Characterization of hydrophobic surfaces by experimental study of static and dynamic contact angles

Abstract

The phenomenon of marine biofouling represents a significant challenge in the maritime sector, as it considerably affects ship operational efficiency by increasing hydrodynamic resistance, fuel consumption, and CO2 emissions. The growth of fouling depends on several phenomena, including water temperature, depth, physicochemical properties, etc. Conventional solutions, based on biocide-containing paints such as tributyltin, have been progressively phased out due to their high environmental impact, necessitating the development of more sustainable and effective alternatives. The need for alternative solutions has led to the design of innovative coatings capable of providing antifouling performance without compromising environmental sustainability. The approach adopted in this study is based on polymeric matrix coatings functionalized with nanofillers to modify surface properties and reduce biological adhesion. This type of paint not only definitely reduces fouling but also possesses hydrophobic properties that can further affect CO2 reduction by, for example, calculating the latter using the formula that defines the EEDI. In this work, an experimental evaluation of the degree of both static and dynamic hydrophobicity was carried out on epoxy matrix surfaces treated with different percentages of titania. The tests were conducted using a Photron FASTCAM Mini UX100 high-speed camera, calculating by images processing the advancing (θA) and receding (θR) angles and determining the contact angle hysteresis (Δθh). The results showed a significant increase in the contact angle for the treated samples, with values exceeding 120°, indicating high hydrophobicity. Dynamic analysis revealed that the functionalized coatings promote rapid retraction of the liquid film, reducing water retention on the surface and limiting marine organism adhesion. Additionally, the surface energy, calculated using the Baier diagram, confirmed that the developed formulations fall within the category of fouling-release materials, capable of preventing biological adhesion without releasing biocides. The combination of high hydrophobicity and dynamic behaviour suggests that these coatings could be a viable alternative to currently available solutions, with potential advantages in reducing biological accumulation and improving the hydrodynamic performance of vessels by decreasing the EEDI index.