The wettability of ultra-high molecular weight polyethylene surfaces was modified by atmospheric plasma treatment controlling exposure time and distance. The two-factor experimental design included treating samples for 0.5 and 1.5 s, placed at 2.0 and 4.0 cm from the plasma. The behavior of wettability was monitored for 90 days via the sessile drop method. Right after treatment, contact angle decreased from 85 to nearly 40 degrees. These changes coincided with an increase in the proportion of the orthorhombic crystalline phase and a reduction in the amorphous phase of the material. Later on, these structural changes were reversed. After 90 days of the plasma treatment, the contact angle was 66 and 73 degrees in samples located 2 and 4 cm away from the plasma, respectively. Although the plasma treatment increased the roughness of the polyethylene surface by 6 nm, it basically retained its mirror finish, except for a few blemishes here and there.
- Atmospheric plasma
- Atomic force microscopy