PTFE Offers High-Performance in Key Industries
PTFE Offers High-Performance in Key Industries Polytetrafluoroethylene (PTFE) offers features and benefits for a wide range of high-performance applications in industries such as medical, aerospace and defense, chemical processing, water management, oil & gas and more. PTFE can withstand the heat, steam and chemical sterilization processes, has a wide temperature working range, superior thermal control (up to 300°C or 572°F) and best-in-class dielectric properties. It is resistant to aircraft fuels and fluids, and has a low trace metals content. It is also corrosion-resistant which makes it the perfect choice for applications that may be exposed to numerous fluids.

Medical Industry
The medical industry demands high-performance plastics that must meet stringent specifications and government regulations. PTFE is one of only three nonmetallic materials that can withstand the heat, steam and chemical sterilization processes used in the medical industry. PTFE is totally chemically resistant and inert and meets the requirements for a very low coefficient of friction and temperature resilience.

Producers of medical sample kits regularly utilize PTFE with ultrasonic welded silicone or PTFE seals, in addition PTFE seals are also used for medical test vials that require an FDA approved sealing plastic.

PTFE provides a number of benefits in these applica¬tions. These products need to be TSE/BSE compliant, which indicates that the material cannot transmit dis¬eases. In some applications that require glass-filled and/or carbon-filled PTFE, the products must meet FDA 21CFR177.1550 regulations and must be approved for use in contact with food, potable water, and pharmaceutical products.

To meet these requirements, manufacturers like Enflo have developed several materials that can provide the features needed by the medical industry. The Enflon® 105 Premium 25% glass filled material is used to produce basic shapes that are machined into various types of seals and components. Milled glass fibers have the least effect on chemical and electrical properties and add greatly to the mechanical properties of unfilled PTFE. The addition of glass improves compressive properties by as much as 40%, and improves dimensional stability, heat distortion temperature, and wear resistance greatly. These compounds resist acids and oxidation, but can be attacked by alkalis.

Since PTFE is chemically inert and can withstand low pressure liquid chromatography, it has a diverse number of uses in the Medical and Biosciences markets. PTFE premium skived sheets are used for cap liners for vials as well as other applications in the medical industry. In addition to being TSE/BSE compliant, Enflo’s products meet USP Class VI, the most stringent of the classes since PTFE has passed systemic injection testing, intracutaneous testing and implantation testing. They are also FDA Compliant to FDA 21CFR177.1550 Reg. Enflo’s PTFE premium molded sheets are typically ma¬chined into high viscosity agitators as well as seals used in rotary evaporators.

Aerospace/Defense/Missile/Naval Industry
PTFE is also suitable for a wide range of applications in industries as diverse as aerospace/defense, the food and drink industry, pharmaceuticals, and telecoms.

The requirements found in many aerospace and defense applications require high performing plastics. Specially, PTFE is widely used in these applications due to its chemical inertness, wide temperature working range, superior thermal control (up to 300°C or 572°F), best-in-class dielectric properties, resistance to aircraft fuels and fluids, and low trace metals content.

One particular application utilizing PTFE is in valve components such as ball seats which are used in nuclear naval ships and submarines. The corrosion-resistant features of PTFE make it the perfect choice for use in check valves exposed to numerous fluids. Relief valves use PTFE seals to assure a perfect seal against liquids and gases. Reinforced PTFE (glass or carbon fibers) is used for valve seals with very low cold flow at ambient and cryogenic temperatures, and high extrusion resistance up to 500°F. PTFE is a standard product for aircraft fuel and fluid control valve seals.

Besides the obvious benefits provided by the physical properties of PTFE in these applications, PTFE does not require the tooling investment associated with molded PFA parts. The main advantages of PTFE in valve designs are that it is ideal for both high purity and highly corrosive applications because it is virtually impervious to corrosion, as well as being extremely low in terms of leaching. It is also excellent for valve seats due to its low frictional properties which reduce the break-away torque requirement when a valve is actuated, effectively reducing valve actuator size, and cost.

