Medical Design Briefs - May 2021 - 16

HCR Versatility
Transfer or compression molding.
Best suited for creating solid or hollow
parts, such as cuffs, O-rings, valves, or
balloons, these processing methods provide an economic molding process for
low- to medium-volume parts compared
to LSR injection molding. Transfer and
compression molding require the use of
less expensive equipment, offering simpler mold/part design and less set up
time. Although transfer and compression molding are both manual processes,
they can still be productive, cost-effective
ways to fabricate unique components.
Calendering. This processing method
creates a flat continuous sheet with a uniform thickness that can be used for further
processing (e.g., die-cutting). Calendering
using HCRs offers a variety of processing
options, depending on the final desired
sheet, whether it is a single sheet of material being produced or whether the HCR
is being applied to a substrate like fabric or
between substrates, multi-layered.
The sheets can be provided in either
cured or uncured forms. Uncured sheeting can be used as an adhesive between
two devices or components. Calendered
HCRs are typically in sheets with thick-

nesses ranging between 0.005 and 0.250 in.
The sheeting is cured by applying heat
after the calendering process is complete.
Choosing a Specialty Silicone
Manufacturer
Material selection is about more than
choosing a silicone with the right elastomeric properties and performance characteristics. Specialty silicone manufacturers
have the capability to formulate a wide variety of silicones, from adhesives to elastomers and offer customization to help
device manufacturers gain more control of
their final component or device. Material
selection depends on three key factors:
* The intended use of the implant
(external device or disposable device).
* The cure profile (the need to control
the HCR's cure rate with an adjustable
cure profile).
* The table life (the need for a standard
or extended work time).
It is essential for medical device manufacturers to collaborate closely with
suppliers. A supplier should be brought
into the process as early as possible,
preferably during the product idea or
design stage. An expert supplier can nar-

row down the material selection based
on performance requirements for the
application. The supplier can also help
achieve performance of the end product, which is especially critical in a highly
regulated industry like medical devices.
During downstream processes, like
assembly, a supplier can also help ensure
that materials from different parts of the
device are compatible.
Just as importantly, they can provide
guidance and regulatory support that
can lead to faster and smoother commercialization and more successful final
end-use. A materials partner with established relationships with regulatory bodies across the globe can prove invaluable
and save the device manufacturer time
and money. From established medical
use to high mechanical properties to
cost-effective fabrication, HCRs offer
manufacturers the versatility they need
to produce safe devices that provide
essential therapeutic support for people.
This article was written by John Freedman,
Director of Biomaterials, and Alex Santayana,
Applications Engineer, NuSil from Avantor,
Radnor, PA. For more information, visit
http://info.hotims.com/79413-342.

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