The finished product of the joint coating heat shrinkable sleeve is well expanded, that is to say, the heat shrinkable sleeve is pre expanded according to different pipe diameters, and then the flame heating shrinkable sleeve is used. Therefore, expansion is an important part in the production of heat shrinkable sleeve. The speed of expansion determines the efficiency of production and the quality of products. When the expansion speed is fast, the production efficiency is improved, but when the material is stressed, the defects increase, and the surface is easy to fold; when the expansion speed is slow, the surface of the material hardens due to too fast cooling, which makes the expansion load increase, resulting in the expansion difficulty; on the other hand, when the expansion speed is too slow, the internal stress caused by the expansion tension in the material is also slow, and the established stress may occur Under the action of heat, the relaxation speed is faster, and the orientation is reduced, so that the thermal shrinkage speed of the material is slow. Therefore, the expansion should be as high as possible.
The control of expansion speed has always been a difficulty. Now with the development of science and technology, the expansion speed has been well controlled. This makes the heat shrinkable sleeve also improve the production efficiency, making it the most common product for joint coating and anticorrosion.