Why isn't there any post-insertion heat shrink tubing?

Why isn't there any heat shrink tubing that can be inserted later?

Heat-shrinkable tubing is a type of tubing that uses its characteristic of shrinking in diameter when heated to insulate and protect wiring and terminals. It is often used for connecting and terminal processing of electrical wires, and is passed through the object before shrinking, and then heated with a heat gun or hair dryer to seal it tightly.

While this "shrinking" characteristic is a major advantage, it has the limitation that "it cannot be threaded later." Many users have asked, "Is there a type that can be threaded later?"

In this article, we will explain from a technical and structural perspective why "post-insertion heat shrink tubing" basically does not exist.

Basic principles of contraction structure

Heat shrink tubing is manufactured by cross-linking, extrusion, and cooling to a larger diameter than its original size. It then has a "shape memory" property that allows it to return to its original shape (i.e., smaller diameter) when reheated for use.

Therefore, if a slit is made in the tube to allow for later insertion, the slit will open when heated during the shrinking process, making it difficult to achieve complete adhesion and protection. It also reduces the insulating and waterproofing performance, and electrical insulation is not guaranteed, making it an extremely dangerous method of use. Pressure is also applied during shrinkage, causing the tube to shift or peel away from the slit.

"Cannot be added later" = "Care must be taken at the design stage"

Heat shrink tubing is a product that is designed to be passed through beforehand. Therefore, if you plan to use heat shrink tubing from the wiring design stage, you need to pay attention to the following points.

• Be sure to pass the tube through before connecting

• Estimate the length and shrinkage rate of the tube in advance.

• If it is difficult to insert the tube later, consider using other protective materials (spiral tubes or slit tubes).

What to do if you have no choice but to add it later

If it is difficult to pass the heat shrink tubing through first, use a tube with a high shrink rate. For example, our Rokuichi Tube can be inserted over a connector with a diagonal of over 30 mm and can cover cables with an outer diameter of up to 5 mm.

Rokuichi Tube

summary

Due to its nature, heat shrink tubing cannot generally be "later inserted." To maintain safety and performance, it must be "pre-inserted." In situations where post-insertion is required, it is important to select an alternative product that suits the application.

If you are unsure about which product to choose, please feel free to contact us.