Coatings and Metal-Bulk Interphases

Xa and Xe were determined for both systems (initially DGEBA-lPDA and DGEBA-DETA were mixed in the stoichiometric ratio (o/e=l), then they were applied to the metal surface and state 3 had room temperature before the curing cycle was started) and photographed (e.g., see Fig. 7.5) Xa for DETA and Xe for IPDA were quite constant and equal to 1, whatever the coating thickness. In addition, as observed by p-lR spectroscopy (e.g., see Fig. 7.4), Xa decreased near the metallic surface for the IPDA, while Xe decreased near the metallic surface for the DETA system. The only difference between the two systems was the crystallization of organometallic complexes for the IPDA system, whereas DETA complexes never crystallized. Whatever the amine was (either IPDA or DETA), 

DETA systems vitrify at room temperature in less than an hour, contrary to DGEBA-IPDA systems, which vitrify at 60°C. When we cured the DGEBA-DETA systems (after 3 h at room temperature), they were already vitrified, preventing any etherification reaction. 

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