Impact Scale Factor on Adhesion and Viscoelastic Behaviour of Epoxy Networks in Adhesive Connections.

Investigation of a scale factor effect on adhesion and viscoelastic properties of adhesive based on epoxy resin curried with polyamine was carried out. By using dynamic mechanical analysis method the viscoelastic behavior of both free epoxy films and adhesive joints in whole was studied. The sickness of adhesive layer and free films as a scale factor was varied in interval of 50-900 mkm. The increase of epoxy adhesive layer thickness was shown to result in the nonmonotonic decrease in an adhesive strength value. The dramatic drop of adhesion strength was observed for adhesive layers having thickness less 200 mkm and more slowly degradation occurred in case of thicker ones. Along with this the correlation between adhesive layer thickness and polymer ability to dissipate mechanic energy took place. It was also shown that layer thickness influenced not only adhesion and viscoelastic behaviors of adhesive but coupled with the effect of substrate (duralumin) surface caused the changes in topology and morphology of epoxy networks. Particularly the appearance of shoulder associated with additional relaxation transition on the rising wing of the maximum at loss module temperature dependence for sample of adhesion joint with adhesive layer of 800 mkm indicated the fluctuation of cross-linking density of epoxy network. [ABSTRACT FROM AUTHOR]