INFLUENCE OF THE DEBINDING METHOD ON THE MECHANICAL-PROPERTIES OF PLASTIC FORMED CERAMICS

A new method of extraction of organic additives, by a supercritical fluid is presented. Flexural strengths and Weibull moduli of extrusion molded alumina, debinded by classical pyrolysis and by supercritical CO2 extraction are compared. Better mechanical properties are obtained after a short time (3 h) of supercritical treatment (sigma = 277 MPa, m = 13.7) than after 18 h of pyrolysis (sigma = 253 MPa, m = 12.4). The binder extraction from green pieces by supercritical fluids is limited by two factors, solubility and diffusivity of organic compounds. The major factors causing defects in the pyrolytic binder removal, such as binder redistribution in the liquid phase and the outward diffusion of degradation products, do not take place in the supercritical debinding method.