Supramolecularly Functionalized Zirconium Phosphate Strategy for High-Performance, Fire-Retardant TPU in Automotive Applications

Enhancing the fire safety of thermoplastic polyurethane (TPU), a polymer prized throughout the automotive industry, without degrading its mechanical properties is a critical industrial challenge. While two-dimensional zirconium phosphate (ZrP) nanosheets offer promising flame-retardant capabilities, their intrinsic aggregation tendency severely compromises their effectiveness in polymer matrices. Herein, ZrP nanosheets were functionalized via the surface self-assembly of a bio-based nitrogen-phosphorus supramolecule derived from phytic acid (PA) and chitosan (CS), yielding the novel nanohybrid PC@ZrP. This nanohybrid's exceptional dispersion and interfacial compatibility within the TPU matrix enable a remarkable dual functionality. At 1 wt% loading, the TPU/PC@ZrP nanocomposite achieves a 42.6% enhancement in tensile strength alongside a 6.1% improvement in elongation at break. The material's fire safety is also substantially enhanced: a 3 wt% incorporation reduces the peak heat release rate and total heat release by 35.5% and 22.6%, respectively, while effectively suppressing smoke and toxic gas emissions. Mechanistic investigations revealed that this performance stems from synergistic flame-retardant actions in both the condensed and gas phases. This work provides a robust, eco-friendly strategy for creating multifunctional additives that bolster the fire safety and mechanical strength of polymer nanocomposites, paving the way for safer materials in demanding sectors like automotive manufacturing.