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

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 SiO 2 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 CO 2 detector and AtmosFIR, specially, it is found that the toxic gases (CO, CH 4 , C 2 H 6 , TOC) are turned into CO 2. 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 SiO 2 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, SiO 2 , 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. Image 1 • Chemical inertness of h-BN nanosheets was overcame. • Heat release of TPU was decreased by h-BN@SiO 2 @PA. • Toxic combustion gases were turned into CO 2. • The break strength of TPU was effectively enhanced. [ABSTRACT FROM AUTHOR]