PTFE sheet is not one material. The same name covers pure white virgin sheet, thin skived rolls, glass- or carbon-filled blocks and soft expanded gasket sheet, and each one behaves differently in service. Pick the wrong grade and you can end up with a gasket that creeps, a bearing pad that wears out early or an insulator that does not hold its voltage.
This guide walks through the main types of PTFE sheet, what each grade is good at, and how to choose one for electrical, chemical or mechanical work.
What Is a PTFE Sheet?
PTFE (polytetrafluoroethylene) is the fluoropolymer most people know by the brand name Teflon. In sheet form it is valued for a set of properties that are hard to find together in one plastic:
- A service temperature range of roughly -200°C to +260°C
- Resistance to almost every industrial acid, alkali and solvent
- Very low friction, so very little sticks to it
- Excellent electrical insulation, with a dielectric constant of about 2.1 and very low dielectric loss
- Practically no moisture absorption, so its properties stay stable in humid conditions
The base polymer is the same in every grade. What changes is how the sheet is made (moulded or skived) and what is mixed into it (fillers or recycled resin). Those two choices decide how the sheet performs.
Virgin PTFE Sheet
Virgin PTFE is made from 100% new PTFE resin with nothing added. It is bright white, slightly waxy to the touch, and has the best electrical and chemical properties of any grade.
Virgin sheet is the right choice when:
- the part is an electrical insulator, such as a spacer, terminal board, coil separator or insulating washer in a motor, transformer or switchgear panel
- it will be in contact with strong chemicals, food or pharmaceuticals
- purity matters more than wear resistance
Its weak point is mechanical. Virgin PTFE is soft and creeps under steady load, a behaviour known as cold flow. A heavily bolted gasket or a loaded bearing pad can slowly deform over time. For load-bearing parts, a filled grade is usually the better option. If you need virgin material for insulation work, see our virgin PTFE sheets.
Reprocessed (Mechanical Grade) PTFE Sheet
Reprocessed sheet uses reground PTFE, often blended with some virgin resin. It is usually off-white or greyish and costs less. Chemical resistance and low friction are largely kept, but the electrical properties are lower and less consistent from batch to batch.
It suits slide pads, liners and general mechanical parts. It should not be used where dielectric performance matters.
Skived vs Moulded PTFE Sheet
These two terms describe how the sheet is produced, not what it is made of.
Moulded PTFE sheet is formed by compressing PTFE powder in a mould and then sintering it in an oven. This produces thick, solid sheets that are machined into bushes, seals, valve seats and insulating blocks.
Skived PTFE sheet starts as a large moulded cylinder called a billet. The billet rotates against a sharp blade that peels off a continuous thin layer, a little like unrolling paper from a roll. Skiving is how thin sheets and long rolls are made, from fractions of a millimetre up to a few millimetres thick.
Skived sheet can also be etched on one side. The chemical treatment roughens the surface so adhesives can bond to it, which untreated PTFE does not allow. Etched sheet is used to line tanks and to bond PTFE onto metal.
A simple rule: thin sheet, tape or lining is skived; thick blocks for machining are moulded.
Filled PTFE Sheet: Glass, Carbon and Bronze
Fillers are added to correct PTFE’s two mechanical weaknesses, creep and wear. Each filler brings its own trade-off.
Glass-Filled PTFE
Glass fibre, typically 15 to 25%, improves wear and creep resistance. It keeps good chemical resistance and reasonable electrical properties, which makes it the most common filled grade for seals, piston rings and valve seats. It can be slightly abrasive against soft mating metals.
Carbon and Graphite-Filled PTFE
These grades offer better wear resistance, higher compressive strength and better heat dissipation. Carbon makes the sheet partly conductive, so it is not suitable for electrical insulation.
Bronze-Filled PTFE
Bronze gives the highest load capacity and good thermal conductivity, so it is used for bearings and guide strips. It conducts electricity and has lower chemical resistance than the other grades.
For electrical insulation, stay with virgin PTFE, or glass-filled PTFE where extra mechanical strength is needed.
Expanded PTFE Sheet (ePTFE)
Expanded PTFE is made by stretching PTFE until it forms a microporous, fibrous structure. The result is soft and compressible, quite unlike the hard, slippery feel of solid sheet.
