PTFE Compounds Explained: What Do Glass Fibre, Carbon, Graphite, Bronze and PEEK Actually Do?

PTFE is well known for its extremely low friction, outstanding chemical resistance, and excellent performance across a wide temperature range. But virgin PTFE is not always the right choice for an industrial component.

By adding carefully selected fillers, it is possible to improve specific properties such as wear resistance, compressive strength, dimensional stability, thermal performance, electrical conductivity, resistance to cold flow, etc..

This is where PTFE compounds become particularly valuable.

At Acoplastic, different fillers and additives are combined with PTFE to create materials with properties tailored to demanding industrial applications. These compounds are used for components such as bearings, piston rings, gaskets, seals, bellows, guides, and other precision-machined parts.

But what does it actually mean when a PTFE compound contains glass fibre, carbon, graphite, bronze, stainless steel or PEEK?

Let’s have a look at the different PTFE compounds below.

 

What is a PTFE compound?

A PTFE compound is a material based on a virgin PTFE that has been mixed with one or more additional materials to achieve specific performance characteristics.

Virgin PTFE already offers extremely low friction and exceptional chemical resistance. However, it can also have limitations in applications involving high mechanical loads, wear, deformation or dimensional requirements.

Fillers can help address these limitations.

The important point is that there is no single “best” PTFE compound. The right formulation depends on the application and the conditions the component will experience. Temperature, pressure, sliding speed, wear, chemical exposure, dimensional requirements, electrical properties, and the mating material can all influence the choice.

 

Virgin PTFE: when the original material is the right choice

Virgin PTFE contains no reinforcing filler and retains the characteristic properties for which PTFE is known.

The main advantages include:

• Extremely low friction
• Exceptional chemical resistance
• Excellent resistance to many aggressive environments
• Wide operating temperature range
• Non-stick characteristics

Virgin PTFE is therefore often selected where chemical resistance and low friction are more important than mechanical reinforcement.

At Acoplastic, virgin PTFE is supplied as ACOFLON® 100 and is used, among other applications, for components in pharmaceutical and food-production machinery.

However, when an application involves significant mechanical loading, wear or dimensional stability requirements, a filled or modified PTFE compound may be more appropriate.

 

PTFE with glass fibre: improved wear and compressive strength

Glass fibre is one of the most used fillers in PTFE compounds.

Adding glass fibre can significantly improve the mechanical performance of PTFE, particularly its:

• Wear resistance
• Compressive strength
• Resistance to cold flow
• Low creep
• Mechanical performance at elevated temperatures

Acoplastic’s ACOFLON® 105 contains 25% glass fibre.

This type of compound can be particularly useful for components that experience mechanical loads and sliding contact. Typical applications include bearings, piston rings, gaskets and seals.

Glass-filled PTFE can therefore be considered when virgin PTFE does not provide sufficient mechanical strength or wear resistance for the application.

The exact formulation is important, however. Different glass fibres and formulations can be selected depending on the chemical and mechanical requirements of the component.

 

PTFE with carbon fibre: combining wear resistance and mechanical performance 

Carbon fibre can be added to PTFE when improved mechanical and wear properties are required.

Acoplastic’s ACOFLON® 212 CF, for example, contains 10% carbon fibre.

According to the specific formulation, carbon fibre can contribute to:

• Improved wear resistance
• Good compression under load properties.
• Good wear properties
• Good thermal conductivity
• Improved mechanical performance
• Good chemical resistance

Carbon-fibre-filled PTFE is commonly considered for applications such as bearings, piston rings, gaskets and seals.

The distinction between carbon fibre and other carbon-based fillers is important. Different forms of carbon produce different effects in the finished compound, so the filler should be selected according to the actual operating conditions rather than simply choosing “carbon-filled PTFE” as a generic material category.

 

PTFE with carbon: low thermal expansion and electrical conductivity

Carbon is also used in PTFE compounds in forms other than carbon fibre.

Acoplastic’s ACOFLON® 215 contains 25% electro-graphitized carbon, also referred to as E-carbon or soft carbon.

This formulation provides a different combination of properties, including:

• Low thermal expansion
• Good pressure resistance
• Good wear resistance
• Reduced cold flow
• Better retention of mechanical properties at elevated temperatures
• Electrical conductivity

The electrical conductivity of carbon-filled PTFE can be particularly useful when components need antistatic properties or are intended for applications with ATEX-related requirements.

Carbon-filled PTFE can therefore be relevant in applications where both mechanical performance and electrical characteristics need to be considered.

Typical applications include bearings, piston rings, gaskets and seals.

 

PTFE with graphite: self-lubricating performance

Graphite is another important filler used in PTFE compounds.

Acoplastic’s ACOFLON® 305 contains 25% graphite.

Graphite can contribute properties such as:

• Its flaky structure contributes to the self-lubricating behavior
• Decreased wear.
• Excellent chemical resistance
• Low adhesion
• Reduced tendency to stick over time

Graphite-filled PTFE can be particularly useful in wet environments and self-lubricating applications.

It is also used for bearings, piston rings, gaskets and seals.

