Why does the PE protective film have bulge at both ends?

After using the PE protective film for a period of time, the performance of the protective film in the middle part will be good, but the two ends of the protective film are convex. What is the reason for this phenomenon? How can we avoid this phenomenon?

The main reason for this phenomenon is that the protective film stretches to a greater extent during the process of pasting with the profile to be protected. After pasting, when encountering a high temperature environment, unnecessary retraction occurred. This problem is more likely to occur in southern customers or in summer. Therefore, in the production process of the protective film, pay attention to the impact of environmental temperature differences on the use of the product, and avoid unnecessary surface stretching during the pasting process.