RELAXATION EFFECTS IN LARGE INJECTION-MOLDED CERAMIC BODIES

Small cubic samples were cut from various positions within large unfired injection moulded ceramic bodies and thermal expansion in different directions was measured by dilatometry. Dramatic heterogeneities and anisotropies in apparent thermal expansion were observed. Negative apparent expansions were noted in some cases.The results have implications for the way in which local deformation occurs during reheating such mouldings to remove the organic vehicle. Small organised displacements of particles resulting from the relaxation of the organic phase during binder removal may contribute to the defects which appear at that stage.