Monofilaments, also referred to as “beading,” “solid core,” or “miniature rod,” are single, thread-like extrusions with no central working channel. With over a half-century of experience, Zeus has developed the expertise and technology to manufacture precision monofilaments from multiple resins, including FEP, PEEK, PEEK Glide™, PFA, and PTFE.
Extruded monofilaments have been extensively utilized in the medical device industry for decades, with applications ranging from LCP monofilaments used as catheter braiding to bioabsorbable monofilaments used in therapies requiring controlled drug delivery. Perhaps the most notable application, however, is the use of extruded monofilaments as forming and support mandrels during catheter construction.
Used to form the inside diameter (ID) of the device during construction, mandrels must provide consistent IDs and a smooth inner surface for the finished catheter. Therefore, choosing the right mandrel material is of critical importance.
PTFE Monofilament
Traditionally, catheter manufacturers have opted for PTFE-coated stainless steel wire as the mandrel for most catheter builds. While stainless steel provides good mechanical strength, the thin PTFE coating applied over the stainless steel wire is prone to flaking during mandrel removal, potentially compromising the build. Extruded PTFE monofilament, on the other hand, does not run the risk of flaking and still provides sufficient tensile and compressive strength for a wide range of catheter designs. PTFE’s ability to be extruded with precise tolerances down to ± 0.0005” (± 0.0127 mm) helps ensure consistent IDs of the finished catheter, and its naturally smooth non-stick surface helps facilitate mandrel removal at the end of construction.
Glass-Filled PTFE Monofilament
For catheter designs that require higher PIC count braiding, such as neurovascular catheters, the mandrel used during construction must be capable of tolerating the additional compressive forces caused by the braid. This higher compressive strength can be achieved by compounding glass particles into the PTFE resin prior to extrusion. The result is a mandrel with enhanced mechanical properties, capable of supporting the most complex catheter builds and braid patterns.
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