Abstract:
The influences of PVP with different molecular weights on the rheological properties and stability of multi-walled carbon nanotubes (MWCNTs) slurry and the electrical conductivity of modified MWCNTs (P-MWCNTs) were systemically investigated with the aim of elucidating the governing dispersing mechanism. The results showed that the PVP with medium molecular weights (PVPK25 and PVPK30) made the MWCNTs disperse uniformly, and the MWCNTs particle size was about 190 nm. As a result, the MWCNTs slurry showed lower viscosity and better stability, which led the slurry to evolving from shear-thinning fluid to nearly Newtonian fluid. Moreover, the P-MWCNTs modified by PVPK25 and PVPK30 also displayed lower electrical conductivity, to be 1/100 of the original carbon nanotube. The mechanism of adsorption of PVP on MWCNTs was investigated by Raman, TG and SEM. It was found that the wave number migration of the G peak was about 10 cm
−1, and the 2D was about 5 cm
−1, indicating that PVP with medium molecular weights had stronger π-π interaction with MWCNTs. The adsorption amounts of PVPK25 and PVPK30 were higher than those of low molecular weights (PVPK17) and high molecular weights (PVPK90) which can generate stronger steric hindrance repulsive force. SEM results directly indicated that the MWCNTs modified by PVPK30 and PVPK25 were dispersed homogenously, while some MWCNTs aggregates were observed for the samples modified by PVPK17 and PVPK90. The dispersion of MWCNTs was ascribed to the π-π interaction and the adsorption amount, leading to that the PVP with moderate molecular weights presented the best dispersibility. This study can not only understand the influences of PVP molecular weights on the dispersion behavior of carbon nanotubes, but also provide guidance for preparing conductive slurry composed of carbon nanotube.