Analysis of water-repellent properties of coatings based on hydrophobized expanded perlite under mechanical abrasion

The object of research in the work is water-repellent surfaces using crushed perlite to form micro-crushing. The existing problem lies in the fact that the level of existing technology of superhydrophobic coatings at the moment is insufficient for wide practical application. The main limiting difficulties are the insufficient resistance of superhydrophobic properties to operational factors, including mechanical wear, the action of vaporous water, as well as the low scalability of classical ways of applying textures to protected substrates. In this work, it is shown that one of the effective ways to obtain scalable coatings with increased water repellency is to use hollow glassy particles, such as perlite, to create a surface microstructure that allows one to achieve a stable Cassie state for water droplets. In this case, the contact area of the surface with the liquid is minimized, since fragments of hollow particles, the orientation of which is close to normal, are used in the coatings. Of practical interest in the application of such structures is the study of their behavior during mechanical wear, in particular, under the action of particles, which is an important operational factor for outdoor coatings. It is shown that coatings based on crushed perlite during abrasive wear retain and at the initial stage of destruction increase water-repellent properties. Crushed perlite was hydrophobized by treatment with polymethylhydrosiloxane, which provided the values of the wetting angle of the powder material at the level of 145°, and the rolling angle of less than 10°. The surface energy of the acrylic-styrene matrix coatings was determined. It is shown that the surface geometry of such coatings is inhomogeneous. An extreme dependence of the contact angles of the surface on the amount of abrasive was determined. As a result, it is found that under the static action of water, the expected decrease in the contact angle of the surface occurs, but there is no complete loss of the Cassie state.