How to control the preheating time during the expansion of heat shrinkable tube?

The quality control of heat-shrinkable tube in the expansion process, as domestic professional heat-shrinkable tube manufacturers do, because the base material of heat-shrinkable tube is polyethylene mixed system, its melting temperature is about115 ~135℃; The initial flow temperature of polyethylene increases with the increase of radiation dose. For heat shrinkable tubes, the radiation dose is generally 100 ~ 150 kgy, and the corresponding initial flow temperature is about 180℃. Therefore, the preheating temperature of the heat shrinkable tube should be controlled between them, that is, 140℃ or so, to ensure that the material is in a high elastic state. When the temperature rises to the melting point, the uncrosslinked polymer changes from glassy state to viscous state, and viscous flow occurs. However, the crosslinked polymer shows a high elastic state and has no viscous flow, which is the function of the three-dimensional network structure formed by the crosslinking reaction in the material. In this highly elastic state, if an external force is applied to the material, the material can be elastically deformed, that is, once the external force is removed, the material can return to its original shape. Therefore, the prerequisite for the expansion process is that the material is in a high elastic state, that is, the material should be preheated to the melting temperature to the viscous flow temperature before expansion.