Análise do comportamento de massa cerâmica para injeção à base de água durante o preenchimento do molde

Abstract

This research aims to study the parameters and proceedings necessary to identify the processability of a ceramic hydroplastic mass, by low-pressure injection at room temperature, using water as a vehicle, based on the concepts of material and processes already established, as for polymer injection. The potential of this technique is the ability to produce pieces of complex geometries. In this research, the materials used were commercial stoneware as ceramic mass and water as vehicle, along with other additives, such as starch, sodium hydroxide and sodium silicate, which improves green mechanical strength. Cornstarch was chosen because of its characteristic of forming gel, that was already explored in others manufacturing techniques. In order to analyze the flow behavior of the material, a study was carried out using a universal testing machine adapted to work as a capillary rheometer. To obtain different shear rates, 9 combinations of piston displacement speeds (10, 50 e 90 mm/min) and nozzle diameters (2.65; 4.40, e; 6.30 mm) were used. The results indicated that only in the case of the smallest diameter used there was a significant increase in the flow force, in the steady state, increasing the speed. After rheology characterization of the ceramic mass as a Bingham fluid, it was injected into a closed mold fixed to an apparatus adapted to a universal testing machine. Only the 2.65 mm nozzle diameter was used in this part of the study, because it showed very different behavior depending on piston speeds, according to rheological characterization. Besides the advantage of operation at room temperature, it was considered a low-pressure injection, according to the maximal strength of 0,835 MPa calculated to fill the mold. This was possible only with the addition of sodium hydroxide to the ceramic mass, what caused the gelation of starch.