Effect of moulding pressure on microstructure and technological properties of porcelain stoneware

The properties of green and fired porcelain stoneware bodies have been studied in samples moulded at different pressures (10, 20, 30 and 40 MPa). In green tiles, higher differences in properties have been found at lower moulding pressure. After the fast-firing process, the tiles have been tested to obtain the technological properties such us lineal shrinkage, water absorption, porosity and bending strength. Results show that higher moulding pressures (30 and 40 MPa) give rise to tiles with similar technological properties. The amount of mullite and quartz remains constant in all pieces after firing process. SEM observations show that mullite crystals are longer as moulding pressure increases, that means that initial moulding pressure has a marked effect on mullite development, which is the main responsible of final properties.