Characterization of different starch types for their application in ceramic processing

Starch is a frequently used pore-forming agent in ceramic technology. Moreover, it can take over the function of a body-forming agent in a recently developed process, called starch consolidation casting. Upon firing the starch polymers are burnt out without residues and leave a pore structure determined by the type of starch applied. In this paper, five commonly available starch types (potato, wheat, tapioca, corn and rice starch) are characterized with respect to size and shape. Size distributions are measured via laser diffraction and microscopic image analysis. Rice starch is found to be the smallest type (median size 4.4–4.8 μm), potato starch the largest (median size 46–49 μm) and the other types intermediate (median size 12–21 μm). The distribution is narrow for corn and tapioca starch (span approximately 1.1), while potato, wheat and rice starch are relatively polydisperse (span approximately 1.35–1.65). The shape of the starch granules is most anisometric for potato starch (average aspect ratio 1.3–1.4). All other starch types, although possibly of polyhedral shape (tapioca, corn and rice starch), are more isometric, i.e. very close to an average aspect ratio of 1.