Epoxy reinforcement with silicate particles: Rheological and adhesive properties - Part II: Characterization of composites with halloysite

Rheological and adhesive properties of epoxy oligomer-halloysite systems were studied. Ultrasound treatment of epoxy-clay systems was used for their homogenization. The results were compared with the data obtained earlier for epoxy resins filled with natural and organomodified montmorillonites (MMTs). Clear correlation between the rheological and bonded joint behavior of epoxy-halloysite systems was observed at 5 wt% of halloysite. A decrease in the viscosity of the systems and the yield stress values after sonication is shown to be caused by nanotube breakage and by formation of agglomerates when the broken nanotubes were lined up in the same direction. It leads to a remarkable drop in joint strength with increasing sonication time for 5 wt% halloysite systems. 2 wt% halloysite addition resulted in an ~30% increase in joint strength, which is less than in the case of MMTs incorporation.