Highly repellent surfaces are constantly being sought in a number of industrial sectors, where accumulation of unwanted material (ice, debris, insects etc…) can cause seriously detrimental effects on function. The chemistry and physics of such surfaces is relatively well-understood, yet their industrial adoption is still very limited, due to their poor durability. Emerging technologies for nanostructured coatings have significant potential for the development of advanced surfaces, where high repellency can be combined with mechanical robustness. However, lack of understanding of the wear mechanism in such coatings and lack of recognised test methodologies to enable comparison of various approaches hinders effective progress in advanced surfaces development. Furthermore, there is no comprehensive classification system that allows categorization of highly repellent surfaces.
New multi-variable analysis methodology for the evaluation of durability in highly repellent coatings was developed in this study. Key coating parameters were identified, including initial wettability, abrasive wear, adhesive wear and ability to retain repellency. Surface performance characteristics were presented in a form of spider diagrams and performance indices and were used to generate figure of merit (FoM). This novel methodology for evaluation of highly repellent surfaces indicates that different coating families can be compared and categorized. The data obtained from FoM supports the statement that there is an inverse relation between repellency and durability of hydrophobic surfaces, yet also reveals that some nanostructured coatings behave beyond this pattern. Addition of novel inorganic building blocks with controlled size and functionalities improves overall coating performance by linking mechanical robustness with desired wetting characteristics.
The progress in testing and classification criteria of repellent coatings enables further development of next generation of materials. This novel knowledge-based approach for highly repellent coatings validation has the potential to accelerate uptake. The findings open a promising new direction in materials development, where advanced coatings and surface treatments can be developed by design, reducing the number of development iterations, ultimately leading to reduced cost and development time.