Preparation and Properties of Modified Lignin/Triphenol Epoxy Composite Coatings for Superhydrophobicity and Corrosion Protection

Coatings are widely used in all aspects of life due to their easy and efficient functional properties. In today's pursuit of green living, people are increasingly looking for green, biosafe materials, so there is a trend to develop simple and economical methods of coating materials using natural polymers. Lignin, as a natural renewable aromatic polymer, has a unique chemical structure that is ideal for the preparation of UV-resistant and superhydrophobic coatings. In this study, a triphenol epoxy resin (PTEP) was synthesized and prepared using vanillin and guaiacol and then using octadecyltrichlorosilane to chemically modify the lignin to prepare modified lignin (OSL) with superhydrophobic properties. Finally, lignin-based superhydrophobic functional coatings (PTEP-OSL and PTEP-OSL/ZnO) were prepared using superhydrophobic modified lignin, PTEP, and nano-ZnO particles. Both the PTEP-OSL coating and PTEP-OSL/ZnO coating have good superhydrophobic properties, and the maximum contact angles can reach 160° and 159°. The superhydrophobic properties of lignin-based coatings are mainly attributed to the high surface roughness they construct and the low surface energy provided by the modified lignin. And compared with the PTEP-OSL coating, the PTEP-OSL/ZnO coating doped with nano-ZnO particles has a smoother surface and good anticorrosion performance. Electrochemical results show that the PTEP-OSL/ZnO coating has a higher impedance (Z = 5.56 × 107 Ω cm2) and higher phase angle value (θ = 80.24°). In addition, both PTEP-OSL and PTEP-OSL/ZnO coatings exhibit good UV shielding properties, which will further expand their practical applications. The lignin-based polymer coating has the advantages of being low-cost, green, and renewable, providing a simple route to value-added utilization of lignin.