Particle morphology dependent superhydrophobicity in treated diatomaceous earth/polystyrene coatings

Abstract

Superhydrophobic surfaces have been prepared from three different types of diatomaceous earth (DE) particles treated with 3-(heptafluoroisopropoxy)propyltrimethoxysilane (HFIP-TMS) and low molecular mass polystyrene. The untreated particles, consisting of CelTix DE (disk shape), DiaFil DE (rod shape) and EcoFlat DE (irregular), were studied using particle size analysis, bulk density, pore volume and surface area analysis (via Brunauer–Emmett–Teller, BET, methods). The treated particles were characterized with thermogravimetric analysis (TGA), contact angles, scanning electron microscopy, profilometry, and FTIR spectroscopy. The minimum amount of silane coupling agent on the DE surfaces required to obtain superhydrophobicity of the particles was determined and found to be dependent on the particle morphology. In the coatings made from different particles with 2.4wt% HFIP-TMS, the minimum amounts of treated particles (loadings) for superhydrophobicity was determined with the less dense CelTix DE requiring about 30wt%, DiaFil DE requiring about 40wt%, and EcoFlat DE each requiring about 60wt% loading of treated particles.