what is Cpp film
CPP film are designed to offer high performance, great appearance and easy converting for flexible packaging and other applications. It is produced from a combination of various grades of PP polymer. Cpp film can be produced transparent and white opaque (lamination and coating grades)
Applications of Cpp
Cast films are used for food and textiles packaging, flower wrapping, as photo album page protectors, as coating substrates in extrusion coating processes or laminated to other materials in the formation of more complex films, among others. Typically, the Cpp film process involves the use of co-extrusion, which is a simultaneous extrusion of two or more materials from a single die to form a multi-layered film. This is because in many cases the final application of the plastic film demands a performance that cannot be achieved if the film is composed of only one material. For example, in many instances food packaging applications require the use of films with oxygen barrier capabilities. To meet the requirement a high oxygen barrier materials is combined with polyolefin materials in a multi-layered structure. Co-extruded films typically contain up to seven layers; however, the use of more layers is becoming more common. The number of layers, their position in the co-extrusion and their individual thickness are all variables that change depending on the particular application of the film.
Basic concept of Cpp film extrusion
In the cast film extrusion process, the molten polymer travels through a flat die system to adopt its final flat film shape. The process starts with the feeding of plastic resins by means of a gravimetric feeding system to one or more extruders. The materials are then melted and mixed by the extruders, filtered and fed to the die system.
Immediately after exiting the die, the molten curtain enters the cooling unit where its temperature is lowered with a water cooled chill roll to “freeze” the film. The film is then passed downstream where the edges are trimmed, corona treatment is applied (if a fabrication process such as printing ,lamination or metal coating is required) and the film is wound into rolls.The main components of a typical cpp film line is presented below.
1-Gravimatric system
2-Extruders
3-Filteration system
4-T-die
5-Cooling section (chilled rolls)
6-Automatic Gauge control system
7-Corona treament unit
8-Winding section
Computerized system(automatic plants)controls the following tasks..
- startup and shutdown
- resin feeding and extruder speed
- throughput , gauge control
- die flow and line speed
- parameters (tension etc)
- recipes and production data
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