Residual stresses in porcelain tiles. Measurement and process variables assessment

This research addresses the residual stresses phenomenon taking place during the manufacture of porcelain tiles. Residual stresses were quantified by the strain relaxation slotting method. The method is based on the fact that stresses are released when a slot is made leading to a curvature change. Once the method was validated, the impact of process variables such as starting body composition, temperature and cooling rate of firing cycle was investigated. Findings showed that cooling rate was the most influencing variable whereas Young’s modulus of fired specimens also play a significant role. Symmetry of the parabolic residual stress profile denoted homogenous cooling on upper and lower tile surfaces during the cooling step. In addition, it was observed that polishing of a stressed tile gives rise to a decreasing of deformation as a consequence of stress release by mechanical grinding

Revisiting pyroplastic deformation. Application for porcelain stoneware tile bodies

In this research an analysis of firing deformation tendency in porcelain stoneware tile compositions was carried out based on pyroplastic deformation measurements. The effect of the amount and nature of some fluxing additives as well as some process variables were addressed. Firing diagram, pyroplastic deformation and microstructure examination of fired specimens of the different compositions were carried out. Findings allowed to verify the effect of particle size and unfired bulk density on pyroplastic deformation. Finer particle size and/or higher unfired compactness effectively contribute to reduce pyroplastic deformation. However, the joint effect of particle size and bulk density differs from that observed with more fluxing (redware) floor tile compositions. At compositional level, the effect of some alkaline–earth containing fluxing compounds on the pyroplastic deformation was observed. Thus, Magnesite showed a high fluxing efficiency with moderate deformation while Dolomite displayed a detrimental effect on both densification range and pyroplastic deformation

Firing deformation in large size porcelain tiles. Effect of compositional and process variables

Ponencia presentada en el XV Congreso Mundial de la Calidad Del Azulejo y del Pavimento Cerámico (QUALICER 18), celebrado en Castellón (Spain) los días 12 y 13 de febrero de 2018.The manufacture of porcelain stoneware has undergone a spectacular growth in the last years, as a result of the good technical and functional performance associated to the impervious feature of the sintered product, together with the great technological advance that the ceramic tile manufacturing sector is experiencing [1]. To such an extent, that today, porcelain stoneware is the most demanded product for use in flooring surfaces, but at the same time, it is becoming important to incorporate in other applications such as ventilated facades