Agglomerate breakdown in fine alumina powder by multiple extrusion
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Repeated extrusion through dies of various diameters and die entry angles was used to determine the rate of agglomerate breakdown in a paste consisting of a fine alumina powder, carbon black and a binder of hydroxyl propyl methyl cellulose in water. It was found that three extrusion passes were enough to break up all but ∼0.4% of the agglomerates. Dies with orifices of approximately 1 mm diameter and die entry angles of 45 to 90‡ (where the elongational strain and the deformation rates were highest) were the most efficient for disrupting and dispersing agglomerates and distributing the moisture evenly. This process of deagglomeration was studied by monitoring the load required to extrude and moisture distribution during five repeated extrusion passes of each test paste. The density, agglomerate area fraction and agglomerate circularity of dried extradates were quantified and plotted.
KeywordsPolymer Alumina Methyl Cellulose Hydroxyl
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