Model:DHST-3X/DHST-4X
Dual Wall Heat Shrinkable Tube (DHST)
Dual Wall Heat Shrinkable Tube (DHST) is manufactured by the co-extrusion of a polyolefin outer jacket and a hot-melt adhesive inner layer. It is specifically designed to provide both electrical insulation and environmental sealing for protected articles. This tubing is widely used to protect wire bundles, cable splices, and metal tubes against water, moisture, and corrosion, ensuring long-term reliability in harsh conditions.
Key Features & Benefits
- Dual Wall Construction: The outer polyolefin jacket provides excellent insulation and mechanical protection, while the inner hot-melt adhesive layer ensures a tight, waterproof seal.
- High Shrink Ratios: Available in 3:1 and 4:1 ratios, allowing a single tube size to fit over a wide range of substrate and connector diameters.
- Superior Environmental Sealing: The melted adhesive flows to fill gaps, preventing moisture ingress and corrosion in outdoor or underground environments.
- Flame Retardant: Meets UL 125°C VW-1 600V and SAE-AMS-DTL-23053/4 standards for enhanced safety and compliance.
- Wide Operating Temperature: Reliable performance in extreme conditions, ranging from -45°C to +125°C.
Common Applications
- Automotive, marine, and aerospace wire harnesses
- Outdoor and underground cable splices and joints
- Protection for metal tubes, fluid lines, and hydraulic hoses
- Environmental sealing of electrical connectors and terminations
- Boat building, agricultural equipment, and outdoor lighting wiring
Product Specifications & Technical Data
- Shrinking Ratio: 3:1, 4:1
- Approvals: UL 125°C VW-1 600V; Meets SAE-AMS-DTL-23053/4
- Operating Temperature: -45°C to +125°C
- Minimum Shrink Temperature: 80°C
- Minimum Fully Recovery Temperature: 120°C
- Standard Color: Black
- Special Colors: Red, Blue, White, Yellow
- Clear Version: Available (Note: Clear version has a non-flame retardant jacket)
Technical Properties
| Item | Test Method | Value |
|---|---|---|
| Tensile strength | ASTM D 2671 | >10.4 MPa (min.) |
| Tensile strength after aging (158°C / 168 hrs.) | ASTM D 2671 | Remains 70% |
| Elongation at break | ASTM D 2671 | >300% (min.) |
| Elongation at break after aging (158°C / 168 hrs.) | ASTM D 2671 | 100% (min.) |
| Longitudinal shrinkage | UL 224 | 0 to -10% |
| Heat shock (250°C / 4 hrs.) | ASTM D 2671 | No cracking, no dropping |
| Cold bend (-30°C / 1 hr.) | ASTM D 2671 | No cracking |
| Voltage withstand (AC 2500V / 60 sec) | ASTM D 2671 | No breakdown |
| Volume resistance | ASTM D 876 | >1014 Ω·cm (min.) |
| Flammability | SAE-AMS-DTL-23053/4 | Self-extinguish in 30 sec. |
| Copper corrosion (158°C / 168 hrs.) | UL 224 | Pass |
| Water absorption | ASTM D 570 | <0.5% |
Dimensions & Specifications
DHST-3X (3:1 Shrink Ratio)
| Size (mm) | Inch | As Supplied I.D. (mm) Min | After Recovery I.D. (mm) Max | After Recovery W.T. (mm) Nom | After Recovery Adhesive W.T. (mm) | Standard Length (m/spool) |
|---|---|---|---|---|---|---|
| 3.2 | 1/8 | 3.2 | 1.00 | 0.95±0.15 | 0.40±0.10 | 200 |
| 4.8 | 3/16 | 4.8 | 1.60 | 1.10±0.15 | 0.40±0.10 | 100 |
| 6.4 | 1/4 | 6.4 | 2.20 | 1.20±0.15 | 0.45±0.10 | 100 |
| 7.9 | 5/16 | 7.9 | 2.70 | 1.35±0.15 | 0.50±0.10 | 100 |
| 9.5 | 3/8 | 9.5 | 3.20 | 1.45±0.20 | 0.50±0.15 | 50 |
| 12.7 | 1/2 | 12.7 | 4.20 | 1.70±0.20 | 0.55±0.15 | 50 |
| 15.0 | 5/8 | 15.0 | 5.20 | 1.80±0.20 | 0.50±0.15 | 50 |
| 19.1 | 3/4 | 19.1 | 6.30 | 2.00±0.20 | 0.50±0.15 | 25 |
