Membrane surface treatment methods include corona treatment, plasma treatment, chemical treatment, photochemical treatment, flame treatment, coating treatment and so on. So what kind of film surface treatment method do we use? The corona treatment process is used, and the corona treatment process is relatively mature, and it is also the most common method for the surface treatment of plastic film at present. Let's take a look at the processing process:
The role of corona treatment: discharge between the electrode and the corona treatment rod through the electrode to ionize the air and form ozone and nitrogen oxide. At the same time, high-energy electrons and ions attack the surface of the film, causing its chain molecules to break, producing free radicals, and oxidizing cross-linking reactions with the corona products of the air to form polar groups such as hydroxyl and carbonyl groups, improving the surface tension and polarity of the film.
High energy electrons and ions are injected into the film to produce small concave dense holes on the surface of the plastic film, which coarses the surface of the film and increases the surface activity. The wetting tension of the film surface is related to the strength of corona treatment. The intensity of corona treatment is related to the electrode voltage and the gap between the electrode and the corona roller. The higher the electrode voltage, the smaller the distance between the electrode and corona roller, the stronger the corona treatment effect; The treatment effect of the film is also related to whether the air is inserted between the film and the corona roll, if there is air between the film and the corona roll, it will lead to the back of the film being treated, which may lead to the deterioration of the heat sealing performance of the film back, in addition, it is also related to the cleanliness of the corona roll and the electrode surface, if the corona roll and the electrode surface is dirty, it will weaken the effect of corona treatment
The addition of additives may also have certain effects on the polarity and surface tension of the film surface. The commonly used additive in BOPET films is an anti-adhesion agent, usually silica. The silicon-oxygen bond in silicon dioxide has strong polarity, and the surface of silicon dioxide particles is often adsorbed with a certain amount of combined water and hydroxyl, so the silicon dioxide particles exposed on the surface of the film help to increase the polarity and surface tension of the film surface, which is conducive to aluminum plating. Sometimes, in order to improve the compatibility of silica particles with PET and promote their dispersion in the PET polymerization process, surface treatment agents (dispersants, coupling agents, etc.) are used to surface treat them to reduce their surface tension and polarity. In this case, the distribution of silica particles on the surface of the film will affect the polarity and surface tension of the film surface, and excessive surface treatment agent may migrate to the surface of the film, resulting in poor aluminum plating performance.
