Synergistically engineered multifunctional composite coating for recombined bamboo with optimized flame retardancy, water resistance and thermal insulation performance

Expanding the application and enhancing the performance of recombined bamboo (RB) materials are crucial for their high-value utilization. In this study, a novel composite coating (FPX) was developed by combining commercial fluorocarbon (FC) with a self-synthesized flame-retardant copolymer (PolyX, X = 1,2,3). The optimized coating, FP3 (1:3) (FC to Poly3 mass ratio of 1:3) exhibited excellent adhesion strength (819 psi), high film hardness (4 H), and enhanced hydrophobicity (moisture content of 13.2 %). When applied to RB, the FP3 coating significantly improved flame retardancy, achieving a Limiting Oxygen Index (LOI) of 31.1 % (a 5.8 vol% increase), and enhancing thermal insulation by delaying heating penetration (38.6 % improvement). Cone calorimetry results for the FP3-treated RB showed a 40.53 % reduction in peak heat release rate (PHRR), a 15.8 % decrease in total heat release (THR), and a 39.7 % reduction in total smoke production (TSP), accompanied by a 13 % increase in char residue. These improvements are attributed to the synergistic effects of Poly3 and FC, which collectively promote char formation and facilitate heat dissipation. Notably, the FC component is crucial for water resistance, while the sole use of FC coatings has indeed been observed to enhance the flammability of the material (LOI drops to 21.9 vol%). This work provides valuable insights for advancing the practical application of RB materials. • Commercial FC and self-synthesized PolyX are combined for multi performances. • The FP3 (1:3) coating achieves high adhesion of 819 psi & hardness of 4 H. • 5 layers of FP3 coating yield LOI of 31.1 % for superior flame retardancy. • FPX coating enhanced thermal insulation and maintains water resistance.