Three different low-temperature plasma-based methods for hydrophilicity improvement of polyethylene films at atmospheric pressure

Three different low-temperature plasma-based methods were used to improve the surface hydrophilicity of polyethy- lene （PE） films, and all the modification processes were carried out by employing an atmospheric pressure plasma jet （APPJ） system. （a） PE films were directly modified by APPJ using a gas mixture of He and 02. （b） Acrylic acid （AA） was introduced into the system and a polymer acrylic acid （PAA） coating was deposited onto the PE films. （c） AA was grafted onto the PE surface activated by plasma pre-treatment. It was found that the hydrophilicity of the PE films was significantly improved for all the three methods. However, the samples modified by Process （a） showed hydrophobicity recovery after a storage time of 20 days while no significant change was found in samples modified by Process （b） and Process （c）. The Fourier transform infrared spectroscopy （FTIR） results indicated that the most intensive C=O peak was detected on the PE surface modified by Process （c）. According to the X-ray photoelectron spectroscopy （XPS） analysis, the ratios of oxygen-containing polar groups for samples modified by Process （b） and Process （c） were higher than that modified by Process （a）.

Influence of air addition on surface modification of polyethylene terephthalate treated by an atmospheric pressure argon plasma brush

An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET)surface in order to improve its hydrophilicity.Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied.Voltage-current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period.Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content,which leads to the better hydrophilicity of PET surface after plasma treatment.Besides,an aging behavior is also observed.The hydrophilicity improvement is attributed to the production of oxygen functional groups,which increase in number with increasing air content.Moreover,some grain-like structures are observed on the treated PET surface,and its mean roughness increases with increasing air content.These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.