PTFE Information

PTFE has many qualities which make it ideal for use in todays modern engine. The most valuable property of PTFE in todays motoring environment is friction reduction - in fact PTFE is listed in the Guinness Book of Records in the physical extremes section of the scientific world as having the lowest friction coefficient of any solid. By using PTFE, you can dramatically decrease the friction in the engine of your car, improving performance and increasing longevity. But if you're curious as to exactly what PTFE is and how it works, read on for a brief history of PTFE and how it works.

PTFE was invented in 1938 by DuPont chemist Dr. Roy Plunkett. Dr. Plunkett was searching for a refrigerant when he discovered a unique, new chemical named Polytetrafluoroethylene, or PTFE. It was soon learned that PTFE had unique properties resisting friction, temperature, chemicals, mechanical action and electrical charge.

In 1946 it was discovered that PTFE had great dielectric strength, or insulating properties against electrical charge, and PTFE is used to insulate aircraft circuitry against lightning strike damage. In 1949 PTFE's low coefficient of friction was tested. It was learned that as the load (or pressure) increases, PTFE's static friction decreases. A test at 1 to 4 kilograms (2.2 to 8.8 pounds) gave the coefficient of friction at 0.04. However, a test at 1360 kilograms (3000 pounds) gave the coefficient of friction at 0.01. This is due to the chemical formula for PTFE - more on this later.

Through the decades PTFE has provided solutions to problems on many high profile projects. It was used on the Manhattan project because of its ability to work with highly corrosive materials, and was used (and still is) extensively in space exploration. For example, ordinary lubricants cannot work efficiently in a weightless environment, so PTFE was used for dry film "boundary lubrication" and many other critical applications. In fact, there was over one ton of PTFE composites in the Apollo Lunar Module - even down to PTFE based fabric in Neil Armstrongs' suit. PTFE is also used for the critical "Thermal Protection System" on the nose cone of the space shuttle, as well as the engine's oxygen pump bearings and the oxygen tank linings.

Specialized PTFE applications include; problem areas such as environmental hazards, exposure to ultraviolet light, exposure to oxidation, discoloration, embrittlement, extreme heat and cold, and extreme climate conditions. Well known applications include fabrics such as Gore-Tex® used by sportsmen, athletes and workers in extreme climates, and Non-stick frying pans such as Teflon®/PTFE coated skillets. (Teflon® is the tradename for DuPont's PTFE.)

The Technical Stuff

PTFE belongs to the fluoropolymer family. Polymer means many parts, and these parts bond to form a "long chain" fluorocarbon. The chemical formula for the PTFE molecule is CF2, CF2 n ("n" means "repeated many times"). C represents one atom of carbon. and F2 represents two atoms of fluorine. Fluorine has very low surface energy, giving PTFE its low coefficient of friction, and fluorine is chemically inert. Chemical bonds between atoms in the PTFE molecule play a critical role in PTFE properties because they provide powerful binding forces. The two forces bonding the PTFE molecular structure are the carbon to carbon bond which forms the backbone of the polymer chain, and the carbon to fluorine bond which forms the shield. Both bonds are very strong and enhance PTFE's unique properties. Notice that the fluorine atoms are larger than the carbon atoms.

These powerful binding forces produce a PTFE molecule with a fluorine shield around the carbon backbone. As this graphic illustrates, the carbon backbone is completely surrounded and enclosed by large, chemically inert fluorine atoms, creating a protective shield or sheath. This provides PTFE with the following properties and benefits:

• Low surface energy provides a low coefficient of friction, like "wet ice on wet ice," and non-sticking properties.
• The powerful atomic bonds provide resistance to fracture and high thermal stability, effective at extremes of high and low temperatures.
• The fluorine atoms are larger than the carbon atoms, causing the fluorine atoms to spiral around the carbon backbone, preventing a zig-zag molecular structure, preventing other atoms from penetrating the shield and bringing rigid stability.
• Also, fluorine is chemically inert. Therefore other chemicals cannot attach the carbon backbone and weaken the molecular structure.

The carbon/fluorine structure repeats many times to create a "long chain" fluorocarbon molecule. This gives PTFE high molecular weight. Most other PTFE treatments use "micro powder" PTFE with a comparatively low molecular weight. QMI's PTFE has a very high molecular weight with higher tensile strength, improved stiffness,greater resistance to fracture, and improved flex strength and life. Therefore, QMI's PTFE is very tough and resilient and resists fracture on impact.

The molecular structure of PTFE allows "orientation," or long chain alignment of the PTFE molecules under pressure. The red bars in the illustration represent PTFE fused into one friction surface, and the black bars represent PTFE fused into the opposing friction surface. Light loads result in little alignment of the PTFE as the friction surfaces rub against each other. However, under heavy loads, increased pressure causes the PTFE to increase alignment. As these PTFE "long chain" molecules become more aligned under increasing load, the PTFE molecules slide along each other with less friction, rather than rolling over each other. Tests show that this phenomenon increases shear strength by 45%, and reduces friction by 30%. The dynamic of these combined factors explains the earlier slide showing increased load with decreased static friction: the alignment of long, slippery PTFE molecules as loads increase causes the coefficient of friction to decrease significantly.

In summary, we will review the list of properties that result from unique PTFE chemistry. PTFE resists: friction, temperature, chemicals, mechanical action and electrical charge. This produces the PTFE phenomenon, "Like wet ice on wet ice."