Fluoropolymers
Fluoropolymers: are a family of high-performance plastics. The best known member of this family is called PTFE. PTFE is one of the smoothest materials around, and very tough!
- History
- Properties
- Applications
- Processes
- Recycling
- Faq
History
The story of Fluoropolymers began on April 6, 1938, at DuPont's Jackson Laboratory in New Jersey. Dr. Roy J. Plunkett’s first assignment at DuPont was researching new chlorofluorocarbon refrigerants. Plunkett had produced 100 pounds of tetrafluoroethylene gas (TFE) and stored it in small cylinders at very low temperatures preparatory to chlorinating it. When he and his helper prepared a cylinder for use, none of the gas came out—yet the cylinder weighed the same as before. They opened it and found a white powder, which Plunkett had the presence of mind to characterise. He found the substance to be heat resistant and chemically inert and to have very low surface friction.
PTFE is inert to virtually all chemicals and is considered the most slippery material in existence. These properties have made it one of the most valuable and versatile materials ever invented, contributing to significant advancement in areas such as aerospace, communications, electronics, industrial processes and architecture.
PTFE has become recognised worldwide for the superior non-stick properties associated with its use as a coating on cookware and as a soil and stain repellent for fabrics and textile products.
Following the discovery of PTFE a large family of other fluoropolymers has been developed. The introduction of the combination of fluorinated or non fluorinated monomers allowed the industry to design a large number of different polymers with a wide range of processing and use temperatures.
Properties
Applications for fluoropolymers are driven by their superior physical and chemical properties.
Chemical Inertness
Fluoropolymers are used in harsh environments where their chemical resistance has made them very useful in the many industrial processes such as linings for vessels and piping, fly ash collector bags, gasket packing, semiconductor equipment, carrier materials, chemical tanks and as packing for lithium-ion batteries.
High Dielectric
The dielectric properties of these unique polymers have made possible the miniaturisation of circuit boards. This concept is responsible for the very latest in high-speed, high-frequency radar and communications found in the newest defence systems as well as in the next generation of ultra high speed computers.
Flame Retardancy
Fluoropolymers meet exacting industry standards in relation to electrical properties and flame retardancy. Examples of these applications are wire coating (robots, personal computers, communication industry, response to high frequencies, electrical systems in aircraft, etc.) fibre optics, cable coating and electrical and electronic components.
Low Friction
Fluoropolymers exhibit very low coefficients of friction. For example PTFE is uniquely used as bearing pads for bridges. Where this characteristic is used in abrasive environments inert fillers are often added to improve their abrasion resistance. For example high performance automotive and aircraft bearings and seals are now commonly made from fluoropolymers.
Non Stick
Fluoropolymers are used in everyday life as their unique characteristics offer advantages. They are used in household kitchenware coatings (pans, rice cookers, knives etc.), fixed rolls for printers, parts for transferring paper in photocopiers.
Weatherability
The performance of fluoropolymers does not deteriorate significantly in an outdoor environment. They are suitable for use over long periods of time without maintenance. They are used in architectural applications, as films for greenhouse applications, photovoltaic cell film cover and UV resistant paints.
Inertness and Barrier Properties
The bio-medical field uses fluoropolymers in devices such as catheters and other parts with which to perform diagnostic and therapeutic procedures. Fluoropolymers’ superior barrier properties are exploited in pharmaceutical packaging where their high resistance to moisture protects pharmaceutical products. Fluoropolymers have a high resistance to gasoline and this property is exploited in parts manufactured for the automotive industry.
Applications
Fluoropolymers are used in:
- High-performance automotive and aircraft bearings and seals, to improve the performance and safety of aircraft and automobiles
- Flame retardants, to reduce fire risk in high-rise buildings and reduce industrial and automotive pollution
- Coatings on many kitchen products, such as pots, pans, knives, spatulas etc. thanks to their high thermal stability and non-stick properties
- The linings of piping and chemical tanks, and in packing for lithium-ion batteries, thanks to their ability to handle harsh environments
- Cable coating in the telecommunications and computer industries, because of their high electrical resistance and good dielectric properties
- Implantable parts and catheters for bio-medical applications, because of their resistance to chemicals
Processes
PTFE is used here as an example of fluoropolymer manufacture.
(PTFE is a polymer made of long, linear polymer chains containing only carbon and fluorine atoms. This gives the polymer its exceptional properties. It is produced from tetrafluoroethylene (TFE) which is the starting material (called a monomer). TFE is made in several steps starting from common salt (sodium chloride NaCl), methane and from an ore called fluorspar. TFE gas is introduced into a closed vessel under pressure and is polymerised using a catalyst to form very long chains. Polymerisation reactions are often initiated with active molecules called "free radicals”. Radical initiated reactions can run very fast and give out a great deal of heat. To prevent such reactions running out of control, the reaction vessels are water cooled; even so, great care must be taken not to allow reaction conditions to become unstable. As well as temperature control, polymer chemists can modify reaction conditions by the use of chemicals (chain transfer agents) and can modify the polymer itself by the use of different comonomers to produce copolymers.
Recycling
Recovery
Fluoropolymers are usually employed in small components in specific complex applications such as electronic equipment, transport (cars, trains and airplanes) or as very thin layer coatings on fabrics and metals. Where sufficient quantities of fluoropolymers can be recovered and may be sufficient to warrant recycling then they should be shipped to specialist recyclers.
A very substantial market exists for recovered fluoropolymers as low friction additives to other materials. For example PTFE is typically ground into fine powders and used in such products as inks and paints.
Disposal
Fluoropolymer waste should be incinerated in authorised incinerators. Preferably, non-recyclable fluoropolymers should be sent to incinerators with energy recovery. Disposal in authorised landfills is also acceptable.
