Rationally assembled sandwich structure of MXene-based phosphorous flame retardant at ultra-low loading nanosheets enabling fire-safe thermoplastic polyurethane

Rationally designing the surface structures of Two-dimensional-based flame retardants is a primary approach to address the issues of poor compatibility with polymers and low grafting of traditional organic flame retardants on their surfaces. Herein, a novel flame retardant (PB-MXene) with a sandwich structure was prepared by grafting organophosphorus (PB) onto the surface of Ti3C2TX, and then incorporated into thermoplastic polyurethane (TPU) to produce composites. The results demonstrate that this sandwich structure enhances the interactions between PB-MXene and TPU, leading to more uniform dispersion and improved mechanical properties compared to the simple blending of PB and Ti3C2TX. Further, the composites with the addition of just 0.5 wt% Ti3C2TX loaded with 7.5 wt% PB, a significant reduction of 72.6 % in peak heat release rate (PHRR) was achieved compared to TPU. Moreover, the vertical burning tests and limiting oxygen index reached V-0 rating and 32.2 %, respectively. Particularly, as compared to other literature, it vividly demonstrates the advantages of PB-MXene in reducing PHRR. In conclusion, the established flame retardancy mechanisms of PB-MXene encompass both condensed and gaseous phases, achieved by examining distinct compounding techniques for Ti3C2TX and PB. Hence, this work showcases an uncomplicated yet promising approach to formulating effective synergetic 2D-based flame retardants.