Two-dimensional MXene-anchored P, N copolymer/MoS2 nanosheets with hierarchical nanostructures for improved flame protection of waterborne epoxy coatings

Herein, bio-based dopamine (DA) and phosphorus-rich hexachlorocyclotriphosphine (HCCP) were firstly assembled onto the MXene surface (MXene/DHP) via copolymerization. Notably, the formation of the DHP copolymer introduced a large amount of P and N flame-retardant elements, while the abundant amino/hydroxyl groups in its structure provided active sites for further surface modification. Subsequently, small-sized molybdenum disulfide (MoS 2 ) nanosheets were uniformly anchored onto the MXene/DHP surface, forming a composite flame retardant with a hierarchical nanostructure (MXene/DHP@MoS 2 ). The MXene/DHP@MoS 2 enhanced EP composite coating achieved the lowest back temperature (167.7 ± 3.3 ℃) and the highest expansion height (24.8 ± 0.99 mm), directly indicating its superior thermal insulation capability due to the excellent thermal insulation properties of the two-dimensional structures of MXene and MoS 2 . The MXene/DHP@MoS 2 /EP composite coating displayed the lowest smoke density rating (42.2 ± 1.32 %) while retaining the highest residual carbon content (29.9 %). This is attributed to that the abundant P and N groups in MXene/DHP@MoS 2 , along with multiple metal ions, catalyzed the conversion of more pyrolysis intermediates into char at high temperature. Additionally, the MXene/DHP@MoS 2 /EP composite exhibited the most complete and dense residual carbon after calcination, with titanium dioxide and molybdenum trioxide uniformly embedded in the carbon layer framework, significantly enhancing its thermal insulation performance. Overall, this hierarchically structured composite flame retardant significantly improved the flame protection capability of water-based epoxy intumescent coatings, further driving the rapid development of fire-resistant coatings.