Surface Modification and Hydrophobic Recovery (Aging) of Polyolefin Exposed to Plasma

Near-Plasma Chemical Surface Engineering

“…Indeed, it has recently been discussed that electron interactions during plasma chemical etching in a remote plasma without ion bombardment can reduce surface damage, including atom displacement, surface roughness, and the removal of undesired materials [ 26 ]. Furthermore, the influence of trapped charges should be considered for aging effects [ 35 ]. It has been reported that accelerated ions hitting a polymer surface can become trapped at defect sites within the near-surface polymer region [ 48 ].…”

“…It has been reported that accelerated ions hitting a polymer surface can become trapped at defect sites within the near-surface polymer region [ 48 ]. Trapped charge carriers, both positive and negative, i.e., including electrons, might contribute to the thermodynamic relaxation of plasma-activated PTFE surfaces through their decay over time—beside the mobility of fragments formed by the plasma interaction and the structural rearrangement of macromolecules [ 35 ]. The observed attenuated hydrophobic recovery might thus be related to the reduced NPC destruction effects and charge trapping (limited to electrons) by avoiding ion bombardment.…”

“…Plasma activation has been recognized to induce defluorination, oxygen incorporation, and changes in morphology [ 32 , 33 ]. Aging processes, however, result in surface reorientation of the modified PTFE via thermodynamic relaxation, yielding so-called hydrophobic recovery [ 34 , 35 ]. Different plasma processing methods and gas compositions have thus been investigated to attenuate a hydrophobic recovery that typically yields an almost complete loss of hydrophilicity on PTFE within several days [ 31 , 36 , 37 ].…”