Stretching film is used for the sale and transportation of various commodities, and its secondary function is to stabilize, cover, and maintain the commodities. Expansion film must have high puncture resistance, good expansion properties, and a certain degree of expansion stress. During the expansion process, the film must not have pores. Due to the fact that expansion films are often suitable for outdoor use, it is necessary to participate in UV anti UV agents.

1. Temperature control

The tension is usually not greater than 10kg, and if it is too high, the stress will remain in the film roll, causing a decrease in elongation and other functions, which can easily lead to the phenomenon of film breakage. The influence of cooling roller temperature. The temperature of the cooling roller decreases, yielding to an increase in strength, but other functions decrease. Therefore, it is advisable to control the temperature of the ordinary cooling I roller between 20 ℃ and 30 ℃. The tension of the casting line affects the flatness and winding tightness of the film. If PIB or its masterbatch is used as the adhesive layer, it also affects the migration of PIB and reduces the final viscosity of the film.

Due to the long and narrow flow channel, fast movement speed, and generally controlled melt temperature range between 250 ℃ and 280 ℃, the temperature of the casting cooling roller is controlled between 20 ℃ and 30 ℃, and the winding tension should be low, usually within 10kg, to facilitate the migration of adhesive and increase the internal stress of the finished film.

2. Control of viscosity

Mixing VLDPE has slightly poor viscosity, but there are no special requirements for the equipment. The viscosity fluctuates absolutely and is not controlled by time, but is also affected by temperature. It is absolutely sticky when the temperature is above 30 ℃, and slightly worse when it is below 15 ℃. The amount of LLDPE in the adhesive layer can be adjusted to achieve the desired viscosity. Good adhesion makes the packaging film layer and layer inside the goods stick together to make the goods strong. There are two ways to obtain adhesion: one is to add PIB or its masterbatch to the polymer;

Another approach is to mix VLDPE. PIB is a semi transparent and thin liquid, and indirect addition requires public equipment or equipment modification. Generally, PIB masterbatch is used. The migration process of PIB usually takes three days, and it is also affected by temperature. When the temperature is high, the viscosity is strong; When the temperature is low, it is not very sticky, and after stretching, the viscosity is greatly reduced. It is best to store the finished film within a certain temperature range.

Article source: Heshan Pearl Cotton - Heshan Hongli Plastic Products Co., Ltd
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