Tag Archives: Teflon

The Many Uses of Polytetrafluoroethylene Seals (Teflon)

Better known as Teflon in the industry, Polytetrafluoroethylene is widely used in practically every industry on and off the planet (and even beneath its surface!)

Medical Uses

white ptfe o-ring-teflonThis material’s primary claim to fame is its resistance to most chemicals. It inherently has an extremely low coefficient of friction, it’s easily machined from rods, tubes, or compression-molded shapes.

It’s one of the few polymers that are approved for medical implants due to its inertness to bodily fluids — the immune system principally ignores its presence in the body.

Moving away from the body, you’ll find PTFE or Teflon products in medical devices such as heart lung machines, rotary tools for cutting, and sealing devices for maintaining fluid streams for irrigation and pumping. Tiny fragments that may come loose during usage are not harmful to the body, and simply pass through the system.

Pharmaceutical Uses

In the pharmaceutical industry, Teflon is used in the processing of drugs for equipment used to manufacture such as mixers, presses, and bushings. Teflon is found in a variety of applications, as any debris from the seal will pass through the body without consequence.

When considering press machinery (which are often water driven to ensure any leakage will not spoil the product), Teflon seals are often used to help reduce friction — especially in repetitive presses where a build-up of heat would be detrimental to the seal and the product.

Food & Beverage Uses

Mixers are another area to ensure keeping grease and other contaminants from the motor to not descend into the product from the mixer shaft.

Another area is pressure vessels where two shells are clamped together to ensure product remains sealed inside. Failure of these seals usually results in loss of product.

Non-metal bearings that don’t requiring grease in rotary motion are an excellent place for Teflon style bushings. These bushings provide long life with very low friction while not contaminating the product. Shaft wear from the bushing may be eliminated with the use of Teflon.

Types of PTFE (Teflon) Seals

Seals in the medical field can be as simple as a static O-Ring, or a mechanical face seal which is costly and requires special consideration during installation. Most dynamic applications can be resolved with spring-energized style seals, which often have very low friction and can be clean in place (CIP) if required.

There are different styles of springs, such as cantilever or canted coil that provide varying loads. The cantilever-style spring-energized seal provides a linear load based on deflection providing a high level of seal-ability. It can be silicone-filled to provide CIP for ease of washing, and there are a variety of materials that are FDA compliant and that work well in both viscous and pure aqueous fluids.

Canted coil spring-energized seals provide a unique feature of controlling the load the spring exhibits on the sealing element. This allows for control of a device being manipulated during a procedure.

The polymer properties give the user materials with the lowest possible friction, while still sealing in an application. The load from a canted coil spring allows the user to feel a tool in a catheter while passing the catheter through a tube, and still retaining a seal.

As you can see, PTFE has a variety of uses across a broad range of industries. GFS’ partner, Eclipse Engineering, manufactures PTFE and can help provide solutions to customers facing both simple fixes or complex problems.

Contact us today to see if PTFE might be the right choice for your application.


For custom engineered parts, or for more information about a variety of PTFE seals we can provide, contact Gallagher Fluid Seals today.

The original article was written by Eclipse Engineering and can be found on their website.

5 Polymer Bearing Configurations and Their Advantages

Polymer BearingPolymer wear rings were developed to offer an alternative to dissimilar metal wear rings.

One of the advantages to using a polymer material such as nylon or filled-Teflon instead of a metallic bearing . Whereas when you use bronze or metallic bushings, these materials are prone to point loading on the edges of the bearing.

This property of polymer bearings combined with solid lubricants can yield a product that is much less likely to damage moving components.


