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Interview: “Smart coatings go beyond surface protection”
Nanoparticles, smart polymers and fluoropolymer hybrids are redefining what a surface can do. Dr. Eugene Caldona, assistant professor at North Dakota State University’s Department of Coatings and Polymeric Materials, explains how advanced materials enhance corrosion protection, enable self-cleaning properties, and why the interface between filler and matrix is the key to coating performance. Interview by Vanessa Bauersachs
What role do nanotechnology and advanced materials play in the next generation of functional coatings?
Dr Eugene Caldona: Nanotechnology and advanced materials have transformed the next generation of functional coatings from conventionally being able to provide surface protection and aesthetic appearance to demonstrating “smart” behavior and multifunctionality. Inclusion of nanoparticles at very low loadings not only enhances the thermal, mechanical, and electrical aspects of coatings but also offers added functionalities, including but not limited to microbial resistance, self-cleaning property, switchable wettability, and fire retardancy. Nanoparticles that are functionalized or surface-treated provide improved interfacial bonding and can facilitate uniform stress distribution, preventing crack propagation within the coating matrix. Additionally, using polymers with smart moieties can further advance coatings to respond to external stimuli (i.e., pH, temperature, light, and electricity, among others), enabling a broad spectrum of applications. This is especially important when a coating must maintain its structural integrity while still providing the intended or required functionality.
Which functional mechanisms are currently most effective for enhancing corrosion protection?
Caldona: Optimised filler-matrix interactions are crucial because the protective performance of coatings depends on the interfacial characteristics and compatibility between these phases. Therefore, the use of surface-functionalized fillers offers higher coating reinforcement. The functional groups introduced to the filler surface promote strong interfacial bonding with the matrix, leading to minimal to no coating layer defects and increased diffusion path for water and other aggressive species.
The strength of the interfacial bond at the coating-substrate interface is another consideration, as that is the determining factor for adhesion. The protective and adhesive properties of a coating are intertwined because accumulation of water beneath the coating will result in adhesion loss, while a coating with poor substrate adhesion will easily allow water to reach the interface and promote underfilm corrosion.
How can fluoropolymer-based functional coatings combine corrosion resistance with additional properties?
Caldona: By using nanotechnology and hybrid formulations, fluoropolymers as the coating matrix can combine corrosion resistance with mechanical durability and high surface adhesion. Incorporating nanoparticles like silica, nanoclay, titanium dioxide, and graphene oxide enhances both the mechanical and thermal stability of fluoropolymer coatings, while introducing tortuousity in the coating layer that delays the diffusion of corrosive species.
Blending fluoropolymers with other polymers or employing a multilayer coating assembly (i.e., primers, topcoats, etc.) improves the surface adhesion while maintaining maximum corrosion protection. Chemically incorporating reactive groups into fluoropolymers will also lead to the formation of crosslinked networks (with other polymers) for optimised coating integrity.
