Evaluation of β-diketone-containing Polymeric Coupling Agents for Enhancing the Adhesion of Epoxy to Aluminum

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Abstract
β-diketone-containing polymeric coupling agents (PCA) were evaluated as potential adhesion enhancers for an epoxy/aluminum bond system. Torsional shear joint measurements revealed that the β-diketone-containing PCA did not influence the joint strength and durability, positively or negatively, as compared with untreated controls. Grazing angle infrared spectroscopy revealed that despite reactivity of the β-diketone-containing monomer with aluminum substrates, no reactivity of the β-diketone was observed once the monomer was incorporated into the polymer. Deposition studies showed that the resulting PCA coating thickness following treatment and solvent rinsing was not a function of solvent solubility parameter, solution concentration, or immersion time. It was hypothesized that preferential physisorption of the phenyl and/or epoxy functionalities in the PCA inhibited reactivity of the β-diketone functionality.