CERAMIC PROPERTIES OF RAW MATERIALS USED IN PORCELAIN TILE BODIES: A COMPARISON BETWEEN BRAZILIAN PHYLITES AND TYPICAL FELDSPAR

Reference	Presenter	Authors (Institution)	Abstract
16-004	Miguel Yesid Hernández Sánchez	Sánchez, M.H.(Programa de Pós-Graduação Ciência e Engenharia de Materiais/PPGCEM – Universidade Federal de São Carlos (UFSCar)); Boschi, A.O.(Programa de Pós-Graduação Ciência e Engenharia de Materiais/PPGCEM – São Carlos-SP); Melchiades, F.G.(Centro de Revestimentos Cerâmicos);	Brazil is the second major ceramic producer in the world, producing 792 million m2 of ceramic tiles in 2016. Compared to other countries using Feldspar as a flux, Brazil is the one who uses Phyllite (i.e., a mixture of quartz, kaolinite and mica) in the ceramic sector, because of its low cost and easy access. Despite its high acceptance by Brazilian ceramic industry, no systematic study on the implications of substituting feldspar by phyllite is known. This paper compares technological characteristics of raw materials, such as, chemical composition, porosity (estimated as water absorption), linear contraction, colour (L*,a*,b*), dilatometry and thermal behaviour. For the purpose of exploring the relationship among a typical feldspar (Feld), a phyllite of the state of São Paulo (FN) and a phyllite of the state of Minas Gerais (FG), Brazil. Test bodies were pressed with dimensions of 20x60x5mm, 6.5% humidity, and a pressure of 480 Kg-f/cm2 for Feld and FG, and 205 Kg-f/cm2 for FN. Subsequently, the test bodies were fired in fast cycle at different temperatures of 1100°C, 1150°C, 1200°C and 1240°C. The results show the correlation between whiteness and water absorption at different firing temperatures, evidencing a lower variability for Feld, because its low composition of Fe2O3, unlike phyllites N and G, that present brownness colour and curve slopes. The differential thermal analysis presents endothermic peaks corresponding to reactions of constitutional water removal and OH- ions between 400°C and 600°C. Moreover, a significant contraction, and exothermic peaks associated with the formation of crystalline species were observed. There is a significant difference for values of porosity, fired linear retraction, alkalis concentration and colour between the typical feldspar and the phyllites N and G that explains its behaviour as raw materials. Results presented in this paper can be used as a basis for raw material selection to fabricate technical ceramic tiles.
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