Emulsification and coating performance of sustainable waterborne lacquer based on cooperative effect of cashew-derived surfactant and SDS

A biomass-derived surfactant system was developed from cardanol, enabling green and efficient waterborne modification of raw lacquer. • The optimal modification process achieved stable W/O → O/W phase inversion, realizing sprayable and water-dilutable lacquer. • The waterborne raw lacquer film showed a comprehensive improvement vs. RL, with adhesion and drying time significantly optimized. • Aqueous environment enhanced laccase activity and promoted C C bond-dominated cross-linking, forming a denser film network. • This strategy solves RL's poor processability, advancing the industrialization of high-performance sustainable coatings. Natural raw lacquer (RL), a high-performance natural coating, is severely limited in industrial application due to its high viscosity and stringent construction conditions. In this study, a green and efficient waterborne modification of RL was realized by compounding sodium pentadecylbenzenesulfonate (SPBS), synthesized from cardanol, with sodium dodecysulfonate (SDS) as composite surfactant, combined with ultrasonic dispersion. Single-factor and orthogonal experiments were optimized the preparation process, and the effects of modification parameters on waterborne raw lacquer (WRL) emulsion and film properties were characterized from Zeta potential analyze, FT-IR, LF-NMR and XPS. The optimal condition was 5.0% composite surfactant based on RL mass (mass ratio of SDS:SPBS = 25:75), 50.0% deionized water and 9 min ultrasonic treatment (120 W, 40 kHz). Under these conditions, WRL emulsion achieved a stable oil in water (O/W) phase with low viscosity and improved seven-day storage stability, enabling water dilution and spray coating. Compared with RL, WRL film presented a 56.2% improvement in comprehensive performance, with drying time shortened to 165 min, adhesion increased to 1.62 MPa, higher than three times of RL, and pencil hardness up to 4H, while maintaining a high wear resistance and thermal stability. LF-NMR confirmed WRL's higher cross-linking rate and density. The aqueous environment may facilitate laccase activity and ultrasonic treatment reduced particle size, jointly accelerating urushiol cross-linking and C C bond formation for a denser film network. This work solves RL's poor water dispersibility and construction difficulty, providing an experimental and theoretical support for high-performance eco-friendly WRL coatings.