High-performance plastics compared: PEEK, PPS, PSU

High-performance plastics are used wherever conventional plastics reach their thermal, chemical or mechanical limits. Designers and buyers in particular often face the question: PEEK vs. PPS – which high-performance plastic is better suited to the respective application? PSU can also be an interesting alternative, especially when transparency, hydrolysis resistance or sterilizability are required.

PEEK, PPS and PSU differ significantly in terms of temperature resistance, mechanical load capacity, chemical resistance and field of application. The following comparison shows which material plays to its strengths under which conditions.

PEEK – Polyetheretherketone

PEEK belongs to the family of polyaryletherketones (PAEK) and is one of the most capable thermoplastic plastics. The material combines very high temperature resistance with high mechanical strength, dimensional stability and very good resistance to numerous chemicals.

Depending on the material type and operating conditions, continuous service temperatures of around 250 to 260 °C are possible with PEEK. Even at elevated temperatures, the material retains its mechanical properties comparatively well.

The PEEK resistance to numerous acids, alkalis, hydrocarbons, oils, fuels and organic solvents is very high. Limits can however occur with certain strongly oxidising media and concentrated acids, among others. For the specific design, the medium, concentration, temperature and exposure time must therefore always be taken into account.

Further details on structure, properties and processing can be found in our PEEK material science.

Typical areas of application for PEEK are:

• components in aerospace
• highly loaded parts in mechanical and plant engineering
• seals, bearings, guides or gears
• pump and valve components
• electrical insulators and components for electronics
• suitable parts for medical technology

PEEK in medical grade

Special PEEK grades are available for medical applications. However, not every commercially available PEEK type is automatically biocompatible or suitable for implants or direct body contact.

With PEEK in medical grade, material purity, traceability, biocompatibility, documentation and the approvals required for the specific application must be taken into account, among other things. For medical applications, the specific material grade should therefore always be checked.

PPS – Polyphenylene sulphide

PPS is a semi-crystalline high-performance plastic that stands out particularly for its very good chemical resistance, low moisture absorption and high dimensional stability at elevated temperatures.

Depending on the material type and load, PPS can be used at high continuous temperatures and at the same time exhibits a low tendency to creep. The plastic is also inherently flame-retardant and is therefore particularly suitable for technical applications in the automotive, electrical and process industries.

The PPS plastic resistance to many acids, alkalis, fuels and solvents is very high. PPS is therefore often used when chemical resistance and dimensional stability are required, but the maximum performance of PEEK is not necessary.

PPS is frequently used in:

• automotive components such as pump housings and sensor covers
• electrical components and connectors
• pump and valve parts
• filter housings in chemical processes
• parts with high requirements for dimensional stability
• components under elevated thermal load

PEEK vs. PPS: Where are the most important differences?

PEEK and PPS are both high-performance plastics, but they pursue different technical and economic priorities.

PEEK is often the better choice when very high temperatures are combined with high mechanical load, wear or demanding media.

PPS is often of interest when high chemical and temperature resistance as well as very good dimensional stability are required, without the higher performance level of PEEK being necessary.

This makes PPS an economically interesting alternative to PEEK in many applications. Whether a material can actually be substituted must however be checked on the basis of the specific operating conditions.

PSU – Polysulphone

PSU, in contrast to PEEK and PPS, is an amorphous high-performance plastic. It is characterised by transparency, good impact strength and high hydrolysis and hot water resistance.

PSU withstands significantly lower continuous temperatures than PEEK or PPS, but offers advantages in applications where transparent, sterilizable or hydrolysis-resistant parts are required.

