A Comparative Study on the Influence of Nanoalumina and Carbon Nanotubes on Thermal Stability, Adhesion Strength and Morphology of Epoxy Adhesives

Nano-fillers have displayed excellent mechanical properties and are widely used in different polymeric matrices for high performance applications. Recently، epoxy resins modified by nano-reinforcing fillers such as multi-walled carbon nanotubes (MWCNTs) and nanoalumina (Al2O3) have been developed for adhesive applications. In this work، the influence of 1. 5 weight percent of various nanofillers namely nanoalumina، MWCNT، nanosilica (SiO2) and talc on the thermal stability، strength adhesion and morphology of diglycidyl ether of bisphenol A (DGEBA) /epoxy novolac adhesives was studied. Thermal stability and degradation، adhesion strength and morphology were measured by the thermogravimetry analysis (TGA)، lap shear strength test and scanning electron and transmission electron microscopic techniques، respectively. The results showed that incorporation of the nanoalumina and MWCNT into the DGEBA/epoxy novolac adhesives increased the lap shear strength. Moreover، the thermal stability of the epoxy adhesive in terms of onset of degradation temperature and char yield (after 800°C) was improved to some extent. By addition of one and half weight percent nanoalumina and/or MWCNTs in the epoxy adhesives، the lap shear strength increased by about 70 and 25 percent، respectively. Among the investigated fillers، nanoalumina demonstrated the best performance in terms of improvements in the lap shear strength، thermal stability and degradation of the epoxy adhesives. When a combination of nanoalumina and MWCNTs reinforcing fillers (0. 75 weight percent nanoalumina and 0. 75 weight percent MWCNTs) was used as a hybrid filler in the epoxy adhesive، a synergism effect on the char yield was observed.