How is PE Protective Film Blown Out?

PE Protective Film is a common plastic product in our daily life. It is produced by calendering process, extrusion process, blow molding process and other methods. The method of film blow molding is to melt and extrude the raw material into a thin tube through the extruder, and then blow it with compressed air while it is hot, and then cool and shape it into thin film products.

The main materials for blow molding film are LDPE, HDPE, LLDPE, EVA, PVC, PP, PS, PA, etc.

Forming process of polyethylene blown film

After plasticizing and extruding, the material forms a tube, which is then inflated, cooled, drawn and coiled.

In the process of blow molding film, according to the different extrusion and traction direction, there are three methods: flat blowing, up blowing and down blowing. This is a common molding process, and there are also special blow molding methods. As for the extrusion and blowing method, let's take a look at the differences between these methods.

1、 [horizontal extrusion and upward blowing method] this method is to use a right angle die, that is, the discharge direction of the die head is straight with the extruder, the extrusion pipe is broken upward, and after pulling to a certain interval, it is clamped by the herringbone plate. The extruded tube is inflated into a bubble tube by compressed air introduced from the bottom, and its transverse size is controlled by the amount of compressed air, and the longitudinal size is controlled by the traction speed The blown film can be obtained by cooling and shaping. The main types of plastics suitable for up blowing are PVC, PE, PS, HDPE protective films.

2、 [horizontal extrusion and blow down method] this method uses a right angle die, and the process of the bubble tube leading out from the bottom of the die is known as the flat extrusion and blow down method. This method is especially suitable for materials with low viscosity and plastic films requiring high transparency. Such as PP, PA, PVDC (vinylidene chloride).

3、 [flat extrusion and blowing method] this method uses a flat die which is concentric with the extruder screw, and the foam tube is on the same horizontal plane with the center line of the die. This method is only suitable for blowing small caliber films, such as LDPE, PVC and PS films. The horizontal blowing method is also applicable to the production of heat shortened films.

The above three processes have their own advantages and disadvantages. Now, compared with the advantages of the surface process, the flat extrusion upper blowing tube is hung on the cooling pipe, with stable traction, small floor area, convenient operation, and easy production. The thick protective film requires high workshop and high cost, and is not suitable for processing the plastic with high fluidity, which is not conducive to the cooling and production of the protective film Low production efficiency, flat extrusion and blow down is beneficial to the cooling of protective film and high production efficiency. The plastic extruder with high processing fluidity is higher from the ground, which is inconvenient to operate The flat extruding and blowing machine head with thin protective film is of central type, simple structure, uniform thickness of protective film, convenient operation, simple blowing ratio of film drawing, which is not suitable for processing protective film with high relative density and large bending diameter, covering a large area and slow cooling of foam tube, which is not suitable for processing plastic with high fluidity.