Contact angles corona discharge

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

The effect of corona discharge treatment on the surface physico-chemistry of PP and PET films has been investigated using surface energy measurements from contact angles, XPS and AFM. The information gathered from these techniques, in addition to practical adhesion measurements, has enabled identification of the dominant mechanisms of adhesion of silicones to these plastic films. The physisorption mechanism and the mechanism of mechanical interlocking are not the cause of... 

A corona freafment was applied to different wood tablets (Teak, Birch and Pine) and the wettability of the modified surfaces was measured by water contact angles which decreased from 90° to less than 40°, after a 24kJm discharge [3]. The adhesion of a water-based lacquer was also improved. 

Plasma Arc Treatment - In adhesive and solvent bonding, a method for treating the surfaces of parts prior to solvent and adhesive bonding, in which an electrical current between two electrodes in a gas at low pressure exeites the gas particles, producing free radicals. Contaminants are stripped from the surface of the part, and wettability is increased by reduction of the contact angle. Also ealled plasma discharge, plasma treatment. See also Corona Discharge Treatment... 

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