Specification Standard Requirements
See the PET (Polyethylene Terephthalate) heat shrink tubing (PHST) specification standard requirements.
PHST Requirements
'Drawing Down' Heat Shrink Tubing
The ability to "draw down" PET heat shrink tubing allows you to reduce tube diameter by up to 70% while maintaining a high-strength, thin-wall heat shrink tube.
- PET heat shrink tubing ratios are different from those of other tubing:
- Tight fit is best: 15% gap or less
- PET should be sized no larger than 15% above the maximum diameter of your part
- Target ratio is 1.1:1
- Shrinking temperature:
- Approximately 70°C (158°F)–190°C (374°F)
- Typical shrinking temperature recommended for most applications: 150°C (302°F)
Controlling Shrinkage
Unrestricted, PET heat shrink tubing will shrink both radially and axially. In most cases, the best overall performance comes with minimal shrinkage (less than 15%–20%), except when the tube drawing process is used as described below, or unless you restrict axial shrinkage.
You can restrict axial shrinkage by holding the ends of the heat shrink tube during the heating process to prevent the tube from shrinking in length. This will result in a heat shrink tube with radial shrinkage up to 50% or more, depending on temperature.
Tube Drawing for High Radial Shrinkage
Use the tube drawing process to achieve very high radial shrinkage (up to 50% or more). Simply apply axial tension, stretching the heat shrink tube while you're heating it. You can reduce the diameter by more than 50% at temperatures below 100°C (212°F); with even greater diameter reductions at higher temperatures, up to about 190°C (374°F).
For more information about proper sizing, visit the Medical Heat Shrink Tubing Online Store and select a tubing item, or contact us.
