Polytetrafluoroethylene

Polytetrafluoroethylene. It is a synthetic fluoropolymer of tetrafluoroethylene, renowned for its exceptional chemical resistance and low friction. This high-molecular-weight compound consists wholly of carbon and fluorine, forming one of the strongest single bonds in organic chemistry. Its discovery revolutionized materials science, leading to widespread use in industries from aerospace to cookware.

Properties

The material exhibits extreme inertness, resisting attack by nearly all chemicals, including potent agents like aqua regia and chlorine trifluoride. It possesses one of the lowest coefficients of friction against any solid, a property leveraged in non-stick applications. Its high melting point, around 327°C, and excellent dielectric strength make it valuable in electrical insulation, as seen in components for the Manhattan Project. The polymer is also highly hydrophobic, a trait utilized in functional textiles like Gore-Tex.

History

The compound was accidentally discovered in 1938 by Roy J. Plunkett while working for Kinetic Chemicals, a joint venture of General Motors and DuPont. Plunkett was researching new refrigerants when he found a white, waxy solid inside a pressurized cylinder of tetrafluoroethylene gas. This serendipitous finding was patented by DuPont, which later trademarked the name Teflon. Its first significant use was as a corrosion-resistant sealant in the Manhattan Project, specifically for handling uranium hexafluoride at facilities like Oak Ridge National Laboratory.

Production

Industrial synthesis typically occurs via free-radical polymerization of tetrafluoroethylene, often using initiators like ammonium persulfate or disuccinoyl peroxide. The process can be conducted in aqueous media, yielding granular forms, or using surfactants to produce dispersions. Major manufacturers include Chemours (a 2015 spin-off from DuPont), Daikin Industries of Japan, and Gujarat Fluorochemicals in India. The polymerization reaction is highly exothermic and requires careful control to prevent runaway reactions, a concern addressed in modern plants like those operated by 3M.

Applications

Its primary use is as a non-stick coating for cookware and bakeware, a market dominated by the Teflon brand. In the aerospace industry, it is used in wire insulation for aircraft, such as those produced by Boeing and Airbus. The medical field employs it in implantable devices like vascular grafts and catheters, benefiting from its biocompatibility. It is also critical in industrial sealing, forming the basis for Garlock Sealing Technologies gaskets and John Crane mechanical seals used in petrochemical refineries.

Safety and environmental concerns

A significant issue involves perfluorooctanoic acid (PFOA), historically used as a processing aid in its manufacture. PFOA has been linked to health risks, leading to legal actions and the 2006 U.S. Environmental Protection Agency stewardship program with eight major companies, including DuPont and Daikin Industries. Thermal degradation above 260°C can release toxic fumes, a hazard noted by organizations like the National Institute for Occupational Safety and Health. While the polymer itself is inert, its persistence in the environment and role in per- and polyfluoroalkyl substances contamination are subjects of ongoing research by agencies such as the European Chemicals Agency.

Category:Fluoropolymers Category:DuPont Category:Plastics