Surface modification of carbon nanotubes by a bifunctional amine silane; effects on physical/mechanical/thermal properties of epoxy nanocomposite

Abstract

Weak interfacial interactions between MWCNTs and epoxy matrix causes agglomeration of the nanotubes and declines in the nanocomposite performances. In this study, MWCNTs were surface modified by a bifunctional amino silane (i.e. Bis (3-triethoxysilylpropyl)amine) at different concentrations. The nanotubes were previously functionalized through acid oxidation to increase silane grafting ratio. The pure, functionalized and silanized carbon nanotubes were characterized to assess the success of silane grafting. The pure and modified nanotubes were applied at different contents (0.5, 1 and 2 wt%) to epoxy resin. The tensile, flexural and compressive properties of the nanocomposites were evaluated. The nanocomposites were also characterized using water contact angle test, DSC, DMTA and FE-SEM/EDS analysis. It was observed that silanization of nanotubes caused considerable increment (32°) in the water contact angle of epoxy films. The results showed that incorporating the pure nanotubes (at 0.5 wt%) to epoxy resin enhanced the mechanical strengths but decreased the modulus of the epoxy sample. It was found that incorporating 0.5 wt% of modified MWCNT into epoxy binder caused 33, 53 and 40 % improvement in the tensile, flexural and compressive strengths and 56, 85 and 110 % increment in the tensile, flexural and compressive modulus compared to the pure MWCNT containing nanocomposite. The modified MWCNTs participated in curing of epoxy resin through reaction of silane amide groups with resin epoxide groups that this increased enthalpy of curing up to 25 %.