IMPROVED ADHESION STRENGTH BETWEEN ALUMINUM AND ETHYLENE COPOLYMERS BY HYDRATION OF THE ALUMINUM SURFACE

By immersing aluminum in boiling water, a hydroxyl-covered pseudoboehmite layer is formed on the aluminum surface. The adhesion strength between aluminum foils, hydrated in boiling water for short times, and ethylene copolymers, with vinyl acetate, n -butyl acrylate, and acrylic acid, was examined. The laminates were obtained by pressing with 1.2 MPa at 250-degrees-C and the peel strengths were measured by a T-peel test. By hydrating the aluminum foils, the adhesion strength was doubled for the ester copolymers, while a moderate effect was observed for the acrylic acid copolymer. To understand the adhesion mechanism, the chemical and topographic transformations were followed, using FTIR, SEM, TGA, and BET surface-area analysis. The adhesion mechanism was found to depend on many factors, such as mechanical effects and increased surface area, due to the porosity of the hydrated film formed. The improved adhesion after hydration of the aluminum can also be explained by the fact that new, stronger interactions are formed. A carboxylate formation of carboxylic acid groups and a catalyzed hydrolysis reaction of the ester bond at the interface is also proposed. These reactions change the functionality on the polymer surface and the formation of stronger bonds between the materials is possible.