Modification of raw lacquer sap with styrene for improving its film properties

Lacquer sap is a precious natural emulsion collected from lac tree, mainly used as a coating. In order to improve its performance and reduce its usage cost, styrene was mixed into raw lacquer sap for modification. Under an oxygen atmosphere, the copolymerization of styrene and urushiol was achieved through the catalysis of laccase contained in the raw lacquer sap. The copolymerization process was characterized by GPC and NMR. To maintain the fluidity of the copolymerized lacquer, styrene couldn't be completely polymerized. Excessive reaction time could lead to explosive polymerization. Thus, controlling reaction time was particularly important. The copolymerized lacquer had a shorter drying time than the raw lacquer sap. The results from NMR, FT-IR, pyrolysis GC–MS and UV–Vis spectra showed that styrene had successfully polymerized into the dry lacquer film. Due to the introduction of styrene, the color of the lacquer film changed from dark brown to light yellow, and its pencil hardness and flexibility were improved, reaching 5H and 2 mm, respectively, while maintaining its excellent resistance to organic solvents. In addition, the thermal stability of the lacquer film was improved as well.