Rheological characterization of carbon black/polystyrene solution systems
Abstract
Steady-shear measurements of suspensions of carbon blacks (CB) in polystyrene (PS)/di-(butyl phthalate) (DBP) solution were investigated as a function of volume fraction (ϕ) of CB to clarify the effect of the primary particle size and the structure of CB aggregates on the rheological properties. The suspensions show a typical shear-thinning behavior in the range of a shear rate studied. The Casson model was applied to evaluate the viscosity at infinite of shear rate η∞ and the yield stress σy for the suspensions. Relative viscosity η∞/ηm, (ηm: medium viscosity) thus obtained was compared to the high-frequency viscosity for the ideal hard-sphere silica suspensions to evaluate the effective volume fraction ϕeff of CB aggregates. The ϕeff value was larger for the higher-structure CB with higher DBP absorption value, irrespective of the primary particle size. The yield stress σy had almost the same ϕeff dependence for neutral furnace CB/(PS/DBP) suspensions, although it was larger for acetylene black (AcB)/(PS/DBP) suspensions. These results demonstrated that the effective volume fraction is the most important quantity to characterize the CB aggregates on the rheological properties. It was also found that the correction of the medium viscosity changes due to polymer adsorption on the CB surface is important since neutral furnace CB adsorbs PS polymers but AcB hardly adsorbs PS polymers in the solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
