Effect of Polymeric Coatings on Strength of Soda-Lime Glass

Abstract

The effectiveness of polymeric coatings (acrylic, epoxy, and silicone) in preventing stress corrosion was determined by measuring the loading rate sensitivity of bend strength for coated, abraded and acid-polished soda-lime glass. The coatings were found to limit the availability of water to the glass surface and, thereby, cause an increase in the strength of abraded glass. The coatings also significantly improved the mechanical abrasion resistance of the acid-polished glass. However, the coatings did not eliminate the stress corrosion reaction between water and the glass surface and, hence, did not affect the sensitivity of glass strength to loading rate. During our testing program, it became evident that significant friction can arise during the bending test due to the supports “digging” into the coatings. Therefore, the differential equations governing beam deflection in four-point bending were solved to include frictional forces between the test samples and the supports. The results of the bending analysis showed that frictional forces become significant at large deflections and can cause an increase in the observed strength.