4-formylphenyl)-phenyl-phosphonate (ABPO). ACS in association with ammonium polyphosphate (APP) and organic modified montmorillonite (OMMT) were used to prepare flame retardant thermoplastic polyurethane (TPU) composite through melt blending. For the TPU sample containing 10% flame retardants, the limiting oxygen index was increased from 20.8 to 29.0%, the vertical burning (UL-94) rating was upgraded from no rating to V-0, and the peak heat release rate was decreased from 1090 to 284 kW/m2. The thermal gravity analysis (TGA) indicated that ACS had excellent char formation ability and could greatly enhance the thermal stability of TPU. The tensile strength and elongation at break for flame retardant sample could reach 16.5 MPa and 1443% respectively.