Surface modification of a group of polymers using a low temperature cascade arc torch

Surface modification treatments were performed on six different types of polymers using low temperature cascade arc torch (LTCAT) of Ar with or without adding reactive gas of O-2 or H2O vapor. The effects of the treatments on the wettability enhancement, surface degradation from oligomer formation, and surface stability from the mobility of surface moieties and hydrophobic recovery were investigated. Surface characterization techniques included the static Sessile droplet method and dynamic Wilhelmy balance method. Experimental results indicated that Ar LTCAT treatments of the polymers with shorter treatment times (2 s in most cases) resulted in stable and hydrophilic surfaces without any surface damage from oligomer formation, with the exception of nylon-6. The excellent results from Ar LTCAT treatments were attributed to the CASING effect (crosslinking via activated species of inert gas). Addition of O-2 into Ar LTCAT resulted in greater wettability of the treated surfaces, but increased surface damage from oligomer formation. Adding H2O vapor into Ar LTCAT produced extremely hydrophilic surfaces on the polymers, but pronounced surface damage. The surface oligomer formation was attributed to alkoxy degradation reactions and chain scission from overexposure to high energy species. Comparisons of the treatment outcomes for each type of polymer are discussed with respect to the degree of wettability enhancement, the stability of the treated surfaces, and the susceptibility to degradation. (c) 2007 Wiley Periodicals, Inc.