Effects of PVP incorporation on the properties of injection-molded high-performance ceramics with PEG-based binders

PEG/PMMA binder systems are among the most widely used water-soluble binders for ceramic injection molding. Binder-induced binder segregation in PEG/PMMA systems is mainly caused by the difference between crystallization temperature of PEG (below 50 degrees C) and glass transition temperature of PMMA (similar to 120 degrees C). In this study, we have adopted the method of introduction of appropriate amount of PVP to reduce the binder-induced defects. A principle model was thus established for the suppression of PEG crystallization by PVP molecules. It was revealed that the mechanism by which PVP suppresses PEG crystallization is hydrogen-bonded formation between the carbonyl group of PVP and the hydroxyl groups of PEG molecules. This compresses the crystallization space of PEG molecules, and suppresses their crystallization. It was determined that the range of PVP content that can be safely removed via water debinding is 0-30 wt/wt% PEGS. The incorporation of PVP could effectively enhance the homogeneity of the compact, reduce the size of pores formed after thermal debinding in the compact, promote densification, reduce defects after sintering and enhance the mechanical performance of the sintered bodies. Furthermore, the performance of the molded product was optimal when 20 wt/wt% PEGS of PVP was added to the binder; the flexural strength and density of the resulting sintered body were 811 MPa and 98.7%, respectively.