Extrusion: Why this is important for catheter development
Vistamed, part of Freudenberg Medical, highlights the importance of extrusion in catheter development.
The extrusion and catheter finishing processes are inextricably linked and balancing these processes can be a complex undertaking.
There are a number of variables that can ultimately affect the performance of a finished catheter, the most paramount are the properties of the raw material and the extrusion process.
Careful consideration of the extrusion process is essential to ensure consistency and repeatability. Including extrusion engineers in the development decision making process is integral, and collaborative communication between customer and supplier will also enhance concept development and ultimately get devices to market faster.
It is important to keep in mind that there is far more to tubing than dimensions. Establishing a "see it, say it, fix it together" culture is key to getting a tube from concept to production.
Control inputs and outputs
The manufacture of high-quality extrusions used in sophisticated catheter systems is greatly affected by tight control of the "inputs".
Initially, the inputs start with people, because people can influence the other inputs like training, material handling, storage conditions, control of drying and equipment, tooling design, etc. Therefore, having the right mix of people is a good starting point. The greater the control of inputs to the extrusion process, the higher the probability of achieving the desired output necessary to develop and manufacture high quality extrusions.
"Outputs" begin with process stability, and then the spotlight turns to achieving the agreed upon customer specifications, such as critical dimensions, visual criteria, and functional performance.
The tolerance expectations from customers are constantly challenging the boundaries of extrusion capability. It has become more significant than ever for tubing manufacturers to maintain close control of their inputs and process.
Polymer science and material behaviour
A good understanding of polymer science and material behaviour is undeniably crucial for producing high-quality catheters and balloons.
The morphological structure of the thermoplastic material can change with varying thermal conditions which, in turn, determines key physical properties such as strength and flexibility. The polymer exits the die head of an extruder in an amorphous state and the rate and length of the cooling downstream from an extruder controls the degree of crystallinity in the final product.
In some medical applications, such as balloon forming, it is critical that the extruded tubing is amorphous prior to the balloon forming process. Therefore, the cooling parameters and cooling method used are critical to ensure that crystallisation does not occur in the tube during the extrusion process.
In other applications, such as the extrusion of polyether ether ketone (PEEK) tubing, it is critical that the PEEK tubing achieves a relatively high level of crystallinity during extrusion to ensure that the tubing utilizes the outstanding properties that PEEK possesses.
To produce high quality balloons and catheter systems, it is fundamental to have all the extrusion inputs under control. A capable process with high quality melt is critical to produce tubing for consistent balloon quality and desired performance. Additionally, a sophisticated extrusion process with precise in-line monitoring and control is also crucial to achieve high quality balloon tubing.
Small process variations can undoubtedly hinder the quality and performance of the final product. These variations potentially impact melt homogeneity and can result in variability in balloon tubing performance.