Thomas Barrett, CEO of Applied Plastics, a coating solutions specialist company, explains how to pick the perfect polytetrafluoroethylene (PTFE)-coated mandrel.
For any manufacturer developing advanced catheter components and devices, coated forming mandrels are as essential for increasing output, as resin and custom dies are for producing precise medical extrusions.
Mandrels are used in a variety of applications, ranging from catheter fuse welding and tipping operations to extrusion mandrels which are used for manufacturing catheter tubing that provides a smooth, slippery surface for faster production.
Coated mandrels are also commonly used as a catheter shaft manufacturing tool to:
1. Simplify removing the catheter
2. Limit shrinkage during the reflow process
3. Permit faster catheter production
PTFE coated forming mandrels and catheter manufacturing have gone hand-in-hand for decades. For example, who remembers the days of calling forming mandrels “blockers” before what we now simply refer to as “coated mandrels?”
Over the years, coating options have grown in the medical device market to improve production processes in several different ways, and with so many material and coating options available today, choosing a coated mandrel to match your unique manufacturing needs can seem particularly daunting. Therefore, here are five factors to consider when you’re choosing a coated mandrel, in order to make that decision much easier.
1. Work backwards
Firstly, think about the end use application and what the primary goals of the device are. Whether you are manufacturing an advanced delivery system with multiple lumens or extruding over a multi-tapered mandrel, knowing how the end-product will be used will help you to identify the key characteristics required of the coated mandrel.
2. Make a list
Write out all of types and durometers of polymers which are needed to reach proximal and distal shaft performance requirements, such as kink resistance and steerability. It will also be important to understand how the reflow process operating temperatures may affect each polymer e.g. some PTFE coatings can withstand 550°F continuous temperatures with excursions to 700°F
3. Test your options
Now that you’ve identified the temperature ranges you can work with, you need to consider which mandrel substrate material to use. While there are material cost savings that can be gained when considering one material over another, you must consider what material characteristics and benefits each mandrel material would provide during production. It is helpful to find a supplier who can provide multiple substrates of coated mandrels like stainless steel, nitinol and silver-plated copper. Then you can test each mandrel material to determine what’s best for your application and budget. The best way to make this decision is to put your options to the test.
4. Identify lubricity requirements
Identifying lubricity requirements will help to ensure the coating process results in a longer mandrel lifetime during the manufacturing process. Pull wires and guide wires used in interventional procedures must navigate through the inner diameters of catheters seamlessly, making a high-quality lubricious coating like PTFE imperative. Other variations of PTFE fluoropolymer coatings, such as PTFE Natural, can provide performance benefits like achieving a 0.05 coefficient of friction to simplify catheter removal in fuse welding and tipping operations.
5. Key coating features to look for
Lastly, whether you are designing a pull wire or a delivery system, always look for a quality coated mandrel which features a uniform, precise, non-flaking finish.
Key coating features:
1. Close tolerances
2. Abrasion resistant
3. Chemically inert
4. Chemical resistant
5. Bio compatibility
6. Corrosion resistant
A lubricious coating, such as PTFE, becomes increasingly important to the catheter manufacturing process as complexity increases and French size decreases. Durability is also crucial to ensure safety and performance for any components included in the final device.