Development of superhydrophobic coatings for textile and glass surfaces

• Main Author: Jardim, Maria Raquel de Vasconcelos Barros
• Publication Date: 2018
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.13/2222
• topic: Superhydrophobicity; Hydrophobicity; SiO2-PDMS; Textiles; Glass; Contact angle; Superhidrofobicidade; Hidrofobicidade; Têxteis; Vidros; Ângulos de contacto; Nanochemistry and Nanomaterials; .; Faculdade de Ciências Exatas e da Engenharia

Superhydrophobic surfaces have been widely explored by the scientific community and commercial market due to their remarkable properties as these surfaces are expected to repel water and show self-cleaning properties. These surfaces induce the beading of water drops, repelling them and dragging the accumulated dirt on the surface with them. This kind of surfaces has a wide range of applications. The present study is the result of a partnership between a private company, Extermínio, and the R&D centre, CQM (a National Research Laboratory). The goal of this partnership was the development of a superhydrophobic coating that could be applied to already existing surfaces, namely textiles and commercial glass, in order to turn them into superhydrophobic surfaces with the aim of making them easier to clean and increasing their durability, consequently decreasing the chemical products consumption used in those processes. For textiles, the selected samples were table linen, namely 100% cotton samples, both white and coloured and 50%/50% polyester/cotton coloured samples, and for commercial glass samples, flat glass was chosen. Different variables were considered when developing the coating solutions: pre-treated (chemically etched) and non-treated surfaces; different formulations but all silica-based (SiO2 10nm, SiO2 20nm and SiO2-PDMS); diverse solvents system; different concentrations; coating methods (dip coating and spray coating); number of coating layers; durability of the coatings (1hour, 24hours and 2 months) and contact angle measurements (24hours and 2 months). The different variables tested showed distinct results on both type of samples, but regarding the nanoparticles used, the SiO2-PDMS nanoparticles were the ones that revealed the best results. Lasting hydrophobic results were achieved for both type of samples (θ≥126°) which is an indicator that these coatings will ease the cleaning process and increase the durability the surfaces. No superhydrophobicity was attained (θ=180°), and therefore no self-cleaning property is expected from these coatings. The accomplished results are promising. More tests should be performed to understand the relationsip between the surface and the applied coatings. The first part of this dissertation is the presentation of the project framework and motivation that lead to its development as well as the intended goals. The work methodology and its structure are also briefly explained. The second part is dedicated to the theoretical introduction, in order to facilitate the concepts perception of this subject, starting with the historical perspective of superhydrophobic surfaces and its applications, as well as theoretical concepts as wettability and contact angle, surface roughness, contact angle hysteresis and measurements, as well as the creation of superhydrophobic surfaces. On the third part, the materials and methods applied to the development of the laboratory activities are described. The forth part is dedicated to explaining the choices of approach and also the presentation of the obtained results and its interpretation. Lastly, the fifth part is about the conclusions of the present work, as well as the learning’s and main difficulties found and some suggestion about future work that could be done to follow up the study carried out in this essay.