Preparation and evaluation of natural rosin-based zinc resins for marine antifouling

[Display omitted] •Natural rosin-based zinc resins are designed based on natural rosin and Zn(OH)2 by a facile one-pot method.•The hydrolysis rate and surface hydrophobicity of resins can be controlled by adjusting the content of Zn(OH)2.•Pure RZn-x resins without toxic antifouling agent can maintain their antifouling performance for more than 6 months in a real marine environment. Currently, it is highly desirable to develop a novel antifouling resin with a controllable hydrolysis rate and stable and effective antifouling performance for marine antifouling coatings. In our study, we prepared natural rosin-based zinc (RZn-x) resins by a relatively facile and green synthetic method from Zn(OH)2 and antimicrobial natural rosin, which is considered a toxicity-free raw material, thus ensuring the green and antimicrobial character of the material. In their optimal combination, the RZn-x coating surface exhibited ideal peeling behaviour upon immersion in seawater, which caused the WCA of the material surface to change from 55° before immersion to 135° after immersion for 60 days and enhanced the antifouling properties. Dynamic simulation experiments of these resins also demonstrated that the hydrolysis rate of this material immersed in dynamic seawater was related to the zinc content, and we could control the self-polishing ability of the resins by adjusting the content of Zn(OH)2 participating in the reaction. Moreover, hydrolysis led to a hydrophobic surface, which could prevent fouling organisms from adhering. Laboratory bioassays against BSA adsorption (immersed for 4 h: 1.986 μg/cm2), bacterial (over 95 % reduction) and marine algal adhesion (more than 60 % reduction) revealed outstanding anti-protein, bacteriostasis and anti-algal growth and adhesion properties compared to pure rosin and the control sample. The long-term antifouling capability in marine field tests indicated that the RZn-x resins maintained their antifouling activity for more than 6 months, especially RZn-50, which showed excellent antifouling performance.