Lightweight dense/porous bi-layered ceramic tiles prepared by double pressing

• A novel production method for lightweight bi-layered ceramic tiles was described.
• The simplicity of the production method enables mass and low-cost production.
• Tiles with reduced weight and noticeably low thermal conductivity were produced.
• The tiles assure both coating and insulation suitable for innovative applications.

This work reports the production process of bi-layered ceramics tiles, formed from two layers with different densities – dense and porous – and with adjustable thickness. The novel production method comprises a double pressing action, fast and easy to implement industrially, that ensures the development of a perfect interface bonding between layers.The bi-layered ceramic tile is formed by an upper layer with density similar to a conventional porcelain stoneware tile, and a porous bottom layer, which promotes weight reduction of the product maintaining suitable mechanical strength. The introduction of porosity is achieved by means of the incorporation of pore forming agent – polypropylene (PP) – into the ceramic formulation, which undergoes complete and non-harmful thermal decomposition during firing. For comparison, polymethyl methacrylate (PMMA) was also tested as porogen. The rapid and complete combustion of PP is suitable for fast-firing ceramic products, such as porcelain stoneware. In addition, the polymer decomposition does not induce defects in the ceramic pieces, and is environmentally acceptable.The produced tiles are lighter than conventional porcelain stoneware tiles, thus decreasing their transport and distribution costs. Additionally, the thermal attenuation provided by the porous layer could be valuable in innovative applications, such as ventilated facades.