A bio-based flame retardant with micro core-shell structure and its effect on flame retardancy and mechanical properties of thermoplastic polyurethane

The promotion of thermoplastic polyurethane (TPU) was limited due to its flammability. Flame-retardant modification of TPU always leads to compromised mechanical properties. To address this issue, a bio-based flame retardant KPCMS with micro core-shell structure was developed in order to achieve superior fire resistance and enhanced mechanical properties in TPU. KPCMS demonstrated remarkable thermal stability with an initial decomposition temperature of 320 °C, and achieved an excellent char residue of 61.6 % at 800 °C. After introducing KPCMS into TPU, the mechanical properties, thermal stability, and flame retardancy were analyzed systematically. The enhanced interfacial interactions between polymer and KPCMS contributed to improvements in both tensile strength and elongation at break. Specifically, the tensile toughness of sample TPU/1 %KPCMS increased by 44.1 % compared with pure TPU. For sample TPU/3 %KPCMS, the residue increased from 4.0 % to 7.9 % at 800 °C compared with pure TPU, and increased by 38.6 % compared with the theoretical value. Sample TPU/1 %KPCMS exhibited an increased limiting oxygen index (LOI) value of 24.5 %, passed the UL-94 V-0 rating, and showed improved anti-dripping behavior. The flame-retardant mechanism of TPU/KPCMS composites was derived from the synergism of barrier, quenching and dilution effects.