16.10 Glass and Ceramics

Glass and ceramic substrates are generally high surface energy materials, and most adhesives wet them readily. One problem in bonding optically clear glass is to select an adhesive that is optically clear and does not change the optical characteristics of the glass. Another problem is that shrinkage of the adhesive or differences in thermal expansion coefficients could provide high internal stresses that cause catastrophic failure of the brittle glass substrate.

Adhesives used for glass substrates are generally transparent, heat setting resins that are water- and UV-resistant to meet the requirement of outdoor applications. They are usually flexibilized systems in order not to place stress on the glass substrate either after cure or during thermal cycling. These adhesives include polyvinyl butyl phenolic butyral, phenolic nitrile, neoprene, polysulfide, silicone, vinyl acetate, and flexible epoxy adhesives. Polyvinyl butyral adhesives are commonly used to manufacture safety glass. Commercial adhesives normally used to bond glasses are described in Table 16.24. Optical adhesives used for bonding glass lenses are usually styrene modified polyesters and styrene monomer-based adhesives. Epoxies are also beginning to be used in this application.