Design of antifouling and fire-resistant epoxy composite coatings via rosin–TiO2 hybrid particles and hydrophobic silanes

Biofouling poses a critical challenge with significant economic consequences, particularly in the naval industry, where it can increase fuel consumption by up to 40 % due to impaired hydrodynamics. With growing environmental regulations limiting the use of toxic biocides and the increasing demand for high-performing nextgeneration materials, effective multifunctional protective coatings have never been more desirable. Herein, we present a sustainable solution based on antifouling epoxy-based coatings incorporating rosin-modified hybrid TiO₂ particles, synthesized via the sol-gel method and functionalized in situ with hydrophobic alkylsilanes. Our results demonstrate a robust antibacterial and antifungal effect, driven by the formation of charge transfer complexes between rosin (i.e., a biowaste derived from the secretion of pines) and Ti⁴⁺, which generate reactive oxygen species on the coatings’ surface, effectively inhibiting microbial colonization. The addition of alkylsilanes enhances the antifouling performance by promoting the migration of the hybrid fillers to the surface, conferring superior hydrophobicity and hindering fungal adhesion. Crucially, the synergistic presence of silanes and TiO₂ also delivers a remarkable 38 % reduction in the peak of the heat release rate, boosting fire safety without compromising coating integrity. This work highlights an intriguing waste-to-wealth biocide-free strategy for engineering next-generation flame retardant, antimicrobial, and antifouling coatings, offering a scalable and environmentally conscious alternative for a wide range of industrial applications.