In order to reduce the environmental pollution damage and enhance the environmental protection in packaging, many manufacturers will choose to use cast film to package the product after the production of the product, so what functions and advantages does the cast film have? In the production process What are the common problems in all? The following article will give you a brief introduction.Functions and advantages of cast film:
1. Features:
The cast film can continue to be stable at room temperature, but after heating, it can produce a shrinking effect.
The cast film belongs to polyethylene. The cast film is a non-toxic, colorless, odorless and environmentally friendly material that can be recycled. The cast film makes the original mother film lighter and thinner, and the physical tensile strength and wrapping force remain unchanged. And it can be packaged without any tools.
2. Advantage:
The use of cast film not only reduces the amount of waste disposal, but also reduces the amount of cast film processing and recycling, accordingly.
The cast film can be recycled and recycled, using green environmental protection film. Not only can reduce environmental pollution, but also can recover the cost of packaging.
The use of cast film can not only reduce atmospheric pollution, but also reduce transportation energy consumption, exhaust emissions, and reduce costs.
Second, the problems that often occur in the production of cast films:
Casting film has many crystal points
The crystal point is caused by a small amount of resin with too high molecular weight in the raw material that cannot be plasticized. When the temperature of the barrel is insufficient or too high, and the temperature is low, the raw materials cannot be completely plasticized; when the temperature is too high, the melt pressure is small and the shear force is small, which is unfavorable for the plasticization of polyolefin plastics.
In addition, the melt pressure is low, so that the degree of shear is small, and the plasticization is poor; the extrusion speed is slow and the shear is not enough; the raw materials used are poor, and the materials with large differences are mixed. These reasons may cause the cast film to have many crystal points.
Cast film rolls have strong tendons
The cast film has bursting ribs, because the thickness is uneven, even if it is very small, it can accumulate enough to cause obvious bursting ribs, affecting the appearance and use. When the film thickness is uneven, the winding tension is too large, and the film roll is too tight, the melt pressure is unstable and the thickness is uneven.
Improper position and direction of the air knife or uneven air outlets cause uneven thickness; the shrinkage rate after the film is placed is large, and it needs to be adjusted from the raw material production process and film roll storage. These reasons may cause the cast film roll to have strong ribs.
Poor slip of cast film
Slip is an important requirement in the actual use of the film, and the slip agent is generally added to the resin to ensure its good. However, the problem of poor slipperiness may also occur during production.
When the crystallinity of the raw material is low; the additives in the raw material precipitate out more; the distance between the die head and the quench roll is too large; the extrusion pulling speed is so fast that the cooling is insufficient and frictional heat is generated. These are all unfavorable and cause poor slip of the cast film.
The lateral strength of the cast film is small
The cast ratio of the cast film is small, and the orientation of the macromolecules is small, but there is a certain draft in the longitudinal direction to produce orientation. Especially when producing a thin film (0.030mm), the lateral strength is easy to be small.
When the extrusion speed, the traction speed is too fast; or the gap of the die lip is too large, the thick film extruded is pulled thin by traction, and the orientation is caused by slippage. The gap should be less than 20 times the film thickness; the cooling temperature is too low. These are caused by the lateral strength of the cast film is small.
Cast film shrinks greatly
The crystallization, cooling, internal stress, etc. of the cast film make the stored cast film have a certain shrinkage. When the melt index of the raw material is relatively large; the density of the raw material is relatively high and the crystallinity is high.
During processing, the temperature is high and the winding tension is high; the cooling temperature is high and the quenching effect is poor; the storage temperature is high, the molecular chain movement is large, and the retraction increases. This line will cause large shrinkage of the cast film.
The above article is about the function and advantages of cast film and the problems that often occur in production. I hope that the above content can bring effective help to readers and friends.