Change of PET film surface by low-temperature plasma.

Abstract

PET films stretched under different conditions were treated by radio frequency low-temperature plasma with various gases, and the surface topographical change was investigated by wettability and the introduction of functional groups. The results indicated that undrawn and biaxially drawn films treated with plasma were etched irregularly and randomly, but regular etching structure (seashore structure) which was made at right angle to the stretching direction was observed on uniaxially drawn films treated with plasma. This tendency was especially conspicuous, in oxygen and argon gas plasma treatment, but the degree of etching of the surface treated with nitrogen-containing gas plasma such as nitrogen and ammonia was small because nitrogen atoms were incorporated into PET surface during plasma treatment, Untreated PET films exhibited different wettability according to stretching conditions, but once they underwent the low-temperature plasma treatment, they showed nearly equal wettability irrespective of stretching conditions. The results showed that the oxygen gas plasma improved surface wettability exceedingly among the gasses used in this study, and it gave the greatest critical surface tension. Hydrophilic functional groups may have been introduced into PET surface treated with oxygen gas plasma, judging from the ratio of dispersion force and polar force calculated from expanded Fowkes equation.