Adhesive-lined heat shrink - how does it seal watertight?

How does adhesive-lined heat shrink work?

Adhesive-lined tubing combines two elements: an outer cross-linked polyolefin wall that shrinks when heated and an inner layer of thermoplastic hot-melt adhesive. As you apply heat the tube contracts while the glue melts, flows into every gap and bonds to the cable jacket and insulation to form one sealed unit.

Once cooled, the adhesive solidifies into a lasting moisture barrier. The result is a joint that reaches ingress protection IP68 even on cable entries and splices, guarding against water, dust, vibration and pull-out.

Which shrink ratio and size is right?

Adhesive-lined tubing is commonly offered in 3:1 or 4:1 shrink ratios, meaning it shrinks to a third or a quarter of its supplied diameter. A high ratio matters when you bridge very different diameters, for example over a connector boot or a wiring-harness breakout.

Choose a supplied diameter at least 20 percent larger than the biggest part you cover, and a recovered diameter smaller than the thinnest cable. Only then does the tube grip firmly and the glue fill the gap completely.

• Pick a supplied diameter at least 20 % over the largest part.
• The recovered diameter must be smaller than the thinnest cable.
• Thick-wall versions carry more glue and add mechanical protection.
• Prefer 4:1 for breakouts and Y-transitions.

How do you shrink the tube correctly?

Clean and degrease the surface, slide the tube over the joint with enough overhang and heat it evenly with a hot-air gun. The hot-melt adhesive typically activates between 80 and 120 °C. Work from the centre outward so trapped air can escape.

• Do not overheat one spot with an open flame or the polyolefin chars.
• Position the tube centrally and allow for overhang before heating.
• Let the joint cool undisturbed after shrinking.
• Visual check: a continuous glue bead at both ends.

Frequently asked questions