Tests to evaluate surface textures and deffects in coatings
The texture is a surface property of a piece which can be felt when touching and seeing, so it affects to aesthetics. They are repetitive or random alterations of the piece’s nominal surface. The most usual properties that can characterize it are roughness and wavyness.
- Roughness. It is the most common measure to characterize the surface texture. It assesses the small vertical diversion of the nominal surface that are normally determined by the plastic material characteristics, the piece transforming process or those given by the own coating. Therefore, AIMPLAS uses a roughness metre that proportionates the average depth of the deviations absolute values, Rz and the average value of these deviations in a surface specific length, Ra as most stressed parametres.
- Wavyness. It is defined as a higher spacing deviation. It is commonly considered as a defect of the coating caused by a bad extensibility of it. A really marked wavyness or in very high brightness level can be unattractive aesthetically and it is known as orange peel. This effect can be evaluated visually but also can be measured by Wavescan.
Any defect and contamination that is produced when the film is being formed will affect the final aspect and the coating protective properties. Therefore, it is important to detect them by visual inspection of the surface or by means of a surface analysis with a magnifying glass or a microscope. AIMPLAS has light and scanning microscopes that allow to carry out comprehensive analysis of the surfaces.