Dupont Teflon, a trademarked name, is also available in polytetrafluoroethylene (PTFE). This fluoropolymer is one of the most widely recognized compounds used throughout the world. Its applications are near endless.

Dupont PTFE is a product formed by free radical vinyl polymerization of tetrafluoroethylene (TFE) and is known to have a continuous service temperature of 500 F. Much higher temperatures can be satisfactorily sustained for shorter exposures.

Mechanical properties include, but are not limited to, flexibility at low temperatures, stability at high temperatures, and low coefficient of friction.

For chemical corrosion resistance, consider, too, Dupont Teflon PFA, FEP, or ETFE. Absorption rates are comparatively lower than almost all other thermoplastics. They absorb practically no common acids or bases at higher temperatures (350 degrees Fahrenheit for ETFE). Weight increases are generally less than 1% when exposed at elevated temperatures for long periods. Aqueous solutions are absorbed little. Moisture absorption is typically less than 0.01% at ambient temperature and pressure.

Gases and vapors, too, show low permeation rates with Dupont Teflon, PFA, FEP, or ETFE, than for other thermoplastics. In general, permeation increases with temperature, pressure, and surface area contact, but decreases with increased thickness.

There have been many practical non-lubricated mechanical systems developed with coefficient of friction as low as 0.05-0.08. Even at higher dynamic PV (8,000 to 10,000) coefficient of friction around 0.10 is feasible.

These Teflon resins exhibit exceptionally low friction in non-lubricated environments, especially at low surface velocities and pressures higher than 5 pounds per square inch. The coefficient of friction actually increases with sliding speed up to 100 feet per minute, under all pressure conditions. It is this phenomenon that prevents ‘stick-slip’ tendencies. In addition, no ‘squeaking’ or noise occurs, even at the highest speeds. Above 150 feet per minute, sliding velocity has little effect (on friction) at combinations of pressure and velocity below the composition’s PV limit. Static friction decreases with increasing pressure.

PV limits define the maximum combinations of pressure and velocity at which these materials will operate continuously without lubrication. PV limits approach zero at temperatures between 550F and 600 F (Teflon PTFE), 400 degrees Fahrenheit (Teflon FEP), and 350 degrees Fahrenheit (Teflon ETFE). However, useful PV limits must take into account the composition’s wear characteristics and allowable wear for the application.

When considering Dupont products (or others) for corrosion protection, you may sometimes need to consider creep and cold flow.

Generally, a plastic material subjected to continuous load experiences a continued deformation with time called creep or cold flow. Deformation can be significant, even at room temperature or below; hence, the name ‘cold flow’.

Creep is the total deformation under stress after a specified time in a given environment beyond that instantaneous strain which occurs immediately upon loading. Independent variables affecting creep are time under load, temperature, and load or stress level.

As long as the stress level is below the elastic limit of the material, performance is sustainable. And beyond a certain point, creep is small and may be neglected for many applications. In many cases, too, there is compressive recovery from various percentages of strain. Nearly complete where the original strain does not exceed the yield strain.

Among the Teflon fluoropolymers, ETFE (ethylene-tetrafluoroethylene copolymer) has the best impact strength, mechanical toughness, wear resistance, and creep resistance, along with its excellent resistance to chemical corrosion.