Investigation of chemical interactions at the steel/polymer interface by FT-IR diffuse reflectance spectroscopy

Interactions between a steel surface and an ethylene-vinyl acetate copolymer grafted with maleic anhydride have been investigated by Fourier transform infrared (FT-IR) diffuse reflectance spectroscopy. The failed surfaces obtained after a mechanical separation of the polymer/steel assemblies have been analyzed. The results show that a new peak appears, characteristic of a carboxylate group. A model system composed of maleic anhydride deposited on iron prates has been studied in order to consider more specifically the reactivity of maleic anhydride. Peaks characteristic of metallic carboxylate complexes are present in the spectrum. A two-step mechanism has been proposed: the opening of the anhydride cycle by a hydrolysis reaction, leading to the formation of a carboxylic diacid, followed by the reaction of the acid with some oxidized metallic elements present at the metal surface. This study underlines the contribution of FT-IR reflectance techniques to the understanding of the adhesion mechanisms.