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 evolve,Teflon evolve

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:3D print,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

Moldmaker & Molding Process

A moldmaker (mouldmaker in British English) or molder is a skilled trades worker who makes molds for use in metalworking and other manufacturing industries. It is sometimes regarded as a variety of the trade of the toolmaker.
Moldmakers are generally employed in foundries, where molds are used to cast products from metals such as aluminium and cast iron. Moldmakers may also be employed in the plastics, rubber or ceramics industries. The process of manufacturing molds is now often highly automated.
While much of the machining processes involved in mold making use computer-controlled equipment for the actual manufacturing of molds (particularly plastic and rubber injection and transfer). Moldmaking is still a highly skilled trade requiring expertise in manual machining, CNC machining, CNC wire EDM, CNC Ram EDM, surface grinding, hand polishing and more. Because of the high skill and intense labor involved much of the mold making in the US has been outsourced to low wage countries. The majority of plastic and rubber parts that are in existence today are made using injection or transfer molds- requiring a mold to be manufactured by a moldmaker. The actual molding process is very highly automated.
Molding or moulding (see spelling differences) is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have been made using a pattern or model of the final object.
A mold or mould is a hollowed-out block that is filled with a liquid or pliable material such as plastic, glass, metal, or ceramic raw material. The liquid hardens or sets inside the mold, adopting its shape. A mold is the counterpart to a cast. The very common bi-valve molding process uses two molds, one for each half of the object. Articulated moulds have multiple pieces that come together to form the complete mold, and then disassemble to release the finished casting; they are expensive, but necessary when the casting shape has complex overhangs.Piece-molding uses a number of different molds, each creating a section of a complicated object. This is generally only used for larger and more valuable objects.
A manufacturer who makes molds is called a moldmaker. A release agent is typically used to make removal of the hardened/set substance from the mold easily. Typical uses for molded plastics include molded furniture, molded household goods, molded cases, and structural materials.

Plastic forming machine

A plastic forming machine, or plastic molding machine, is developed on the basis of rubber machinery and metal die-casting machine. Since the polymer injection molding process and molding equipment in the 1870s, as an industry, plastic forming machines were rapidly developed until the 1930s, with the gradual commercialization of plastic molding equipment, injection molding and extrusion molding became the most common industrialized processing methods. Blow molding is the third-largest plastic molding method after the injection molding and extrusion blow molding method, it is also the fastest development of plastic molding method.
Forming the parison firstly, with compressed air (and tensile rod) to the radial Inflation (axial stretch) type blank, to make it close to (stretch) the blow molding cavity, then the cavity shape and size are given to the plastic products and make it cool.
Types of plastic forming machine
Plastic injection molding machine is called usually injection molding machine for short,using the injection and molding method. Plastic injection molding of thermoplastics and thermosetting plastics made from a variety of plastic products molding equipment.
To plastic extrusion machine, plastic extruder is usually called the host, and its follow-up equipments are called the plastic auxiliary equipments. With about 100 years of development, plastic extruder derived from single screw to twin-screw, multi screw or no screw and other models. Plastic extruder (the host) can match with the pipe, film, holding materials, monofilament, flat, packing tape, crowded network, plate (sheet) material, profile, granulation, cable coating and other kinds of plastic molding auxiliary equipment, composed of a variety of plastic extrusion production lines, to produce various plastic products. Therefore, either now or in the future, plastic extrusion machine are used widely in plastics processing industry.
Plastic blow molding machine is also called blow molding machine for short. The process of blow molding has two basic steps.

Plastics Extrusion Products & Type

Plastics extrusion commonly uses plastic chips or pellets, which are usually dried, to drive out moisture, in a hopper before going to the feed screw. The polymer resin is heated to molten state by a combination of heating elements and shear heating from the extrusion screw. The screw, or screws as the case with twin screw extrusion, forces the resin through a die, forming the resin into the desired shape. The extrudate is cooled and solidified as it is pulled through the die or water tank.
A “caterpillar haul-off” (called a “puller” in the US) is used to provide tension on the extrusion line which is essential for overall quality of the extrudate. Pelletizers can also create this tension while pulling extruded strands in to be cut. The caterpillar haul-off must provide a consistent pull; otherwise, variation in cut lengths or distorted product will result. In some cases (such as fibre-reinforced tubes) the extrudate is pulled through a very long die, in a process called “pultrusion”. The configuration of the interior screws are a driving force dependent on the application.
Mixing elements or convey elements are used in various formations. Extrusion is common in the application of adding colorant to molten plastic thus creating specific custom color.
A multitude of polymers are used in the production of plastic tubing, pipes, rods, rails, seals, and sheets or films.
Type:Blown film extrusion;Sheet/film extrusion;Tubing extrusion;Over jacketing extrusion;Coextrusion;Extrusion coating
A great advantage of extrusion is that profiles such as pipes can be made to any length. If the material is sufficiently flexible, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal.

Engineering plastic properties & list

Engineering plastics are a group of plastic materials that have better mechanical and/or thermal properties than the more widely used commodity plastics (such as polystyrene, PVC, polypropylene and polyethylene).
Being more expensive, engineering plastics are produced in lower quantities and tend to be used for smaller objects or low-volume applications (such as mechanical parts), rather than for bulk and high-volume ends (like containers and packaging).
The term usually refers to thermoplastic materials rather than thermosetting ones. Examples of engineering plastics include acrylonitrile butadiene styrene (ABS), used for car bumpers, dashboard trim and Lego bricks; polycarbonates, used in motorcycle helmets; and polyamides (nylons), used for skis and ski boots.
Engineering plastics have gradually replaced traditional engineering materials such as wood or metal in many applications. Besides equalling or surpassing them in weight/strength and other properties, engineering plastics are much easier to manufacture, especially in complicated shapes.
Each engineering plastic usually has a unique combination of properties that may make it the material of choice for some application. For example, polycarbonates are highly resistant to impact, while polyamides are highly resistant to abrasion. Other properties exhibited by various grades of engineering plastics include heat resistance, mechanical strength, rigidity, chemical stability, self lubrication (specially used in manufacturing of gears & skids) and fire safety.
List of engineering plastics:
Acrylonitrile butadiene styrene (ABS);Nylon 6;Nylon 6-6;Polyamides (PA);Polybutylene terephthalate (PBT);Polycarbonates (PC);Polyetheretherketone (PEEK);Polyetherketone (PEK);Polyethylene terephthalate (PET);Polyimides;Polyoxymethylene plastic (POM / Acetal);Polyphenylene sulfide (PPS);Polyphenylene oxide (PPO);Polysulphone (PSU);Polytetrafluoroethylene (PTFE / Teflon).