Plastic film is a common kind of plastic product, it can be produced by the calendering method, extrusion method, blow molding, and other process methods, blow molding film is the plastic raw material through the extruder to melt the raw material into a thin tube, and then hot with compressed air will blow it, after cooling finalize the film products.
1. Advantages and disadvantages of the blow-molding process for film production
(1) Advantages of the blow molding process
The blow-molding process has the following advantages compared with other processes:
1) Simple equipment, less investment, fast effect;
2) Compact equipment structure, small area, low plant cost;
3) After stretching and blowing, the film has high mechanical strength;
4) Less material, waste, and low cost;
5) Wide radiation, less weld, easy to make bags;
(2) The shortcomings of the blow molding process
Blow plastic film its main raw materials: LDPE, HDPE, LLDPE, EVA, PVC, PP, PS, PA, etc.
Compared with other forming processes, its disadvantages are as follows:
1) Poor uniformity of film thickness;
2) Low production line speed and low output (for calendar);
3) Thickness is generally 0.01∽0.25mm, folding diameter 100-5000mm;
2. Polyethylene blow plastic film forming process
Blow-molded film process, material plasticizing extrusion, forming pipe bad blowing molding; Cooling, traction, winding. The process of blowing film forming, according to the direction of extrusion and traction, can be divided into three kinds of flat blowing, up blowing, and down blowing, which is the main molding process and also has a special blowing method, such as extruded blowing method.
(1) Flat squeeze blowing method
This method is to use a right Angle head, that is, the discharge direction of the head is perpendicular to the extruder, the extrusion tube is bad up, pulled to a certain distance, by the miter plate clamp, the extruded tube by the compressed air introduced at the bottom will blow it into a bubble tube, and the amount of compressed air volume to control its transverse size, to control the longitudinal size of the traction speed, the bubble tube can be cooled and shaped to get blown film. As shown in the picture. Suitable for blowing up the main plastic varieties are PVC, PE, PS, and HDPE.
(2) flat squeeze down blowing method
This method uses the right Angle head, a bubble tube from below the head of the process called the flat extrusion blowing method, this method is especially suitable for the low viscosity of raw materials and high transparency of the plastic film. Such as PP, PA, and PVDC (vinylidene chloride).
(3) flat extrusion and flat blowing method
This method uses a flat head concentric with the extruder screw, the bubble tube, and the center line of the head on the same horizontal plane process called flat extrusion and flat blowing method, this method is only suitable for blowing small diameter film products, such as LDPE, PVC, PS film, the flat blowing method is also suitable for blowing heat shrink film production.
3.Conclusion
Each of the above three processes has advantages and disadvantages, compared with the table process advantages and disadvantages of flat extrusion on the bubble tube hanging on the cooling tube, traction stability covers an area of small, easy to operate and easy to produce large folding diameter, thick film requires high workshop, high cost is not suitable for processing plastic fluidity is not conducive to film cooling, Low production efficiency flat extrusion blowing is conducive to film cooling, high production efficiency and high flow processing plastic extruder is higher from the ground, Inconvenient operation is not suitable for the production of thin film flat extrusion blowing head for the center type, simple structure, film thickness is more uniform convenient operation, film easy to blow expansion ratio can be larger is not suitable for processing relatively large density, folding diameter of the film covers an area of large bubble tube cooling is slow, is not suitable for processing large flow of plastic.
