Surface properties of porcelain stoneware tiles: the influence of different protective coatings (Comunicazione a convegno)

Type
Label
  • Surface properties of porcelain stoneware tiles: the influence of different protective coatings (Comunicazione a convegno) (literal)
Anno
  • 2006-01-01T00:00:00+01:00 (literal)
Alternative label
  • Raimondo M., Zanelli C., Dondi M., Guarini G., Matteucci F., Biasini V., Gardini D. (2006)
    Surface properties of porcelain stoneware tiles: the influence of different protective coatings
    in 8th World Congress on Ceramic Tile Quality, QUALICER 2006, Castellón (Spain), 12-15 February 2006
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Raimondo M., Zanelli C., Dondi M., Guarini G., Matteucci F., Biasini V., Gardini D. (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • CNR ISTEC (literal)
Titolo
  • Surface properties of porcelain stoneware tiles: the influence of different protective coatings (literal)
Abstract
  • Among the available commercial products, porcelain stoneware stands out as a material in which the physical-mechanical properties determine excellent performances and service life; in addition, the as-fired surface is characterized by excellent hardness, high fracture toughness and stain resistance. However, the polishing process, which is industrially performed to improve the aesthetic appearance of the product, can promote irreversible damages leading to a strength degradation of the processed surface. In order to reduce these drawbacks, in the last years, the possibility of surface coating with organic films was investigated as one of the most interesting solutions. The comprehension of the interaction between the surface and the coating layer is fundamental in order to evaluate the behaviour of the composite material. For this purpose, two different typologies of commercial porcelain stoneware tiles, glazed (G) and unglazed (UG), were taken into account. Both typologies were industrially polished and subsequently coated with fluoro-carbon, silicon based (in aqueous and non-aqueous media) and UV thermo-hardened resins, in order to obtain twelve different working surfaces. All products were extensively characterized by measuring the main physical properties (water absorption, bulk density and open porosity (ISO 10545-3), total and closed porosity (He pycnometry), obtaining data referring to both the bulk and the working surfaces. The wetting properties of these latter were furthermore investigated by measuring the surface energy and the contact angle with a polar (H2O) and non polar (CH2I2) liquid (DataPhysics OCA15). The stain resistance of all samples was assessed according to ISO 10545-14, and the results were appraised through colourimetric measurements (ISO 10545-16). The wear performance of the different surfaces was simulated by chemical (ISO 10545-13) and abrasion resistance (ISO 10545-7), as well as by the temperature (60°C, 7 days) effect. SEM investigation was also utilized to evaluate the surface microstructure and the effectiveness of the different coating in reducing the superficial dishomogeneities. Commercial tiles (G and UG) present a very low water absorption of the bulk (0.06%), with the working surfaces having a higher degree of accessible pores (water absorption 0.3%) and a total superficial porosity of about 6-7%. The polishing process slightly lowers the surface energy, while a more pronounced decrease is promoted by polymer coating, expecially when the silicon based one in non-aqueous media is used. Moreover, according with the different surface treatment, a modification of the ratio between the polar and non-polar component of the total energy is also observed. The coating with a UV thermo-hardened resin does not substantially change the surface properties. Stain resistance tests highlighted that all the surfaces give a quite complex picture of their behaviour in correspondence of the different chemical composition of the staining suspensions. Generally, we can conclude that UV thermo-hardened resins are able to protect the working surface from the action of oily substances containing dirty particles; the fluoro-carbon and silicon resins in non aqueous media, indeed, are more effective against, respectively, the water-resistant pens and aqueous colouring agents. The silicon resin film in aqueous media seems to be the only one able to provide an \"average protection\" against all the different staining agents. The behaviour of the surfaces after the wear simulating treatments depends on the different coating, but generally a lowering of their performances, expecially in terms of stain resistance, is observed. The results provided by this work emphasize the role played by some of the surface treatments on the ceramic product performances and their service life; in the same time, the need of a better understanding of the interaction mechanisms, in order to design suitable ceramic coating with innovative properties, also comes out. (literal)
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