5 Advantages to Polymer Wear Rings

  1. Polymer style bearings can be held to very close tolerances in the radial dimension to provide support without excessively opening the extrusion (E) gap by a large amount. Polymer bearings such as filled Teflon can support a compressive load up to 1000 PSI. Nylons up to 36,000 PSI and polyester fiber with resin, up to 50,000 PSI.
  2. Hydraulic cylinders that are found in excavators often use higher compression materials because they experience extreme side and shock loads. However, most applications do very well with filled Teflon materials.
  3. Bearings come solid or split. If designed properly, split bearings provide equivalent support, while improving installation options with no compromise in performance. Solid bearings, or bushings, are convenient when installing on the outboard side of a rod groove. Split bearings are essential when installing in a piston groove designed to function internally in a system.
  4. Nylon or composite bearings are typically cut to allow for installation due to their stiffness. However, a Teflon bushing can be made into a ring, or cut from a roll of sliced strip.
  5. The only time a bushing needs to be cut from a ring is if installation does not allow the strip to be deformed for a clean install. Strip installation allows for variability in length, lower manufacturing costs, and the product can generally be acquired off the shelf.

Materials for Polymer Bearing Configurations

When selecting materials, we must consider the maximum load, the speed of the system, and whether there is any lubrication in the system.

The load (or pressure over area) that the bearing will see is the first consideration. This dictates which materials will be the best fit.

It’s important to use a material that has a minimum compressive strength rating so that it will not fail under the highest loading condition. The industry standard is to employ a safety factor so that the bearing is specified to be used well beyond its design limit.

Teflon should be your first consideration due to cost and ease of installation. Nylon or composites will provide much higher load rating, but the cost and installation need to be considered.

Teflon and composites provide service without lubrication, and the composites provide excellent service in aqueous solutions. Bushings are typically used in medium to slow reciprocating service. Rotary creates challenges that may or may not work depending on the design of the bushing.

There are many series of injection molded nylon bushings. However, nylon in low-lubrication or high-loading may create high-friction, and can be noisy. Nylon, as a low-cost bushing, can be used in some high load situations.

A final consideration before going into large scale production is the cost of taking a bearing design into high production. Some bearing materials are expensive and can only be processed by machining, which limits the cost reduction scenarios at high volumes.

Eclipse Seal

Materials such as filled-PTFE or thermoplastics that can be molded offer cost competitive solutions for high-production applications. Eclipse provides bearings in everything from low-quantity applications, such as bridges and dams, to mid-quantity applications in aerospace.


Gallagher Fluid Seals is a preferred distributor of Eclipse Engineering. Call us at 1-800-822-4063 for more information on Eclipse seals.

Article written by Cliff at Eclipse Engineering, Inc. For the original article, visit their website.

How AMS3678 Ensures Consistency in Sealing Materials

When it comes to designing and developing seals, the aerospace and industrial industries need a basis to allow production anywhere in the world.

One of the first PTFE (Teflon) standards, AMS3678, describes Teflon and the addition of fillers. This was used in conjunction with Mil-R-8791, which is one of the Mil specs describing a backup ring device.

The origin of all these specs dates back to the creation of the O-ring.

AMS3678The Origin of the O-Ring Patent

In 1939, Niels A. Christensen was granted a U.S. Patent for “new and useful improvements in packings and the like for power cylinders.” These referred to improved packing rings made of “solid rubber or rubber composition very dense and yet possessive of great liveliness and compressibility.” These products were suitable for use as packings for fluid medium pistons (liquid or air). The improved packing ring is the modern O-ring.

There was a progression of standards for the O-rings created by individual countries, such as AS568, BS 1806, DIN 3771, JIS B2401, NF T47-501, and SMS 1586. Eventually, AS568 became more accepted in the industry.

The backup ring was originally created to help improve the O-ring’s ability to resist extrusion. Teflon was widely used as one of the materials for backup ring devices. Standards were created to unify the production of this Teflon device.

The Progression of Mil Specs

The progression of standard changes has led to AMS3678/1 for Virgin PTFE through AMS3678/16. These standards describe a group of Virgin- and filled-PTFE materials accepted by the industry for manufacturing seals and back-up ring devices.

Mil-R-8791 was canceled in February 1982. This spec was superseded with AS8791, which eventually evolved into AMS3678.

AMS3678 is a tool used by customers and Teflon suppliers to create uniformity in the manufacturing and processing of seal and bearing materials. The standard is inclusive of most of the compounds upon which the industry was built.

When customers approach with an old “mil spec”, they are pushed to the new AMS spec which is currently active. Eclipse manufactures to the spec so their customers will have the confidence that they manufacture to a known standard.

