Double-walled heat shrinkable tube inner layer is a layer of hot melt adhesive, Hot melt adhesive is ethylene and vinyl acetate in high pressure copolymerization, and then with adhesives, viscosity regulators, antioxidants and other made of hot melt adhesive. Hot Melt Adhesive is a non-solvent, no moisture, 100% solid melt of the polymer, at room temperature for the solid, heating melting to a certain extent into a liquid adhesive that can flow and has a certain viscosity, its melting is light brown translucent body or white.

Hot Melt Adhesive has the following characteristics:

1. That is, curing, usually solid at room temperature, when heated to a certain extent, melt into a liquid, once cooled below the melting point, and quickly become a solid. When used, as long as the hot melt adhesive heating melted into the required liquid, and applied to the sticky object, after compression in a few seconds can complete the bonding curing, within a few minutes can achieve the degree of hardening cooling and drying;

2. Re-stickiness, heat shrinkable tube glue applied to the adhesive on the cooling and curing of the adhesive layer, can also be heated and melted, re-become adhesive body and adhesive bonding, with a certain degree of re-stickiness;

3. Strong toughness, with fast curing, low pollution, strong adhesion, adhesive layer has a certain flexibility, hardness, but also a certain degree of toughness.

According to the above can be further learned that the double-walled heat shrinkable tube than the ordinary single-walled heat shrinkable tube is better waterproof, more insulating, so double-walled heat shrinkable tubing is more and more widely used.

双壁管用热熔胶的特点

双壁热缩套管内层是一层热熔胶，热熔胶是乙烯与醋酸乙烯在高压下共聚而成的，再配以增粘剂、粘度调节剂、抗氧剂等制成热熔胶。热熔胶是一种不需溶剂、不含水份、100％的固体可熔性的聚合物，在常温下为固体，加热熔融到一定程度变为能流动且有一定粘性的液体粘合剂，其熔融后为浅棕色半透明体或本白色。

热熔胶有以下特点：

1. 即固化性，在室温下通常为固体，加热到一定程度时熔融为液体，一旦冷却到熔点以下，又迅速成为固体。使用时，只要将热熔胶加热熔融成所需的液态，并涂抹在被粘物体上，经压合后在几秒钟内就可完成粘结固化，几分钟内就可达到硬化冷却干燥的程度；

2. 再粘性，热缩管胶液涂抹在被粘物上冷却固化后的胶层，还可以再加热熔融，重新变为胶粘体再与被粘物粘接，具有一定的再粘性；

3. 强韧性，具有固化快、公害低、粘着力强，胶层既有一定柔性、硬度、又有一定的韧性。

据上述可进一步得知，双壁热缩管比普通的单壁热缩管的防水性更好，绝缘性更强，所以双壁热缩管越来越被广泛使用。