Modification of surface properties of polyethylene by Ar plasma discharge

Polyethylene (PE) surface was modified by Ar plasma discharge. The changes of surface morphology and surface wettability (characterized by contact angle) were followed using AFM microscopy and standard goniometry, respectively. The changes of chemical structure of PE polymeric chain were characterized by FTIR and XPS techniques. A nanoindenter was used to study mechanical properties (microhardness, elasticity module and microscratch test) of modified PE. After exposition to the plasma discharge a fast decline of the contact angle is observed. The decline depends on the discharge power and the time elapsed from the plasma exposition. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Surface morphology of modified PE depends on the plasma discharge power and exposure time. Maximum microhardness and elastic module, observed on PE specimens exposed to plasma discharge for 240 s, may be connected with PE crosslinking initiated by plasma discharge.