Medical Design Briefs - May 2021 - 23

ene (PTFE)-encapsulated silicone or FKM; each of these has
benefits, as well as conditions to which they are not suitable.
Although inert, silicone breaks down under high pH conditions, and it doesn't tolerate steam sterilization well. It is therefore not safe for all life sciences applications, since it may be
impossible to sterilize completely.
EPDM rubber can be manufactured to be compatible with
steam but may suffer degradation when in contact with nonaqueous solutions. As a result, some cleaning products are not
compatible, and processes involving animal fats or fatty molecules could attack the material's surface and lead to quality
issues. FKM can handle nonaqueous materials, but, like silicone, breaks down under high pH conditions. The common
cleaning product sodium hydroxide (lye) - used to remove
organic matter in bioprocessing, chromatography, medical
device decontamination, and many more applications - is
thus incompatible with FKM seals.
Encapsulated seals, which utilize PTFE over silicone or FKM,
are sometimes used in life sciences applications as seals on
doors or lids that have to open and close. This is an inappropriate use of this kind of seal, as the PTFE becomes brittle over
time and cracks. Once cracks form, the process fluids swell the
silicone or FKM, resulting in catastrophic failure of the seal
and then contamination of the pharmaceutical product.
Each of these seal materials can be useful as long as their specific end use is known - and these exceptions can be avoided.
All of them, however, can be dangerous - and expensive - if
used in the manufacture of products whose end uses are
unknown, and incompatible conditions occur. The expense
occurs in the case of failure, when seals must not only be
replaced, but manufacturing or processing must halt. These
halts usually last for a week or more, as teams across the organization determine the cause of failure, design corrective actions,
and implement necessary maintenance. In life sciences applications where both labor and product costs are high, unplanned
downtime and discarding batches of products after a failure can
be extremely costly, even to the order of millions of dollars.
Meeting Challenges
How, then, can manufacturers ensure that their parts are meeting the needs of all their customers, whether in research, food,
or pharmaceuticals? The key is selecting a seal material with the
greatest possible compatibility across a wide range of temperatures, chemical profiles, clean procedures, and more. One such
material is perfluoroelastomer (FFKM), like Greene Tweed's
Chemraz®, which has been specified into a variety of critical
applications, including life sciences, for more than 30 years.
These perfluoroelastomers contain higher amounts of fluorine than other sealing materials, thus ensuring stability in
higher temperature conditions up to 350 °C, a wider chemical
compatibility range, and minimization of leachables and
extractables. The material is inert to nearly all solvents and
reactants. Combining this inertness with its high temperature
profile and other features, perfluoroelastomers can safely be
sterilized repeatedly with steam, chemicals, or radiation and
remain functional and safe.
This kind of wide compatibility range can lead to cost savings
in the long term. Seals manufactured from Chemraz, for exam-

Medical Design Briefs, May 2021

ple, deliver an increased mean time between repairs (MTBR),
and so they can be replaced less frequently, require less maintenance, and minimize unexpected downtime for failures. In
addition, they minimize adulteration and batch loss because of
their robustness in nearly all conditions.
Chemraz materials are suited for life sciences up to 260 °C
for continuous operations, for example; other portfolio
options exist for excursions up to 350 °C. Greene Tweed engineers consult with engineers in life sciences applications in
order to understand what material would best suit each individual manufacturing process.
Perfluoroelastomers have been proven to deliver significant
benefits in a number of life sciences applications. Chemraz
products, for example, have been used by a major pharmaceutical manufacturer responding to the COVID-19 crisis, using
the seals in syringe pumps to ensure compatibility with active
pharmaceutical ingredients. They have also been used as a
replacement for silicone in plasma cutters thanks to their
excellent thermal resistance. By ensuring compatibility across
a wider range of solvents and temperatures than other materials, these materials improve reliability and uptime throughout
life sciences manufacturing applications.
This article was written by Ray Daugherty, New Business
Development - Life Sciences, and Mathew Griffin, Product Marketing
Analyst, Greene Tweed, Charlotte, NC. For more information, visit
http://info.hotims.com/79413-345.

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Medical Design Briefs - May 2021

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