Corona and Plasma Treatment Processes
When it is necessary to bond plastic materials to metals or other plastics, or to simply print on a plastic surface, quality results depend on the ability of the liquid, adhesive or ink to adhere to the surface and this is where corona and plasma treatment comes into place. Adhesive strength relies on one specific property of the surface: the surface tension.
Surface tension energy is measured in dyne/cm (mili N/m). Surface tension energy is the deciding factor on how well a liquid adheres to a polymer surface. For a proper bond to exist between a liquid and a substrate surface, the substrate’s surface tension energy must exceed the liquid’s surface tension energy by about 2-10 dyne/cm. The higher the surface tension energy of the solid substrate in relation to the liquid, the better its ‘wettability’. For information regarding necessary dyne levels and surface tension energy, please see the chart below.
Many engineering plastic materials have insufficient surface tension energy for printing or bonding. Polypropylene and polyethylene are prime examples. These materials have many useful properties, which make them materials of choice. However, their poor wettability creates severe limitations when it comes to design choices.
Read more about the different processes and necessary dyne levels
- The Corona Process
- The Plasma Process
- Necessary Dyne Levels