What is Glue-Lined or Dual Wall Heat Shrink?

Understanding Glue-Lined (Twin-Wall/Dual-Wall) Heat Shrink Tubing

Glue-lined, also known as twin/dual-wall heat shrink tubing is a specialized protective sleeve made of polyolefin or other shrinkable plastic that is engineered with a dual-layer construction:

Outer Layer: The external shell of the tubing is made from a durable, heat-shrinkable material that contracts when heated. This layer provides mechanical protection against abrasion, cutting, and crushing.
Inner Layer: Inside the outer heat-shrinkable layer is an inner wall of thermoplastic adhesive. When heat is applied, this adhesive becomes activated, melting and flowing around the wires or components it is enclosing.

As the name suggests, the 'twin-wall' or 'dual-wall' refers to these two distinct layers—the protective outer sleeve and the inner adhesive lining. Upon heating, the outer layer shrinks down, and the inner glue layer melts, creating a tight, seamless bond. This process ensures that the tubing adheres closely to the underlying material.

Benefits of Glue-Lined Heat Shrink Tubing

Environmental Sealing: The adhesive lining creates a waterproof seal that prevents the ingress of moisture, dust, and other contaminants, protecting electrical connections from corrosion and environmental damage.
Enhanced Durability: The combination of the outer shell's toughness and the inner adhesive's sealing properties provides a rugged protective layer that can withstand harsh conditions.
Improved Electrical Insulation: The tubing adds an extra layer of insulation to electrical connections, enhancing their safety and reliability.
Ease of Application: Glue-lined heat shrink is easy to apply, only requiring a heat gun to shrink the tubing and activate the adhesive for a secure fit.
Versatility: This type of tubing can be used across a variety of applications, including automotive wiring, marine cables, electrical repairs, and any situation where a robust, insulated, and sealed connection is necessary.
Aesthetics and Organization: It offers a neat and tidy finish to cable runs and assemblies, while also allowing for color-coding of wires for easy identification.

Comprehensive Application Guide for Heat Shrink Tubing

1. Selecting the Right Size of Heat Shrink Tubing

Choosing the correct size is crucial. The heat shrink should not be too tight over the cable before shrinking. A good rule of thumb is to use tubing that is 20-30% larger in diameter than the cable or wire bundle. This ensures it can slide over easily and shrink down to a snug fit.

2. Determining the Appropriate Length of Heat Shrink Tubing

Cut the heat shrink tubing so that it extends beyond the joint or damaged insulation by at least 25mm on each side. This extra length ensures that the entire area is protected and the tubing has enough space to grip onto the cable.

3. Assessing the Mechanical Strength of Heat Shrink Tubing

While heat shrink tubing provides good mechanical protection, it may not be as strong as the original insulation in high-stress environments. In cases where the cable is subject to frequent movement or abrasion, additional mechanical protection, such as conduit or braided sleeving, is recommended.

4. Step-by-Step Heat Shrink Tubing Application Process

Measure and Cut: Measure the length of tubing needed and cut it to size, allowing extra length on each side of the joint or damaged area.
Slide Tubing Over Cable: Slide the heat shrink tubing over the cable or wire, ensuring it covers the entire area needing insulation.
Apply Heat Evenly: Use a heat gun to evenly apply heat to the tubing, starting from one end and moving slowly to the other. Avoid overheating, which can cause damage to the cable or the tubing itself.
Ensure a Secure Fit: Once the tubing has shrunk and cooled, ensure it's tightly secured around the cable without any gaps or loose ends.

In summary, glue-lined heat shrink tubing is an advanced solution for anyone looking to provide maximum protection and longevity for their electrical and cable connections, particularly in environments where exposure to moisture and mechanical stress is a concern.