Material Selection Requirements
Metallization of plastic substrates is accomplished in many different ways including electroless plating, electrolytic plating, vacuum deposition and sputtering etc. Electroless plating is accomplished by a chemical reaction between a reducing agent and metal ions without the need of an electric current. It is thus ideally suited for non conductive materials like plastics and is, therefore, widely used to produce conductive coating on them for subsequent electroplating. Electroplating not only gives a metallic appearance to plastics, but also increases surface hardness, chemical resistance and weathering properties etc. Even though ABS remains the most commonly electroplated material, other materials like polycarbonates and its blends, nylons, polyesters, polyacetals, polypropylenes, polysulphones etc. are routinely electroplated. Stress and contamination free moldings are a prerequisite for successful electroplating. Vacuum metallizing process uses vacuum to avoid oxidation of a heated metal which is evaporated and then deposited on plastic surfaces in very thin layers. Aluminum is the most used coating material. Plastic films are often vacuum coated for packaging and for use as hot stamping foils. Sputtering process also takes place in vacuum where atoms of coating material are displaced by impact, rather than heat, with heavy inert gas plasma such as argon. Sputtered coatings have better adhesion and are more abrasion resistant than vacuum metallization, and have successfully replaced electroplating process in certain applications. |