Insight into the chemical adhesive- surface interaction in epoxy-aluminium joints

 
The mechanical and chemical properties of thermoset adhesives cured in the presences of adherents may discern from their bulk properties [1,2]. Investigating the local chemical properties of so called "buried interphases" inside adhesive joints has been an everlasting challenge. In this paper, a novel experimental approach to gain insight into the chemical adhesive-surface interaction in epoxy-aluminum joints will be discussed. Microtome slices of epoxy polymer in proximity of the adherent surface were prepared with a rotary microtome (MICROTEC, CUT 4050) equipped with a tungsten carbide knife. Slices obtained from the center area inside the adhesively bonded joint were compared to those adjacent to the adherent surface by FT-IR-microscopy (HYPERION, Bruker) in transmission. Integration methods of the OPUS software-package (Bruker) were used to evaluate characteristic peaks in the relevant MIR spectral range. A pronounced shift of the Ether-Hydroxy-ratio in the polymer interphase near the surface of the aluminum adherents indicates that chemical properties are different from those of the bulk region.