Ultem Vs. Peek: An In-Depth Comparison

ultem vs peek

Do you have an application with high thermal or electrical requirements? Do you need superior strength and durability? Are you looking for a material lighter than metal? Ultem or PEEK could be the answer. But which one?

These high-performance plastics have properties that make them ideal for many demanding applications. Choosing between Ultem vs. PEEK isn’t always easy, though.

Learn more about Ultem and PEEK to see which one might be the best fit for your project.

What Is Ultem?

Ultem is the brand name for polyetherimide (PEI). It’s an amorphous thermoplastic resin. Amorphous plastics gradually transition between soft and hard states. They’re easy to thermoform and have less shrinkage than other plastics. However, they’re more prone to material fatigue.

Ultem has applications in many industries. Some typical uses include:

  • Medical instrument components
  • Reusable medical devices
  • Scientific equipment components
  • Electrical connectors
  • Electrical insulators
  • Semiconductor components
  • Chip test sockets
  • Underwater connector bodies

Ultem is available in several grades with additional chemical, heat, and elasticity benefits. You can find Ultem in transparent and opaque colors.

What Is PEEK?

Polyetheretherketone (PEEK) is a semi-crystalline thermoplastic. Semi-crystalline thermoplastics remain solid until they absorb a certain amount of heat. Then they quickly change to a liquid. Semi-crystalline polymers have good stiffness, strength, and toughness. However, they can be difficult to work with.

PEEK is useful in applications across industries. Some common uses include:

  • Screws for consumer electronics
  • Vehicle seals and brake components
  • Reusable medical devices
  • Medical instrument components
  • Medical implants
  • Semiconductor components
  • Bearings
  • Piston parts

Different grades of PEEK are available with specific enhanced capabilities, like increased bearing and wear properties.

Properties of Ultem vs. PEEK

Ultem and PEEK are both high-performance thermoplastics. They perform well in applications with high thermal and/or electrical requirements. Comparing their similarities and differences can help you decide which material will best meet your needs.

Properties of Ultem

Ultem has very good heat resistance. It can withstand service temperatures up to 340ºF and it maintains its strength and rigidity in long-term heat exposure. Ultem has excellent hydrolytic stability.

Ultem PEI is flame retardant. It has low smoke output and is a low outgassing material. It has the highest dielectric strength of any commercially available thermoplastic. It is also resistant to UV and gamma rays and has high chemical resistance.

Properties of PEEK

PEEK has excellent heat resistance. It will support operating temperatures up to 480ºF. It has very good hydrolytic stability. PEEK has high resistance to radiation and chemicals. It’s creep-resistant, it provides excellent strength, dimensional stability, and stiffness.

Ultem vs. PEEK

Ultem and PEEK are both flame-retardant. Standard grades are FDA compliant. You can find grades that comply with standards for medical applications.

Key factors when choosing between Ultem and PEEK are operating temperatures, chemical resistance, and cost. PEEK maintains its performance at higher temperatures than Ultem. It’s a better choice for high-load, high-temperature applications.

Both Ultem and PEEK offer excellent chemical resistance. PEEK has an edge, though. Concentrated sulphuric or nitric acid are the only substances that will dissolve it.

PEEK has better friction and wear properties. Ultem has a higher dielectric strength. However, Ultem is more likely to have stress cracking. PEEK is one of the most expensive thermoplastics available. Ultem gives you similar properties at a much lower cost.

Machining Ultem vs. PEEK

You can machine Ultem and PEEK. Both materials need some special handling, though. Preventing contamination is important for industries like aerospace and medical. The cutting tools for Ultem and PEEK should be reserved for plastics.

Machining Ultem

Ultem needs annealing to relieve stress before starting the precision machining process. Annealing reduces the likelihood of surface cracks or internal stresses. It helps prevent warping.

Grades of Ultem with glass reinforcement need coolant during machining operations. Non-aromatic, water-soluble coolants are best. Petroleum-based coolants can attack Ultem. You shouldn’t use high-speed steel cutting tools on reinforced grades of Ultem.

Machining PEEK

Like Ultem, PEEK needs annealing before the machining process. More than one annealing stage may be necessary. Silicon carbide cutting tools will work on PEEK in most circumstances. PEEK reinforced with carbon fiber needs diamond tools. Diamond tools are also the best choice to get very tight tolerances.

PEEK needs cooling during precision machining. Standard liquid coolant is acceptable. However, liquid coolant can affect the biocompatibility of PEEK. Pressurized air is the preferred coolant for medical parts for this reason.

Injection Molding Ultem vs. PEEK

Injection molding is another option for processing Ultem and PEEK. It’s more cost-effective than machining if you need to mass-produce plastic components. Designs with features like sharp internal corners are easier to achieve with injection molding. If you may need to change the design later, though, machining will give you more flexibility.

Injection molding has good accuracy and repeatability. However, CNC machining tools can generally give you tighter tolerances. The main challenge with injection molding Ultem and PEEK is the materials’ high melting points. They’re at the upper end of the capabilities of many injection molding machines.

A machining and molding expert can work with you to decide which process is the best option for your Ultem and PEEK components.

Working with Ultem vs. PEEK

Ultem and PEEK are high-performance thermoplastics. Their properties make them useful for many applications in a variety of industries. They’re suitable for precision machining and injection molding. The experts at Severna can help you decide between Ultem vs. PEEK. Our design and engineering resources help ensure you get the right material and processing to meet your specifications. We’re committed to providing you with the best quality and service in the industry.

Contact us today to discuss your project. We look forward to working with you.


David Taylor Digital | Digital Marketing Agency