combinations, especially with regards to multi-layer extrusions,”
said Tom Moore, technical sales manager for Raumedic AG, a
German provider of thermoplastic and silicone extrusion tech-
nologies with U.S. operations in Leesburg, Va.“For example, co-
extrusions with silicone and thermoplastics, with a strong bond
between the two layers, are in high demand. The silicone mate-
rial on the outside offers flexibility and strong bonding charac-
teristics with fittings, while the thermoplastic materials provide
One of the most challenging aspects of co-extrusion is getting
the silicone to adhere to the increasing variety of substrates that
are requested by OEMs for multi-layered designs.
“Sometimes a primer or preparation of the surface by plasma
or corona etching is required to enhance bonding,” said Mazelin.
“Silicones bond readily to themselves, so there are typically no
issues for layered silicone extrusions.”
Mazelin noted there is increased interest by designers in the
chemical-resistance properties of various silicone polymers.
“For example, fluoro silicones or diphenyl silicones exhibit
better chemical-resistance properties than do the significantly
less expensive poly dimethyl siloxane silicones,” he said.“In order
to provide tubing with the proper chemical-resistance proper-
ties, and still control the costs, we can jacket the less-expensive
material on the outer diameter to provide much less expensive
Sometimes OEMs don’t realize that all plastics cannot be ex-
truded together when it comes to multi-layer products, which
can lead to re-design or different material selections.
“Because many plastics are incompatible in terms of their
heat profile, they cannot be co-extruded,” added Moore. “There
is also concern with bonding—even materials with similar melting points sometimes need tie-layers so they can be properly adhered to each other.”
Polymer Solution Casting
With most co-extrusion technologies, bondable materials are
located either on the OD or ID for ease of assembly of complex medical devices. It’s a multi-step process—depending on
the complexity of the part or product and performance expectations, some extruders provide up to three or four materials
on an extrusion run, followed by multiple pass options. Many
of these materials are not ideally compatible for bonding and
require a tie-layer to hold them together, or a multiple-step
An alternative to co-extrusion is polymer solution casting, which utilizes a liquid polymer layering process to create an “all in one” continuous piece with no bonded joints
and increased design flexibility. Polymer solution casting
provides the ability to add multiple components and varying wall thicknesses or diameters along the length of the
device. It also is possible to embed components in virtually any
configuration—a production capability that expands the
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Avalon Polymer Solution Casting TM Technology
polymer science, unique
and innovation to
provide new and
distinctive solutions for
medical device companies.
Avalon utilizes liquid polymers to produce superior
tubing for medical devices. Polymer solution
casting methods allow us to incorporate materials
with different properties - including strength,
lubricity, flexibility, color and multi-lumens -
to customize tubing for any application.
Avalon has a full team of engineers that create
uncompromising, cost-effective medical devices.
Engineering expertise includes development,
manufacturing, quality and material science.