Films are generally metallized and brightly printed before they are combined together to make the packaging we see all around us. In the manufacture of these films, it is necessary to change the surface so that the ink and aluminum layers will stick to them. Without this film surface treatment, the films could not be made into the packaging that we use and take for granted. The treatment is often carried out by passing the film through a corona discharge, where the film surface is burned (i.e., oxidized) by the intense corona produced by the treater. This process is called “corona treatment” and is used widely throughout the world to treat plastic films.

The corona is produced by passing a high voltage discharge through a thin layer of air between a metal bar and an insulating roller. This process consumes electricity to create the corona discharge. This project was designed to determine how much electricity is necessary to corona treat the film. It turns out that the amount of electricity needed to create the corona is controlled by the insulating roller, which has to have a tough, durable insulating surface. Usually the roll is made of metal so that it is strong enough to use. The coating is applied to the outer surface of the roller to protect it from the high voltage. The coating must have excellent electrical properties and be tough. Many different types of coatings can be used, such as epoxy plastic coatings, silicone rubber sleeves, ceramic coatings and glass coatings. In practice, the epoxy and silicone sleeves are prone to damage because they are relatively soft and are easily scratched and cut, which leads to an electrical failure of the roll. The ceramic and glass rollers are much more scratch resistant and have been favored in recent years.