Medical PI Tubing: 7 Key Properties Medical Device Engineers Should Know

Property 1: High Tensile Strength in a Thin Wall

One of the most cited reasons for choosing medical PI tubing is that it can hold significant tensile strength while maintaining a very thin cross-section. This matters directly in catheter design, where every fraction of a millimeter of wall thickness can be reallocated toward a larger inner lumen or a smaller outer diameter, both of which improve device performance.

Because the material carries load efficiently at a thin gauge, ultra thin wall polyimide tubing is frequently specified for liner layers in microcatheters and other small-profile devices where every increment of wall thickness competes directly with usable lumen space.

Property 2: Thermal Stability Across a Wide Temperature Range

Polyimide tubing retains its mechanical and dimensional properties across a broad temperature range compared with many general purpose polymers. This becomes relevant not only during clinical use but also throughout manufacturing steps such as reflow soldering of nearby components, heat-set bonding, and sterilization-related processing, where the tubing must not soften, deform, or lose dimensional accuracy.

This wide thermal stability window is one reason medical grade polyimide tubing continues to hold dimensional consistency through steps of the device assembly process that would soften or distort many alternative tubing materials.

Property 3: Broad Chemical and Solvent Resistance

Medical device manufacturing and clinical use both expose tubing to a range of chemical contact points, including cleaning agents, contrast media, bonding solvents, and physiological fluids. Polyimide is generally recognized for resisting degradation from many common solvents and chemicals encountered during both production and device use, which helps preserve tubing integrity over the life of the component.

Common Exposure Points During Manufacturing and Use

• Bonding and adhesive solvents used during catheter shaft assembly
• Cleaning and degreasing agents used in production environments
• Contrast media and saline solutions encountered during procedures
• Coating and lubricant chemistries applied to the outer tubing surface

Property 4: Tight Dimensional Tolerances and Wall Consistency

Consistent inner diameter, outer diameter, and wall concentricity are essential for tubing that will later be reinforced, coated, or bonded into a multi-layer catheter shaft. Polyimide tubing manufactured through precision extrusion or solvent-cast processes can achieve narrow tolerance bands, which supports repeatable assembly and predictable mechanical behavior across a production lot.

This level of dimensional control is a key reason many engineering teams request thin wall microcatheter tubing built specifically to match a target inner lumen while staying within a defined outer diameter range for the finished device.

Property 5: Biocompatibility for Body-Contact Applications

Polyimide used in medical tubing is selected for formulations suited to body-contact applications, supporting its use as a liner material in catheters and other devices that come into contact with vascular tissue or bodily fluids during a procedure. Biocompatible polyimide tubing is typically produced under controlled manufacturing conditions to help maintain material purity and consistency from batch to batch.

Why Biocompatibility Matters for Tubing Selection

Device teams generally evaluate biocompatibility alongside mechanical performance rather than as a separate consideration, since a tubing material must satisfy both requirements simultaneously to be viable for catheter or introducer applications. This is one reason polyimide continues to be paired with reinforcement layers rather than replaced outright by other polymer options.

Property 6: Controlled Flexibility and Predictable Bend Behavior

While polyimide alone is comparatively stiff next to some elastomeric tubing materials, its bend behavior is highly predictable, which allows engineers to design catheter shafts with known flex characteristics rather than variable ones. This predictability is often more valuable in catheter design than raw flexibility alone, since a shaft with erratic bend response is harder to control during navigation.

Because bend behavior is more predictable than flexible on its own, polyimide liners are commonly combined with reinforcement layers when a catheter design calls for both flexibility and controlled recovery, particularly in polyimide tubing for microcatheters that must track through narrow, curved vessels.

Property 7: Compatibility with Reinforcement and Coating Processes

A practical property that often gets less attention than raw material strength is how well a tubing substrate bonds with secondary processes such as braiding, coiling, and outer jacket coating. Polyimide surfaces generally accept braid reinforcement and secondary coatings well, which is part of why it functions effectively as a liner layer inside a multi-layer catheter shaft rather than only as a standalone tube.

This layered compatibility is why medical PI tubing for catheters is frequently supplied as a base liner component intended for further processing rather than as a finished stand-alone product.