Revisiting pyroplastic deformation. Application for porcelain stoneware tile bodies

Abstract

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.