When people think about medical catheters or minimally invasive devices, they usually focus on the visible parts, such as the stent, the balloon, or the guidewire. One key, but less visible component of a catheter is the PTFE liner, which exists inside the catheter device itself. The utilization of PTFE as a liner material has grown in use, especially with the growing trend toward minimally invasive procedures. This is due to PTFE’s very low coefficient of friction (CoF) and superior chemical stability.
PTFE Liners play a critical role in the performance of a catheter. They greatly influence many things, such as the movement of fluids and devices through the inner diameter of the catheter during the procedure for which it was designed.
The manufacturing process used to make a PTFE liner affects catheter performance. In addition it has significant implications for the overall success of the procedure and the handling of the catheter by the physician.
However, not all PTFE liners perform the same. Performance differences may arise from the method of manufacture used to produce the linings. In addition, PTFE’s overall structure when it is produced will affect how well it performs in different applications.1-3
There are two major types of PTFE liners commonly used in medical devices: extruded PTFE liners and cast PTFE liners. Both are widely used across the medical industry. Each type offers different advantages depending on the application it is used for.
Many devices require either additional support/pushability or flexibility of the liner. This is needed to assist with navigating the device through anatomical pathways that have many bends and turns. Therefore, producing the correct type of liner will be a significant engineering consideration for the manufacturer when developing a medical device. It will also be a major consideration for procurement personnel when choosing a specific product.
In this article we utilize Hydromer®, Inc.’s expertise to comprehensively compare extruded vs cast PTFE liners. We will look at the each, the differences between the two, and determine which one is better for different medical applications. If you are a biomedical engineer, healthcare procurement professional, or other interested party this article is intended to help you make better choices about materials and product design.
Why PTFE Is So Important in Catheter and Minimally Invasive Devices Design
PTFE is widely used in medical devices. This is because it combines several key properties that are difficult to achieve with most polymers.4
The material possesses:
- Extremely low friction (high lubricity)
- Excellent biocompatibility
- Chemical resistance
- Thermal stability
- Long-term durability
- Resistance to moisture absorption
Lubricity is probably the most valuable characteristic of catheter systems. PTFE liners provide a very smooth, low friction inner surface. This enables guidewires, coils, balloons, and stents, as well as fluids to move through the catheter with little or no resistance. 5
Even small increases in friction can significantly impact device handling. This is specially important in instances where devices must traverse long vascular pathways or move through highly tortuous anatomy.
But not all PTFE Liners are the same.
So how do extruded vs cast PTFE Liners compare?
Both PTFE extruded linings and PTFE cast liners are manufactured from the same material. However, their mechanical behavior is affected by their method of manufacturing. Hence, this is why extruded and cast PTFE liners are not the same.
We look at each type of liner in more detail below.
And if you are interested to find out more, you can read our guide on the Science Behind PTFE Low Friction Medical Tubing and Liners.
Intro to Extruded PTFE Liners, and Suitable Uses
Extruded PTFE liners are made using a method called “paste extrusion.” This means that the material is pushed through a die under pressure, then sintered at a high temperature. When an extruded product is made, the extrusion process must create alignment or orientation of the PTFE molecules in the direction of the tubing. This creates a molecular structure that is both stronger and stiffer than those without orientation or alignment in the direction of the tubing.1,3
If you want to learn more about you can read our comprehensive guide on Extruded PTFE Liners.
Benefits
Because of this, extruded PTFE liners have the following benefits:
- Better pushability
- Higher tensile strength
- Improved torque response
- Greater dimensional stability
- Stronger shaft support
In simple terms, extruded liners help give catheters more stability and responsiveness during procedures.
Another advantage of manufacturing process is the ability to manufacture extruded liners that have extremely precise dimensional tolerances. This provides uniformity that is critical for today’s catheter systems.
Suitable Uses
As a result, physicians can utilize catheters to provide improved transfer of force between both ends of the catheter. This is due to an increase in efficiency when transitioning from the proximal (base) to the distal (tip) ends of the catheter.
This property is especially helpful in cases, such as those below:
- catheter-based interventions across a resistant lesion
- supporting the delivery of State-of-the-art implants like stents
Intro to Cast PTFE Liners, Benefits, and Suitable Uses
Cast PTFE liners are produced differently. Instead of aligning the molecules in one direction, the casting process creates a more evenly distributed internal structure.1,3
As a result, cast PTFE liners are softer and more flexible compared with extruded liners.
