Research Progress on Modification and Application of Raw Lacquer

Raw lacquer is a kind of natural polymer coating with excellent performance. The lacquer film formed after drying of pure natural raw lacquer has the advantages of hard quality, heat resistance and corrosion resistance. However, natural raw lacquer also has some disadvantages. For example, it must be dried at a specific temperature and humidity to form a film, difficult to spray, dark color, poor alkali resistance, easy to cause human skin allergy and so on. Due to urushiol is the main film-forming material in raw lacquer, its performance and drying film-forming process will directly affect the properties of the lacquer film. Taking advantage of the particularity of its structure, urushiol can be modified in its drying film-forming process, so as to speed up its drying film-forming process or obtain a modified lacquer film with excellent performance. Thus, the research on raw lacquer and its modification mainly focuses on the modification of urushiol, the main film-forming substance of the raw lacquer. This paper reviews the modification and combined methods of the natural urushiol by researchers in recent years, mainly including urushiol polymerization catalyzed by proton acid, urushiol polymerization initiated by UV irradiation, copolymerized with other polymer materials, reacted with metal compounds to form urushiol metal polymers, and formed composite coatings with multi-wall carbon nanotubes, graphene oxide, nano-TiO2 and so on. The modified lacquer has shown excellent performance in some aspects, such as the gloss and hardness of the lacquer film have been significantly improved, the heat resistance, acid and alkali resistance have been enhanced, the ageing resistance and solvent resistance have been improved, the impact strength and toughness have been enhanced, the curing time of the lacquer film has been greatly shortened and so on. Then the application fields and development trends of the modified raw lacquer are discussed, hoping to provide a theoretical basis for the further development and utilization of raw lacquer.