Characterization of brazilian plastic and flux raw materials for application and innovation in the ceramic coating industry.

The ceramic tile industry has resumed its growth around the world post-Covid 19, and Brazil ranks third among the largest producers and consumers. Among the products manufactured in Brazil, two stand out: porcelain tiles, produced by the traditional wet process, and semi-porous slabs, produced by the dry process, developed in Brazil. Porcelain tiles, the subject of the work presented here, are produced in two main Brazilian centers, Criciuma and Santa Gertrudes, located in the south and southeast of Brazil. Current production is expected to reach 200 million square meters in 2023. Porcelain tiles are made from a mixture of raw materials, particularly plastic and superplastic clays, which account for 30 to 40% of the total, and feldspars, which make up around 25 to 40%. Given the growing need for supplies for the manufacture of porcelain tiles, especially with regard to feldspars and plastic clays, this research focused on exploring and geologically, geochemically and technologically characterizing new sources of these traditional raw materials, as well as special fluxes and alternative sources of raw materials in different geological environments, especially in the southeast and northeast regions of Brazil. The methodology adopted involved carrying out geological mapping in pre-selected regions, which included the description of lithofacies, lithogeochemical characterization using techniques such as X-ray diffraction, X-ray fluorescence and the analysis of thin sheets, as well as the evaluation of ceramic properties, including water absorption, apparent density and mechanical strength, among other parameters. For some samples with innovative potential, additional analyses were carried out. Preliminary results indicated that some samples showed promise as raw materials for the manufacture of porcelain tiles, especially the alkaline fusion raw materials and plastic clays. Among the alkaline source rocks, nepheline syenite and anorthosite stood out, with an estimated composition of 60 to 90% feldspars, as well as 20% nepheline and 15% cancrinite, which showed high sum values of fusing elements (Na₂O + K₂O), reaching more than 18%. Another focus of analysis was diopside, which showed mineralogy composed of diopside, quartz and feldspar, with high levels of (CaO + MgO), which favored fusibility during firing, improving mechanical strength and decreasing water absorption, and reducing energy costs. With regard to plastic clays, some Quaternary and Permian deposits, consisting mainly of quartz minerals, feldspar (microcline) and the clay minerals kaolinite, illite and smectite, have shown remarkable ceramic performance, with high plasticity, high dry mechanical strength and light colors after firing. The initial results suggest that it is viable for use in coatings, but further research could expand its potential, including the search for new products through technological innovations. The authors gratefully acknowledge the financial support of FAPESP - Fundação de Amparo à Pesquisa do Estado de São Paulo, Process nº 2023/01939-0, project, Prospection and characterization of brazilian raw materials for the production of porcelain tiles.