Production characteristics of heat shrinkable film
DATE：2022/2/22 8:44:43 / READ： / SOURCE：This station
Production characteristics of heat shrinkable film
Shrink film packaging was first used in France in 1936 and was widely used in the 1960s. The most common production method is to use a circular die extrusion blowing method or a narrow and long die extrusion casting method. For PVC, it can also be produced by a calendering method and a solvent casting method, and the film thickness is uniform. Good performance, but due to large investment in production equipment and high production costs, it is rarely used. The shrink film is made by stretching the polymer sheet or tube at a temperature above the softening point to orient the polymer chain, and fixing the orientation by cooling. When in use, as long as the film-wrapped article is heated to the temperature during stretching, the film will shrink, releasing the stress and energy stored during stretching. The shrinkage of the film is determined by the degree of stretching during the orientation process, and is also related to the composition of the polymer and the process conditions during production. The total shrinkage of the shrink film can reach 15% to 80%, while the general use only needs 15% to 30%, and the products with strange shapes need a shrinkage rate of more than 50%. For the packaging of sleeve-like articles and shrink-label films, only one-directional shrinkage is required.
The shrinkage temperature is generally between 65.5 ~ 176-6 °C (under 150T ~ 350), which varies with the type of film. For example, the shrinkage temperature of PVC shrink film is 655 ~ 148.8 °C (under 150F ~ 300), while the shrinkage of P The temperature was 1655C (330F). Some heat shrinkable films have good temperature tolerance and can be heated multiple times to obtain packaging with different shrinkage rates. The principle is to use minimal heat and time to obtain sufficient shrinkage.
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