Production, characteristics and performance of heat shrinkable film
DATE：2021/8/20 8:39:54 / READ： / SOURCE：This station
Production, characteristics and performance of heat shrinkable film
Shrink film packaging was first applied in France in 1936, and has been widely used since the 1960s. The most common production method is to use round die extrusion inflation method or narrow die extrusion casting method. For PVC, it can also use calendering method and solvent casting method to produce, and the film thickness is uniform. Good performance, but due to the large investment in production equipment and high production costs, it is rarely used. The shrink film is made by stretching a polymer sheet or tube at a temperature above the softening point to make the polymer chains oriented, and then fixing this orientation by cooling. When in use, as long as the film is packaged and heated to the temperature at the time of stretching, the film will shrink and release 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 it only needs 15% to 30% for general use. The odd-shaped product requires a shrinkage rate of more than 50%. Generally, a shrink film with a balanced shrinkage rate in the vertical and horizontal directions is required. For packaging and shrink label films for tubular goods, only one-way shrinkage is required.
The shrinkage temperature is generally between 65.5～176-6℃ (under 150T～350), depending on the type of film. For example, the shrinkage temperature of PVC shrink film is 655～148.8℃ (under 150F～300), while the shrinkage of P The temperature is 1655C (330F). Some heat shrinkable films have good temperature tolerance and can be heated multiple times to obtain packages with different shrinkage rates. The principle is to use the minimum heat and time to get a full harvest.
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