A study of the adhesion between steel and an ethylene-acrylic acid-acrylate terpolymer

The interfacial interaction of an ethylene-acrylic acid-t-butyl acrylate (EAA) terpolymer with metals (mild steel) has been studied by spectroscopic techniques (XPS, AES, and IR), SEM, and mechanical testing. Using peel tests it was shown that the copolymerization of small quantities of acrylic acid and t-butyl acrylate with ethylene induces polymer/metal adhesion values rather higher than in plain polyethylene. The fracture surfaces were analyzed by XPS, AES, and SEM. It was shown that the fracture is cohesive and occurs within the polymer. Some specimens were aged under various conditions. In this case, the failure was located at the polymer/metal interface. In fact, SEM, XPS, and AES did not show the presence of polymer on the metal surface. Iron corrosion is then considered responsible for the failure of the joint. Since a thin layer of metal oxide covers the surface of mild steel, so to understand the polymer/ metal interfacial interaction better, IR spectroscopy was performed on polymer/metal oxide (goethite and hematite) composites. It was shown that the carboxyl groups of the polymer react with hydroxyl groups present at the metal surface. Adsorption isotherms of the polymer on iron oxides were also obtained, showing remarkable EAA terpolymer chemisorption, while there was no evidence of bonding between iron oxides and plain polyethylene.