Different plastic film with different forming methods

Plastic PVC film is common in our daily life, like book covering, furniture decoration. In addition to PVC film, do you know there are many kinds of plastic films with different usages?

( 1 ) Classify according to raw materials: polyethylene film, polypropylene film, polyvinyl chloride film, polyester film, etc.

( 2 ) Classify according to usages:  there are agricultural films (they can be divided into mulch films and greenhouse films according to the specific uses of agricultural films); packaging films (packaging films can be divided into food packaging films, beverage films, etc.) ; decorative film for furniture, wallpaper, door.

( 3 ) Classify according to forming methods: there are films that are extruded and then blow-molded, called blown films; films that are extruded and plasticized, and then the molten material is cast from the die orifice, called Cast film; there are several rollers on the calender that roll the film made of plasticized materials, called calendered film.

The introduction of three general plastic film forming methods below: The casting method is a non-stretched, non-oriented flat-extruded film produced by melt-salting and quenching. There is no obvious orientation structure.

In general, extrusion methods include unidirectional stretching and biaxial stretching, and biaxial stretching is a production method that has been paid close attention in recent years. The basic principle of the bidirectional stretching technology is that the polymer raw material is heated and melt extruded into a thick sheet through an extruder, and then in a suitable temperature range above the glass transition temperature and below the melting point, through the stretching machine to carry out a certain lengthwise and transverse direction The multiple stretching makes the molecular chains oriented and arranged in a plane parallel to the film, and then heat-set under tension to fix the oriented macromolecular structure, and finally formed a film by cooling and subsequent processing.

The blow molding method is usually manufactured by extrusion blow molding, the material is plasticized and extruded to form a tube blank to be inflated, and then cooled, pulled, and coiled. The blown film is oriented.

The different forming methods of the above three processes cause the film's conductivity to be significantly different; at the same time, compared with the unstretched film, the barrier performance of the stretched film is improved, the permeability to gas is reduced, and the optical performance, transparency and surface gloss are improved. Good dimensional temperature and uniform thickness performance.