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Fillers for PTFE
The properties of PTFE can be modified by adding a range of fillers. Because PTFE is an inherently soft material making it ideal for sealing applications, it usually needs reinforcement to enhance the wear and creep resistance. Chemical inertness and electrical properties are also affected by fillers.
There are many filler types used as additives to PTFE. Subsequently there are over 300 different grades of PTFE Compound available on the market. Many of these have become industry standards, such as 25% Glass Filled PTFE and many are custom made, such as 10% carbon fibre + 5% bronze filled PTFE.
Some points to consider:
- There may be more than one grade of a particular type of filler. For example, there are more than 4 different types of bronze filler - each will produce different properties.
- There are several manufacturers of PTFE Compound raw powder materials. They all use different manufacturing techniques and different suppliers for their PTFE base resins and fillers
- The processing method used to convert PTFE Compound raw materials into a semi-finished stock shape will affect the properties of your finished component. You should work with a supplier who, like us, has total control over this part of the manufacturing process.
The following provides an introduction to the main fillers but please consult us with your exact requirements:
- Milled Glass Fibre
- improves creep resistance at low and high temperatures
- chemically stable
- little effect on electrical properties
- improves wear and friction behaviour
- Carbon (hard and soft (electro-graphitised))
- one of the most inert fillers (except in oxidising environments-use glass)
- improves creep resistance
- increases hardness
- raises thermal conductivity
- chemically inert
- good dry running properties
- Carbon Fibre
- lower deformation under load
- increased hardness
- better thermal conductivity than glass filler
- lower wear against opposing surface (esp. metal)
- less abrasive
- good properties in water environment
- chemically inert
- resistant to hydrofluoric acid
- Graphite
- excellent wear properties especially against soft metals
- displays high load bearing capability in high-speed contact
- chemically inert
- improved thermal conductivity
- often combined with other fillers
- Bronze
- improved thermal conductivity
- better creep resistance
- low abrasion
- increased compressive strength
- Molybdenum disulphide
- adds to hardness
- improves sliding properties
- little effect on electrical properties
- normally used in low % with other fillers
- Polymeric Fillers
- such as polyimide (PI), Polyphenylene Sulphide (PPS), Ekonol, PEEK, etc...
- low wear rates
- low abrasion of mating surface - ideal against soft surfaces
- improved deformation under load
- Aluminium Oxide
- good electrical properties
- Calcium Fluoride
- good with chemicals that attack glass
- electrical applications
- good chemical resistance
- Stainless Steel
- good chemical resistance
- improved thermal conductivity
- reduced cold flow
- Mica
- low shrinkage
- low thermal expansion
- poor mechanical properties
- Pigments
- some improvement on wear resistance
- colour coding