One important consideration is that graphite and carbon are not interchangeable simply because both are carbon-based materials. Their structure and behavior in a PTFE compound are different, which means they can produce different performance characteristics.

The correct choice should therefore be based on the application’s actual requirements.

 

PTFE with bronze: high-temperature and high-pressure applications

Bronze is added to PTFE when increased mechanical and thermal performance is required.

Acoplastic’s ACOFLON® 408 contains 40% bronze.

The addition of bronze provides several important characteristics:

• Improved mechanical properties at high temperatures
• Increased heat conductivity
• Excellent wear resistance
• Electrical conductivity

The increased thermal conductivity can be particularly useful where a component needs to deal with elevated temperatures and pressure.

Bronze-filled PTFE is commonly used for:

• Bearings
• Piston rings
• Gaskets and seals
• Self-lubricating components

The choice of bronze-filled PTFE should, as with any material selection, also take the surrounding materials and operating environment into account.

 

PTFE with stainless steel: for demanding abrasive wear 

For particularly demanding applications involving abrasive wear, PTFE can also be compounded with stainless steel.

Acoplastic’s ACOFLON® 510 contains 50% stainless steel particles based on AISI 410L.

The resulting material provides:

• Improved mechanical properties at high temperatures
• High thermal conductivity
• Extremely high wear resistance
• Low cold flow

Stainless-steel-filled PTFE is often considered where there is significant abrasive wear between opposing surfaces.

Typical applications include bearings, piston rings, gaskets and seals.

The high filler content gives this type of compound substantially different mechanical characteristics from virgin PTFE, making it suitable for applications where mechanical robustness and wear resistance are priorities.

 

PTFE with PEEK: combining low friction with dimensional stability

PEEK is a high-performance engineering thermoplastic with excellent mechanical and thermal characteristics.

When PEEK is combined with PTFE, the resulting compound can offer a useful balance between the low-friction characteristics of PTFE and the mechanical and dimensional stability associated with PEEK.

Acoplastic’s ACOFLON® 813 contains 20% PEEK.

The material provides:

• Low friction
• Excellent chemical resistance
• Excellent wear and abrasion resistance
• Low cold flow
• High dimensional stability
• Good tensile and bending strength
• Good dimensional stability at elevated temperatures
• Great in non-lubricated (dry) applications

This combination makes PTFE with PEEK relevant for demanding applications where virgin PTFE may not provide sufficient mechanical or dimensional stability.

Applications include pharmaceutical and food-production machinery, bearings, piston rings, gaskets, seals and self-lubricating components.

 

So which PTFE compound should you choose?

There is no universal answer.

The best PTFE compound depends on what the component has to do.

As a starting point:

 

Requirement	PTFE compound to consider
Maximum chemical resistance and very low friction	Virgin PTFE
Improved wear resistance and compressive strength	Glass-filled PTFE
Improved wear resistance and mechanical performance	Carbon-fibre-filled PTFE
Low thermal expansion and electrical conductivity	Carbon-filled PTFE
Self-lubricating performance, particularly in wet environments	Graphite-filled PTFE
High-temperature performance, pressure resistance, and heat transfer	Bronze-filled PTFE
Very high wear resistance and low cold flow	Stainless-steel-filled PTFE
Low friction combined with dimensional stability and mechanical strength	PTFE with PEEK

 

This table is a useful starting point, but material selection should never be based on one property alone.

For example, a component operating at high temperature may also experience pressure, sliding movement, chemical exposure, and dimensional tolerances. The interaction between these factors can determine which compound is appropriate.

 

PTFE compound selection should start with the application

Before selecting a PTFE compound, it is useful to define the actual operating conditions.

Consider:

Temperature: What are the minimum and maximum operating temperatures?

Pressure: What mechanical and compressive loads will the component experience?

Movement: Will the component slide, rotate, reciprocate, or remain stationary?

Wear: Is the component exposed to continuous sliding or abrasive contact?

Chemical environment: Which chemicals, solvents, gases or cleaning agents will be present?

Dimensional requirements: How important are tolerances and dimensional stability?

Electrical requirements: Does the component need to be electrically insulating, conductive or antistatic?

Mating material: What material will the PTFE component run against?

Regulatory requirements: Does the component need to meet specific requirements for food, pharmaceutical, medical or other regulated applications?

These factors provide a much better basis for material selection than simply choosing the most advanced or most expensive compound.

 

The right PTFE compound can make a significant difference

PTFE is not one material with one fixed set of properties.

Through modification and the addition of carefully selected fillers, PTFE can be engineered for a wide range of industrial applications.

From virgin PTFE for highly chemically resistant components to glass-, carbon-, graphite-, bronze-, stainless-steel- and PEEK-filled compounds for more demanding mechanical applications, the material can be adapted to specific operating requirements, and other fillers can also be added.

At Acoplastic, PTFE compounds are developed and supplied for demanding industrial applications, with more than 50 years of experience working with PTFE and other high-performance plastics.

If you are unsure which PTFE compound is suitable for your application, the most useful starting point is not necessarily the material name. Start with the operating conditions, component design and required performance. From there, the appropriate compound can be identified and, where necessary, further customized.

 

If you have any questions or inquiries please do not hesitate to contact us.