Effects of various dispersants on the rheogoly of soft porcelain casting slips

EFFECTS OF VARIOUS DISPERSANTS ON THE RHEOGOLY OF SOFT PORCELAIN CASTING SLIPS Selçuk ÖZKAN Department of Ceramic Engineering, Master's Thesis, 2014 Thesis Supervisor: Prof. Dr. İskender IŞIK SUMMARY At GP company, the sodium silicate (Na2SiO3) is used as dispersant agent in soft porcelain casting slips. This dispersant has been used in different ratio for same recipe due to physical and chemical properties of utilized clays, causing the different rheological behaviour. In this study, the porcelain casting slips were prepared using the synthetic electrolyte (Dolapix SPC-7) and polycarboxylic acid (Dolapix PC 67). According to obtained flow curves, the dispersants were used in equal 0.2, 0.4 and 0.6 % of the dry weight of the slips. The prepared slips were physically and chemically tested under the company conditions and the obtained results were compared with existing slips with sodium silicate as electrolyte. Polycarboxylic acid in the ratio of 0.2 % yielded good results. It shows a stable flow between 0.1 - 0.8% and also, had wide working range. It is thought that the casting time can be decreased due to fast getting thickness during casting period. On the other hand, the low shrinkage properties of green body would be useful to reduce shaping defects (crack, deformation) which occur during drying and firing process. As a result of this, it is expected that the manufacturing losses are reduced in all fabrication periods. The obtained results among three different dispersants showed that the polycarboxylic acid can be utilized for casting slips. However, it was seen that there were a significant differences between prices of sodium silicate and Dolapix PC-67 in term of mass production expenses. Keywords : Deflocculant, Sodium silicate, Thixotropy, Soft porcelain casting slip.