Causes And Prevention Of Excessive Shrinkage Of PE Stretch Film1

As the name suggests, PE stretch film is a shrinkage performance is very good film, in many areas to play the product packaging effect is very significant, but in the production process of the product will be found a problem - shrinkage is too large. Although the frequency of this problem is small, once it appears, it will have a great impact on the product. So, the first thing we need to do to solve the problem of excessive shrinkage is to understand what causes it. Below we will analyze the reasons together, and give the relevant prevention methods.

First, the cause of excessive shrinkage phenomenon:

The raw material of PE stretch film is an amorphous polymer. When the tensile force is greater than the yield strength within a certain temperature range, plastic extension deformation occurs. In the deformation process, the structural units of polymer (chain segments, macromolecules and microcrystals) begin to Orient due to stretching. With the increase of the degree of orientation, the interaction between macromolecules increases, which leads to the increase of polymer viscosity and the hardening tendency, and the deformation tends to be stable instead of developing. This phenomenon is called "stress hardening". When the temperature is properly raised, the ductility of PE stretch film is further improved, the tensile ratio can be increased, and even some polymers with poor ductility can be stretched. The deformation near very low working temperatures, usually at room temperature, is called "cold stretching". The stress hardening of the polymer during the stretching process limits the flow of polymer molecules and prevents further improvement of the tensile ratio. The PE film with "cold stretching" restores to its original state after the tensile force is lifted, resulting in a larger retraction.