English
The shrinkage behavior of heat shrink film is the result of the rearrangement of the molecular structure of polyolefin materials when heated. When heat shrink film is heated, its molecular chains begin to move and attempt to adjust their arrangement to adapt to the new environment. In this process, the molecular chains try to shorten in length, thereby reducing the overall volume of the material. This behavior leads to the shrinkage of the heat shrink film. This shrinkage behavior is not simply deformation occurring on the original structure, but involves the disentanglement and rearrangement of polyolefin molecular chains.
When heated above the glass transition temperature (Tg), the molecular chain movement of the heat shrink film becomes active. At this point, external forces are applied to the material for unidirectional or bidirectional stretching, aligning the macromolecular chains, followed by cooling and shaping. However, this "shaping" possesses "memory". When the material is heated again above the stretching temperature, these molecular chains begin to "unfreeze", and the ordered molecular structure leads to shrinkage stress within the material, transitioning from an ordered to a disordered state, thus causing shrinkage and achieving tight wrapping of the packaged items, serving the purpose of protecting the items.
The shrinkage behavior of heat shrink film is also influenced by its production process. During manufacturing, heat shrink film typically undergoes a series of stretching and cooling steps, which affect its final shrinkage behavior. For example, if the heat shrink film is biaxially stretched during the manufacturing process, then upon heating, these stretched portions may attempt to revert to their original size, resulting in shrinkage.
Furthermore, the shrinkage behavior of heat shrink film is also related to environmental temperature and humidity. In high temperature and high humidity environments, the shrinkage behavior of heat shrink film may be more pronounced. This is because in such environments, the activity of the molecular chains increases, making it easier for rearrangement and deformation to occur. The shrinkage behavior of heat shrink film is the result of the rearrangement of polyolefin molecular chains when heated and is also influenced by factors such as production process, environmental temperature, and humidity.
PVC SHRINK FILM Self-Adhesive Protective Film Stretch Film
