Shrink film is a common type of packaging film. In packaging applications, it is often used to shrink the imagination of heat to achieve skin effect or cluster wrapping; At the same time, it is used to protect the contents from contamination or damage. The principle of thermal shrinkage is that when producing the film, the active molecular chain segments are oriented at the melting point or glass transition temperature, and then cooled below the junction or glass transition temperature to quickly solidify the molecular orientation; When reheated above the melting point or glass transition temperature, the polymer segments will regain their activity, and the originally oriented molecular segments will begin to curl up and be oriented, macroscopically manifested as film shrinkage.

Classification of heat shrink films

Heat shrink films can be broadly divided into two categories, barrier shrink films and non-barrier shrink films. Under the two large categories, there are also hypothetical small categories. Let's give you a brief introduction to the characteristics of each shrink film.

Barrier shrink films are mostly made with barrier materials (EVOH. PVDC) 5~9 layers of co-extrusion structure, produced by three-bubble blown film process. Generally, it is used in meat or fresh food packaging where oxygen barrier is required. This type of shrink film is specific to the market, but the production technology is difficult, so the added value is high.

Non-barrier shrink films have many classifications. According to the different raw materials and processes, it is roughly divided into four categories (PVC shrink film, nick shrink film, R2L shrink film, and other shrink film).