Improved green strength of ceramic bodies through extrusion using hydroxypropyl methylcellulose as binder

Different amounts of hydroxypropyl methylcellulose (HPMC) and starch in the form of powder were utilized as binder in the extrusion of silicon nitride green bodies. Their three-point flexural strength and microstructure of fracture surface are investigated. It is found that HPMC can markedly improve the green strength compared with the use of starch. The bending strength with 10% HPMC addition is 29.3 +/- 3.1 MPa, which is approximately 7.5 times that of starch counterpart. The dramatic improvement of strength can be attributed to the rough fiber-like HPMC particles, which were aligned along the direction of extrusion and were pulled out during bending tests. This work represents a step towards a simple but effective way to extrude high-strength ceramic green bodies.