Surface hydrophilization of two polyester films by atmospheric-pressure plasma and ultraviolet excimer light exposures

Abstract

Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films were treated with an atmospheric-pressure plasma (APP) jet and a 172-nm ultraviolet (UV) excimer light in air. The advancing and receding water contact angles on both films decreased after the treatments, especially after APP treatment. After the treatments, the hydrophobic recovery was observed and almost diminished within a week. The dispersive component of the surface free energy of the two polyester films did not change due to the APP and UV exposure, whereas the acid–base component drastically increased after the treatments. The X-ray photoelectron spectroscopy results showed that the polyester film surfaces were oxidized by the treatments. From the AFM images, the topographical change on the film surfaces due to the treatments was clearly observed. It was found that the APP treatment of the PET film prevented the deposition of particulate soils in air due to the decrease in the contact area between the film and the soil particle. Furthermore, the soil release in the aqueous solutions was promoted as a result of the hydrophilization of the polyester films due to the APP treatment.

Keywords:

• atmospheric-pressure plasma jet
• ultraviolet excimer light
• polyester films
• PET
• PEN
• contact angle
• surface free energy
• soil deposition
• soil removal

Acknowledgments

Gratitude is expressed to the Ministry of Education, Sports, Culture, Science, and Technology, Japan for a Grant-in-Aid for Scientific Research. Yuki Kuroda of Nara Women’s University is thanked for her assistance in the evaluation of the polyester surface performance.