Adhesion mechanisms at amine-cured epoxy/aluminium interfaces

Because the structure and the chemical composition of the interface can have a large effect on the adhesion properties of polymeric materials to metallic surfaces, many investigations have concentrated on the study of the interphase region. However, the complexity of the materials often leads to the use of model compounds to mimic the interfacial reaction. We have presented a critical discussion of three different approaches which have been used to understand the adhesion mechanism at amine-cured epoxy/aluminium interfaces: i) fracture of "real world" joints; ii) deposition of model (amino-alcohol) molecules on "real world" substrates; i) deposition of model (amino-alcohol) molecules on clean, oxidised and hydroxylated Al (100) surfaces. We have shown that model compounds can adequately duplicate the interface chemistry observed in "real world" joints. However, a detailed understanding of the exact nature of the interactions and of the role of the different reactive sites can only be achieved through studies performed on a model surface under controlled ultrahigh vacuum conditions.