Fabrication of liquid-repellent Coatings on Cellulosic and Glass Surfaces for Various Industrial Applications

Abstract

One of the foremost fascinating properties of materials in nature is the superhydrophobic and self-cleaning abilities of various insect wings and plant leaves. Superhydrophobic/Ultrahydrophobic surfaces exhibit high water repellence, and oleophobic surfaces resist the wetting of liquids which have low surface tension than water. The present research work focuses on surface modification of numerous types of substrates like cellulose-based materials (e.g., filter paper, cotton fabric) and glass substrates by creating superhydrophobic/superoleophobic and superliquiphobic coatings for the different types of applications such as self-cleaning, oil-water separation, biodegradation, stain-resistance, anti-bio adhesion, and transparency. Silica nanoparticles, polymers, and silanes are starting materials are used to produce superhydrophobic coatings by different synthesis techniques such as solution-casting, dip coating, immersion, etc. To optimize the synthesis process, the material variables such as the concentration of polymer, silanes, and nanoparticles are being varied. The process parameters, like immersion time and ambient temperature, are also being needed to vary.
In this thesis, the superhydrophobic coating was developed on the filter paper surface by using polymethyl methacrylate-co-ethyl acrylate polymer (PMMA) /silica nanoparticles (SiO2) by employing the solution-casting technique. The superhydrophobic filter paper was developed by the solution-casting method using hexadecyltrimethoxysilane (HDTMS)/ SiO2 nanoparticles. The superhydrophobic and superliquiphobic cotton fabric was fabricated with Carnauba wax (C.wax)/HDTMS/SiO2 nanoparticles composite. Superhydrophobic/superoleophobic coating on filter paper surface and superhydrophobic coating on glass surface were fabricated using sol-gel of PMMA, 1H, 1H, 2H, 2H, perfluorooctyltrichlorosilane (PFOTS), and SiO2 nanoparticles by employing the dip-coating technique. The prepared superoleophobic/superliquiphobic surfaces were able to repel liquids with surface energy as low as 27 mN/m.
Different structural characterizations viz., the wettability, surface morphology, surface roughness measurement, functionalization of the materials were evaluated. For industrial and practical applications, superhydrophobic surfaces should last under extreme surroundings. So, the stability and durability of these surfaces were widely and systematically inspected under a sequence of extremely harsh conditions. The coatings were assessed at harsh conditions like annealing at high temperatures (40 - 400 °C), irradiation by UV light, and pH resistance at different alkali and acidic conditions (pH 2 - 13), and mechanical durability by performing water-jet, abrasion, sand abrasion, adhesion, and washing (ultra-sonication) tests.
The contact angles were measured, and it has shown more than 170 ° ± 1.5° on all substrates of filter paper, cotton fabric, and glass surfaces. Additionally, the coated samples exhibit excellent self-cleaning, > 96% separation efficiency was studied of oil-water mixtures and emulsion separations in all prepared filter paper samples and cotton fabric. All the filter papers, viz., uncoated, coated, and tested for the separation process, were shown biodegradation. The coated fabrics were shown stain-resistance, anti-bio adhesion (microbial activity) properties. 93% of the transparency was achieved on the coated glass surface. All the results indicate that such types of coatings could also be used for self-cleaning, oil-water separations, stain-resistance, anti-bio adhesion, and transparent coatings at the industrial level applications.