Jiuzhi Knowledge: Polyethylene film blown film forming process

The production of films by blow molding processes and other processes have the following advantages:

1. Simple equipment, low investment, and quick results;

2. The equipment has compact structure, small floor space and low construction cost;

3. The film is stretched and inflated, and the mechanical strength is high;

4, the product is infinite, less waste, low cost;

5, wide amplitude, less welds, easy to make bags;

Compared with other molding processes, its disadvantages are as follows:

1. The film thickness uniformity is poor;

2, the production line speed is low, the output is low (for calender);

3, the thickness is generally 0.01 ∽ 0.25mm, the diameter is 100-5000mm;

The main raw materials for blown film: LDPE, HDPE, LLDPE, EVA, PVC, PP, PS, PA, etc.

Polyethylene blown film forming process:

Blown film process, material plasticizing extrusion, forming tube bad inflation molding; cooling, traction, coiling. In the blow molding process, depending on the extrusion and traction directions, it can be divided into three types: flat blow, upper blow, and lower blow. This is the main molding process and also has a special blow molding method.

1. Flat extrusion method

The method uses a right angle handpiece, that is, the discharge direction of the machine head is perpendicular to the extruder, the extrusion pipe is broken upward, and after being pulled to a certain distance, it is clamped by the herringbone plate, and the extruded tubular air is introduced from the bottom to compress it. Inflated into a bubble tube, and its transverse dimension is controlled by the amount of compressed air gas, the longitudinal dimension is controlled by the traction speed, and the blown film can be obtained by cooling and setting the bubble tube. The main plastics suitable for the upper blowing method are PVC, PE, PS, HDPE.

2, the flat extrusion method

The method uses a right angle handpiece, and the process of drawing the bubble tube from under the machine head is called a flat extrusion method. This method is particularly suitable for raw materials with low viscosity and plastic films requiring high transparency. Such as PP, PA, PVDC (vinylidene chloride).

3, flat extrusion blow method

The method uses a straight head that is concentric with the extruder screw. The process of the bubble tube and the center line of the head is on the same level. The method is only suitable for blowing small-diameter films, such as LDPE. PVC, PS film, flat blowing method is also suitable for the production of blown heat shrinkable film.

The above three processes have their own advantages and disadvantages. Compared with the advantages and disadvantages of the process, the blowpipe is hung on the cooling pipe, the traction is stable, the floor space is small, the operation is convenient, and the film with large diameter and thick thickness is easily produced. It is required that the high plant and high cost are not suitable for processing plastics with high fluidity, which is not conducive to film cooling;

The production efficiency is low, the extrusion is favorable, the film is cooled, the production efficiency is high, and the plastic extruder with high fluidity can be processed from the ground. The operation is inconvenient. It is not suitable to produce a thin film flat-blown flat head. Simple, uniform film thickness, easy to operate, easy to inflate the film. It is not suitable for processing. The film with large relative density and large folding diameter has a large cooling area and is not suitable for processing plastics with large fluidity.