PES

PES plastic, also known as polyethersulfone or by the ISO abbreviation PESU, is an amorphous thermoplastic high-performance plastic. The material combines high temperature resistance with good mechanical strength, pronounced hydrolysis resistance and stable electrical properties.

Polyethersulfone is therefore used for components that are permanently exposed to heat, hot water, steam or alternating thermal loads. Typical areas of application are found in medical technology, the food industry, the electrical industry, filtration and in mechanical and plant engineering.

Martan Plastics supplies PES as a semi-finished product, cut piece or component machined to drawing. The suitable material grade is selected on the basis of temperature, mechanical load, media used and required approvals.

What is PES plastic?

PES stands for polyethersulfone. The standard-compliant short designation according to ISO 1043 is PESU. In industrial practice, however, the material is still frequently referred to as PES.

Polyethersulfone belongs to the polysulfone family and is one of the high-performance plastics. The material has an amorphous molecular structure and, in unreinforced form, is transparent to amber-coloured. Unlike semi-crystalline plastics, PES does not have a defined melting point. As the temperature rises, the material gradually softens.

The glass transition temperature is approximately 220 to 225 °C, depending on the material type. For many unreinforced grades, a long-term service temperature of around 180 °C is specified. The actually permissible service temperature depends, however, on the duration of load, the component geometry, the mechanical forces and the contact medium.

The most important properties of PES

PES is not chosen solely because of its high temperature resistance. What is decisive is the combination of several properties that are retained even under demanding operating conditions.

• high long-term service temperature
• good strength and stiffness
• low creep tendency at elevated temperature
• good dimensional stability
• very good resistance to hot water and steam
• repeated sterilisation of suitable grades
• good electrical insulation properties
• inherent flame retardancy
• low smoke development in the event of fire
• transparency in unreinforced material types

Temperature resistance

Polyethersulfone is one of the amorphous plastics that are particularly resistant to thermal load. Unreinforced standard grades can, depending on the manufacturer and operating conditions, be used long-term at temperatures up to around 180 °C. Higher temperatures are possible for short periods.

The heat deflection temperature is significantly above that of standard plastics such as PP, PA or ABS. As a result, PES remains comparatively dimensionally stable even in heated assemblies, electrical systems and during recurring cleaning and sterilisation processes.

A temperature specification alone is not sufficient for material selection, however. With a permanent mechanical load, aggressive media or frequent temperature changes, the permissible service temperature may be lower. For component design, the technical data sheet of the specific PES grade and the actual operating conditions are therefore always decisive.

Mechanical strength and creep resistance

PES has high stiffness and strength. These properties are retained over a broad temperature range. The material also exhibits a low creep tendency, which is why it is suitable for components that are under pressure or mechanical preload over a longer period.

During design, however, notches, sharp transitions and high internal stresses must be avoided. As with other amorphous thermoplastics, unfavourable component geometries or certain chemicals in combination with mechanical stresses can lead to stress cracks.

Dimensional stability and thermal expansion

Polyethersulfone has good dimensional stability and comparatively low mould shrinkage. The material is therefore suitable for precise housings, insulators, holders, functional parts and components with tight tolerances.

However, thermal expansion is still higher than that of metallic materials. For metal-plastic connections, fits and bolted components, sufficient room for movement must therefore be allowed. Glass fibre reinforced PES grades can offer higher stiffness and lower thermal expansion, but exhibit different machining and wear behaviour.

Hydrolysis resistance and steam sterilisation

One of the most important properties of PES is its high resistance to hot water and steam. The material can be used for components that are repeatedly cleaned, disinfected or steam sterilised.

This property makes PES particularly interesting for applications in medical technology, laboratory technology, food processing and filtration. Whether a specific grade is suitable for repeated autoclave cycles must be checked on the basis of the manufacturer's data sheet and the required sterilisation conditions.

