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Print version ISSN 0366-6913
HOFFMANN, F. S.; SANTOS, G. dos and MORELLI, M. R.. Study of flux and mudstone with potential for using in porcelainized stoneware tile compositions. Cerâmica [online]. 2012, vol.58, n.346, pp.174-185. ISSN 0366-6913. http://dx.doi.org/10.1590/S0366-69132012000200007.
The porcelain tile is distinguished in the current market for ceramic tiles, with excellent technical and esthetic characteristics. In the present study traditional ceramic raw materials were selected and a standard formulation conventionally reported in the literature was adopted aiming to replace the melting phase (feldspar) of the composition for a raw material that forms liquid phase at high temperature, and replacement of the clay fraction by a mudstone of lower refractoriness. The aim of this study was to evaluate the use of these materials as alternative techniques and lower cost, since, in a mass of porcelain tile, the amount of flux is very large (representing approximately 50% of total raw materials used). The nepheline syenite was the natural raw material selected to replace the feldspar due to the fact that it belongs to the family of feldspathoids, and has similar physicochemical characteristics, therefore, a high fluxing efficiency. To replace the clay fraction was chosen a mudstone naturally occurring, abundant in the region of Santa Gertrudes, SP. Substitutions to the feldspar and clay fraction were completely and/or partially by means of combinations between the flux and mudstones. The masses were processed from the mixing of powders, wet milling, drying, disagglomeration, compaction and firing. In addition to the vitrification curves, techniques such as dilatometry, measurements of porosity, flexure strength test, electron microscopy and X-ray diffraction were used to characterize the material after firing at various temperatures. The results showed that, in principle, it is possible the combination of raw materials such as nepheline and mudstone to replace potassium feldspar and S. Simão clay, as they provide the vitrification at lower temperatures. Compositions with both materials showed lower values of water absorption (<0.1%) and high mechanical strength (> 45 MPa), despite higher pyroplastic strain at 1150 ºC.
Keywords : stoneware tile; raw materials; ceramic flux former.