Anti-fog properties and aging of polyethylene terephthalate (PET) treated by atmospheric pressure plasma

Polyethylene terephthalate (PET) is widely used in packaging due to its high clarity and transparency. However, some applications require anti-fog surfaces, which untreated PET cannot provide. In this study, PET films were treated using two plasma systems: an atmospheric pressure plasma jet (APPJ) and a dielectric barrier discharge (DBD), both operating with nitrogen as the working gas and aiming to develop anti-fog properties. The effect of treatment time on wettability and anti-fog properties was investigated. An increase in wettability was observed after all plasma treatments. The stability of the surface modification was also evaluated after 7 days. Treatments with the APPJ exhibited significant hydrophobic recovery after aging, while those with the DBD maintained stable hydrophilicity. Anti-fog properties were assessed in samples treated with the DBD system, revealing that the anti-fog area persisted after aging, with a reduction of 20%–30%, depending on the treatment time. These findings demonstrate the potential of atmospheric pressure plasma as an effective method for modifying PET surfaces to achieve anti-fog functionality.