Low pressure plasma treatments inside a closed package

An object is sealed under reduced pressure in a flexible plastic package. If it is put in a vacuum chamber the residual gas in the package inflates it. Adjusting the pressure inside the package and in the chamber, it becomes possible to generate a plasma inside the package by applying an external electrical field. This plasma can be used to alter the surface properties of the object. After the treatment, the package will prevent a contamination of the clean and modified surfaces. Polyethylene and polystyrene incorporate substantial concentrations of oxygen and nitrogen in their surfaces during a plasma treatment in a package, which contains air or nitrogen as a residual gas. The contact angle with water is decreased accordingly to approximately 40°. The XPS C1s spectra show features of amide/imide structures. In the polyethylene surface we also found a component that represents urethanes.