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Patients Who suffeR from stomach or intestinal
tumors can experience constriction of the digestive
tract—a condition called stenosis, which prevents food
from passing through. In these cases, a stent—an elastic,
tube-shaped, self-expanding wire mesh that
unfolds following placement in the esophagus or the
affected section of the intestine—reopens the pathway
for food. The stent does not cure the patient’s
disease, but it does alleviate suffering and improves
the patient’s quality of life.
Traditionally produced from polyamide or polyester,
stents can now be made from Evonik’s polyetheretherketone
(PEEK) VESTAKEEP® as well. The
material boasts not only excellent biocompatibility,
which Evonik has verified in numerous tests by
external testing institutes, but also high biostability.
The latter is a direct result of the aromatic, partially
crystalline properties of the PEEK polymer, which
not only imparts outstanding resistance to corrosion,
hydrolysis, and chemicals but also renders it inert to
bodily liquids—the material retains its stability, even
under aggressive conditions.
The stents are one of the new medical applications
Evonik has opened up with VESTAKEEP®. The fact
that EPT—Evonik Polymer Technology GmbH, which
manufactures PEEK semi-finished products—is certi-
Synthesis of PeeK. the aromatic,
partially crystalline properties
of the PeeK polymer make it highly
resistant to chemicals and bodily
fluids
fied to EN ISO 13485:2003 simplifies marketing of the
material. This certification makes it easier for the
producers of medical products to qualify as suppliers,
and ensures specific medical standards of care and
traceability are met. This completes a key hurdle in
advancing new applications.
In addition to its biostability and biocompatibility
(see also elements34, p. 30 ff), the advantages of
VESTAKEEP® include its outstanding mechanical
properties, such as high dimensional stability based
on low water intake, high stiffness at low weight, high
resistance to heat distortion, and a long-term service
temperature of 260 °C. This high-performance plastic
is also easy to work into versatile shapes—an argument
not only for the filigree construction of stents
but also for use as an extremely thin-walled battery
housing in cardiac pacemakers, in dental technology,
or as an implant pump for patients who, for instance,
suffer from excess fluid in the abdomen as a result of
liver disease. 333
Orthopedics: A growing
field of applications
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+
na2CO3 – naF
– H2O O OH
– CO2 O
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MedICAL teCHnoLoGY
O
O
evonik produces veStAKeeP®
in a Class 10000 clean room,
which commenced operation
in April 2011
n
29
elements39 Issue 2|2012