Elastic properties of epoxy system coatings on aluminum substrate

In the present work elastic properties of the epoxy system coatings deposited on aluminum-based alloy substrate were investigated using internal friction methods i.e. i) vibrating reed technique (frequency about 100 Hz) and ii) torsion pendulum (1 Hz). The apparent Young's modulus γ2E (γ — adhesion coefficient, E — Young's modulus of the coating) was determined for different state of substrate surface and curing temperatures. It was shown that γ2E correlates linearly with the bond shear strength obtained from tensile tests by applying Instron machine (destructive method). Moreover, the dependence γ2E versus curing temperature shows a maximum at 350 K. Isothermal measurements of mechanical loss tangent Q− 1(t) versus curing time show that the curing reaction of the epoxy material is observed as an asymmetric peak whose position shifts towards shorter times with increasing curing temperatures. Activation energy of the curing process determined from this shift is found to be Ea = (51 ± 3) kJ/mol.