CONTRACTION CHARAClFRlSTlCS OF MOLDED CERAMICS DURING DRYING

ABSTRACT The characteristics of drvine and contraction (shrinkage) of molded ceramics were expenmentally studied to clarify the effects of drying conditions on contraction behaviors or deformation during drying processes. Mikawa-Shanshu clay molded into spheres or slabs was used as a sample which underwent convective drying by hot air. Three periods of preheating, constanl rate and falling rate existed, and the contraction was observed mainly in the preheating and constanl rate periods for all samples. It is also observed that the behavior of ihe contraction of molded clay is inflienced significantly by drying conditions. The higher drying rate makes the contraction of clay more remarkable in the preheating and constant rate periods. This behavior could not be explained from the difference of the moisture content distribution among runs. However, it is suggested that the inside parts of molded ceramics may be subjected to the strong compressional stresses and the strain-stress in the sample would Influenc...