Dispersion stability of functionalized MWCNT in the epoxy-amine system and its effects on mechanical and interfacial properties of carbon fiber composites

There are many complex interactions between the functionalized multi-walled carbon nanotube (MWCNT) and curing agent/resin molecules, which result in the unstable and unsatisfactory enhancing effects of nanoparticles in epoxy-amine system as a matrix of carbon fiber composites. In this paper, the surface chemical characteristics of carboxyl-functionalized MWCNT (MWCNT-COOH) and amino-functionalized MWCNT (MWCNT-NH2) were analyzed. The reactivity of MWCNT-COOH and MWCNT-NH2 in the epoxy matrix before and after adding amine curing agent was discussed through non-isothermal DSC analyses and micro-morphology observation. The results showed the surface functional groups affected the dispersion stability of MWCNT during the mixing and curing process of the epoxy-amine matrix. The potential chemical mechanisms behind the improved properties of epoxy resin containing MWCNT were specifically studied. The MWCNT-COOH tended to re-aggregate during the fabrication process of epoxy matrix, whereas MWCNT-NH2 can maintain the dispersion stability due to the presence of amine curing agents, which would ensure MWCNT-NH2 more efficiently participated in the cross-linking reaction of epoxy resin and the interface strengthening between carbon fiber and resin matrix, and then resulting in the improved mechanical performances compared to the carbon fiber composites based on the neat epoxy and MWCNT-COOH reinforced ones. (C) 2016 Elsevier Ltd. All rights reserved.