Glass strengthening by silica particle reinforced organic-inorganic coatings

The influence of a hybrid organic-inorganic coating reinforced with nano-sized silica particles on the strength of window glass was investigated using ball-on-ring (BOR) and ring-on-ring (ROR) tests, focusing on the effect of coating curing conditions and coating layer thickness. Strengths obtained for uncoated glass using the BOR and ROR tests are about 425 and 135 MPa, respectively. Results for coated glass show a similar to 55% strengthening for coating cured at 300 degrees C. Strength of coated glass increases with increasing coating thickness. On the basis of the coated glass strengthening optimum obtained, and FT-IR and NMR analyses performed on the coating, network forming of the inorganic groups by condensation is inferred to be completed at 300 degrees C. At higher temperature, oxidation of organic groups is expected to become important, leading to coating degradation. Dependence of strengthening on coating layer thickness is inferred to be caused by the formation of a compressive coating layer and by prevention of water diffusion to the crack tips. (C) 1998 Elsevier Science B.V. All rights reserved.