Many people do not clearly distinguish between one-way stretching and bi-directional stretching of protective films. Many people mistakenly think that one-way stretching is stretching from one side and bi-directional stretching is stretching from both sides respectively, but it is not like that.


Stretching is the adjustment of the molecular order of plastic film by stretching in the longitudinal and transverse directions of the heated plastic film, thus changing the characteristics of the film. called two-way stretching.


Here it is clear that bi-directional stretching is transverse and longitudinal stretching, while uni-directional stretching is only from one of the directions.





Plastic films suitable for biaxial stretch production include polyester, polypropylene, polyamide, polystyrene and polyimide films.


The use of precise stretching techniques, especially in optical films such as phase contrast films, not only increases viewing angles but also improves polarization, both of which are critical in products such as LCD displays.


Stretch technology is also used in the dry manufacturing process for lithium battery separators, which can be subdivided into unidirectional and bidirectional stretch processes. The dry unidirectional stretching process is used to prepare a low crystallinity highly oriented polypropylene or polyethylene film by producing hard elastic fibers, which are then annealed at high temperature to obtain a highly crystalline oriented film. This film is first stretched at low temperature to form micro-defects, and then the defects are pulled apart at high temperature to form micro-pores.