Polyester heat shrink tubing is often used to cover braided catheter shafts, spring
coils, radio-opaque marker bands, and other parts that require a thin but tough
protective covering. The tubing provides smooth transitions over sharp edges and
can be sealed against fluid leakage. One manufacturer uses it over a rotary spring
cutter to keep debris from clogging the coils and to act as a bearing surface inside
the device. It provides a fluid seal, yet the cutter remains flexible. And the very
thin walls add virtually no dimensional increase to the device.
Clear polyester covering (top) holds a thermocouple against
a molded plastic probe. Clear polyester covers a coil spring (middle). Three tubes
and two wires are bundled with clear polyester tubing (bottom). The wires are not
visible in the photo.
The tubing is also used to provide strain relief on catheters and other tubes to
prevent kinking. A braided catheter will tend to kink at the point where the braid
ends, but encapsulation with heat shrink tubing provides a quick, easily applied
reinforcement providing a smooth transition over the two surfaces. Using shrink
tubing is a repeatable, consistent and efficient alternative to coatings. It eliminates
the solvents and chemicals required in the coating process, as well as the inherent
issues of uniformity and pin holes in coatings.
Endoscopes and other devices can be downsized or have more features added without
a size increase with the use of ultra thin wall tubing. Unique devices can be produced
using polyester heat shrink tubing to bundle various components into the smallest
possible space. Components such as plastic and metal tubing, wires, optical fibers,
etc. can be compressed and protected. Connecting tubes at the ends of a device can
be made of thin wall polyester, too, to save valuable space. The thinner walls of
polyester tubing can free up enough space to add another working channel inside
an endoscope. Or it might enable the designer to reduce the size of the device by
a whole French catheter size.
The key advantages of using polyester tubing as a protective cover or encapsulation
material are:
- Very thin wall adds virtually no dimensional increase
- Smooth transitions made over sharp edges
- Provides strain relief to prevent kinking
- Easy, quick application
- Repeatable and consistent
- Adhesive can be UV-cured through the clear tubing
- Provides chemical protection