THE PROPERTIES AND ADVANTAGES OF PTFE

Polytetrafluoroethylene or PTFE (more commonly known as Teflon) is a particularly versatile ivory-white and opaque plastic fluoropolymer; it is made by the free-radical polymerisation of many tetrafluoroethene molecules, and is suitable for a wide range of applications in industries as diverse as aerospace, the food and drink industry, pharmaceuticals and telecoms.

Produced by AFT Fluorotec in rods or tubes of any size, or filled with glass, carbon, stainless steel or many other materials to increase wear resistance and strength, whatever your project or build, we are sure to have a material that will work for you.

THE MAIN PROPERTIES OF PTFE

If you were trying to invent a highly flexible, chemical resistant, thermal resistant, non-stick and electrically resistant material, and it hadn’t already been done, you’d be hoping you could come up with a material somewhere nearly as good as PTFE is in these areas.

PTFE’s melting point is around 327°C, and pure PTFE is almost totally chemically inert, highly insoluble in most solvents or chemicals, and thermally stable enough to be used between -200 degrees C and +260 degrees C without degrading.

Other useful PTFE properties are its high flexural strength, even in low temperatures, high electrical resistance and dielectric strength, resistance to water (owing to fluorine’s high electronegativity), and low coefficient of friction. PTFE’s density is also very high, at 2200 kg/m3.

In fact, beyond reaction to some chemical agents and solvents (for example, chlorine trifluoride, cobalt(III) fluoride, xenon difluoride or elementary fluorine if at a high pressure and temperature), the only factor to be taken into consideration when using PTFE is that it does not have a good resistance to high energy radiation, which will cause breakdown of the PTFE molecule.

MODIFIED PTFE PROPERTIES

In addition to pure PTFE, there are two co-polymers which are equally as useful as PTFE, but with some different properties.

PFA or Perfluoroalkoxy has very similar properties to PTFE in that it is very chemically resistant, flexible and thermally stable (with continuous use up to 260 degrees C), but while PTFE does have some tendency to creep, PFA is creep resistant and is excellent for melt-processing, injection moulding, extrusion, compression moulding, blow moulding, and transfer moulding.

TFM, known as PTFE-TFM, is polytetrafluoroethylene with perfluoropropylvinylether as an additional modifier, giving a denser material which is stiffer, also creep resistant like PFA, and weldable.

FILLED PTFE

Pure or virgin PTFE can deform badly under a load, but the use of fillers can help with this, though it should be noted that not all filled PTFE is suitable for use with food.

Adding a filler to PTFE can increase its strength, improve resistance to abrasion, add electrical conductivity and more; however, adding fillers can also reduce some of the advantageous PTFE properties, such as chemical resistance which will be limited by that of the filler.

Fillers used can range from glass in various percentages, stainless steel, molybdenum disulphide, carbon or graphite, depending on which properties are to be improved.

ADVANTAGES AND BENEFITS OF USING PTFE

The biggest advantage of PTFE is its versatility, and the range of applications over so many products and different industries for this material is staggering.

The use of PTFE can have massive benefits in manufacturing and engineering, not just in making tubes or liners for handling or storing corrosive chemicals, but by coating parts such as bearings or screws to increase the lifetime of both the parts themselves and the machinery they are part of.

A PTFE-coated screw will be resistant to corrosion, due to PTFE’s ability to repel water and oil, and lubricated by the material to smoothly drive into whatever surface you are fastening to, with reduced friction, resulting in less wear on both the screw and the surface, and a longer-lasting, more secure finish.

Friction and wear can also be factors with bearings, and a PTFE coat can give the same benefits as with coating screws, with the additional advantage that the coating will also be heat-resistant.

It’s clear that longer lasting, higher-performance parts can add to the efficiency of any machinery, reduce the need to constantly acquire replacement parts, both saving money and the time needed to fit the replacements, as well as reducing waste. This will also reduce maintenance needs as there are less likely to be faults with the equipment, and also greatly reduce, or even eliminate, any expensive manufacturing downtime due to faults or repairs.

