Estudo de modificações superficiais para efeitos hidrofóbicos e hidrofílicos: uma abordagem para o desenvolvimento de superfícies autolimpantes

Abstract

The self-cleaning properties of surfaces are of high technological interest due to their ability to remove contaminant particles through the action of water. This phenomenon occurs through two distinct mechanisms: on superhydrophobic surfaces, the reduced wettability causes water droplets to roll, dragging away contaminants, which adhere with greater affinity to the water droplet than to the substrate. In contrast, a superhydrophilic surface also exhibits self-cleaning properties due to its high wettability: the water-surface interaction is so intense that it forms a continuous aqueous film, preventing adhesion and facilitating removal. Superhydrophobicity is typically achieved on surfaces that combine high roughness with low surface energy. Superhydrophilicity is achieved on high surface energy substrates, where an increase in roughness expands the contact area and enhances the effect. In this context, the present work investigates the modification of the wettability of aluminum and glass substrates through three experimental approaches: surface treatment of aluminum with silane, hydrophilic coating of glass with TiO₂, and with carnauba wax. The characterization of the surfaces was performed by means of contact angle measurements (goniometry) and scanning electron microscopy (SEM). The results showed a notable increase in the hydrophobicity of the silane-treated aluminum, which reached an average contact angle of 119°, compared to 61.34° for the untreated substrate in a sample obtained from an aluminum test specimen. On the commercial aluminum sheet, the treatment increased the contact angle from 32.02° to 57.71°, indicating a reduction in wettability. The glass coated with TiO₂ showed a slight increase in hydrophilicity, with the average angle reducing from 26.86° to 22.82°. Finally, the glass coated with carnauba wax had its average contact angle increased to 42.40°, indicating a reduction in surface wettability.