Optical clarity of polypropylene products

Abstract

The number of products where transparency and optical clarity are basic requirements increases continuously. Articles used in medicare represent very good examples of such applications, where optical clarity is not only an aesthetical demand, but a necessary condition for the quick identification of the product. Earlier amorphous polymers, e.g. polyvinyl chloride (PVC) and polystyrene (PS), were used in such areas, since, in semicrystalline polymers, light scattered on the different units of their structure made the products opaque. In polyolefins, the incident light is scattered on the crystallites, spherulites and also on the interface between the amorphous and crystalline phases having different refractive indices [1]. Often the size of the crystalline units is large enough to interfere with visible light and this interference results in considerable haze. The advantageous price/performance relations of polypropylene (PP) and development both in processing as well as additive technology lead to a breakthrough for its use also in fields where optical clarity is needed.