Electrical properties

PES has good electrical insulation properties that remain comparatively stable over a broad temperature and frequency range. These include a high volume resistivity, good dielectric strength and favourable dielectric properties.

The material is therefore used in the electrical industry for insulators, coil formers, connectors, switch components, relay parts and temperature-loaded housings, among other things.

Fire behaviour

Polyethersulfone is inherently flame retardant and, for many grades, requires no additional halogen-containing flame retardants. Depending on the material type and material thickness, high UL 94 classifications can be achieved.

In addition, PES develops comparatively little smoke in the event of fire. This is particularly relevant for components in electrical systems, transport systems and aviation. The specific fire protection classification must, however, always be verified for the selected material grade and component thickness.

Transparency and natural colour

Unreinforced PES is transparent and typically has a slightly amber natural colour. It is therefore suitable for components where visual monitoring of a medium or a process is required.

For completely colour-neutral or highly transparent applications, it must be checked whether the natural colour of the material is acceptable. Further transparent materials and their differences are compared in the article on transparent engineering plastics.

Chemical resistance of polyethersulfone

PES has good resistance to many aqueous media, dilute acids, alkalis, salt solutions, oils and greases. The stability in hot water and steam is particularly advantageous.

By contrast, the material has only limited resistance to certain organic solvents. Above all ketones, esters and some aromatic or polar solvents can cause PES to swell, cause stress cracks or dissolve it.

Chemical resistance does not depend on the medium alone. The following factors must also be taken into account:

• concentration of the medium
• operating temperature
• duration of contact
• mechanical stress in the component
• cleaning and sterilisation cycles
• specific PES formulation

For safety-relevant applications, resistance should be tested under real operating conditions. General resistance tables can support a preliminary selection, but do not replace an application-specific test.

Technical data of PES plastic

The following information serves as an initial guide. The values may differ depending on manufacturer, material type, reinforcement, test method and conditioning.

Property	Typical guide value
Density	approx. 1.37 g/cm³
Tensile strength	approx. 80 to 100 MPa
Modulus of elasticity	approx. 2,500 to 2,700 MPa
Glass transition temperature	approx. 220 to 225 °C
Long-term service temperature	often up to approx. 180 °C
Water absorption after 24 hours	approx. 0.3 to 0.5 %
Linear coefficient of thermal expansion	approx. 50 to 60 × 10−6 K−1
Thermal conductivity	approx. 0.2 to 0.3 W/(m·K)
Colour of unreinforced grades	transparent to amber-coloured

For the design and approval of a component, only the values of the specific material data sheet may be used.

Typical applications of PES plastic

Polyethersulfone is used for components where high temperatures, mechanical loads and contact with water, steam or chemicals coincide.

Medical technology and laboratory technology

In medical technology, PES is used for sterilisable housings, instrument components, filters, membranes and components of analytical devices. Suitable grades withstand repeated steam sterilisation and offer good dimensional stability.

For medical applications, the required biological, regulatory and sterilisation-related evidence must always be available for the specific material grade. Fundamental membership of the PES material group does not in itself constitute medical approval.

Filtration and membrane technology

PES is an important material for microfiltration and ultrafiltration membranes. The material is used, among other things, for water treatment, laboratory filtration, pharmaceutical processes, medical filters and applications in food processing.

In addition to membranes, filter supports, housings, holders and other media-carrying components can also be manufactured from PES. For components in drinking water and process water technology, the requirements of the respective application and the required approvals must be checked separately.

Food and beverage industry

In the food industry, PES is suitable for temperature-loaded components, filter parts, housings and components that are regularly cleaned with hot water or steam.

Not every PES grade is automatically approved for food contact. A material- and application-related declaration of conformity is required. Regulation (EU) No. 10/2011, national regulations and requirements of the US FDA, among others, may be relevant here.

Electrical engineering and electronics

Due to its thermal stability, flame retardancy and electrical insulation, PES is used for connectors, coil formers, relays, switches, sensor components and electrical housings, among other things.

