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Heat Shrinkable Tube Expansion Technology

2022-11-14
The Heat Shrinkable Tube has the characteristics of insulation protection, sealing and moisture-proof, strong mechanical property, identification and so on. It is widely used in various industries such as electronics, electrical, aerospace, military, shipbuilding, high-speed rail, automobile and nuclear power. The key manufacturing processes of heat shrinkable tube include radiation crosslinking and expansion molding. Radiation crosslinking can change the molecular structure of polymer materials, endow high molecular materials with memory function, and make them have heat shrinkable performance. Generally, the radiation dose is 80-150KGy; The axial shrinkage rate of heat shrink backbone is the most concerned technical index of users, which requires it to be stable and small.

Expansion technology plays a decisive role in the axial shrinkage rate. During expansion, the Heat Shrinkable Tube before expansion is first heated to 110℃-130℃, so that it reaches a high elastic state. The temperature of the heating medium is generally about 20℃ higher than that of the high elastic state. Expansion methods include continuous expansion and intermittent expansion, continuous expansion is divided into internal pressure expansion and internal pressure and vacuum joint expansion, internal pressure and vacuum joint expansion efficiency is high, is widely used, internal pressure expansion is suitable for high radiation dose of Heat Shrinkable Tube expansion, using this technology to make the heat shrinkable tube shrinkage force is large, insulation sealing is more safe and reliable.


Heat Shrinkable Tube


Combined expansion technology of internal pressure and vacuum

Combined expansion with internal pressure and vacuum requires that the gel content of the Heat Shrinkable Tube before expansion should not be greater than 55%, otherwise it cannot expand smoothly. Because the maximum negative pressure a vacuum can produce is 1 atmosphere, it is difficult to expand using only vacuum; The internal pressure of the Heat Shrinkable Tube before expansion should not be too large. Otherwise, the Heat Shrinkable Tube before expansion will produce uneven and uncontrolled expansion, resulting in the failure of expansion. The vacuum chamber of internal pressure and vacuum joint expansion technology is divided into single vacuum chamber and double vacuum chamber.

The traditional vacuum expansion device is composed of a mold, a mold mouth, a vacuum chamber and a cooling chamber. There are small holes on the mold, which are connected with the vacuum chamber, and the mold mouth plays a vacuum sealing role. Generally, there is compressed air in the Heat Shrinkable Tube before expansion, and the Heat Shrinkable Tube before expansion expands under the combined action of internal pressure and vacuum, then enters the cooling chamber for cooling, and finally the Heat Shrinkable Tube is obtained. This expansion device has two defects, one is that the axial shrinkage rate of the Heat Shrinkable Tube is unstable, the other is that the axial shrinkage rate of the Heat Shrinkable Tube is large.

Internal pressure expansion technique

Internal pressure expansion technology is to use the compressed air inside the Heat Shrinkable Tube for expansion. The pressure of compressed air can reach 0.2MPa-0.6MPa, with strong expansion ability and gel content up to 70%, it can also expand smoothly.

The expansion capacity of internal pressure expansion is strong, the shrinkage force of the Heat Shrinkable Tube is large, the shrinkage speed is fast, and the insulation seal is safe and reliable. Combined expansion of internal pressure and vacuum, double vacuum chamber, no mold in the vacuum chamber and sealing means at both ends of the mold, good expansion stability, small axial shrinkage of the heat shrinkable tube. The expansion mold with a cone can control the expansion speed of the Heat Shrinkable Tube and prevent its free expansion. The axial shrinkage rate of the Heat Shrinkable Tube is small and the wall thickness uniformity is good. The lubrication fluid in the mold can reduce the friction between the Heat Shrinkable Tube and the mold, and reduce the axial shrinkage rate of the Heat Shrinkable Tube.


Heat Shrinkable Tube

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