Evaluation of shear and friction characteristics of wet powder by intrusion method using conical rotor

The shearing and friction characteristics of a powder bed consisting of porous particles under conditions of various liquid content have been evaluated by means of the apparent viscosity coefficient eta(a). In the present case, Rumpf's model has been applied to estimate the shearing force H at the contact point between two particles measured by the intrusion method. According to the tendency to change in eta(a) and H with the ratio of liquid to powder weight w, the states of the powder can be classified into the three regions. In the region I (0 less than or equal to w less than or equal to 0.89), eta(a) and H have similar values in the dry state, respectively, i.e. no change in surface condition due to absorption of the liquid into the pore spaces of the particles. In the region II (0.89 less than or equal to w less than or equal to 1.50), the powder property changes from the pendular to the funicular state, so eta(a) and H increase with increasing w, and H does not change in the void fraction epsilon. I-n the region III (w greater than or equal to 1.50), the powders are in the capillary states, eta(a) and H decrease with increasing w, and H increases with decreasing epsilon.