Preparation and Performance Study of Ultrathin and Transparent Epoxy Resin Coating Flame‐Retardant Carbonized Wood

ABSTRACT In recent years, carbonized wood has shown promising application prospects due to its excellent anti‐corrosion properties. However, the application of carbonized wood is somewhat limited due to its flammability and hygroscopicity. To address the issues of flammability and hygroscopicity in carbonized wood, an ultrathin and transparent flame‐retardant carbonized wood (PPOA/EP/M‐C‐wood) has been developed. Specifically, the wood was vacuum impregnated in a mixture of phenylphosphonic acid (PPOA) and silica sol, then carbonized and coated with a flame‐retardant epoxy resin coating treated with PPOA. The thickness of this coating was only 0.3–0.5 mm. The PPOA/EP/M‐C‐wood passed UL‐94 V‐0 rating during vertical burning tests with the limiting oxygen index (LOI) of 31.7%, and the residual char reached 18.4 wt% at 600°C. Compared to pure wood, the bending strength of carbonized wood (C‐wood) was increased by 52.6% and the water absorption rate was reduced by 95.2%. Therefore, the prepared flame‐retardant PPOA‐EP coating possessed good water resistance, flame‐retardant efficiency and mechanical properties for carbonized wood (C‐wood) substrate. This method provides a feasible strategy for preparing high‐performance flame‐retardant coatings and flame‐retardant carbonized wood, and has good prospects in the application of carbonized wood with excellent comprehensive properties.