Supramolecular-Wrapped α-Zirconium Phosphate Nanohybrid for Fire Safety and Reduced Toxic Emissions of Thermoplastic Polyurethane

In the current study, a facile approach is introduced to enhance the flame retardancy of thermoplastic polyurethane (TPU) using a supramolecular-wrapped α-zirconium phosphate nanohybrid (CPP@ZrP). The CPP@ZrP nanohybrid was successfully synthesized by enveloping a phytic acid-doped polypyrrole shell and linking it to cobalt ions via the multivalent anions of phytic acid. The CPP@ZrP nanohybrid exhibited relatively uniform dispersion within the TPU matrix, leading to strong interface between TPU and CPP@ZrP and hence high mechanical and flame-retarding properties. The strength of TPU increased by 37% with 850% elongation at break at 5.0 wt % CPP@ZrP. Similarly, adding CPP@ZrP into TPU substantially reduced the peak heat release rate by 41.8%, peak smoke production rate by 25.8%, and total CO production by 32.9%. The average effective heat of combustion from the TPU/CPP@ZrP composite was reduced by 25% which confirms the reduction in flammable volatile substances. The experimental measurements and morphology of char residuals reveal that the CPP@ZrP nanohybrid reduces the flame retardancy of TPU in the gas and condensed phases via reacting with the flammable volatiles and preventing heat transfer to the flames. The study introduces a facile approach to designing a metallic-organic–inorganic hybrid flame retardant, CPP@ZrP, with high efficacy in reducing fire risks and mitigating smoke toxicity in polymers.