Novel experimental setup for the determination of the photocatalytic stability and activity of pigments and coatings
In the past photoactive pigments have been surface passivated to reduce the photoactivity and thereby to avoid chalking. In new applications highly photoactive types of these pigments are used on glass or ceramic substrates for self cleaning and pollution reduction purposes. This initiated attempts to develop photoactivity test devices. In this contribution a test chamber method is presented which is based on a previous setup. The samples are placed in a chamber where various climatic and atmospheric conditions can be applied and controlled including exposure to model pollutants. During irradiation by UV light a FTIR spectrometer records the amount of pollutants and their decomposition products. This technique does not only allow to follow the photoactivity of the pigment and pigmented coating regarding the decomposition of model pollutants, but also to determine the photocatalytic stability of coatings by detecting products of the decomposition of the polymeric binder.
Key words: photocatalytic activity, stability
The effect of overpainting period of epoxy coatings on adhesion of topcoats and protective properties of whole paint system
The dependence of surface properties of aged and non-aged intermediate coats on adhesion and durability of coating systems were tested. The intermediate coats were aged 500 h in UV chamber. The surface free energy and polar groups were estimated after ageing. The results have showed that adhesion of polyurethane topcoats depends on degradation of epoxy intermediate coats. Coatings with good adhesion have good protective properties even when the temporary blisters have occurred.
Key words: epoxy coatings, polyurethane coatings, ageing of epoxy coatings, adhesion, corrosion protection
Determination of coating adhesion. Part 1: Pull-off method
Current standard legislation concerned evaluation and research methods of coating adhesion has been presented. This part relates to methodology and conditions of measurements by pull-off method with regards to different legislation requirements for laboratory and on-site conditions. The proposals of results interpretation have been presented as well as difficulties and possible ways of overcoming them for coatings controlled on industrial constructions.
Key words: coating adhesion, pull-off method, paint coatings