Electrical corona discharge treatment

Pure ozone for ozonolysis of OA was generated from pure carbon dioxide by electric corona-discharge treatment, thus offering an industrially affordable process [65]. 

Electrical ( corona ) discharge treatment of polyethylene and polypropylene film has been used for many years in order to render these surfaces printable and suitable for lamination or coating. In this process the polymer film is passed over a grounded metal roller covered with a "dielectric" (insulating) material. Separated from the film by mm is an electrode bar to which a high voltage is applied (typically 15 kV at 20 K Hz). Air in the film-electrode gap is ionised, the corona discharge thus formed is stable and this "treats" the film surface. 

Electrical corona discharge treatment It is a method for rendering inert plastics, such as polyolefins, more receptive to inks, adhesives, or... 

Figure 4.12 Schematic diagram of the electrical ("corona ) discharge treatment process [35]. 

Adherability of the film may be enhanced by its treatment with flame, electric (corona) discharge, boron trifluoride gas, activated gas plasma, dichromate sulfuric acid, and a solution of alkali metal in liquid ammonia (104-107). A... 

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... 

Today, corona discharge is the electrical method used most widely and is one of the most popular for preparing the surfaces of polyolefin films. It relies on establishing a corona discharge between an electrode and an earthed roller covered by a dielectric layer the film is passed over the roller and the discharge renders the surface of the film receptive to inks. Sherman and co-authors12 described the theoretical electrical relationships in the treatment equipment and by means of the Lissajous technique for measuring power demonstrated how much true power was dissipated in the material under treatment. Table XX lists some relevant patents. 

Metallized polypropylene (PP) is used today in many different fields such as automotive, decoration, electrical. In order to obtain a good adhesion between the aluminium and the polymer a pretreatment of the film prior to the metallization is necessary. Indeed, the very extreme surface of the polymer has to be modified in order to prepare it to a good adhesion with the metal. Thus the polymer is placed in a low pressure plasma of nitrogen with a corona discharge configuration of electrodes, and the metallization is carried out in situ after the pretreatment in nitrogen. This process, which simulates an industrial polymer film treatment has proven a great efficiency for very short treatment times (23 ms) (1).However, the mechanisms responsible for the improvement of adhesion are not totally explained yet. 

Figure 11-62. Destruction-removal efficiency (DRE) and electric power input as a function of the pulse repetition rate for treatment of acetone (diluted in air) in pulsed corona discharge. Initial acetone concentrations are 5, 20, 200, and 1000 ppm.

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