Self-cleaning properties and free surface energy of ethylene vinyl acetate (EVA) nanocomposite coatings reinforced with silica nanoparticles

The preparation of coatings involving the least material components and fabrication route is one of the today’s challenges in the development of hydrophobic nanocomposite films. This study aims at the fabrication of a hydrophobic polymer nanocomposite coating and the evaluation of the interplays amongst hydrophobicity, microstructure, fillers loading and free surface energy of the coatings. To achieve this, hexamethyldisilazane functionalized nano-silica as the filler and ethylene vinyl acetate (EVA) as the matrix were used. Toluene was used as the solvent. The concentration of 3% was employed as the optimized solvent ratio to create polymer film. The loadings of 10,20 and 30 wt% of nanomaterials were added into the solvent followed by a spray technique due to its single step approach. The analyses showed the coating filled with 30 wt% of nano-silica resulted in a porous interconnected structure, in good agreement with the Cassie-Baxter surface energy model. The 30 wt% nano-silica nanocomposite coatings resulted in a static water angle of ~121 ͦθ exhibiting a 34% increase with respect to that in the case of pure EVA and a sliding angle of 8 ͦθ with 90% reduction compared to the 10 wt% filled coatings due to the high surface roughness. Three surface energy models of Fowkes, Owens-Wendt and Van Oss were utilized were employed through which, unlike from the Van Oss model, the Fowkes and Owens-Wendt models exhibited that with the addition of fillers, the polar component of the free surface energy decreases confirming the increase in the estimated water angle contact.