PTFE Classic Mixing Formulas Explained Simply

Conclusion:There is no single“golden secret formula”for PTFE that the whole industry uses.

According to current public information from Chemours/Teflon, filled PTFE usually means adding 5–40 wt% inorganic fillers to the PTFE powder. Teflon™ PTFE 7C X is clearly listed as “recommended for mixing with fillers,” especially metal powders. After cross-checking this with Daikin’s published standards, 3M Dyneon’s filler ranges and comparison charts, and old DuPont data, the formulas that keep showing up again and again in real PTFE production are the ones below.

All percentages are by finished weight (wt%).

(1)85/15:PTFE+15%Glass Fiber

This is the most common general-purpose strengthened grade. Daikin lists it openly as 15GL. 3M also names glass fiber as one of the most used fillers, normally up to 25 wt% and as high as 40 wt%. It gives good size stability, resists cold flow, and handles heat well. Downside: it wears the mating surface more, so not good with soft metals.

(2)75/25:PTFE+25%Glass Fiber

This is the heavy-duty version of the 15% glass fiber mix and one of the oldest standard formulas. Daikin lists it as 25GL. 3M’s comparison samples also include 25% glass fiber. It is harder and resists creep better than 15%, but it wears the mating surface even more.

(3)80/15/5:PTFE+15%Glass Fiber+5%Graphite

One of the most classic low-friction seal formulas. 3M’s published wear chart uses exactly 15% glass fiber / 5% graphite as a low-wear example. Old DuPont data also puts the glass-fiber-plus-graphite mix in the low-wear area for mild steel.

(4)80/15/5:PTFE+15%Glass Fiber+5%MoS₂

Daikin lists the standard grade 15GL5M. 3M says MoS₂ is usually added as a secondary filler up to 5 wt%, and the lowest friction often comes from graphite or MoS₂ alone or mixed with glass fiber. DuPont data also places glass fiber/MoS₂ in the low-wear zone.

(5)85/15:PTFE+15%Graphite

An old-school low-friction formula that is kinder to soft mating surfaces. Daikin lists it as 15GR. 3M notes graphite is commonly used at about 5 wt% as a secondary lubricant filler, but can go up to 20 wt% to improve heat conduction. Graphite formulas usually give the lowest friction coefficient.

(6)75/25:PTFE+25%Carbon

Another classic PTFE line, split into hard carbon and soft carbon. Daikin lists both 25CAR (hard carbon) and 25CAR/R (soft carbon). 3M’s typical range is soft carbon up to 25 wt% and hard carbon up to 35 wt%. Hard carbon is used more for high load, wear resistance, and piston rings. Soft carbon is used more for dry running and seal bushings.

(7)90/10:PTFE+10%Carbon Fiber

A very typical formula for water-lubricated or hydraulic seals. Daikin has 10CF. 3M says carbon fiber is commonly used up to 15 wt% and is clearly good for liquid conditions. DuPont’s water-environment guide also puts carbon fiber in the low-wear side.

(8)60/40:PTFE+40%Bronze

One of the oldest PTFE families for high-pressure hydraulics. Daikin lists 40BRR. 3M says bronze powder filling can go as high as 60 wt%, focused on high wear resistance, high-pressure hydraulics, and good heat conduction. DuPont data also puts bronze in the low-wear area for mild steel. Downside: weaker chemical and electrical performance, and not suitable for water.

(9)60/30/10:PTFE+30%Bronze+10%Carbon Fiber

This is more of a “classic heavy-load version” than a universal standard. 3M’s wear chart uses 30% bronze / 10% glass fiber and shows it has the lowest wear factor in that chart — typical high-PV, heavy-duty wear thinking.

If we boil all the above down to one short list, the most classic PTFE mixing formula family is: 15% glass fiber, 25% glass fiber, 15% glass fiber + 5% graphite, 15% glass fiber + 5% MoS₂, 25% carbon, 10% carbon fiber, 40% bronze.

This is not any one company’s official “only answer.” It is simply a summary that comes from crossing Chemours/Teflon’s filler guidelines, Daikin’s standard grades, 3M’s typical contents and charts, and old DuPont records.

Two quick reminders at the end. First, almost all public catalogs use wt%, but some old DuPont discussions mention “around 20 vol% for lowest wear.” You cannot compare wt% and vol% directly because bronze, glass fiber, and carbon have very different densities. Second, PTFE friction and wear are strongly affected by filler shape, amount, load, speed, mating material, and environment. The same “classic formula” can rank very differently in dry steel running versus water-lubricated conditions.