Cleaning of equipment can also be reduced in some cases as a PTFE coat is non-wetting, facilitating self-cleaning of parts.

And Teflon textile finishes can even help the environment, because, when applied to fabric, the finish will repel water and oil stains, reducing the need to use dry cleaning, and fabrics will also dry more quickly, using less energy with tumble drying, and last longer due to reduced wear.

With the added advantages that PTFE is non-toxic, has only a minor contraindication for humans from polymer fume fever (only if the temperature of any Teflon-coated pans reaches 260 degrees C) and is FDA approved and food-safe, this material really is of great benefit in many different areas.

INTERESTING USES OF PTFE

As well as coating everything from pans to bearings, PTFE is also used to stop insects climbing walls as the material is so ‘non-stick’ that insects (and even geckos) are unable to grip.

The polymer is used frequently as a coating on catheters to inhibit bacteria and infections and is also used as a graft material in surgery.

You’ll have heard of Gore-Tex, and it’s PTFE again, this time as a thin, porous membrane to make breathable rain wear, or for medical implants, wiring insulation and sealants.

Bearing in mind that PTFE was discovered by happy accident in 1938, it’s difficult to imagine our world today without it.

If you’re interested in using PTFE for any of your projects, or if you’d like to find out more information about the properties of PTFE, please do get in touch and we’d be happy to talk you through your options.

Tags:PTFE,Polytetrafluoroethylene

PTFE A Miracle Material Evolves

Since its discovery nearly 80 years ago, polytetrafluoroethylene (PTFE), has become one of the world’s most versatile and useful materials. Originally used for military applications, it can now be found in many other applications, such as a non-stick coating for cookware. Approximately half of the PTFE resins produced today go into aircraft wiring and computer-related products such as semiconductor fabrication equipment and printed circuit boards. It is also used extensively in the pharmaceutical and valve industries due to its chemical inertness and thermal properties.

PTFE is constructed of carbon and fluorine molecules which, when combined, produce a compound with a high molecular weight that possesses excellent insulating properties, resists moisture, can withstand both hot and cold temperature extremes and have an extremely low coefficient of friction. These properties make it suitable for numerous applications in the medical device, aerospace, oil and gas, electronics and chemical processing industries.

Types of PTFE

There are four general types of granular PTFE material: virgin, modified, reprocessed and filled. Virgin PTFE, as the term implies, is the purest form of the material. Modified PTFE is a copolymer resin manufactured by adding a small percentage of a melt processable fluoropolymer to enhance the final product. Reprocessed PTFE is made from reclaimed virgin PTFE scraps that have been chopped, cleaned and pelletized for reuse. Filled or compounded PTFE is virgin or modified material blended with various types and proportions of fillers to add strength, abrasiveness, lubricity, color or other desired characteristics

Virgin PTFE is excellent for applications requiring high purity, mechanical performance or superior electrical properties. Premium virgin PTFE resins are used to make products such as semiconductor equipment components, pharmaceutical valve liners, gaskets for the chemical industry and components subject to FDA compliance such as gas-line manifolds, filtration housings and others. Reprocessed PTFE is typically used for cost savings in applications not requiring the proprieties associated with a premium PTFE such as flange gaskets. Modified PTFE offers weldability and improves deformation characteristics. It also has greater resistance to permeation of chemicals and exhibits a higher dielectric breakdown voltage.

Fillers

There are a number of standard fillers for enhancing the performance of PTFE while maintaining some of its basic properties. Glass fiber is added to increase compressive strength, rigidity and wear and reduce creep and cold flow in sealing applications. There is minimal effect on chemical and electrical properties.

Carbon increases compressive strength, hardness, wear and load properties, and provides good chemical resistance. Often, carbon and graphite are combined as fillers to further increase strength and reduce friction and initial wear. Carbon fillers can also be added in various loadings to make the product conductive or static dissipative.

