Effect of Nanoclays on Silica Network for Hydrophobic Coatings by Sol-Gel Method

摘要

Hydrophobic coatings were prepared through sol-gel polymerization technique using tetraethoxysilane (TEOS), octyltriethoxysilane (OTES) precursors and were coated on soda lime glass substrates. TEOS and OTES derived sol-gel moieties were chemically modified to design hydrophobic characteristic (Si-CH_3) surface. In this study, nanoclays of cloisite Na~+ and cloisite 15A were used as nanomaterials and they are endowed for higher thermal stability and hydrophobicity. Thermogravimetric Analysis (TGA) showed that after the addition of nanoclays, there is an increase in thermal stability from 179 ℃ to 240 ℃ with respect to silica network. The surface morphology of the silica nanocomposites was greatly influenced by the presence of nanoclays i.e., Small humps with uniform distribution of nanoclays were observed by using the Scanning Electron Microscope and Transmission Electron Microscopy. The hydrophobic behavior of the coatings was done by the contact angle measurements. The unmodified SiO_2 shows 31° contact angle while OTES with nanoclay could reach upto 121°. This is a simple and cost-effective method that could be used for multifunctional water repellent self-cleaning coatings on large areas.