UV Protection and Coatings for Plastics in the Automobile Industry
The material itself is subject to a natural aging process, which begins as early as manufacture, due to extreme processing conditions that occur at times. To delay the degradation as long as possible, so-called process and long-term stabilizers are added. If the component is exposed to the elements without protection, degradation is further accelerated. In addition to the compulsory long-term stabilization, the polymer also needs an additional UV-stabilization package.
This, however, exacerbates the problem of migration1: the organic substrate makes it possible for the stabilizers to migrate into the plastic and also permits the migration of the plastic stabilizers to the top surface of the coating. With a decrease in the concentration of UV protector in the paint surface, the protective function of the coating, by definition, also decreases. Plastic stabilizers migrating upwards from the substrate cause yellowing in the topcoat or, in the worst case, can even lead to complete loss of adhesion.