Flowability of fine, highly cohesive calcium carbonate powder was improved using high energy mixing (dry coating) method consisting in coating of CaCO3 particles with a small amount of Aerosil nanoparticles in a planetary ball mill. As measures of flowability the angle of repose and compressibility index were used. As process variables the mixing speed, mixing time, and the amount of Aerosil and amount of isopropanol were chosen. To obtain optimal values of the process variables, a Response Surface Methodology (RSM) based on Central Composite Rotatable Design (CCRD) was applied. To match the RSM requirements it was necessary to perform a total of 31 experimental tests needed to complete mathematical model equations. The equations that are second-order response functions representing the angle of repose and compressibility index were expressed as functions of all the process variables. Predicted values of the responses were found to be in a good agreement with experimental values. The models were presented as 3-D response surface plots from which the optimal values of the process variables could be correctly assigned. The proposed, mechanochemical method of powder treatment coupled with response surface methodology is a new, effective approach to flowability of cohesive powder improvement and powder processing optimisation.

In this work Response Surface Methodology and Central Composite Rotatable Design were applied to find high-energy mixing process parameters enabling flow properties of highly cohesive Disulfiram powder to be improved. Experiments were conducted in a planetary ball mill. The response functions were created for an angle of repose and compressibility index as measures of powder flowability. To accomplish an optimisation procedure of mixing process parameters according to a desirability function approach, the results obtained earlier for potato starch, as another cohesive coarse powder, were also employed. Coupling these results with those achieved in a previous work, it was possible to develop some guidelines of practical importance allowing mixing conditions to be predicted towards flow improvement of fine and coarse powders.