How Sterilization Affects TPU-Based Medical Devices

Choosing the right material for a medical device is tough enough on its own. Add sterilization to the mix, and the puzzle gets even trickier. Most developers and engineers are focused on the product—how it functions, fits, and affords patients a better experience. But if the sterilization process doesn’t hold up, your best materials and design won’t either. Thermoplastic polyurethanes (TPUs) are a perfect example—these polymers are a reminder that sterilization isn’t just a technical detail but something that can shape the success of a medical device from multiple angles.

With that in mind, let’s unpack what makes TPUs unique and walk through the best methods for sterilization.

Why TPU Sterilization Is So Critical

TPU sterilization is not a one-size-fits-all procedure because, unlike metals or glass, polymers respond differently to various methods. Choosing incorrectly can compromise material integrity, degrade mechanical properties, discolor the device, or create toxic byproducts. For example, sterilizing a polymer meant for medical tubing in an autoclave (high-temperature steam) could degrade the material to the point where it becomes brittle or even unsafe.

TPUs bring a rare combination of stretch, strength, and safety to the table—qualities that are hard to replicate with just rigid polymers or soft silicones. The catch? Unlike silicones, which typically sail through steam sterilization, TPUs need a bit more finesse when it comes to choosing the right method.

Generally speaking, developers and OEMs have a basic knowledge of TPU sterilization compatibility but often seek deeper insights into how it can affect mechanical properties and appearance.

Common Sterilization Methods

Medical device developers usually have a few go-to sterilization methods to choose from. Here’s how the most common measure up when it comes to TPUs:

Ethylene Oxide (EtO)

If there’s a sterilization workhorse for TPUs, it’s ethylene oxide (EtO). Using this method, TPU-based medical devices are exposed to EtO gas, followed by aeration to remove residual gas. This process effectively kills microbes while preserving TPU mechanical integrity and appearance. Because EtO can deeply permeate complex shapes and narrow channels, it’s well-suited for sterilizing TPU components like catheters and implants.

There is, however, a growing conversation around ethylene oxide and its environmental impact. During sterilization, some of the gas can be released into the surrounding air, either intentionally, as part of the aeration process, or unintentionally due to equipment leaks or poor containment. While the FDA doesn’t classify EtO as a human carcinogen in its guidance, it does acknowledge the designations made by other agencies like the EPA and the International Agency for Research on Cancer (IARC), both of which label EtO as a known human carcinogen. As a result, even small amounts of EtO emissions are considered a potential public health concern, especially near sterilization facilities. The FDA’s focus remains on balancing that risk with the need to ensure a steady supply of sterile medical devices.

EtO isn’t disappearing overnight, but regulators are starting to take a closer look at emissions and are setting higher expectations for facilities that use it. As a result, more medical device developers are proactively asking about alternatives, even for products that have historically relied on EtO. If you build flexibility into your development process, like qualifying materials for multiple sterilization methods, you’re far less likely to be caught off guard if the rules or supply chains shift.

Gamma Radiation and Electron Beam (E-Beam)

Gamma and electron beam (e-beam) sterilization are both radiation-based methods commonly used when EtO isn’t the best fit. Both techniques work by using ionizing energy to destroy microorganisms, but they differ in how deeply that energy penetrates materials.

Gamma sterilization, which typically uses a Cobalt-60 radioactive source, delivers very deep penetration. That makes it ideal for ensuring that dense or bulky products receive full sterilization.

E-beam sterilization, on the other hand, uses a high-energy beam of electrons generated by an accelerator. It’s very effective but has a shallower penetration depth compared to gamma. This makes e-beam a better choice for products that are thinner or less dense, or that only need surface-level treatment.

However, radiation methods like gamma and e-beam aren’t a perfect match for every type of TPU. The difference often comes down to whether the TPU is aromatic or aliphatic.

Aromatic vs. Aliphatic TPUs
Aromatic TPUs are built using chemical structures that contain benzene rings (aromatic groups), which generally give them excellent strength and durability. But these structures have a trade-off: under radiation, they’re more likely to change color (being especially prone to yellowing). This typically will not affect how the material performs, but if your device needs to stay transparent or color-stable, you’ll want to think twice.