Benefits
Key advantages of this type of liner include:
- Better flexibility
- Improved conformability
- Enhanced navigation
- Greater bending capability
Suitable Uses
The unique and specialized qualities of cast liners are ideal for use in catheter applications that need to pass through fragile or extremely curved structures.
Neurovascular interventions frequently demand that the catheter be able to course through very fine, difficult to navigate, and highly convoluted vessels (i.e., the cerebral vascular tree).
Catheters that are too rigid may not navigate well and could even increase your likelihood of injuring the vascular structure.
Cast PTFE liners will assist in developing soft catheter systems that will transition much more similarly to the way they would move through the body.
Comparing Extruded vs Cast PTFE Liners in 5 Key Performance Attributes
The difference between extruded and cast PTFE liners becomes clearer when looking at how the devices behave during actual procedures.1,5-7 We compare the two on several key performance attributes below.
1. Pushability and Support
Pushability is the nature of the force moving through the catheter shaft when being pushed forward by the doctor when using the device.
Extruded PTFE liners generally do better than other types in this regard due to the aligned molecular structure of the material that allows more axial rigidity. As a result, the catheter will have the adequate pushability during these more difficult-to-perform procedures.
This ability is particularly useful in:
- Coronary interventions
- Peripheral vascular procedures
- Structural heart applications
- Stent delivery systems
Devices that require strong support often rely on extruded liners to maintain consistent performance.
Cast liners, while more flexible, tend to absorb some of the applied force. This can slightly reduce shaft support compared with extruded designs.
2. Flexibility and Trackability
Stiffness gives you the benefit of support. However, too much stiffness makes it difficult to navigate through any torturous anatomical path.
This is where cast PTFE liners perform especially well. Their softer nature allows surgeons to curve the catheter into a new shape and follow a curved vessel. This improves trackability and helps physicians access difficult-to-reach anatomical targets with better safety than otherwise possible.
Applications that often benefit from cast PTFE liners include:
- Neurovascular microcatheters
- Electrophysiology devices
- Pediatric catheters
- Distal access catheters
In these cases, flexibility becomes more important than shaft rigidity.
3. Kink Resistance
When properly incorporated into the design of a catheter, both types of liners will demonstrate a measure of kink-resistance. However, the two will react to bend stress differently.
Because of the rigidity of their construction, extruded PTFE liners hold their inner-lumen profiles very well. However, if the overall system is too rigid, severe bending may produce localized high-stress points.
On the other hand, cast PTFE liners have a more compliant structure and are therefore less hindered by repetitive bending. As a result, they allow for a more uniform distribution of stress throughout the catheter. For applications that require continuous motion or complex curves in the anatomy, the flexibility of a compliant liner can be extremely helpful.
4. Dimensional Precision
Modern minimally invasive devices require extremely precise dimensions. Even very small changes in lumen size can affect guidewire movement and implant delivery.
Extruded PTFE liners generally offer tighter dimensional control. This is because the extrusion process, especially when performed by an expert liner manufacturing company is highly consistent.
This makes extruded PTFE liners especially suitable for:
- Balloon catheters
- Guiding catheters
- High-pressure lumens
- Stent delivery systems
Cast liners can also perform well, but extrusion generally provides greater manufacturing precision.
5. Friction and Device Movement
PTFE is known for having an extremely low coefficient of friction. As a result, both extruded and cast PTFE liners have superior lubricity.
However, in general, extruded liners tend to result in a smoother and more consistent interior surface. As a result, extruded liners may provide guidewires with smoother passage and reduced resistance. This is important in procedures with multiple device exchanges and/or long procedures.
For the majority of clinical uses, both types of liners provide adequate frictional reduction. In many cases, the overall catheter design is likely to play a larger part in determining the end performance than the liner type.
