FUNDAMENTAL-STUDIES OF EPOXY-RESINS FOR CAN AND COIL COATINGS .3. EFFECT OF BISPHENOL STRUCTURE ON RESIN AND COATING FLEXIBILITY

Many workers have reported improvements in coating flexibility by blending and grafting flexibilizers with Bisphenol A based epoxy coatings or by using aliphatic epoxies. These techniques are often limited by the rigidity of the Bisphenol A unit or by loss of other desirable properties. Systematic variation in the structure of the groups bridging the phenol units of diphenols is correlated with flexibility of the corresponding epoxy resins and ultimately with coating performance of the cured resins. This technique, combined with optimum curing conditions, can give coatings as flexible as aliphatic epoxies while retaining the adhesion, chemical resistance, and reactivity characteristic of Bisphenol A based epoxies.