Superhydrophobic surfaces with silane-treated diatomaceous earth/resin systems
In a study, superhydrophobic coatings were prepared using fluorosilane-treated diatomaceous earth (DE) with either polyurethane or epoxy binders.
The surface wettability and morphology of the films were analysed using contact angle measurements and scanning electron microscopy (SEM), respectively. The water contact angles were studied as a function of the fluorocarbon fraction on DE and the particle loadings of treated DE in the coating.
Contact angles exceed 150° for coatings
The contact angles exceeded 150° for coatings with at least 0.02 fluorocarbon fraction (mass of fluorosilane/mass of particle) on the DE and with 0.2 particle loadings (mass of treated particles/mass of coating). The water contact angles of the surfaces were dependent on the nature of the binder below 0.2 particle loadings of the superhydrophobic DE particles, but were independent of the binder type after attaining superhydrophobicity.
Treatment with fluorosilanes restricts pores in DE
The results were consistent with the superhydrophobicity resulting from the migration of the superhydrophobic DE moving to and covering the surfaces completely. It was also shown that the treatment with fluorosilanes restricted the pores in DE and reduces the specific surface area of the material. However, these changes had effectively no effect on the superhydrophobicity of the coatings. The results of this work clearly identify some important considerations relative to producing superhydrophobic coatings from inexpensive diatomaceous earth.
The study is published in: Journal of Applied Polymer Science 2016, 133, 44072.