Molybdenum sulfide increases hardness, rigidity and wear, and like glass fiber has little effect on chemical and electrical properties. Bronze fillers are often added to increase hardness, wear resistance, compressive strength and dimensional stability required for bushing or bearing applications. However, it is not recommended for corrosive or electrical applications. In addition to these fillers that enhance mechanical properties, pigments can be added for identification, visibility or branding purposes.

Molding methods

PTFE material and products are produced by a variety of molding methods, including compression, isostatic, automatic compression and granular ram and fine powder extrusion. Compression molding and extruding granular PTFE are the most common methods used in forming component parts for machining. Sheets, rods and cylinders are typically processed using a mold that is close to the finished part dimensions, minimizing clean-up during the machining process. Cylinders and rods also can be customized in length to meet component dimensions or to maximize yield.

In compression molding, granulated PTFE is poured into a mold and compressed to yield a sheet, solid rod, cylinder or tube. After removal from the mold, the material is sintered or cured in an oven. In isostatic molding, granulated PTFE is poured into a near-net mold surrounded by a rubber bladder. Unified air or water pressure is then applied to the entire mold to form the near-net shape. The shape exits the mold in a green state and too must be cured. Unified pressures applied to all areas of the mold result in highly uniform and consistent density throughout, which is important when tight tolerances and consistency are required. This process lends itself to producing more complex components for machining in the form of tapered sleeves, closed-end cylinders or buckets and even parts with appendages. Because this process molds parts to near-net shape, it uses significantly less material than the more conventional use of blocks and cylinders.

Automatic compression or auto molding involves a press with a custom mold configuration to form finished or near-net-shape parts requiring a secondary machining operation. Granulated PTFE is placed into a single- or multi-cavity mold, compressed to produce a part and released. Finished and semi-finished parts produced by this method likewise require curing. This process allows a wide variety of shapes and geometries to be produced in volume where tight tolerances are not required, thus minimizing or eliminating the need for machining. This process also reduces stress defects in parts as well as machine scrap.

In granular ram extrusion, granular PTFE powders are poured into a hopper then extruded through mold with an OD (outside diameter) to produce a rod or an OD/ID (inside diameter) pin to produce a tube. As the material is forced through the extruder die, heat and pressure are applied simultaneously, so it exits the extruder completely cured.

In fine powder extrusion, the PTFE is blended with a surfactant and compressed into a small billet or charge, which is then forced through a small orifice and extruded into PTFE tape, film, tube or custom shape. The material exiting the die can be either sintered or unsintered depending on the final product or application.

Sintering/annealing

As noted above, sintering cures the PTFE, converting it from a compressed or “green” state to a solid state. Sintering cycles are customized depending on the thickness and length of the material, type of material (virgin, filled, modified, etc.) as well as the overall size. The product is typically placed into an oven in a freestanding state. The oven is heated in a controlled manner to ensure even transition of the polymer through the melt point of 621°F/327°C. The maximum temperature is held for a prescribed length of time to ensure complete bonding of the polymer. The temperature is then brought down to ambient by a controlled cool down which controls the crystallinity of the molding. These steps are just as important as the initial compression molding as they affect the microporosity and crystalline structure of the finished article.

If extremely tight tolerances are required for the finished component, annealing (also known as stress relieving), is often required to stabilize the material. This process involves placing the sintered material into an oven and applying a controlled heat to the molding that exceeds the service temperature of the finished part. The molded shape is held at this temperature for a calculated period of time, after which the temperature is slowly brought back down to ambient. The material is not heated past the melt temperature of the polymer during this process.

Products/applications

There are many applications in multiple industries for the various forms of PTFE. Valve manufacturers use machined virgin and filled PTFE valve seats, seals and O-rings. Depending on the type of valve, the manufacturer may also use machined virgin or filled PTFE valve liners.

Chemical companies use molded and skived virgin PTFE sheet to line tanks containing corrosive materials. Chemical plants also use large quantities of PTFE-based gaskets.

