Enhanced anti-biofouling ability of polyurethane anti-cavitation coating with ZIF-8: A comparative study of various sizes of ZIF-8 on coating

Biofouling and cavitation erosion are the key important factors causing the degradation and fatigue failure of metal materials in seawater. Herein, a series of polyurethane (PU) /ZIF-8 (PHZ) composite coatings were successfully synthesized with different sizes of ZIF-8 nanoparticles (NPs) for antifouling property combined with cavitation erosion resistance. The morphology and structure of the PHZ composite coatings were characterized by XRD, ATR-FTIR, SEM and AFM. The static water contact angle, dynamic mechanical analysis and thermo gravimetric tests further confirmed that the ZIF-8 NPs could improve the hydrophobic, mechanical and thermal properties of the PU coatings. Importantly, the effect of the ZIF-8 NPs with different sizes on the performance of the PHZ coatings was also investigated. The PHZ1 coating with the ZIF-8 NPs (similar to 50 nm) displayed the highest static water contact angle (1051, the largest tensile strength (6.78 MPa) and the best thermal stability among these PHZ coatings. The antifouling properties of the PHZ coatings were also tested against marine diatom (Nitzschia closterium). Especially, the biofouling attachment rate of the PHZ1 coating was 0.51%, which was far less than that of pure PU coating (92%). Moreover, the mass loss of the PHZ1 coating was only 8.9 mg after cavitation test for 24 h. Notably, both antifouling and anti-cavitation properties of the PHZ coatings were inversely proportional to the particle size of the ZIF-8 NPs. The present study offers a simple and green coating technology that combines the antifouling and anti-cavitation to promote the development of ZIF/PU nanocomposite systems for practical applications.