The material is particularly suitable for components that are simultaneously exposed to high temperatures and electrical loads.

Mechanical and plant engineering

In mechanical and plant engineering, PES is used for dimensionally accurate functional parts, insulators, valve components, pump parts, housings, holders and visual components.

For media-carrying components, pressure, temperature, chemical load and design stress must be considered together. PES is not automatically suitable for every sliding or wear component. Under dynamic friction, specially modified plastics or semi-crystalline high-performance plastics may be more advantageous.

Aviation and transport technology

The combination of low weight, temperature resistance, flame retardancy and low smoke development enables the use of suitable PES grades in aerospace and in other transport applications.

Here, the respective fire, flue gas and approval requirements must be verified for the specific material and the finished component.

PES semi-finished products and available delivery forms

Depending on grade and manufacturer, polyethersulfone can be supplied in various delivery forms. These include in particular:

• PES sheets
• PES rods
• PES cut pieces
• CNC-milled components
• CNC-turned components
• Drawing parts
• Injection moulding granules
• Powder and membrane materials for special applications

Martan Plastics supplies plastic semi-finished products and supports you in selecting a suitable PES grade. In addition to simple cut pieces, mechanically machined finished parts to drawing or CAD data are also possible.

Machining and cutting PES

PES semi-finished products can be machined by sawing, milling, turning and drilling. For tight tolerances and geometrically demanding components, precise plastic machining is advisable.

During cutting, the thermal and mechanical properties of the amorphous material must be taken into account. Excessive heat input or unsuitable clamping technology can cause internal stresses, deformation or chipping.

Notes for CNC machining

• use sharp and suitable tools
• limit heat input by adapting cutting parameters
• fix the component in a low-stress manner and over a large area
• avoid notches and sharp internal radii
• take climatic conditions into account for tight tolerances
• if necessary, provide for intermediate machining and annealing

Complex contours can be manufactured by CNC milling. Rotationally symmetrical components such as bushes, rings, insulating bodies or spacers can be produced by CNC turning.

Design notes for components made of PES

So that the material properties can be reliably utilised in the finished component, PES should be designed in a plastic-appropriate manner.

Reduce mechanical stress

High preloads, sharp notches and abrupt changes in cross-section should be avoided. Internal radii and uniform wall thicknesses reduce local stress peaks.

Assess temperature and medium together

A material may achieve a different service life under dry heat than under simultaneous contact with steam, cleaning agents or process chemicals. Temperature and chemical resistance must therefore not be considered separately from one another.

Take thermal expansion into account

For press fits, bolted connections or metal-plastic connections, the differing thermal expansion must be taken into account. Rigid clamping can generate high stresses during temperature changes.

Allow sufficient safety reserves

For permanently loaded or safety-relevant components, neither the maximum temperature nor the maximum mechanical load of the data sheet should be fully exhausted. An application-appropriate safety reserve improves reliability and service life.

Advantages and disadvantages of PES

Advantages	Limits to be observed
high long-term service temperature	higher price than standard plastics
very good hot water and steam resistance	limited resistance to certain solvents
good stiffness and dimensional stability	risk of stress cracks with unfavourable combination of media and load
good electrical insulation	limited weather and UV resistance without stabilisation
inherent flame retardancy	not every grade has the same approvals
transparent in unreinforced version	amber natural colouration
can be precisely machined	plastic-appropriate clamping and machining technology required

PES, PSU, PPSU or PEI – which material is suitable?

Like PSU and PPSU, PES belongs to the polysulfone family. PEI plastic also has similar areas of application. However, the materials differ in temperature resistance, toughness, chemical resistance and price.

Requirement	Often suitable material
high temperature resistance and good hydrolysis resistance	PES
more economical solution at somewhat lower temperature load	PSU
very high impact strength and frequent sterilisation cycles	PPSU
high stiffness and good electrical properties	PEI
highest temperature and chemical resistance	PEEK

PES is often the balanced choice when temperature resistance, dimensional stability, transparency and steam resistance are required together. PPSU is usually more suitable when maximum impact strength or a particularly high number of sterilisation cycles is the priority. PSU can be more economical for lower thermal requirements.