Chemical Processing/Water Management and Oil & Gas Industries
Other useful PTFE properties are its high flexural strength, even in low temperatures, and its high electrical insulation and dielectric strength, which makes PTFE useful as a low pressure, high dielectric material for interconnecting devices. PTFE is resistant to hot, cold, and chlorinated water due to the fluorine’s high electronegativity. This characteristic makes PTFE useful in water management applications such as centrifugal and piston pumps seals and bushings. PTFE’s low friction, low wear characteristics and chemical resistance to water and fluids, enhances equipment mean time between repairs (MTBR).

Virgin PTFE is white and has the advantages of a very high temperature rating, extremely high lubricity, and being inert to most caustic fluids. While a possible disadvantage may be that it is very soft, fillers can be blended into PTFE to increase its durometer hardness and wear resistance. Adding a filler to PTFE can also increase its strength, improve resistance to abrasion, add electrical conductivity and more.

A specific valve application is the seat of a ball valve. PTFE is suitable for filling the void between the body and ball eliminating product build up. Carbon/Graphite filled PTFE and Carbon filled PTFE are frequently used as ball seat materials. The reason is that these materials provide sufficient ductility to provide a reliable seal and dimensional stability to ensure the ball valve seat retains its shape for reliable sealing and performance. PTFE provides very low friction to keep stem torque at a minimum, thus facilitating valve actuation, and offers a low coefficient of thermal expansion so that the ball valve seat retains its shape when temperature changes occur.

Additional features of PTFE in the ball seat valve application include excellent wear resistance for a long service life, chemical compatibility with virtually all media and low moisture absorption to prevent dimensional changes in the presence of water or high humidity.

In applications such as chemical processing equipment components as well as oil field downhole drilling and production tools, where there may be presence of hot water, steam, drilling and completion fluids, and harsh chlorinated chemicals, PTFE’s low water and fluid absorption, combined with exceptional chemical resistance, will allow the component to maintain performance despite repeated steam exposure, or sterilization. In the case of equipment seals, PTFE’s non-elastomeric characteristics will also pro¬vide good performance in the presence of sudden decom¬pression (i.e., pressure drops over 650 psi). PTFE’s excellent performance in sudden decompression applications is demonstrated by the use of PTFE seals for many decades in seal stacks employed in downhole production and completion tools. PTFE seals have performed at 450°F in high pressure conditions without exhibiting explosive decompression. The Oil & Gas industry has learned to rely on PTFE as a dependable non-explosive-decompression seal material.

PTFE has many of the same properties as PEEK, but involves even lower friction, dry running capabilities, and more extensive chemical compatibility. Like PEEK, it is available in FDA-approved grades and can handle cryogenic temperatures down to -50°F and high temperatures up to 550°F as well as pressures up to 5,000 psi, even up to 10,000 psi when properly equipped with metallic back-up seals. Also, like PEEK, PTFE can continue to perform even when repeatedly exposed to hot water and steam.

In low and mid pressure conditions, PTFE, just like PEEK, has performed for many years as the standard material for piston ring and rod packing applications in reciprocating compressor equipment. The low wear and chemical resistance of PTFE compounds (carbon/ graphite filled PTFE), coupled with its inertness in various process gases, has rendered PTFE as the go-to product for both Reciprocating and Centrifugal Compressor equipment manufacturers. While PTFE does not perform well in the presence of fluorine or alkalis, it is easy to clean and available in glass or carbon-reinforced grades that can provide improved wear characteristics, less propensity to cold creep, and lower thermal conductivity.

Written by Ed Alvarez (Altek), Mark Lamoureaux, CEO and Karl Forsander, VP Technical Sales of Enflo LLC, one of the largest, privately owned manufacturers of Polytetra¬fluoroethylene (PTFE) in North America. Founded in 1954, Enflo is a PTFE specialized solution provider with proven expertise in manufacturing Virgin, Reprocessed and Filled (Enflon®) PTFE basic shapes. Enflo is an ISO9001 certified company that regularly supplies PTFE product forms to other ISO, AS9100, and ITAR certified companies in a wide range of industries such as medical, construction and bridges, food and beverage, oil and gas, electronics, auto¬motive, aerospace and defense, chemical, energy, and in¬dustrial, where high quality products built by proven manufacturing operations are critical for success. For more information, contact Enflo LLC at 888-887-4093/860-589-0014, www.enflo.com.