Physisorption of ionic salts to carbon nanotubes for enhancing dispersion and thermomechanical properties of carbon nanotube-filled epoxy resins

Cation–π effect on physisorption of aromatic ionic salts to multi-walled carbon nanotube (MWCNT) was demonstrated by the excess adsorption over their pre-ionized aromatic compounds through thermogravimetric analysis. Their adsorption layer on the surface of MWCNT was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Ionic salt-adsorbing MWCNT showed better dispersion in acetone than pristine and pre-ionized compound-adsorbing MWCNT. Incorporation of 1 wt% ionic salt-adsorbing MWCNT is able to gel the epoxy resin at room temperature according to the rheological study. Based on our proposed model, 1 wt% fully-dispersed MWCNTs are enough to form an interconnected network in epoxy resin resulting in gelation. After crosslinking with amine curing agent, the epoxy nanocomposites incorporating 1 wt% ionic salt-adsorbing MWCNT displayed substantially higher glass and ß transition temperatures than that incorporating pristine MWCNT.