HYDROPHOBIC RECOVERY AND MISTING BEHAVIOR OF PLASMA TREATED PS AND PC SURFACES

Oxygen plasma treatments of transparent polymers such as polystyrene (PS) and polycarbonate (PC) were performed. Then the hydrophobic recovery of treated surfaces and its effect on their misting behavior was studied. Surface investigations, such as XPS and water contact angle measurements, were combined with the characterization of misting behavior by light transmission methods. In the case of PS it was found that the composition and wettability of the surface layer is insensitive to extraction in water. Hydrophobic recovery leads to decreases of advancing angles upon aging by a mechanism involving macromolecular motions. Misting follows rather closely the behavior of water advancing angles. Oxygen plasma treatment of PC surfaces induces the formation of low molecular weight species which can be extracted by water. Both non-extracted and extracted surfaces were found to undergo hydrophobic recovery with the same mechanism observed in the case of PS. In both cases the misting behavior can be well explained on the basis of wettability.