An operable platform towards functionalization of chemically inert boron nitride nanosheets for flame retardancy and toxic gas suppression of thermoplastic polyurethane

Abstract The inherent chemical inertness presents a huge challenge for the functionalization of hexagonal boron nitride (h-BN), thus limiting its potential in flame retardant and toxic gas suppression of thermoplasticity polyurethane (TPU). Here, with the assistance of Lewis acid-base interactions, an operable platform formed by SiO2 coating is constructed onto the surface of h-BN nanosheets, offering an opportunity for introducing phytic acid (PA). The resultant h-BN nanohybrids present an enhancement effect for flame retardancy of thermoplastic polyurethane (TPU), confirmed by obvious reductions in peak value of heat release rate (−23.5%) and total heat release (−22.1%). Meanwhile, the smoke product rate and total smoke release of TPU composite containing 2.0 wt% h-BN nanohybrids are decreased by 29.2% and 8.6%, respectively. Through CO2 detector and AtmosFIR, specially, it is found that the toxic gases (CO, CH4, C2H6, TOC) are turned into CO2. Through a series of analytic methods, it was found that the introduced PA suffered from a pre-gradation process to release P-containing compounds, reacting with TPU matrix to produce protective char. In addition, the presence of SiO2 was also contributed to improve the robustness of char residue. In view of high temperature condition, the catalysis effect of h-BN is responsible for the conversion of toxic gases. Therefore, the enhanced fire safety of TPU was attributed to the cooperation mechanism of h-BN, SiO2, and PA. Such a functionalization approach provides a novel route to overcome the chemical inertness of h-BN, thus promoting its application in fire safety fields of polymer materials.