When is PES plastic the right choice?

Polyethersulfone is particularly suitable when several of the following requirements must be met at the same time:

• permanent service temperatures significantly above the capabilities of standard plastics
• regular contact with hot water or steam
• repeated cleaning or sterilisation cycles
• high dimensional stability under thermal load
• good electrical insulation
• inherent flame retardancy
• transparency or possibility of visual monitoring
• precise manufacturing as a CNC component

PES is less suitable for permanent contact with critical organic solvents, for unprotected outdoor use or when a particularly high notched impact strength is required. In these cases, alternative high-performance plastics should be considered.

Available PES types and modifications

Polyethersulfone is available in different types and modifications in order to cover various technical requirements. These include PES NATURELL ULTRASON® E2010 as an unreinforced, natural-coloured variant for applications with high thermal and mechanical loads. For higher stiffness and dimensional stability, glass fibre reinforced versions such as PES GV30% NATURELL ULTRASON® E2010 G6 and PES GV30% NATURELL VERADEL® AG 330 NT are available. In addition, PES GV20% SCHWARZ LAPEX® A G/20 3302 is suitable for components where, in addition to glass fibre reinforcement, black colouring is required. The selection of the suitable PES type depends in particular on the requirements for strength, temperature resistance, dimensional stability and visual finish.

Request PES plastic cut to size

For the selection of the suitable PES grade, information on the application should be as complete as possible. This includes:

• maximum and permanent operating temperature
• mechanical load
• contact media and their concentration
• duration and frequency of media contact
• cleaning or sterilisation method
• required dimensions and tolerances
• required food, medical or fire protection certificates
• desired quantity

Martan Plastics supplies PES sheets, rods and cut pieces and, on request, manufactures precise drawing parts. Send us your drawing, CAD data or technical requirements. We will check the required delivery form, the machinability and the material grade suitable for your application.

Frequently asked questions about PES plastic

What does the abbreviation PES mean?

PES stands for polyethersulfone. The current standard-compliant short designation is PESU. In technical usage, the abbreviation PES is still frequently used.

Is PES a thermoplastic?

Yes. PES is an amorphous thermoplastic high-performance plastic. The material can be processed under the influence of heat and, for example, extruded or formed by injection moulding.

How temperature-resistant is PES?

Many PES grades can be used long-term at temperatures up to around 180 °C. Higher temperatures are possible for short periods. The permissible temperature depends on the material type, load, medium and duration of use.

Can PES be steam sterilised?

Suitable PES grades have very good hydrolysis and steam resistance and can be repeatedly sterilised in an autoclave. The permissible number and temperature of sterilisation cycles must be taken from the data sheet of the specific grade.

Is PES food-safe?

Not fundamentally. PES grades with corresponding food conformities are available. A valid declaration of conformity from the manufacturer must be available for the respective application.

Is PES transparent?

Unreinforced PES is transparent and usually has an amber natural colouration. Reinforced or coloured grades are not transparent.

Is PES UV-resistant?

The weather and UV resistance of unmodified PES is limited. For permanent outdoor use, suitable stabilisations, coatings or alternative materials must be considered.

How can PES be machined?

PES can be sawed, drilled, milled and turned. For dimensionally accurate components, sharp tools, adapted cutting parameters and low-stress clamping are required.

What is the difference between PES and PPSU?

PES offers high temperature resistance, good stiffness and very good hydrolysis resistance. PPSU generally has a significantly higher impact strength and is particularly suitable for mechanically stressed components with frequent sterilisation cycles.

In what forms is PES available?

Depending on the material grade, PES is available as sheet, rod, cut piece, granule, powder, membrane material or finished machined drawing part.