Extruded PTFE Liners: Critical Role in Catheters & Medical Devices

Polytetrafluoroethylene (PTFE) is a class of fluoropolymer that is widely used in medical devices. This is due to its low coefficient of friction (CoF), high chemical resistance and thermal stability properties, and biocompatibility. One of the most common uses of the material is as extruded PTFE liners. The liners act as the internal surfaces of minimally invasive medical devices, such as catheters, guiding systems, and delivery tools. 

The PTFE lining creates a low-friction surface within the device. This allows for smooth movement of minimally invasive medical devices through tortuous, winding passages of the human body. At the same time it provides the surgeon with the ability to perform precise movements while ensuring patient safety. ^1,2

Demand for minimally invasive surgical and diagnostic procedures has increased dramatically recently. This is especially true in fields including cardiology, neurology, gastroenterology, and urology. Because of this increased demand, medical device manufacturers are continually developing new-generation catheters designed to provide greater performance characteristics. 

For today’s minimally invasive procedures, devices need to be able to easily push, respond instantly, resist kinks, bend as necessary, and follow the pre-determined path. PTFE liners into the catheter gives the device these performance capabilities. They do this by providing a low-friction surface on the catheter shaft that allows the catheter shaft to work in a controlled manner. ^3,4

In this article we will look at the properties of PTFE, the manufacturing methods used for producing extruded PTFE liner products, the engineering principles used to develop the design of extruded PTFE liners, and how these liners are used in medical device finished goods for their clinical applications.

Fundamental Properties of PTFE

Chemical Structure

PTFE is a fluorocarbon polymer composed of repeating tetrafluoroethylene monomers:

(-CF₂-CF₂-)_n

Material Characteristics

The strong carbon–fluorine bonds give PTFE very high chemical and thermal stability. Due to its make-up PTFE has several useful properties:

• Very low coefficient of friction (CoF)
• Excellent electrical insulating (dielectric) properties
• High chemical inertness (it does not react easily)
• Resistance to absorbing moisture
• High resistance to heat
• Good biocompatibility (it works well with living tissue)

PTFE’s coefficient of friction is one of the lowest among engineering plastics. This is why it is often used in catheter liners and delivery systems. 

Its hydrophobic, nonreactive surface reduces contact with biological tissues and with devices that move through the lumen.

Extruded PTFE Liners: Definition and Functions

Definition

PTFE extrusions are thin, tubular components. They can be manufactured from an extruded PTFE material using the extrusion process. These extrusions form the inner layer of a multi-layer catheter, and their primary function is to provide a smooth surface for the movement of other components within (or through) the catheter.

Functions of PTFE Liners

A PTFE liner has several important functions:

1. Acts as a barrier that prevents chemicals from passing between device parts and bodily fluids
2. Lowers friction between the catheter’s inner wall and any parts that move inside through the lumen
3. Helps the device reach its target easier (better deliverability)
4. Improves how well the catheter responds to pushing and twisting (pushability and torque transmission)
5. Keeps the lumen’s shape and function when the catheter bends

Extruded PTFE Liners Manufacturing Methods

Thermoplastic Polymers ordinarily melt & flow when subjected to heat. However, PTFE does not melt or flow when it is heated. Therefore, it is not possible to use traditional methods to manufacture PTFE liners using Standard Melt Processes. Due to this fact, PTFE liners must be manufactured utilizing unique methods.

The primary manufacturing techniques used to make PTFE Liners include:

1. Free extrusion 
2. Extrusion over-the-wire (OTW) 
3. Film-cast liner fabrication 

Among these, free extrusion and OTW extrusion are widely used for advanced catheter manufacturing.

Below we discuss each of these PTFE manufacturing techniques in more detail. 

1. Free Extrusion Technology

Free extrusion involves forcing PTFE paste through a die without an internal mandrel support during the extrusion phase. Subsequent sintering stabilizes the structure.

Advantages of Free Extrusion

• Excellent tensile strength 
• Strong axial molecular orientation 
• Superior rigidity 
• Tight dimensional tolerances 
• Ultra-thin wall capability 

Free extrusion promotes fibrillar alignment within the PTFE matrix, increasing longitudinal strength. 

Clinical Relevance of Free Extrusion

The high pushability and dimensional stability of free-extruded liners make them ideal for applications such as:

• Coronary guide catheters 
• Peripheral intervention systems 
• Structural heart delivery systems 

2. Extrusion Over-the-Wire (OTW)

OTW extrusion incorporates a mandrel or core wire during processing.

Advantages of OTW Extrusion

• Increased flexibility 
• Reduced wall thickness 
• Better navigation through tortuous anatomy 
• Improved trackability 

This technology is especially valuable in neurovascular and microcatheter applications where flexibility is critical. 

3. Film-Cast PTFE Liners

Film-cast liners are manufactured by coating PTFE dispersions onto mandrels and subsequently sintering the material.

Benefits

• Very thin walls 
• Flexible construction 
• Continuous processing capability 

Limitations

• Potential pinhole defects 
• Lower structural uniformity 
• Greater variability in mechanical performance 

Recent manufacturing innovations, such as those by Hydromer®, Inc. have aimed to reduce imperfections and improve reliability.

Exception Performance Properties of Extruded PTFE Liners

Below we discuss the characteristics of extruded PTFE liners that make them such a good fit for medical device applications.

