Critical factors that determine the percolation threshold of carbon nanotube (CNT)‐reinforced polymer nanocomposites are studied. An improved analytical model is developed based on an interparticle distance concept. Two dispersion parameters are introduced in the model to correctly reflect the different dispersion states of CNTs in the matrix—entangled bundles and well‐dispersed individual CNTs. CNT–epoxy nanocomposites with different dispersion states are fabricated from the same constituent materials by employing different processing conditions. The corresponding percolation thresholds of the nanocomposites vary over a wide range, from 0.1 to greater than 1.0 wt %, and these variations are explained in terms of dispersion parameters and aspect ratios of CNTs. Important factors that control the percolation threshold of nanocomposites are identified based on the comparison between modeling data and experimental results.

A new method is developed to chemically functionalize multi-walled carbon nanotubes (MWCNTs) based on silanization reaction for use as the reinforcement for polymer matrix composites. To oxidize and create active moieties on the MWCNTs, the samples were exposed to UV light within the ozone chamber, followed by silanization using 3-glycidoxypropyltrimethoxy silane after the oxidized MWCNTs were reduced by lithium aluminum hydride. FT-IR, TEM and XPS were employed to characterize the changes in carbon nanotubes surface morphology, chemistry and physical conditions at different processing stages. The results indicate improved dispersion and attachment of silane molecules on the surface of the MWCNTs.

Abstract:The effects of silane functionalization of multi-wall carbon nanotubes (CNTs) on properties of CNT/epoxy nanocomposites are investigated in this work. Epoxy-based nanocomposites reinforced with CNTs with and without functionalization were prepared. The properties of nanocomposites were characterized extensively using the scanning electronic microscopy (SEM), electrical conductivity measurement, thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA), three-point bending test and fracture toughness measurement. The results showed that grafting silane molecules onto the CNT surface improved the dispersion of CNTs in epoxy along with much enhanced mechanical and thermal properties as well as fracture resistance of nanocomposites compared to those containing CNTs without functionalization. The electrical conductivity of nanocomposites decreased due to the wrapping of CNTs with non-conductive silane molecules. These findings confirmed the improved interfacial interactions arising from covalent bonds between the functionalized CNTs and epoxy resin.