The aim of the project was to produce a coating that could accept a dye sublimation transfer and achieve a Moh's hardness of 4 and improve both the chemical and physical durability of the product as well as improving its light fastness. However it was discovered very early in the project that it was not possible to obtain a high cross linking coating giving the required hardness, and achieving the high level of sublimation required to obtain the vibrancy of the colours that makes this process unique, therefore a two-coat process, with the base coat providing the sublimation and the topcoat providing the desired durability properties was formulated.
Both coatings were tested for hardness to see if the objective of Moh's hardness of 4 had been achieved. The original dye sublimation coating had a Moh's of 1-2 and the development UV over-coating lacquer had achieved the objective with a Moh's of 4. The choice of photoiniators also achieved the objective of producing a coating that was within the acceptable parameters of yellowing.
Tiles and mugs of both the standard dye sublimation coating and the development UV overcoating lacquer were tested for a number of different scenarios. In the majority of tests the development UV overcoating lacquer outperformed the original dye sublimation coating, and in no instance did perform worse than the standard dye sublimation coating.
Both the standard dye sublimation coating and the development UV overcoating lacquer were tested for dishwasher durability using the European standard detergent IEC 436 Type A. The standard dye sublimation coating showed progressive fading of the colour with increasing cycles on both the tiles and mugs, whereas the development UV overcoating lacquer displayed no fading of colour but flaking of the lacquer was observed.
The coatings were tested for toxic metal release using the German lip test and both complied with the regulations with results of <0.1Pb and <0.01 Cd mg per article.
The coatings were tested for light fastness. The standard dye sublimation coatings showed severe colour fading after 40 hours of testing whereas the development coating showed a slight colour change, although this would probably not be noticed for this test duration.
There was not a great deal of difference in the performance of either coating with regards to chemical testing or stain resistance with the exception of disinfectant in the sanitaryware test where the standard dye sublimation coating was completely removed. The graffiti test left a slight mark on the standard dye sublimation coating after removal of the 'magic marker' the development coating was clear after removal, however the spray paint was could only be partially removed where it could not be removed at all from the standard coating.
The abrasion resistance tests (PEI and Sheen) showed some big differences between the coatings. Both the dye sublimation coatings showed very poor durability whereas the development overcoat UV lacquer performed considerably better, giving a Class III result for the PEI test and a result approaching the acceptable standard for the Sheen test. The CERAM Research scuffing test showed no visible marks on the development overcoat UV lacquer whereas a degree of damage was observed on the standard dye sublimation coating.
The appearance of ceramic goods is a major factor in determining their attractiveness and appeal to the consumer and hence their value. An important element in this is the decoration applied to the surface of the articles.
However, the type of decoration which can be applied in traditional ceramic product/on is limited by technical considerations, in particular, the need to fire the decoration at temperatures of 800øC or higher. This limits the choice of decorative materials to a restricted number of inorganic pigments and hence a limited colour palette. Many of these pigments use heavy metals which have to be carefully, controlled to eliminate the hazard from these materials. The use of many of these elements is of concern environmentally because of their toxicity and potential health and safety problems. Dye sublimation, or dye diffusion, printing has the potential to overcome many of these problems.
Firstly, no heavy metals are present in the dyes used, the environmental and health and safety advantages are therefore obvious. The quality of reproduction is photographic and the co/our palette available is almost infinite. Where one off designs or short production runs are required dye sublimation has distinct advantages, the technology' allows one off designs to be achieved cost effective/y as easily as mass produced items Dye diffusion offers design flexibility, the ability for manufacturers to produce to order (de, reduced work in progress) and to produce cost effective samples that will match the final product run. In addition vivid, photographic quality decoration is possible through access to a full organic colour palette. The proposed technology, using less energy and reducing organic emissions to atmosphere, is therefore in accordance with FEPF (F‚d‚ration europ‚enne des industries de Porcelaine et de Faience de table et d'ornementation) guidelines aimed at promoting best environmental practices within the table/ornamental ware industry by the year 2000 Currently the limiting factor in the use of the technology in ceramics is the hardness of the coating which accpets the dyes.The main objective of the project is to develop a coating which is more durable and has a Mohs' Hardness of 4 while retaining all the advantages of the present coating.
Funding SchemeCRS - Cooperative research contracts
ST4 7LQ Stoke-on-trent
82152 Planegg / Krailling
531 19 Lidkoping
3020 Torre De Vilela
2600 JA Delft
IG6 3XH Ilford