ABSTRACT
Bentadjine et al. [23] have explained the interphase formation for such systems. Because of the basic behavior of the curing agent (IPDA), the outer part of the oxide (and/or hydroxide) layer is dissolved when liquid monomer mixture is applied onto a metallic substrate leading to metallic ion diffusion within the liquid prepolymer coating. An organo-metallic complex is then formed between amine groups and metallic ions. When the concentration of the organo-metallic complex is higher than its solubility product, these complexes precipitate to form needle-shape crystals. Flowever, the unprecipitated part of organo-metallic complex forms a new network with the epoxy prepolymer (DGEBA) during the curing cycle. Then after curing, a new network is associated to the initial one. This new bi-phase material contains crystals which act as short fibers randomly dispersed in a polymer matrix inducing an increase of the Young modulus (5 GPa) and a decrease of the elongation. It
Figure 4. Equivalent Young’s modulus ( £ ) eq as a function of the coating thickness for chemically etched and anodized aluminium substrates.
