Poly(tetrafluoroethylene) Chemische Eigenschaften,Einsatz,Produktion Methoden
R-S?tze Betriebsanweisung:
R41:Gefahr ernster Augensch?den.
R36/38:Reizt die Augen und die Haut.
R45:Kann Krebs erzeugen.
S-S?tze Betriebsanweisung:
S26:Bei Berührung mit den Augen sofort gründlich mit Wasser abspülen und Arzt konsultieren.
S39:Schutzbrille/Gesichtsschutz tragen.
S24/25:Berührung mit den Augen und der Haut vermeiden.
S45:Bei Unfall oder Unwohlsein sofort Arzt zuziehen (wenn m?glich, dieses Etikett vorzeigen).
S22:Staub nicht einatmen.
S53:Exposition vermeiden - vor Gebrauch besondere Anweisungen einholen.
S23:Gas/Rauch/Dampf/Aerosol nicht einatmen(geeignete Bezeichnung(en) vom Hersteller anzugeben).
Beschreibung
Tetrafl uoroethylene (TFE), also known as perfl uoroethylene, is a colorless, fl ammable, toxic gas. It is the monomer used for polytetrafl uoroethylene (PTFE), which is sold under the DuPont tradename of Tefl on. TFE is co-polymerized with other compounds to produce a variety of Tefl ons. TFE is produced by heating chlorodifl uoromethane (CHClF2, Freon-22) or trifl uoromethane (CHF3, Freon-23). TFE is used almost exclusively as a monomer in the production of PTFE. PTFE is a vinyl polymer, which means it is made from a monomer with carbon-carbon double bonds. PTFE is made from TFE by free radical polymerization.
PTFE’s unique physical properties are due to its chemical structure. PTFE consists of long
chains of carbon atoms surrounded by fluorine atoms. The fluorine atoms act as a protective
barrier that shields the carbon-carbon bond from chemical attack. The fluorine atoms repel
other atoms, making it diffi cult for anything to stick to PTFE. PTFE resins have very low
coeffi cients of friction (< 0.1). The strong fluorine-to-carbon bonds and high electronegativity
of fluorine make PTFE very stable. The long chains of PTFE pack closely together to give
a dense crystalline solid. The packing, which can be compared to stacking boards, produces
little cross-linking.
Chemische Eigenschaften
white powder, or white solid with a slippery feel
History
The polymerized form of TFE was discovered accidentally by researchers at DuPont in 1938. During the mid-1930s, DuPont was investigating the development of new chlorofl uorocarbons (CFCs) for use as refrigerants. DuPont joined with General Motors to form a company called Kinetic Chemicals to combine their efforts in this area. Plunkett examined the properties of the substance. He discovered that the substance was inert to other chemicals, had a high melting point, and was very slippery. Plunkett also worked on duplicating the conditions necessary to produce it from TFE. He applied for a patent for polytetrafl uoroethylene polymers in 1939, which was granted in 1941 (U.S. Patent 2230654). He assigned the patent to Kinetic Chemicals. DuPont registered the term Tefl on in 1945 and introduced Tefl on products the next year.
Teflon is best known for its use in cookware, but its use in this area followed original industrial
applications in gaskets, sealers, tape, and electrical insulation. Th ese applications were a
direct result of the use of PTFE for military purposes during World War II.
Verwenden
Poly(tetrafluoroethylene) is used in hundreds of applications in addition to cookware. Poly(tetrafluoroethylene) is used in inks, plastics, coatings, and lubricants.Poly(tetrafluoroethylene) can be molded into gaskets, seals, bearings, gears, and other machine parts. Poly(tetrafluoroethylene) is used as liners, insulation, membranes, and adhesives. Tefl on tape is commonly used in plumbing work. Poly(tetrafluoroethylene) is used to produce rainproof garments.
Definition
ChEBI: A polymer composed of repeating tetrafluoroethyl groups.
synthetische
The preferred commercial method of preparation of polytetrafluoroethylene
(PTFE) is by suspension polymerization. The details of the procedures
employed have not been disclosed but it appears that two main processes are
in use. In the first process, the conventional techniques of suspension polymerization are used to produce a granular product suitable for moulding and
extrusion. The tetrafluoroethylene is polymerized under pressure in stainless
steel autoclaves with a free radical initiator such as ammonium persulphate.
