During and after the application of a coating system, surface defects can often occur that affect the optical properties of the coating and its protective function.
Typical surface defects are:
Poor substrate wetting
Cratering
Formation of Bénard cells, floating
Poor leveling, orange peel
Air-draft sensitivity
A key parameter for all these sorts of defects is the surface tension of the materials involved; in particular, differences in surface tension lead to the formation of surface defects. Surface tension differences can originate from the system itself (evaporation of the solvent, cross-linking reaction of the binder) or can be caused by external sources overspray or dust particles (contamination of the substrate).
To avoid these surface defects, additives are used to influence the surface tension of the coating and/or minimize surface tension differences. Such products are primarily polysiloxanes (silicones) and polyacrylates (acrylate additives).
