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How to judge whether the viscosity of stretch film is enough?
Source:Mingye Packing Materials Co.,Ltd   Release date:2020-12-22   Hits:406
In industrial production, the tackifier for polyethylene stretched  films can make low-molecular-weight polyisobutylene (PIB), ultra-low-density polyethylene (VLDPE) with a density lower than 0.905, and ethylene-vinyl acetate copolymer (EVA). PIB, as a tackifier for polyethylene stretched film, has a wide range of viscosity adjustment, convenient adjustment and obvious price advantages.

Stretch film requires excellent peel adhesion and excellent lap adhesion. The higher the peel adhesion, the smaller the possibility of opening the tray. The better the sealing performance of the stretch film. The stretch film is only affected by the longitudinal direction. The less likely it is, so in order to obtain a strong package, the peel adhesive of the stretch film needs to be balanced.

1. The influence of molecular weight on the adhesion of stretched wrapping film
Different molecular weights will lead to different adhesion, high molecular weight polyimide will make the stretched wrapping film have a higher final peel adhesion, but as the molecular weight of polyimide increases, the overlap adhesion will decrease.
However, if the molecular weight is too low, the viscosity retention time will be greatly shortened due to its easy evaporation. Therefore, only by selecting a polyimide with an appropriate molecular weight can the stretched film have good properties.

2. The effect of addition on the viscosity of stretched film
The viscosity of the stretched film is positively correlated with the amount of PIB involved. However, after PIB is incorporated more than 3%, the self-adhesiveness of the stretched film will improve and become insignificant. If the incorporation of PIN continues to increase, PIB will be in the film. The outer surface is separated into pieces, resulting in uneven self-adhesion of the film, and even the film roll is difficult to open.
In order to ensure the final function of the stretched film and take into account the cost of raw materials, the amount of PIB added should be controlled between 1% and 3%. Polyimide has a process of exudation, which usually takes three days to make the stretch The outer surface of the stretched film produces a suitable viscosity.

3. The influence of stretched film storage temperature on viscosity
The migration speed of polyimide is related to the storage temperature. The higher the temperature of the environment, the faster the migration speed of polyisobutylene and the higher the viscosity. Therefore, in order to achieve the required viscosity, the stretched film should be stored at a higher temperature.
However, if stored at a temperature higher than 30 degrees Celsius for a long time, PIB will precipitate in a large amount, and the film size head or paper core will fall off easily.
Therefore, after the stretched film meets the viscosity requirement, PIB-Kangge should be stored at -15°C to 40°C as much as possible.

In order to facilitate production, people have developed a high-concentration polyisoprene thickening masterbatch for the production of polyethylene wrapped stretch film. This masterbatch is made by mixing polyisobutylene and polyethylene in a certain proportion. It is similar in shape to various master batches commonly used in the production of plastic products, has good fluidity and is convenient to use.



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