Mechanical behavior of glass reinforced with SiO2 hybrid sol–gel coatings

Hybrid sols were prepared from tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and 3-(methacryloxypropyl) trimethoxysilane (γ-MPS) in an acid medium at different TEOS/MTES and TEOS/γ-MPS ratios. An organic monomer, 2-hydroxyethyl methacrylate (HEMA), was free-radical co-polymerized with γ-MPS, with 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. We report the preparation of coatings from different sols on amber beer bottles and soda-lime glass rods and slides by a dipping process. Various withdrawal rates and heat treatments (from 150 to 500°C) were used to prepare the coats in order to determine the best conditions as a function of composition. In all cases, transparent and crack-free coatings with good adhesion were obtained. Rods and slides of soda-lime glass were mechanically tested using four-point flexure and ring-on-ring tests. The results indicate that the TEOS/γ-MPS coated rods and slides treated at 150°C show the best behavior. The scale factor was increased by 26.5% and 22.8% in rods and slides, respectively. In the case of beer bottles, two different types of container were used: untreated and protected bottles with a hot-end SnO2 coating. The bottles were tested using the normal standards of hollow glass: scratch resistance, sliding angle, and internal pressure. Mechanical properties of the coated bottles were analyzed for possible industrial application. The internal pressure of TEOS/γ-MPS coatings is similar to standard values, while especially good scratch resistance was observed for TEOS/γ-MPS/HEMA/PEG coatings, more than 15 cycles at 294N.