Medical Design Briefs: 2021 Technology Leaders - 33

Adding Color. Heat shrink tubing can
be colored for identification or aesthetic
purposes, such as to cover a joint or to
provide a smooth transition between a
tube and a connector.
Manufacturing Polyolefin Heat Shrink
Tubing
Once the heat shrink tubing is
designed, it is then extruded to very
tight tolerances. Extruding to precise
tolerances is imperative to ensure the
expanded dimensions will consistently
meet the critical requirements.
Once it is extruded, the tubing is
crosslinked via electron beam irradiation.
The irradiation step causes crosslinking
of the chemical backbone of
the tubing, strengthening it and giving
it the memory characteristics required
for the heat shrink process. During
development, the irradiation step is an
iterative process until the appropriate
dosage of radiation is determined to
meet the unique product specifications.
If the tubing is over-irradiated, it
won't expand large enough to achieve
the minimum expanded diameter
required. And if the tubing is underirradiated,
it will over-expand and will
be larger than the required expanded
diameter.
After completing the irradiation
step, the heat shrink tubing is then
expanded in either a continuous or a
discrete method. The proper expansion
method depends on the desired
size and expanded wall thickness of the
tubing. For large, thin-walled tubing, a
discrete expander is the ideal choice
because of the delicateness of the walls.
For example, a tube expanding from
0.020 to 0.200 in. with an expanded
wall thickness of 0.0002 in. will not be
suitable for a continuous expander
because the walls are so thin that they
may burst during the expansion phase.
The diagrams in Figure 1 illustrate the
extrusion, irradiation, and expansion
processes.
Ensuring Success for Your Heat Shrink
Tubing
With a high shrink ratio, low recovery
temperature, and good surface lubricity,
polyolefin offers distinct advantages for
heat shrink tubing. It is the ideal material
for use with transition tubing, electrodes,
and other applications that re -
quire extreme flexibility, thin walls and/
or low temperature shrink.
During development of heat shrink
tubing, it is important to consider the
cost implications of the design - especially
with regard to expanded ID,
recovered ID, length, and storage
needs. Manual processes and tight
specifications requiring careful inspection
will increase the cost of the final
product, so it is important to determine
tolerance requirements up front.
An extrusion expert can help ensure
design for manufacturability.
This article was supplied by Lubrizol Life
Science, Cleveland, OH. For more information,
visit http://info.hotims.com/79412-345.
Precision matters.
Medical Extrusion Technologies-Texas, Inc.
(MET-Texas)
FEP Heat Shrink Tubing
The precision quality and consistency of the FEP heat
shrink you use matters. Just as important, working
with a partner well-versed in sophisticated medical
device industry standards.
MET maintains precise, low
elongational growth and consistent recovery results for
I.D. and wall thickness. Manufactured at time of order
to your exact specifi cations. Precision also comes with
industry leading lead times, competitive pricing, and the
service levels you require. Need FEP? Contact MET.
MET Heat Shrink
Best in Performance
Best in Clarity at Expansion
Best in Finish at Recovery
Finish First with FEP from MET
Facilities: California | Minnesota | Texas
Please contact us today for samples, quotes or questions:
MET@medicalextrusion.com
TM
www.MedicalExtrusion.com
Medical Design Briefs 2021 Technology Leaders
www.medicaldesignbriefs.com
26608 Pierce Circle, Murrieta, CA 92562
800-618-4346 | PH: 951-698-4346 | FX: 951-698-4347
33
Standard draw
down ratios:
1:3 1:6 Custom Sizes
Cut to length Scored on 2
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