A novel organic-inorganic composite flame-retardant coating with excellent compatibility provides superior flame retardancy and smoke suppression for wood

Abstract

Wood is a sustainable biomass material, valued for its renewability and environmental friendliness. The intrinsic flammability of wood can restrict its functional applications. The application of flame retardant coatings represents an efficient strategy to enhance the fire retardancy profiles of wood. However, currently used inorganic flame retardants with organic acrylic emulsion (AE) suffer from easy caking and reduced flame retardancy. A novel organic-inorganic CaAl-AA-LDH@AE composite flame retardant coating system based on wood was developed using environmentally friendly and highly thermally stable calcium-aluminium-type layered double hydroxide (CaAl-LDH) as the flame retardant. The successful synthesis of the organic-inorganic CaAl-AA-LDH composite flame retardant was confirmed by characterisation analytical techniques. The results of the surface roughness testing demonstrated that the average values of surface roughness (Ra) and irregularity height (Rz) for the organic-inorganic composite flame retardant paint exhibited notable reductions of 57.91 % and 54.72 %, respectively, compared with the unmodified flame retardant paint. The excellent compatibility of the organic-inorganic CaAl-AA-LDH in organic acrylic coatings markedly enhances the overall aesthetic and flame retardant properties of composite flame retardant coating. The heat release rate (HRR) of the organic-inorganic composite flame-retardant coating treated wood was reduced by 56.21 % and 20.78 %, the total smoke production (TSP) was decreased by 49.69 % and 20.25 %, and the residue mass increased by 64.13 % and 16.20 %, compared to unflame retarded wood and wood treated with unmodified flame retardant coating, respect tively. The organic-inorganic CaAl-AA-LDH@AE composite flame-retardant coating exhibits favourable, compatibility and flame-retardant properties, contributing significantly to the sustainable development and application of wood-based materials. • Sodium dodecyl sulphate was intercalated into the layers of Ca-Al hydrotalcite, resulting in a notable increase in the spacing between the layers. The organic macromolecule acrylic acid was successfully intercalated into the inorganic CaAl hydrotalcite layers by ion exchange method, resulting in the preparation of the organic-inorganic CaAl-AA-LDH new flame retardant. • The synergistic effect between CaAl-AA-LDH and organic acrylic emulsion significantly enhances the compatibility of the two materials. • CaAl-AA-LDH@AE demonstrates excellent flame retardant and smoke suppression effects.