Silicone-grafted carbonaceous nanotubes with enhanced dispersion stability and electrorheological efficiency

Carbonaceous particles are types of important fillers or dispersed phases of electro-responsive electrorheological (ER) suspensions. But carbonaceous particles, in particular with nano-order size, are easy to aggregate in oils. This characteristic limits the application of ER suspensions based on carbonaceous particles. In order to improve dispersion stability and ER efficiency, in this paper, we develop silicone-grafted carbonaceous nanotubes (CTs) by grafting oxidized carbonaceous nanotubes with epoxy-terminated silicone. The samples are characterized by Fourier transform infrared spectra, x-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The wettability and dispersion stability of nanotubes in silicone oil are investigated by wetting curves and sedimentation tests. The ER properties of CTs when dispersed in silicone oil are measured by a rheometer under electric fields. It demonstrates that grafting with silicone can distinctly improve the wettability of CTs in silicone oil and decrease the re-aggregation of CTs. As a result, the suspension of silicone-grafted CTs in silicone oil shows high dispersion stability. Compared to the suspension of bare CTs, the suspension of silicone-grafted CTs exhibits lower zero-field viscosity but higher field-induced viscosity; thus it possesses higher ER efficiency. This enhanced ER efficiency is related to the improved wettability of silicone-grafted CTs in silicone oil.