High-Density Polyethylene (HDPE) Surface Treatment Using an RF Capacitive Atmospheric Pressure Cold Ar Plasma Jet

In this study, a high-density polyethylene (HDPE, 5-mm-thick, 0.95 g/cm³) surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet. By using this Ar plasma jet, a hydrophilic HDPE surface was formed during the plasma treatment. In particular, the effects of an additive gas (N₂ or O₂) on the HDPE surface treatment were investigated in detail. It was shown that the addition of N₂ or O₂ gas had an important influence on the HDPE surface treatment. Compared to pure Ar plasma treatment, a lower value of water contact angle (WCA) was obtained when a trace of N₂ or O₂ gas was added. It was also found that besides the quantities of active species in the plasma jet, the treatment temperature played an important role in the HDPE surface treatment. This is because surface molecular motion is not negligible when the treatment temperature is close to the melting point of the polymer.