Enhancement of flame-retardant performance of thermoplastic polyurethane with the incorporation of aluminum hypophosphite and iron-graphene

This article mainly studies synergistic flame retardant effects and smoke suppression properties of iron-graphene (IG) and aluminum hypophosphite (AHP) on thermoplastic polyurethane (TPU), AHP used as main flame retardants and IG used as synergistic agents. A high concentration of TPU/IG masterbatch was prepared by solution-blending method, and then TPU/AHP/IG composites were prepared by melt-blending method. Then, the flame retardant effects of all TPU composites were tested using limiting oxygen index (LOI), UL 94 test, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and thermogravimetric/fourier transform infrared spectroscopy (TG-IR). Remarkably, with 0.25 wt% content of IG and 9.75 wt% content of AHP, sample reached UL 94 V-0 rating, and the LOI value increased by 31.5 vol%, pHRR value decreased by 90% and pSPR value decreased by 72%, etc. SEM images show that char residues become more complete and present lamellar structure. TG-IR data reveal that the incorporation of AHP and IG promoted the release of H2O and CO2, meanwhile reduced harmful gases release.