Flow Properties of Carbon Black Dispersed Printing Ink

摘要

Flow properties of carbon black (CB) dispersed printing inks were studied. In oscillatory rheological measurements, printing inks showed pseudo sol-gel transition behavior, and critical gel concentration (W_gel) was determined. W_gel was applied as an index to express fluidity of the printing inks, since W_gel was found to show fairly good correlation with BET surface area that is known as major factor of the fluidity. Moreover, W_gel showed better correlation with CB's external surface area that was determined from electron microscopy and that from mercury porosimetry. Furthermore, W_gel showed the best correlation with CB's speciffic surface area of the effective volume fraction calculated from relative viscosity in steady state rheological measurements by using a semi empirical model. These results showed that the network structure at W_gel is constructed of complex particle made up of CB and polymer-adsorbed layer on it, not from CB's primary particle as understood generally.