How is the plastic film made?

Plastic film is widely used in daily life, such as vest bag for shopping and fresh-keeping bag for refrigerator.

There are many ways to produce plastic films. First, the plastic is heated and melted, and then it is turned into a film by various methods. One method is like rolling a noodle. The melted plastic is sandwiched between two rollers, rolled into a film, and then stretched to make it stronger. Polyvinyl chloride films are usually made by this method called calendering. Printing color patterns on this film can make tablecloths, bathroom curtains and so on. Another method is to use a machine similar to a meat grinder (that is, an extruder) to extrude molten plastic from the annular gap into tubes. When the pipe becomes hot, compressed air is blown from the inside of the pipe, which makes the pipe expand and stretch in front, and the pipe wall becomes thinner. After cooling, it becomes a tubular film, which can be made into various vest bags. Polyethylene and polypropylene films are usually produced by this method called blow molding. This film is stretched in both longitudinal and transverse directions during production and has good strength. Another method is to extrude a flat plate first, then stretch the front end and widen the two sides, and finally get a flat plate film. This is the production process of polypropylene film like cellophane. The base of the adhesive tape is also produced in this way, but the material is nylon wheel.