Aqueous injection moulding of porcelains

This work studies the different processing parameters involved in the manufacturing of porcelains by injection moulding of an aqueous ceramic suspension. The industrial slip (68 wt.% solids) was optimised for the injection process (through evaluation of the homogenisation procedure) by increasing the solid loading to 72 wt.% (49.5 vol.%) and the dispersants concentration. Agar solutions with concentrations of 3 and 4 wt.% were prepared by heating at 92 °C, but a new procedure for increasing the agar concentration up to 10 wt.% by means of a pressure cooker was applied, also. The evolution of viscosity on cooling was studied for the different agar solutions and porcelain suspensions containing different quantities of agar. The best gel casting performance was reached by adding 0.5 wt.% agar prepared as a 6 wt.% solution. Using this suspension, the injection conditions were optimised for shaping in only one step a cup with handle, through development of a mould prototype and by studying the effects of pressure, residence time, suspension temperature in the tank and in the mould, etc. By controlling these parameters injection moulded cups with handle were obtained with a green density of 60% of theoretical and a weight variation in the dried products within ±2%.