Heat shrink tubing fails for two temperature reasons: it was heated too much, or not enough. Too much heat and the wall thins, bubbles, or cracks. Not enough heat and the tubing never fully recovers, leaving a loose sleeve that slides and doesn't seal. Getting the temperature right is the single most important installation parameter.
Recommended Temperatures by Material
| Material | Recovery Starts | Full Recovery | Max Continuous |
|---|---|---|---|
| LRS-1 (halogen-free PO) | 90°C | 110°C | 105°C |
| SRS (dual wall, adhesive) | 90°C | 120°C | 105°C |
| DWT (medium wall) | 90°C | 120°C | 105°C |
| TLG (railway grade) | 110°C | 130°C | 105°C |
| PTFE | 327°C | 350°C | 260°C |
Note that recovery temperature and maximum continuous operating temperature are different numbers. The tubing needs a brief burst of high heat to shrink, but then operates continuously at a lower temperature.
Heat Gun vs Torch vs Oven
Heat gun — the safest and most controllable option for most installations. Set it to 150-200°C, hold it 50-100 mm from the tubing, and move continuously. Best for: bench work, field repairs, any application where you can plug in.
Propane torch — faster but harder to control. Keep the flame moving and never let it dwell on one spot. Use the blue cone tip, not the yellow flame. Best for: field installations without electricity, large-diameter tubing where a heat gun is too slow. Not suitable for PTFE or thin-wall tubing.
Oven or conveyor — for batch processing pre-cut pieces. Set to 130-150°C for 2-5 minutes depending on wall thickness. Best for: production lines, kit assembly, uniform results across many pieces.
Step-by-Step Installation
- Clean the surface. Remove oil, dirt, and moisture from the object. Adhesive will not bond to a contaminated surface.
- Position the tubing. Slide it over the area to be covered. Center it — remember the tubing will shorten longitudinally by up to 8% during recovery.
- Start from one end. Apply heat at one end until the tubing begins to shrink and the adhesive (if present) starts to flow. Then work toward the other end in a continuous sweeping motion.
- Don't skip ahead. Heating the middle first traps air between the two shrinking ends, causing bubbles. Always work from one end to the other.
- Watch for full recovery. The tubing is done when it's tight against the surface with no gaps or loose spots. For adhesive-lined tubing, you should see a small bead of adhesive at each end.
- Let it cool before handling. The tubing and adhesive need to cool to room temperature before the assembly reaches full mechanical strength.
FAQ
What happens if I overheat the tubing?
The polymer degrades. You'll see thinning at the hottest point, surface discoloration (browning), or small bubbles in the wall. In severe cases the tubing cracks or splits along the length. If you see any of these signs, discard the piece and start over with lower heat.
Can I use a lighter for small tubing?
Technically yes, but it's difficult to control. A lighter's flame temperature is 600-1000°C — far above what polyolefin needs. You'll almost certainly overheat small-diameter tubing. Use a heat gun on its lowest setting, or a small butane torch with a fine tip held well back from the work.
Why is my adhesive-lined tubing not sealing?
Most likely the adhesive didn't reach its flow temperature. The outer wall may look fully shrunk, but the adhesive inside needs 110-120°C to melt and flow. Apply heat for an additional 10-15 seconds at each end until you see the adhesive bead appear.
Written by Long, Sales Engineer at ZZ Heat Shrink. For detailed installation instructions on specific products, see our product pages. For a quotation, contact our engineers.