Semiconductor equipment manufacturers use virgin PTFE machined components in the equipment that processes silicon wafers prior to becoming computer chips. These include gas line manifolds, specialty parts exposed to corrosive materials and seals, among others.

The aerospace industry as noted uses large volumes of virgin and pigmented PTFE tape for insulating aircraft wiring. The pigmentation is primarily for identification purposes for various types of wiring construction. The pharmaceutical industry uses large amounts of thin-wall extruded tubing, thin films, fiber and machined parts made of different forms of PTFE.

In addition to these products, PTFE is used in the production of flange gaskets for industrial piping systems, envelope gaskets, machined O-rings and spring-loaded seals. It is also used for manufacturing films for preserving historical artifacts and fibers for everything from dental floss to architectural membranes for stadium roofs.

In summary, different types of PTFE are available to meet the performance and economic requirements of a wide range of products and applications. Its unique properties can be enhanced with the addition of fillers, and it can be molded and machined into precision components. In addition, the material has been reformulated to make it more environmentally friendly while maintaining its basic characteristics — the characteristics that made it a miracle material when it was discovered in 1938 and still make it one today.

Tags:PTFE,Teflon,PTFE evolves,Teflon evolves

Will PTFE be the next 3D printable material?

The range of available materials is one of the key hurdles to adoption for industrial 3D printing. 3D printing is being rapidly adopted by product manufacturers all around the world, but it still can't compete with many other manufacturing techniques with respect to material diversity. A large number of the most commonly used industrial plastics still aren't widely available for 3D printers, making 3D printing unsuitable for many applications.

A full discussion of materials available for 3D printing and the remaining white spaces can be found in the IDTechEx research report 3D Printing Materials 2016-2026   Industrial polymer giants, 3M, have just widened the range. Through a new patent-pending technology they have successfully 3D printed fully-fluorinated PTFE polymers. Polymer specialist 3M, including its subsidiaries Dyneon GmbH and Dyneon B.V., is one of the world's leading manufacturers of PTFE and similar materials such as fluoroelastomers and fluorothermoplastics. It makes sense for them to be looking to expand into the 3D printed space.  

PTFE (polytetrafluoroethylene) is an extremely useful material, used in many everyday products. It is very hydrophobic, meaning that neither water nor water-containing substances make it wet, so it is used in outdoor clothing. It also has one of the lowest friction coefficients of any solid. It is the only surface a gecko cannot stick to. This property makes it perfect for non-stick coatings for bakeware. Bacteria and other microbes also have a very hard time adhering to the material, making it a very good option for various hospital applications, such as catheters.  

Other fluoropolymers are also heavily used in the oil and gas, chemical, automotive and aerospace industries, and it is possible that the same 3D printing technology could be applied to them. This breakthrough makes it possible to 3D print a whole new class of materials, which will influence many industries.  

Normally, parts made from PTFE and other fluoropolymers are manufactured using expensive traditional processing techniques, which typically create a lot of waste. It is also difficult to create very complex structures. 3D printing has the potential to offer more sustainable manufacturing and a wider variety of designs. The breakthrough is already paving the way for previously impossible applications.  

IDTechEx have been wondering how long it will take for more plastics to become available for 3D printing. The range is currently very limited, but new materials are becoming available all the time. Wacker, with their ACEO brand, recently launched a machine to 3D print silicone, which they will be demonstrating at IDTechEx Show!   3M are looking to offer print-on-demand solutions for spare and custom parts. In particular, this fluoropolymer 3D printing service would be used for parts with particularly complex geometries. This "service bureau" business model is becoming increasingly common as the technologies to print the materials become more complicated and the materials become more difficult to handle. Anyone can extrude PLA at home, so companies can sell thermoplastic extruders. Companies like Organovo offering 3D cell printing or Impossible Objects offering carbon fibre reinforced plastic 3D printing, have complicated equipment, which they keep in house, and sell parts they produce.
Tags: 3Dprint,PTFE

POLYCHLOROTRIFLUOROETHYLENE (PCTFE OR PTFCE) PROPERTIES & APPLICATIONS

Polychlorotrifluoroethylene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer with the molecular formula (CF2CClF)n, where nis the number of monomer units in the polymer molecule. It is similar to polytetrafluoroethene (PTFE), except that it is a homopolymerof the monomer chlorotrifluoroethylene (CTFE) instead of tetrafluoroethene. It has the lowest water vapor transmission rate of any plastic. 