That kind of color shift can be avoided with a different type of TPU. Aliphatic grades are known for their better radiation resistance, both visually and structurally. Since they don’t have benzene rings, they’re less likely to discolor or degrade. Even with aliphatic TPUs, however, developers still need to think carefully about how radiation might impact the final product. If your device depends on how it looks, like a transparent catheter or tubing that needs to stay clear for visual monitoring, it’s worth validating performance through early-stage testing.

Vaporized Hydrogen Peroxide (VHP)

Developers looking to move away from EtO are paying more attention to vaporized hydrogen peroxide (VHP) and for good reasons. It’s fast, highly effective, and now recognized by the FDA as an Established Category A sterilization method. The process works by placing products into a vacuum chamber and exposing them to concentrated hydrogen peroxide vapor. VHP operates at relatively low temperatures and is a great option for materials that can’t handle steam or dry heat.

As sterilization methods go, VHP is usually kind to TPUs—it gets the job done without causing much disruption to material integrity. That said, it’s not completely foolproof. Device manufacturers still need to test their specific TPU formulations, especially if the material includes additives that can react in ways that aren’t always predictable. That’s because some additives don’t take kindly to VHP—colorants can fade, stabilizers might degrade prematurely, and coatings designed to help with friction or feel could end up leaving residue behind.

The bottom line: It’s essential to test the full formulation under real-world conditions, not just the base polymer.

Dry Heat

Dry heat sterilization works by exposing materials to high temperatures for an extended time, usually using heated air. It’s a reliable method for certain materials, but it’s not always a good fit for TPUs as thermoplastic materials can soften or deform under high heat. Prolonged exposure can lead to issues like discoloration, weakening, or material breakdown.

While there are a few specialty TPU formulations that can tolerate it, for most standard grades, dry heat sterilization is typically not the best option unless the material was specifically designed for high-temp resistance.

Autoclave (Steam Sterilization)

Autoclaving—using high-pressure, high-temperature steam—is a widely available and easy-to-implement sterilization method. But for TPUs, it’s generally off the table as well, as the combination of heat and moisture in an autoclave can break down the polymer chains within the TPU (a process called hydrolytic degradation). In some cases, this chemical breakdown can produce harmful byproducts like methylene dianiline (MDA) that are potentially hazardous to health.

Even if the material doesn’t fully degrade, exposure to such conditions can cause warping, loss of mechanical strength, or changes in surface finish. While autoclaving may be ideal for stainless steel tools or certain silicones, developers using TPUs should plan for alternative sterilization methods right from the start.

Planning for Additive Interactions

Core mechanical and biocompatible traits come from the polymer itself, but medical devices often demand more. Additives like colorants, stabilizers, and radiopaque agents give the material its final, functional edge.

Of course, every additive you include has the potential to change how the material behaves during sterilization. And sometimes, those changes aren’t obvious until late in development when fixing them becomes expensive and time-consuming.

Radiation-based sterilization methods like gamma or e-beam are a good example. The base TPU might handle the radiation just fine; the additives might not. Some pigments or fillers can absorb energy differently, leading to discoloration or changes in flexibility. For example, barium sulfate does a great job making catheters or tubes visible on an X-ray, but it can absorb gamma rays in a way that creates hotspots (areas where the material may stiffen or degrade faster than expected).

These effects aren’t always easy to predict, either. Even something as simple as switching pigment suppliers or changing filler concentrations can affect how the finished device responds to sterilization. This again is why it’s critical to test the full TPU formulation.

The ROI of Early Involvement

The recurring message from material specialists is clear: get your polymer experts involved in the project’s earliest stages. Working closely with a team that understands how TPUs (and all the things blended into them) interact with sterilization conditions can save months of development and rework. Before you commit to tooling or file with regulators, they can spot potential risks, recommend adjustments, and steer you toward compatible sterilization approaches.

Lubrizol, for example, works with customers with complex or layered sterilization protocols—cases where collaboration streamlines the process, optimizes material selection, or sometimes points to a more suitable TPU altogether. Early engagement often means avoiding the kind of rework that comes with getting to the table late, giving you more control over the final outcome.

Because sterilization science is always evolving, and this kind of insight matters more than ever. New techniques, like nitrogen dioxide and chlorine dioxide, are beginning to enter the industry conversation as potential alternatives to more established methods. And while they show promise, these approaches still require validation guided by extensive testing of a multiplicity of material and additive combinations.

It’s just another reason why expert collaboration is key to streamlining your device’s pathway to a successful launch—and to long-term success in the healthcare marketplace.