Thermal-triggered insulating fireproof layers: A novel fire-extinguishing MXene composites coating

The use of intumescent flame-retardant (IFR) coatings is one of the most highly effective methods for polymeric materials to improve their fire safety. However, organic IFR coatings show "negative effect" in a large amount of heat and smoke release during the char-forming process. Developing nanocomposite coatings that can reduce their "negative effect" and simultaneously enhance the barrier effect of fireproof char layer is particularly desirable. Herein, a novel UV-curable IFR/MXene nanocomposite coating was developed by incorporation of surface-modified MXene nanosheets in the IFR coating system, and then constructed on the surface of rigid polyurethane (RPU) foam to fabricate coated RPU foams via spray-coating and UV-cured process. The IFR/MXene coated RPU foams show a fast self-extinguished behavior and a remarked decrease in heat and smoke production, indicating the great improvement of RPU fire safety in building. The fireproof layers combined with expanded char and MXene jammed networks generated rapidly during combustion can serve as physical shield to effectively delay the release of heat and volatile products, protecting the underlying substrate from further burning. Moreover, the mechanical properties and dispersion are enhanced due to the co-cross-linking networks between the IFR coating and MXene nanosheets. As a new member of the 2D nanomaterials, MXene nanosheets have potential to be a new choice for developing high-performance nanocomposite coating for polymers to reduce their risk of fire hazard.