When crossing custom materials from well-known sources, customers are driven to an accepted spec that is equivalent to the original source of the material. This helps customers sell their products with internationally-known materials rather than custom, home-grown compounds that are often intended to single source those materials.

There are several qualifications of the spec that suppliers must observe. This includes dimensional stability tests. This test ensures the material has been properly annealed, and that the seal or backup ring will fit and function as it was originally intended.

Eclipse is uniquely qualified to supply parts to the latest AMS3678 specification. They understand the scope of the specification which allows us to ship parts with fully traceable certification.

AMS3678 helps validate a material to a customer to ensure they get the same material processed the same way with each order. Beyond this, there are other ways to determine what makes a part process-capable.

Continue reading How AMS3678 Ensures Consistency in Sealing Materials

FFKMs Protect Components in Enhanced Oil Recovery

FFKMs, also known as perfluoroelastomers, were first developed in the 1960s for applications involving high temperatures and/or aggressive chemicals.  Perfluoroelastomers exhibit many properties similar to PTFE (polytetrafluoroethlyene, or Teflon®), and are considered inert in almost all solvents.  However, PTFE is a plastic, and when compressed, it will not recover to its original shape.  On the other hand, elastomers contain crosslinks, which act as springs to give the material resiliency and the ability to recover after a part has been compressed – this resistance to permanent compression gives the material the ability to maintain a seal over time. (To learn more about perfluoroelastomers, download our Introduction to Perfluoroelastomers White Paper).

The article below was recently published on FlowControlNetwork.com, and discusses how FFKMs are being used in oil & gas exploration, as production companies are increasingly operating in high-pressure, high-temperature (HPHT) downhole conditions.


HOW FFKMS PROTECT COMPONENTS IN ENHANCED OIL RECOVERY OPERATIONS

Companies are increasingly operating in high-pressure, high-temperature downhole conditions.
Enhanced oil recovery uses gas, steam or chemical injection to improve flow rate. All graphics courtesy of AGC

Improving technologies and methods to increase the recovery of oil from existing reservoirs is a global challenge. In the U.S., oil production at reservoirs can include three phases: primary, secondary and tertiary (or enhanced) recovery. The U.S. Department of Energy (DOE) estimates that primary recovery methods — which rely on the natural pressure of the reservoir or gravity to drive oil into the wellbore, combined with pumps to bring the oil to the surface — typically tap only 10 percent of a reservoir’s oil. Furthermore, secondary efforts to extend a field’s productive life — generally by injecting water or gas to displace oil and drive it to a production wellbore — still only push recovery totals to between 20 and 40 percent of the original oil in place. Clearly, much untapped oil and gas remains in existing wells.

Continue reading FFKMs Protect Components in Enhanced Oil Recovery

PTFE as a Sealing Material

Polytetrafluoroethylene (PTFE) is commonly known as a coating for pans under the DuPont trade name Teflon™. It is also superbly suited as a sealant and is superior to many materials in specific ways. For example, it can be used at low and high temperatures and in combination with gasoline, solvents, water and other polar media such as lyes, standard lubricants and brake fluid. PTFE’s chemical resistance is nearly universal.

History

In 1938, while working for DuPont, American chemist Roy Plunkett was looking for a substitute for the fluorohydrocarbon Freon, which his employer was only allowed to sell to General Motors’ Frigidaire division for patent-related reasons. For his research, he had obtained a supply of tetrafluoroethylene (TFE), which was used as refrigerator coolant. He stored it in small pressurized gas cylinders at low temperatures. When he was ready to use the gas after a fairly long storage period, none was left in the container. But its weight was unchanged. After it was opened, there were white crumbs inside and the inner walls of the container were covered with a thin layer. Plunkett quickly realized that the TFE gas had been polymerized into a plastic. This new plastic, PTFE, proved to be completely resistant to chemical exposure. Not even aqua regia¹ could harm it in any way. But its production was so costly that practical uses seemed inconceivable.

PTFE - Used As a Coating on Fishing Lines Continue reading PTFE as a Sealing Material