| 25.4 | 1 | 25.4 | 8.50 | 2.10±0.25 | 0.50±0.15 | 25 |
| 30.0 | 1-1/4 | 30.0 | 10.20 | 2.20±0.25 | 0.60±0.15 | 25 |
| 39.0 | 1-1/2 | 39.0 | 13.50 | 2.40±0.25 | 0.60±0.15 | 25 |
| 50.0 | 2 | 50.0 | 17.00 | 2.70±0.25 | 0.80±0.15 | 25 |
DHST-4X (4:1 Shrink Ratio)
| Size (mm) | Inch | As Supplied I.D. (mm) Min | After Recovery I.D. (mm) Max | After Recovery Total W.T. (mm) | After Recovery Adhesive W.T. (mm) Nom | Standard Length (m/spool) |
|---|---|---|---|---|---|---|
| 4/1 | 5/32 | 4.0 | 1.0 | 1.0±0.15 | 0.4±0.15 | 200 |
| 6/1.5 | 1/4 | 6.0 | 1.5 | 1.1±0.15 | 0.4±0.15 | 100 |
| 8/2 | 5/16 | 8.0 | 2.0 | 1.2±0.15 | 0.5±0.15 | 100 |
| 12/3 | 1/2 | 12.0 | 3.0 | 1.4±0.15 | 0.5±0.15 | 50 |
| 16/4 | 5/8 | 16.0 | 4.0 | 1.7±0.15 | 0.6±0.15 | 50 |
| 20/5 | 13/16 | 20.0 | 5.0 | 2.0±0.25 | 0.6±0.15 | 50 |
| 24/6 | 1 | 24.0 | 6.0 | 2.1±0.25 | 0.6±0.15 | 50 |
| 32/8 | 1-1/4 | 32.0 | 8.0 | 2.4±0.25 | 0.7±0.15 | 25 |
| 52/13 | 2 | 52.0 | 13.0 | 2.4±0.25 | 0.7±0.15 | 25 |
| *Special sizes and custom cutting pieces are available upon request. | ||||||
Frequently Asked Questions (FAQ)
Q: What is the main difference between dual wall and single wall heat shrink tubing?
A: Dual wall tubing (like DHST) features an inner layer of hot-melt adhesive that melts during heating, creating a waterproof and airtight seal. Single wall tubing (such as our HHST series) only provides electrical insulation and mechanical protection but does not seal out moisture or environmental elements.
Q: How does the inner hot-melt adhesive layer work during the shrinking process?
A: When the tubing is heated above its minimum shrink temperature (80°C), the polyolefin outer wall shrinks tightly around the substrate. Simultaneously, the inner adhesive layer melts and flows to fill any voids, gaps, or irregularities, bonding to the cable jacket or connector to block water and corrosion.
Q: Can DHST-3X and DHST-4X be used in outdoor or underwater applications?
A: Yes, absolutely. The dual wall construction with the hot-melt adhesive liner is specifically engineered for harsh environments. Once fully recovered and the adhesive has cooled and solidified, it provides an excellent moisture barrier, making it ideal for marine, underground, and outdoor applications.
Q: What is the recommended heating tool and method for installing this dual wall tubing?
A: We recommend using a hot air gun or an infrared heat gun for even heating. Start heating from the center of the tubing and work your way outward toward the ends. This allows the trapped air to escape and ensures the adhesive flows evenly without creating air pockets. Avoid using open flames.
Q: Does the clear version of this tubing offer the same flame retardant properties as the black one?
A: No. While the black, red, blue, white, and yellow versions are flame retardant and meet UL VW-1 standards, the clear version is manufactured with a non-flame retardant polyolefin jacket. If flame retardancy is required for your application, please select a colored version.
Q: Is DHST suitable for high-voltage busbar insulation or heavier-duty applications?
A: DHST is rated for 600V and is perfect for wire splices and connectors. For high-voltage busbar insulation (1kV to 35kV), please consider our HBBT series busbar insulation tubing. If you need a thicker wall for extra mechanical protection and sealing, our MHST-A medium wall tubing is also an excellent choice.