1. Lubricity

The most important functional characteristic of PTFE liners is its ultra-low friction (Coefficient of Friction or CoF). This ultra low CoF enables:

• Smooth guidewire movement 
• Easier stent delivery 
• Reduced insertion force 
• Improved procedural control 

Low-friction lumens reduce resistance during device advancement in tortuous vasculature. This is particularly true in coronary and neurovascular interventions.

2. Pushability and Torque Response

Catheter performance depends heavily on force transmission. Extruded PTFE liners contribute to:

• Longitudinal stiffness 
• Torque fidelity 
• Improved operator control 

Extruded PTFE liners act synergistically with reinforcing braid or coil structures to optimize shaft mechanics.

3. Kink Resistance

Thin-wall PTFE liners maintain lumen patency under bending stress. This property is particularly important in:

• Cerebral vasculature 
• Peripheral arteries 
• Endoscopic pathways 

Maintaining lumen geometry prevents procedural complications and preserves device functionality.

Hydromer® PTFE Liner Products Advance the Goal of Lubricious Medical Devices

Following a strategic partnership with jMedtech, Hydromer®, Inc. now offers a portfolio advanced PTFE liners and tubing products for minimally invasive medical devices. Our advanced PTFE extrusion capabilities will be combined with our 40+ years in developing highly lubricious, hydrophilic catheter coatings. These technologies will complement each other and help device manufacturers create advanced devices to support procedures in the heart and blood vessels, the brain’s blood vessels, peripheral arteries and veins, electrical heart treatments, and endoscopic procedures.^3,4

Below is an overview of our Hydromer® PTFE Liner products:  

MatrixLiner® Platform

MatrixLiner® is a family of PTFE liners manufactured using three proprietary processing approaches:

• Free extrusion 
• Over-the-wire (OTW) extrusion 
• Film-cast (dip-coated) processing 

These technologies allow optimization of:

• Strength 
• Flexibility 
• Pushability 
• Trackability 
• Dimensional precision 

The MatrixLiner® platform offers ultra-thin wall PTFE liners with thicknesses as low as:

0.00025inch ≈ 6.35μm

and inner diameter tolerances as low as:

±0.0003inch ≈ ± 7.6μm

ToughFlex™ and ElastiFlex™ PTFE Liners

These two specialized free-extruded PTFE liner series were developed to address different clinical and engineering requirements.

ToughFlex™ (TF)

ToughFlex™ is a high-yield-strength PTFE liner designed for:

• Increased column strength 
• Better burst resistance 
• Improved pushability 

The material is engineered for demanding vascular and structural heart procedures requiring strong mechanical support. 

ElastiFlex™ (EF)

ElastiFlex™ prioritizes flexibility and elongation performance, achieving elongation values exceeding 800%. 

The product is designed for:

• Tortuous anatomy 
• Neurovascular applications 
• Steerable catheters 
• High-flexibility delivery systems

Medical-Grade PTFE Liners: Shaping the Next Generation of Catheter Technology

Medical-grade PTFE liners have become an important part of modern medical devices. Because they have low friction, resist chemicals, and are safe for the body, they are commonly used in catheter design. As such, PTFE liners are found in devices like microcatheters, aspiration catheters, and steerable catheters. Their slippery surface helps these tools move smoothly and accurately through the body’s complex pathways, which is important for minimally invasive procedures.

The growing demand for catheters with thinner walls and larger inner diameters has increased the use of advanced PTFE liners. Their flexibility, dimensional stability, and tensile strength let manufacturers build advanced catheter systems that meet strict clinical needs. PTFE liners are also used in stent protection sheaths, where their durability and smooth surface improve device handling and performance. This wider use highlights the key role that PTFE liners play in improving the design and function of next-generation medical technologies.

Conclusion

Extruded PTFE liner products represent critical advancements in modern minimally invasive medicine. Some attributes of these liners include low-friction coefficient and precise dimensions, high chemical resistance, and excellent mechanical durability. These impressive properties make PTFE liners a clear choice in developing advanced catheter and delivery device systems. 

Several manufacturing techniques change the characteristics of PTFE liners for specific clinical needs. Different surface treatment techniques, such as surface etching and incorporating hydrophilic coatings, can enhance the performance of PTFE-lined devices by improving both the exterior and interior surface functionality. 

Many minimally invasive procedures utilize PTFE-lined devices, such as coronary procedures, neurovascular thrombectomies, and electrophysiology. There has been an advancement of new manufacturing techniques involving ultra-thin extrusion processes, composite shaft designs, and surface modification techniques. These should lead to easier catheter navigation, improved safety in usage, and increased accuracy in treatment in the future. 

Since their strategic partnership, Hydromer and jMedtech have developed technologies associated with extruded PTFE liner technologies used in the manufacture of medical device products. State-of-the-art PTFE platforms developed by these companies include MatrixLiner®, ToughFlex™, and ElastiFlex™.  These offer innovative solutions utilizing engineered PTFE to enhance catheter flexibility, lubricity, pushability, and overall procedural performance in minimally invasive procedures.

References

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1. Dhanumalayan E, Joshi GM. Performance properties and applications of polytetrafluoroethylene (PTFE)—a review. Advanced Composites and Hybrid Materials. 2018;1(2):247-268. 

2. Roina Y, Auber F, Hocquet D, Herlem G. ePTFE‐based biomedical devices: An overview of surgical efficiency. Journal of Biomedical Materials Research Part B: Applied Biomaterials. 2022;110(2):302-320. 

3. JMedtech. PTFE Liners and Tubings. https://jmedtech.com/medical-catheter.html

4. Hydromer. PTFE Liners and Tubings. https://hydromer.com/ptfe-liners-and-tubing/