The reaction is rapid and exothermic and requires careful control. The
polymer granules are collected, washed and dried. In the second process,
conditions are adjusted to give a dispersion of polymer of much finer particle
size and lower molecular weight. The product may be stabilized and employed in latex form in such uses as film casting, coating and impregnation of
fibres. Alternatively, the product may be coagulated to give a powder (often
called 'dispersion polymer') used mainly for the extrusion of thin flexible
sections.
Vorbereitung Methode
Polytetrafluoroethylene is generally made from tetrafluoroethylene
gas by free-radical polymerization under pressure
with oxygen, peroxides, or peroxydisulfates. The “granular
resins” have medium-size particles that range from 30 to
600 mm. Colloidal aqueous dispersions, made by a different
process, are concentrated to about 60% by weight of the
polymer and have particles that average about 0.2 mm.
Coagulated dispersions with agglomerates that average
450mm are also available .
The use of PTFE as a release agent in coatings and certain
other food contact applications is permitted under FDA
regulations .
Allgemeine Beschreibung
Poly(tetrafluoroethylene) is a fluoropolymer that is commercially known as PTFE. Its properties include high thermal stability, excellent chemical resistance, low dielectric constant and low surface energy. It is a hydrophobic polymer that is majorly used as a protective coating on the metal surface.
Hazard
Evolves toxic fumes on heating. Question-
able carcinogen.
Health Hazard
Fumes of heated polytetrafluoroethylene (PTFE) cause polymer fume fever,
an influenza-like syndrome.
Industrielle Verwendung
The polymer is insoluble, resistant to heat (upto 275°C) and chemical attack, and, in addition,has the lowest coefficient of friction of any solid.Because of its resistance to heat, the fabricationof polytetrafluoroethylene requires modificationof conventional methods. After molding thepowdered polymer using a cold press, the moldingsare sintered at 360 to 400°C by proceduressimilar to those used in powder metallurgy. Thesintered product can be machined or punched.Extrusion is possible if the powder is compoundedwith a lubricating material. Aqueoussuspensions of the polymer can also be used forcoating various articles. However, special surfacetreatments are required to ensure adhesionbecause polytetrafluoroethylene does not adherewell to anything.
Polytetrafluoroethylene (TFE resin) is usefulfor applications under extreme conditions ofheat and chemical activity. Polytetrafluoroethylenebearings, valve seats, packings, gaskets,coatings, and tubing can withstand relativelysevere conditions. Fillers such as carbon, inorganicfibers, and metal powders may be incorporatedto modify the mechanical and thermalproperties.
Because of its excellent electrical properties,polytetrafluoroethylene is useful when adielectric material is required for service at ahigh temperature. The nonadhesive quality isoften turned to advantage in the use of polytetrafluoroethyleneto coat articles such as rollsand cookware to which materials might otherwiseadhere.
Sicherheitsprofil
The finished polymerized compound is inert under ordinary condtions. There have been reports of “polymer fume fever” in humansexposed to pyrolysis products, whch also are irritants. Smohng should be prohibited in areas where ths material is being fabricated or, in general, where there may be dust from it. Exposure to pyrolysis or decomposition products appears to be the chief health-related problem. Questionable carcinogen with experimental tumorigenic data by implant. Incompatible with fluorine, sodmm potassium alloy. Under the proper conditions it undergoes hazardous reactions with boron, magnesium, or titanium. When heated to above 750°F it decomposes to yield highly toxic fumes of F-.
Carcinogenicity
Animal studies have not demonstrated
that this polymer is carcinogenic. No data are
available in humans. The polymer is not classifiable as to
its human carcinogenicity. However, the EPA found that
perfluorooctanoic acid (PFOA), a chemical used to produce
PTEE is a “l(fā)ikely carcinogen.
Environmental Fate
PTFE is the most stable of all TFE polymers and under physiological
conditions does not release any components (IARC
Monograph 74, 1999). PTFE is very inert chemically; only alkali
metals and fluorine under pressure attack PTFE (Hazardous
Substances Data Bank (HSDB)). There are no known ecotoxicological
effects for PTFE (DuPont MSDS, 2011).
Poly(tetrafluoroethylene) Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
