Filled PTFE: Glass, Carbon and Bronze Compared

30 October, 2026 | Admin

Short answer: Fillers are added to PTFE to reduce
creep and wear. Glass filled PTFE suits general wear and chemical use,
carbon filled PTFE gives good wear and compressive strength and conducts
a little, and bronze filled PTFE has high load capacity and thermal
conductivity but less chemical resistance. Virgin PTFE stays the choice
for purity and chemical contact.

Plain PTFE is soft. Under steady load it slowly deforms (creep) and
it can wear quickly against rough surfaces. Adding a filler improves
those weaknesses. The trade-off is that each filler changes something
else, so the best grade depends on the job.

Free engineering tools

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Table of Contents

Glass filled PTFE

Glass fibre improves wear resistance and reduces creep, and it keeps
good chemical resistance, apart from a few chemicals that attack glass,
such as hydrofluoric acid and strong alkalis. It is a common all-round
filled grade for seals, seats, bearings and gaskets. It can be abrasive
on soft mating metals.

Carbon filled PTFE

Carbon improves compressive strength and wear resistance, and it
gives a smoother, less abrasive running surface than glass.
Carbon-filled grades can conduct electricity slightly, which can be
useful or unwanted. They are common for piston rings, seals and wear
parts in dry or poorly lubricated service.

Bronze filled PTFE

Bronze improves load capacity and heat conduction and gives excellent
wear resistance in many sliding applications. Because it contains metal,
its chemical resistance is lower and it is not suitable for some acids,
strong alkalis or oxidising media, nor for food contact.

Quick comparison

	Virgin	Glass filled	Carbon filled	Bronze filled
Wear resistance	Low	Good	Good	Very good
Creep resistance	Low	Better	Better	Best of the group
Chemical resistance	Best	Very good	Very good	Reduced
Electrical	Excellent insulator	Good insulator	Slightly conductive	Conductive
Typical use	Linings, gaskets, food contact	Seals, seats	Rings, seals	Heavy load bearings

How to choose

Chemical or food contact? Choose virgin.
Need less wear and creep in a chemical environment?
Try glass filled.
Dry running or dynamic seal? Consider carbon
filled.
High load and heat transfer, no aggressive
chemicals? Consider bronze filled.
Unsure? Send us the load, speed, temperature and
fluid.

Filler percentages and exact properties vary between manufacturers,
so check the datasheet for the grade you buy. Read the full PTFE grades guide for more.

Order checklist

Grade, form (rod, sheet, tube), size, quantity, temperature, load and
medium. Every order from Diode Trading EST ships with a Material Test
Certificate. request a quote

Practical examples

A chemical pump wear ring needs wear resistance but
must resist the fluid: glass filled PTFE is often the first trial.
A dry-running compressor ring has no lubricating
fluid to help: carbon filled PTFE is a common choice.
A heavy sliding bearing pad with no aggressive
chemical: bronze filled PTFE can carry more load.
A tank gasket for a food or pharmaceutical line
needs purity: choose virgin PTFE, not a filled grade.

These are starting points, not guarantees. Always check the datasheet
and, for important jobs, test a sample in service conditions.

Common mistakes to avoid

using a filled PTFE in food contact without checking that the filler
and grade are suitable
choosing bronze filled PTFE for acids and then finding the filler is
attacked
forgetting that glass filled PTFE can scratch soft mating metals
such as aluminium or brass
assuming all suppliers’ “25% carbon” grades behave identically

FAQ

Is filled PTFE better than virgin PTFE? Better for
wear and creep, but not for chemical purity or food contact.

Which filled PTFE is best for bearings? Bronze or
carbon filled are common, depending on load and fluid.

Can I use bronze filled PTFE with acids? Check
carefully. Bronze reduces chemical resistance.

Does carbon filled PTFE conduct electricity?
Slightly. It is not an insulator like virgin PTFE.

Products related to this article

Diode Trading EST supplies these PTFE (Teflon) Products from stock in Dammam, with delivery across Saudi Arabia and the GCC.

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