Single-wall and adhesive-lined (dual-wall) heat shrink tubing look similar in a catalog photo, but they do different jobs. Single wall insulates. Dual wall insulates and seals. Choosing between them comes down to one question: will the connection ever get wet?
The Structural Difference
Single-wall tubing is one layer of crosslinked polyolefin. It shrinks onto the object and provides electrical insulation, abrasion resistance, and color identification. It does not create a waterproof seal — moisture can wick along the interface between the tubing and the object.
Adhesive-lined tubing (also called dual-wall) has two layers. The outer layer is crosslinked polyolefin that provides insulation. The inner layer is a hot-melt adhesive that melts at 85-110°C during installation, flows to fill surface irregularities, and solidifies into a waterproof seal as it cools.
When You Need Adhesive
Use dual-wall tubing when the connection will be exposed to:
Moisture. Outdoor installations, underground ducts, marine environments, washdown areas. The adhesive seal prevents water from reaching the conductor even under prolonged immersion or pressure.
Corrosive atmosphere. Salt spray, industrial chemicals, or high humidity. The adhesive layer blocks the path that corrosive agents would take along the tubing-to-cable interface.
Vibration or movement. The flexible adhesive layer acts as a strain relief, absorbing micro-movements that would eventually break a rigid single-wall bond.
Connector exits. Where a wire exits a connector or enclosure, dual-wall tubing bridges the gap and seals the transition point — the most common moisture entry path in field failures.
When Single Wall Is Enough
Single-wall tubing is appropriate when the connection stays dry:
- Interior electronics and PCB assembly
- Wire bundling and color coding inside a panel
- General insulation on harnesses in a passenger compartment
- Temporary protection during transport or storage
Single-wall tubing costs 30-50% less than adhesive-lined, installs faster (no adhesive flow time), and is available in a wider range of sizes and colors.
Cost and Installation Comparison
| Factor | Single Wall (LRS-1) | Dual Wall (SRS) |
|---|---|---|
| Material cost | Lower | 30-50% higher |
| Waterproof | No | Yes (IP67 when properly installed) |
| Installation | Heat until shrunk | Heat until shrunk + adhesive flows |
| Sealing mechanism | Mechanical grip only | Mechanical grip + adhesive bond |
| Rework | Easy — reheat and remove | Difficult — adhesive bonds to surface |
| Typical applications | Indoor insulation, color coding | Outdoor sealing, underground, marine |
FAQ
Can I use single-wall tubing outdoors if I seal the ends with silicone?
It works temporarily but is not reliable long-term. Silicone sealant at the tubing ends degrades under UV exposure and thermal cycling. The interface between the tubing and cable remains a moisture path. For outdoor use, adhesive-lined tubing is the correct engineering solution.
How do I know the adhesive has fully flowed?
Look for a small bead of adhesive squeezing out at each end of the tubing. This indicates the adhesive has melted, flowed, and filled the internal volume. No bead means insufficient heat — apply more until it appears.
Can dual-wall tubing be removed for rework?
Yes, but it requires heating to 110°C or higher to soften the adhesive, then peeling while hot. The adhesive leaves residue that must be cleaned with solvent before re-terminating. Plan dual-wall installations as permanent.
Written by Long, Sales Engineer at ZZ Heat Shrink. For single-wall tubing specifications, see LRS-1 series. For adhesive-lined tubing, see SRS dual-wall series. For a quotation, contact our engineers.