Hydrophobic Recovery of Plasma-Hydrophilized Polyethylene Terephthalate Polymers

Oxygen plasma is widely used for enhancing the wettability of numerous polymers, including polyethylene terephthalate (PET). The treatment with plasma containing oxygen will cause surface functionalization with polar functional groups, which will, in turn, improve the wettability. However, the exact mechanisms leading to the hydrophilic or even super-hydrophilic surface finish are still insufficiently explored. The wettability obtained by plasma treatment is not permanent, since the hydrophobic recovery is usually reported. The mechanisms of hydrophobic recovery are reviewed and explained. Methods for suppressing this effect are disclosed and explained. The recommended treatment which assures stable hydrophilicity of PET samples is the treatment with energetic ions and/or vacuum ultraviolet radiation (VUV). The influence of various plasma species on the formation of the highly hydrophilic surface finish and stability of adequate wettability of PET materials is discussed.

Automated summary

Oxygen plasma is widely used to improve the wettability of polymers like PET, but the mechanisms leading to hydrophilic surfaces are not well understood. Plasma treatment can result in temporary wettability, with a tendency towards hydrophobic recovery. This paper reviews the mechanisms of hydrophobic recovery, while also discussing methods to suppress this effect. It recommends treatment with energetic ions and/or vacuum ultraviolet radiation to achieve stable hydrophilicity of PET samples. The influence of different plasma species on the formation and stability of highly hydrophilic surfaces in PET materials is also discussed.