A Review on Film-Forming Mechanisms, Modification Strategies, and Applications of Natural Lacquer

Originating in the East, lacquer is a natural polymeric material noted for its superior film-forming properties, corrosion resistance, and mechanical robustness. The decorative techniques associated with it have been inscribed on China’s national intangible cultural heritage list. Propelled by recent advances in material modification and digital technologies, lacquer gradually become not only a traditional craft material, but also a contemporary artistic design language. Existing reviews on natural lacquer have primarily addressed the chemistry of urushiol and related phenolic lipids, traditional processing and curing mechanisms, allergenicity, and conventional applications in coatings and cultural heritage conservation. These works provide important background, but they tend to treat chemical structure, modification methods, performance evaluation, and manufacturing considerations separately, and none of them links this molecular and mechanistic basis to quantified coating performance or to the manufacturing choices that determine it. This review provides that missing link. Unlike previous accounts, we connect molecular structure and enzymatic curing behavior directly to four modification routes—chemical modification, organic composites, nanoparticle/organic–inorganic hybrid reinforcement and surface engineering—and compare them by formulation, substrate, film thickness, curing conditions, test method and quantitative result, rather than describing individual studies sequentially. By consolidating dispersed performance data into a single standardized comparison framework, this work makes cross-study comparison of lacquer coatings possible for the first time. In addition to summarizing mechanical, protective, and functional performance, the review discusses sustainability, regulatory and safety considerations, and prospective directions such as digital and automated manufacturing. The aim is to offer a coherent framework for selecting modification and processing strategies according to target performance and application context.