Properties:PCTFE has high tensile strength and good thermal characteristics. It is nonflammable and the heat resistance is up to 175 °C. It has a low coefficient of thermal expansion. The glass transition temperature (Tg) is around 45 °C. 

PCTFE has one of the highest limiting oxygen index (LOI). It has good chemical resistance. It also exhibits properties like zero moisture absorption and non wetting. 

It does not absorb visible light. When subjected to high-energy radiation, it undergoes, like PTFE, degradation. It can be used as a transparent film. 

The presence of a chlorine atom, having greater atomic radius than that of fluorine, hinders the close packing possible in PTFE. This results in having a relatively lower melting point among fluoropolymers, around 210–215 °C. 

PCTFE is resistant to the attack by most chemicals and oxidizing agents, a property exhibited due to the presence of high fluorine content. However, it swells slightly in halocarbon compounds, ethers, esters and aromatic solvents. PCTFE is resistant to oxidation because it does not have any hydrogen atoms. 

PCTFE exhibits a permanent dipole moment due to the molecular asymmetry of its repeating unit. This dipole moment is perpendicular to the carbon-chain axis. 

Appliciations:PCTFE finds majority of its application due to two main properties: water repulsion and chemical stability. PCTFE films are used as a protective layer against moisture. These include:

• moisture barrier in pharmaceutical blister packaging,

• water-vapour barrier for protecting phosphor coatings in electroluminescent lamps (the phosphor chemicals are sensitive to moisture),

• protection of liquid-crystal display (LCD) panels, which are sensitive to moisture.

Due to its chemical stability, it acts as a protective barrier against chemicals. It is used as a coating and prefabricated liner for chemical applications. PCTFE is also used for laminating other polymers like PVC, polypropylene, PETG, APET etc. It is also used in transparent eyeglasses, tubes, valves, chemical tank liners, O-rings, seals and gaskets. 

PCTFE is used to protect sensitive electronic components because of its excellent electrical resistance and water repulsion. Other uses include flexible printed circuits and insulation of wires and cables. 

Low-molecular-weight PCTFE waxes, oils and greases find their application as inert sealants and lubricants. They are also used as gyroscope flotation fluids and plasticizers for thermoplastics. 

Tags: PCTFE PTFCE

Polyether ether ketone (PEEK) Properties

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications. It was originally introduced by Victrex PLC, then Imperial Chemical Industries (ICI) in the early 1980s.

Properties:PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. The processing conditions used to mold PEEK can influence the crystallinity and hence the mechanical properties. The Young's modulus is 3.6 GPa and its tensile strength 90 to 100 MPa.

PEEK has a glass transition temperature of around 143 °C (289 °F) and melts around 343 °C (662 °F). Some grades have a useful operating temperature of up to 250 °C (482 °F).

The thermal conductivity increases nearly linearly with temperature between room temperature and solidus temperature. It is highly resistant to thermal degradation, as well as to attack by both organic and aqueous environments. It is attacked by halogens and strong Bronsted and Lewis acids, as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It is soluble in concentrated sulfuric acid at room temperature, although dissolution can take a very long time unless the polymer is in a form with a high surface-area-to-volume ratio, such as a fine powder or thin film. It has high resistance to biodegradation.


PEEK is finding increased use in spinal fusion devices and reinforcing rods. It is extensively used in the aerospace, automotive, and chemical process industries. PEEK seals and manifolds are commonly used in fluid applications. PEEK also performs well in applications where continuous high temperatures (up to 500 °F/260 °C) are common.