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Title: Investigation into the weathering of organic coated steel and application of mathematical modelling to the data
Author: Wijdekop, Maarten
Awarding Body: University of Wales, Swansea
Current Institution: Swansea University
Date of Award: 2004
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This EngD project is an investigation into how the aesthetic properties of organic coated strip steel are influenced by the weather, A commercial PVC plastisol coating system with a wide range of pigment loadings has been tested. The two main objectives in this work were to investigate the correlation between the pigmentations and the weathering properties of the commercial PVC plastisol coating, and to investigate the correlation between natural and accelerated weathering. The colour fastness and gloss retention of these coatings were evaluated after exposure to natural weathering (in the UK) and to accelerated weathering (in QUV testers). Reflectance spectrometry was used for the colour measurements, as this technique gives most information about colours and is therefore most apt when attempting to correlate colour changes to the chemical processes that take place in coatings during weathering. Three processes that take place in the coating during weathering which can cause colour changes were identified with reflectance spectrometry: PVC dehydrochlorination, organic pigment degradation and chalking of inorganic pigments. A model is proposed to estimate the relative intensities of these processes from the reflectance spectra taken before and after weathering of a coating. With these relative intensities of the three processes the correlations between different types of weathering were investigated. Gloss retention during natural and accelerated weathering was compared, and the correlation of gloss loss and plasticizer degradation was examined and confirmed. The shades with the worst weathering performance were those containing low concentrations of a phthalocyanine green pigment combined with an inorganic yellow Cr-Sb-Ti Oxide. This is thought to be because the inorganic yellow Cr-Sb-Ti Oxide itself is relatively photo-active for a commercial pigment, and on top of that is photo-sensitised by the organic green phthalocyanine. This was confirmed with experiments that measured the photo-electrical response of pigmented PVC coatings using a dye-sensitised solar cell set-up. This concept seems to be a quick and easy way to test the photo-activity of paints.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Eng.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available