Adhesion of epoxy resin to glass

A recently developed fracture mechanics test, which involves pressurization of an internal circular flaw, has been used to investigate the adhesion of an epoxy resin to Pyrex glass. Specimens were tested after various times of immersion in water at 80 °C, and the adhesive failure energy 6 determined as a function of crack velocity. The effects of adding silane coupling agents to the epoxy resin, and the influence of water pH, were particularly studied. The theory of generalized fracture mechanics is used to derive, from 6, an intrinsic adhesive failure energy d0 which is the energy required to break interatomic bonds across unit area of the interface. The decrease of 60 with time follows first-order reaction kinetics with a rate constant controlled by the type and concentration of coupling agent as well as by the pH of the aqueous environment. At zero immersion time the data all extrapolate to a ‘dry ’ 0o-value of 7.25 J m-2, some 24 times the expected van der Waals interaction energy. The results are interpreted in terms of the chemical hydrolysis of interfacial bonds.