Applications: Extruded vs Cast PTFE Liners
Extruded PTFE Liners
Extruded liners are created by pushing raw PTFE (polytetrafluoroethylene) paste or resin through a die using a hydraulic press. This process causes the polymer chains to be aligned in the same direction (axially). It forms tiny hair-like structures (fibrils) to provide strength and rigidity along the length of the liner. 1,8
Extruded PTFE liners may be chosen for medical deviceapplications such as:
- Vascular Device Delivery Catheters: Strong mechanical properties will not deform when delivering tightly compressed devices such as stents, flow-diverters, and aortic scaffolds.
- Mechanical Thrombectomy Catheters: Used in the treatment of stroke where the liner will be exposed to high rotational force and radial pressure and must not collapse.
- High-Pressure Suction Catheters: Must have the ability to resist excessive length and kinking due to high-pressure vacuum aspiration.
Cast PTFE Liners
A liquid PTFE water dispersion is layered onto a core wire mandrel to make the film-cast liners, which are then sintered and pulled off. Since there is no mechanical pressure applied to the cast liners, the polymer chains maintain a random orientation. This results in very thin walls and excellent omni-directional flexibility. 1,7,8
Cast PTFE liners may be chosen for medical applications such as:
- Neurovascular Microcatheters: Perfect for accessing tight, complex, tortuous brain blood vessels.
- Below-the-Knee Peripheral Catheters: Safely access very fragile, narrow, winding infra-inguinal non-occlusive peripheral arteries.
- Ultra-Thin Guide and Midline Catheters: Minimize the outer diameter of catheters while maximizing the inner lumen volume, allowing engineers to include additional braided reinforcements and/or steering components.
- Diagnostic Mapping and Electrophysiology Catheters: Provide highly responsive steering tracking while navigating extremely delicate heart chambers during cardiac ablation or mapping procedures.
The Move Toward Hybrid Catheter Designs
Today, many medical devices combine different material technologies to achieve a balance between support and flexibility.5,9,10
Manufacturers increasingly integrate PTFE liners with:
- Braided reinforcement
- Coil structures
- Variable stiffness shafts
- Hydrophilic coatings
- Multi-layer polymer systems
Some sophisticated catheters now possess a diverse range of rigidity throughout the length of the catheter. The proximal portion can supply rigidity and promote movement, while the distal part can bend easily around bends.
This hybrid technique gives manufacturers the ability to improve catheter functionality for progressively more complicated procedures.
Conclusion
Extruded PTFE liners and cast PTFE liners each have distinct benefits that provide advantages in the design of medical devices.
Extruded PTFE liners are known for their superior strength, pushability, dimensional accuracy, and shaft support. This makes them very well suited for use as guide tubes to facilitate the delivery of catheters, balloon systems, and stents.
Cast PTFE liners, on the other hand, are known for their flexibility, conformability, and ability to negotiate complex anatomies. Thus, it is possible to use them for neurovascular, electrophysiology, and pediatric applications.
So which one is better: Extruded vs Cast PTFE Liners?
Rather than deciding which type of liner is better than the other, it is important to determine what type of liner will work best in the specific application being developed.
Catheter technology continues to improve. In turn, understanding the impact of liner construction on device function will continue to be critical for biomedical engineers who are designing the next generation of minimally invasive medical devices.
Get in Touch
Hydromer’s PTFE liners and tubing, hydrophilic coatings, coating equipment, and contract services can support your product and production needs.
Please feel free to contact Hydromer® to learn more about our PTFE liner products or to request samples.
References
Click here to see all references for this article.
1. JMedtech. PTFE Liners and Tubings. https://jmedtech.com/medical-catheter.html
3. Hydromer. PTFE Liners and Tubings. https://hydromer.com/ptfe-liners-and-tubing/
8. Zeus. Engineering Possibilities: New Liners for Next-Gen Catheters. 2026. https://www.zeusinc.com/wp-content/uploads/2024/05/Engineering-Possibilities-New-Liners-For-Next-Gen-Catheters-V1R4.pdf
9. Mesfin S, Sarkissian C, Malaeb B, Monga M. Catheter design for effective manual bladder irrigation. The Journal of urology. Dec 2011;186(6):2307-9. doi:10.1016/j.juro.2011.07.080
10. Abdessalem KB. A hybrid pneumatic-hydraulic catheter system for cardiovascular hemodynamics: design, modeling, and in vitro characterization. Measurement. 2026/06/02/ 2026:122124. doi:https://doi.org/10.1016/j.measurement.2026.122124
