Surface Treatment of Plastics with Ionic Liquids for Decorative Metal Deposition

Surface treatment of plastics for decorative metal plating has been developed for more than 20 years and is widespread applied in automotive, electronics and faucets industries. Main advantages in contrast to the use of bulk metals are savings of weight and costs, facilitating complex geometries and superior aesthetic appearance. Most applied plastics represent acrylonitrile butadiene styrene polymers (ABS), ABS polycarbonate blends and polyamide. Etching of the plastic surface is required to enable the electroless plating of metals like nickel or copper. State of the Art for surface activation is etching with hexavalent chromic sulfuric acid. It is cost efficient, robust and reliable.^[1] Generally known, hexavalent chromium causes high environmental, health and safety impact. Moreover, the scope of application to different plastics is quite limited. Therefore, a sustainable and environmental-benign replacement of this substance of very high concern is demanded in the near future. Some concepts for the replacement of chromic acid are currently under investigation. The most public approaches are the use of potassium permanganate^[2] or ozone^[3]. Disadvantageously, these concepts improve health, safety and environmental impact only marginally. Moreover, complex waste handling and process equipment limit the potential as suitable substitute.

We report a potential and metal-free replacement approach based on surface treatment with ionic liquids. Employed ionic liquids and additives bear substantial environmental, safety and health advantages. Beyond, they show high potential for broadening the scope of applied plastics.^[4]

References:

[1] H. Midecke, J. McCaskie, N. H. Joshi, DE 19510855 A1, 1995.

[2] A. J. Königshofen, US 2003/0039754 A1, 2003.

[3] T. Bessho, K. Isami, K. Kumagai et al, US 2011/064889 A1, 2011.

[4] I. M. Malkowsky, A. Alemany, PCT Int. Appl. WO 2010/142567 A1, 2010.