It is mainly a gasket material. ePTFE fills scratches and uneven surfaces on flanges, seals at lower bolt loads and resists creep better than solid virgin sheet. You will find it in chemical plants, pharmaceutical lines and on glass-lined or fragile flanges. It is not used for precisely machined parts or as a rigid insulating board.
PTFE Sheet Grades Compared
| Grade | Main strength | Main limitation | Typical uses | For electrical insulation? |
| Virgin | Best purity, chemical and dielectric properties | Soft, creeps under load | Insulators, spacers, chemical liners | Yes, the best choice |
| Reprocessed | Lower cost, low friction | Lower, inconsistent electrical properties | Slide pads, mechanical parts | Not recommended |
| Skived | Thin sheet in long lengths | Thin gauges only | Liners, tapes, layer insulation | Yes, in virgin grade |
| Moulded | Thick blocks for machining | Sheet size limited by the mould | Bushes, seals, valve seats, insulating blocks | Yes, in virgin grade |
| Glass-filled | Wear and creep resistance | Slightly lower electrical properties | Seals, piston rings, valve seats | With care |
| Carbon or graphite-filled | Wear and compressive strength | Partly conductive | Bearings, dynamic seals | No |
| Bronze-filled | Highest load capacity | Conductive, lower chemical resistance | Bearings, guide strips | No |
| Expanded (ePTFE) | Soft, seals at low bolt load | Not for machined parts | Flange gaskets | No, it is a sealing material |
How to Choose the Right PTFE Sheet Grade
Four questions narrow the choice quickly:
- Does the part need to insulate? If yes, choose virgin PTFE and avoid carbon, graphite and bronze-filled grades entirely.
- Will it carry load or rub against something? Use glass-filled for seals and wear parts, and bronze or carbon-filled for bearings.
- Is it a gasket? Expanded PTFE suits most flanges. Virgin or glass-filled sheet works for small, well-supported gaskets.
- What thickness do you need? Thin sheet and rolls are skived. Thick blocks for machining are moulded.
Temperature is rarely the deciding factor, because every grade shares PTFE’s high heat limit. The real limits come from load, wear and electrical requirements.
PTFE is not always the answer. For rigid insulating boards with high mechanical strength, FR-4 glass epoxy sheets often work better, and for very high temperatures muscovite mica sheets are worth a look. Our article on the top challenges in electrical insulation explains how to weigh these trade-offs.
If the job is insulating a wire rather than a flat surface, read our comparison of PVC, PTFE and fiberglass insulated cables, or look at our PTFE insulated cable and Teflon insulation sleeves.
Getting the Grade Right
Use virgin PTFE for insulation and purity, glass-filled for wear, carbon or bronze-filled for bearings and expanded PTFE for gaskets. Choose skived sheet for thin material and moulded sheet for thick parts. Matched to the job, PTFE lasts for years in conditions that break down most other plastics.
Harnawa Insulations supplies PTFE sheets alongside a full range of insulation sheets and electrical insulation components. Contact us with your application, thickness and operating temperature, and our technical team will help you pick the right grade.
Frequently Asked Questions
What are the main types of PTFE sheet?
The main types are virgin PTFE, reprocessed (mechanical grade) PTFE, filled PTFE (glass, carbon, graphite or bronze) and expanded PTFE. Solid grades are produced either as moulded sheet for thick parts or skived sheet for thin material.
What is the difference between virgin and reprocessed PTFE sheet?
Virgin PTFE is made only from new resin and has the best electrical and chemical properties. Reprocessed PTFE contains reground material, costs less and keeps low friction, but its electrical properties are lower and less consistent.
Which PTFE sheet is best for electrical insulation?
Virgin PTFE sheet is the best choice for electrical insulation. Glass-filled PTFE can be used where more mechanical strength is needed. Carbon, graphite and bronze-filled grades conduct electricity and should not be used as insulators.
What is the difference between skived and moulded PTFE sheet?
Moulded sheet is pressed and sintered in a mould, giving thick blocks for machining. Skived sheet is peeled from a rotating moulded billet, giving thin sheets and long rolls.
What temperature can PTFE sheet withstand?
PTFE sheet can generally be used continuously from about -200°C up to +260°C. Load and wear usually limit a part before temperature does.
Is Teflon sheet the same as PTFE sheet?
Yes. Teflon is a brand name for PTFE, so a Teflon sheet and a PTFE sheet are the same material. Grade and quality still vary between suppliers.
