Enhanced fireproof performance of construction coatings by adding hexagonal boron nitride nanosheets

Hexagonal boron nitride (h-BN), commonly called "white graphene ", has received considerable attention thanks to its unique properties such as superior mechanical stability, high thermal conductivity, and exceptional chemical durability. Significant prior works have been dedicated for functionalizing the h-BN nanosheets for improving their optical, electrochemical, and biochemical properties. However, the application of h-BN sheets for the fire retardancy and thermal management of construction coatings has yet to be explored. In this work, we have investigated the thermal resistance and fire retardancy of the composite thin films composed of functionalized h-BN nanosheets deposited on stainless steel foils and fabrics. An efficient three-dimensional ball milling method is employed to synthesize the h-BN nanosheets with oxygen functionalities. We have shown that the h-BN-nanosheet-filled conformal coatings (including gypsum and sodium metasilicate) significantly enhance the fire retardancy of construction buildings. Uniform and homogeneous dispersity of the functionalized h-BN nanoparticles within the construction coatings has been verified by the scanning electron microscopy. Thermogravimetric analysis confirmed that the thermal resistance of the h-BN-filled coating is significantly enhanced with ultra-high thermal resistivity at 700 C. Indeed, the addition of h-BN nanosheets improves the thermal shielding as well as the fire retardancy of the construction coatings, while serving as an efficient thermal insulating barrier. The robust design of h-BN-filled coatings demonstrated in this work paves the way for preparing green (i.e., environmentally friendly) construction materials.