Estimating the effect of fillers on the mechanical properties of epoxy glue coatings by microindentation

Abstract

Epoxy glue coatings based on the ED-20 epoxy-diane resin, filled with nanosized TiO 2 , SiO 2 , Al 2 O 3 and ZnO oxides and applied on an aluminum-magnesium alloy base, are studied by instrumented indentation. Hardness, reduced normal modulus of elasticity and creep are chosen as characterizing parameters. The obtained characteristics are compared with the corresponding values for unmodified glue. It is demonstrated that modification of epoxy glue increases the hardness and reduced the normal modulus of the coating if compared to unfilled glue; however, the degree of increase for each additive is different. In the range of the loading time from 1 to 40 s, at a load of 1 N, all the samples show viscous properties, which are expressed in decreased hardness and lower speed of load application. The magnitude of the reduced normal modulus does not manifest itself as a function of the loading rate. A further increase in the loading time has an insignificant effect on the hardness value for all the samples. The introduction of the TiO 2 , SiO 2 and Al 2 O 3 modifiers does not cause any quantitative change in the creep behavior as compared with the unmodified glue, the creep of these coatings being largely due to the polymer base. In turn, the addition of zinc oxide increases the tendency of the glue to creep, and this is probably due to the plasticizing effect of zinc alkoxides formed on the surface.