The molding process of blown film

16 Feb.,2022

Polyolefin blown film, generally among the temperature is higher than the head temperature, PE thermal stability is good, this is because the olefin is not easy to decompose, the fuselage temperature is high, the plasticization is sufficient, the fluidity is good, and the head temperature is low, and the film is easy to set.

 

Blow molding film molding process, protective film manufacturer Ichikawa film to take you to learn more about the following:

1, the requirements for raw materials: polyethylene blow molding film according to the use of requirements mainly heavy packaging film, general packaging film, agricultural film three kinds. The molecular weight of the polyethylene resin is expressed in terms of the size of the melt index (MI). If the melt index is small, its molecular weight is higher and the tensile strength is also higher, while if the melt index is large, its molecular weight is lower and the tensile strength is also lower.

2. Uniformity of the annular gap of the machine head: The uniformity of the annular gap of the head directly affects the uniformity of the thickness of the product. It has an important impact on the quality of the product. The gap between the die is generally 0.6 ~ 1mmm, and the ring gap of the die is adjusted with a steel stopper ruler to ensure that the division is uniform everywhere. Temperature control: Pe thermal stability is good. < 300 °C without contact with oxygen is not easy to decompose. > 300 °C exposure to oxygen is easy to cause crosslinking.

Polyolefin blown film, generally among the temperature is higher than the head temperature, PE thermal stability is good, this is because the olefin is not easy to decompose, the fuselage temperature is high, the plasticization is sufficient, the fluidity is good, and the head temperature is low, and the film is easy to set.

LDPE hopper temperature should not be too high, to prevent pellets from sticking, barrel temperature up to 180 °C, the head temperature can be 10 ~ 20 °C lower than the fuselage temperature, molding temperature should not be too high or too low, then can not make the film get full plasticization, and produce irregular material flow, can not be sleek expansion and stretching. This is the film is also less tensile strength, and the surface gloss is poor, the transparency is reduced, and even the pattern similar to the annual ring of wood and the unmelted crystal nucleus (fish eye) appear.

3, temperature: temperature control is the key in the blow molding film process, is an important parameter affecting the quality. The advantage of this temperature control method is that the high temperature time of the material is short and not easy to decompose, which can reduce the number of disassembly heads and improve the production capacity of the machine.

4, cooling stereotyping: when the tube bubble is just extruded from the head, the temperature is higher, into a semi-flowing state, and now the cooling capacity is insufficient, the film is bonded to each other under the pressure of the traction roller, and the host capacity cannot be volatilized. The air supply around the cooling air ring should be uniform, otherwise the film thickness is uneven, otherwise the film thickness is uneven. The distance between the wind ring and the mouthpiece is 30~100mm.

5, drafting multiple: the ratio of traction speed to extrusion line speed into a traction ratio, usually controlled at 4-6, the traction ratio is a longitudinal stretch multiple, generally controlled at 2.5-3, so it is easier to operate, and the longitudinal and horizontal strength of the film is similar. The blowing ratio is too large, and the swelling film will swing like a snake, making it difficult to control the uniformity of the thickness.