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English The required viscosity of the stretch film must have both good peeling adhesion and good lap adhesion. The higher the peeling viscosity, the more difficult the tray is to loose, and the better the sealing of the film. The higher the lap viscosity, the less longitudinal displacement of the film. Therefore, to obtain a strong package, the peeling viscosity and overlap of the stretch film are required. The viscosity is balanced.
1. The effect of molecular weight on the viscosity of stretch film
The molecular weight is different, the adhesion performance will be different, the high molecular weight PIB makes the film have higher final peel adhesion, but as the molecular weight of the PIB increases, the lap adhesion will decrease; and if the molecular weight is too low, it is easier Volatilization will cause the viscosity to stay for too short. Therefore, the choice of PIB with appropriate molecular weight can make the stretch film have good performance. Studies have shown that PIB with a number average molecular weight of about 1300 is more suitable for increasing the self-adhesiveness of stretch film.
The molecular weight is different, the adhesion performance will be different, the high molecular weight PIB makes the film have higher final peel adhesion, but as the molecular weight of the PIB increases, the lap adhesion will decrease; and if the molecular weight is too low, it is easier Volatilization will cause the viscosity to stay for too short. Therefore, the choice of PIB with appropriate molecular weight can make the stretch film have good performance. Studies have shown that PIB with a number average molecular weight of about 1300 is more suitable for increasing the self-adhesiveness of stretch film.
2. The effect of adding amount on the viscosity of stretch film
The viscosity of the wrapping film is positively correlated with the amount of PIB added. However, after the addition of PIB exceeds 3%, the improvement of the self-adhesiveness of the stretch film becomes insignificant. If the addition of PIB continues to be increased, PIB will precipitate and form blocks on the surface of the film, resulting in uneven self-adhesiveness of the film, and even the film The volume is difficult to open. In order to ensure the performance of the stretch film and comprehensively consider the cost of raw materials, the amount of PIB added should be controlled between 1% and 3%.
The viscosity of the wrapping film is positively correlated with the amount of PIB added. However, after the addition of PIB exceeds 3%, the improvement of the self-adhesiveness of the stretch film becomes insignificant. If the addition of PIB continues to be increased, PIB will precipitate and form blocks on the surface of the film, resulting in uneven self-adhesiveness of the film, and even the film The volume is difficult to open. In order to ensure the performance of the stretch film and comprehensively consider the cost of raw materials, the amount of PIB added should be controlled between 1% and 3%.
PIB has an exudation process, and it usually takes about three days to stretch the film surface to produce sufficient viscosity.
3. The effect of stretch film storage temperature on viscosity
The migration speed of PIB is related to the storage temperature. As the ambient temperature increases, the migration speed of PIB increases and the viscosity increases. Therefore, to achieve the required viscosity, the stretch film should be stored at a higher temperature, and generally should be prevented from reaching the use requirements after a week. However, if stored for a long time in an environment higher than 30℃, PIB will precipitate out in large quantities, and it is easy to cause the film roll size or paper core to come off. Therefore, after meeting the viscosity requirements, it should be placed in an environment of -15℃~40℃. store.
The migration speed of PIB is related to the storage temperature. As the ambient temperature increases, the migration speed of PIB increases and the viscosity increases. Therefore, to achieve the required viscosity, the stretch film should be stored at a higher temperature, and generally should be prevented from reaching the use requirements after a week. However, if stored for a long time in an environment higher than 30℃, PIB will precipitate out in large quantities, and it is easy to cause the film roll size or paper core to come off. Therefore, after meeting the viscosity requirements, it should be placed in an environment of -15℃~40℃. store.
PIB is a viscous liquid substance. When PIB is co-extruded with polyethylene, the material cannot be extruded smoothly. Special extrusion equipment is required, such as an extruder with a forced feeder in the hopper, which is forced to feed LLDPE. Mix with PIB, or use a special extruder that can pump viscous liquids to pump into PIB. In order to facilitate production, people have developed a high-concentration PIB tackifying masterbatch for the production of polyethylene winding film. This masterbatch is made by mixing PIB and polyethylene in a certain proportion, and it is used in the production of plastic products. The shape of the masterbatch is similar, with good fluidity and easy to use.