Typical areas of use for PSU:

• sterilizable components in medical technology
• transparent technical parts
• containers and housings in the food industry
• hot water applications
• electrical and electronic components

Comparison table: PEEK vs. PPS vs. PSU

Property	PEEK	PPS	PSU
Temperature resistance	very high, typically up to approx. 250–260 °C	very high	high, but significantly below PEEK and PPS
Chemical resistance	very high	very high	moderate to good, depending on the medium
Mechanical strength	very high	high	moderate
Dimensional stability	very high	very high	good
Hydrolysis resistance	very high	good	very high
Moisture absorption	very low	very low	higher than PEEK and PPS
Transparency	no	no	yes
Electrical insulation	very good	very good	good
Sterilizability	very good with suitable grade	application-dependent	very good
Cost-effectiveness	higher price level	usually more economical than PEEK	application-dependent
Typical strength	maximum overall performance	chemical resistance and dimensional stability	transparency and hydrolysis resistance

The values and assessments given serve for material pre-selection. The actual properties differ depending on the material type, reinforcement, manufacturer and operating conditions.

PEEK or PPS – which plastic is better?

There is no blanket answer to the question "PEEK or PPS?" The decisive factors are temperature, mechanical load, medium, service life and the economic requirements of the respective application.

PEEK is particularly suitable when:

• permanently very high temperatures occur,
• high mechanical loads exist at the same time,
• wear resistance is required,
• high requirements for hydrolysis and chemical resistance exist,
• precision parts must remain dimensionally stable in the long term.

PPS is particularly suitable when:

• very good chemical resistance is required,
• high dimensional stability is needed,
• the part is permanently exposed to elevated temperatures,
• electrical properties and flame retardancy are important,
• a more economical alternative to PEEK is sought and its maximum performance level is not required.

PSU, on the other hand, comes into consideration above all when transparency, hot water resistance and sterilizability are weighted more heavily than maximum temperature and mechanical load capacity.

Which high-performance plastic suits your application?

The choice between PEEK, PPS and PSU should not be made on the basis of a single material property alone. A material can, for example, possess high temperature resistance and nevertheless be unsuitable for a particular chemical medium.

For material selection, you should take the following factors into account in particular:

• maximum and continuous operating temperature
• mechanical load
• chemicals and media contact
• moisture and water vapour
• wear and friction
• electrical requirements
• required approvals and conformities
• planned service life
• economic framework conditions

You can also find further guidance in our high-performance plastics for extreme temperatures.

Frequently asked questions about PEEK, PPS and PSU

What is the most important difference between PEEK and PPS?

PEEK offers a higher thermal and mechanical performance overall. PPS stands out particularly for its very good chemical resistance and dimensional stability and can be an economical alternative when the maximum performance of PEEK is not required.

Is PPS more chemically resistant than PEEK?

Both materials possess very high chemical resistance. Which plastic is better suited to a particular medium however depends on the chemical, concentration, temperature and exposure time. A blanket assessment is therefore not sensible.

How resistant is PEEK?

PEEK is very resistant to numerous acids, alkalis, oils, fuels, hydrocarbons and organic solvents. Limitations exist with certain strongly oxidising media, among others. For a specific application, the actual material grade should always be checked under the intended operating conditions.

Is there PEEK in medical grade?

Yes. PEEK grades specifically intended for this purpose are available for medical applications. However, not every PEEK type is automatically suitable for medical applications or implants. Required evidence and approvals must always be checked for the specific material and intended use.

Do PEEK and PPS belong to the high-performance plastics?

Yes. Both PEEK and PPS count among the thermoplastic high-performance plastics. They are used above all where standard and engineering plastics are no longer sufficient in terms of temperature, chemical resistance or mechanical load capacity.

Selecting PEEK, PPS or PSU in a targeted way

PEEK offers the highest overall performance when thermal, mechanical and chemical loads are very high at the same time. PPS is particularly interesting when high chemical resistance, dimensional stability and temperature resistance must be combined with economic requirements. PSU in turn offers advantages with transparent, hydrolysis-resistant and sterilizable parts.

For the specific material selection, the actual operating conditions and the data of the intended material grade should be compared with one another. Martan Plastics supports you in selecting suitable high-performance plastics as well as with semi-finished products, cut pieces and custom-machined parts.