Newsgroup: it.discussioni.energie-alternative
Titolo: TEFLON===> Cancerogeno!

Ho letto questa notizia e mi ha lasciato perplesso.
Mi sembra che venga usata in tanti settori.
Dalle padelle alle racchette da tennis!  :-o 

 
ah...ma il teflon ha a che fare con le energie alternative?



Non credo ;)
Però la lettura di 
http://www.corriere.it/Primo_Piano/Scienze_e_Tecnologie/2006/01_Gennaio/26/teflon.shtml
 
è comunque utile
-- 
Ciao, Adriano
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Togli "rosso" per contatto privato

Si parla di acido perfluoroctanoico (Pfoa)usato nella teflonatura delle 
padelle.
il teflon altresi' ptfe politetrafluoroetilene e' un'altra cosa molto 
diversa.
Questi sono i facili allarmismi dei verdi. :-)

 diversa.
Ecco!
Scusatemi se ho postato qui, credevo che il teflon venisse usato in alcune 
caldaie e alcuni materiali edilizi.
Però la risposta di revenge cambia le carte in tavola:
puoi spiegarci meglio i concetti a noi profani?
Dobbiamo buttare solamente le padelle antiaderenti o altre cose tipo i ferri 
da stiro con piastra in teflon???
Grazie mille 

Eccomi mi sono dimenticato....la teflonatura antiaderente della gelatiera???

 Eccomi mi sono dimenticato....la teflonatura antiaderente della gelatiera???
Bisogna distinguere tra teflonatura che normalmente e' un processo di 
coating di superfici in genere metalliche in cui viene incorporato il 
composto di cui sopra. Non so con precisione se l'acido si aggrappa al 
metallo formando un sale o e' depositato con solvente a dare un 
polimero o addirittura diventa precursore di polimero quindi mi 
informero' e vi faro sapere un po meglio. Se la "teflonatura" e' 
condotta bene ed in modo adeguato non dovrebbe sussistere alcun 
problema, altrimenti puo' restare del composto libero che svolge azione 
dannosa. Dicasi lo stesso di alcuni monomeri liberi nei polimeri non 
ben polimerizzati.
Il teflon della dupont invece e' un polimero ottenuto se ricordo bene 
per addizione radicalica e ha diversi usi tra cui in particolare quello 
di ridurre gli attriti e quello di servire da guarnizione per alte 
temperatura che lo rendono altamente performante.
ALCUNE INFORMAZIONI SUL TEFLON DALL'ENCICLOPEDIA CHIMICA
Polytetrafluoroethylene [9002-84-0] (PTFE) is a straight-chain polymer 
of tetrafluoroethylene (TFE) of the general formula
–(CF2CF2 )n–
It has a high crystalline melting point (327 °C), very high melt 
viscosity (10 – 100 GPa · s at 380 °C), and a high maximum use 
temperature (> 260 °C). In addition, it exhibits unusual toughness down 
to very low temperatures (< –200 °C); its molecular mass is extremely 
high (106 – 107) . It is insoluble in all known solvents and resists 
attack by most chemicals. Dielectric loss is low, whereas dielectric 
strength is high; antistick and antifriction properties are most 
unusual. Although these properties give PTFE great commercial value, 
they also rule out processing by conventional thermoplastic techniques.
Polytetrafluoroethylene is produced in three forms: Granular PTFE is 
prepared by suspension polymerization. The coarse product is cut to 
uniform particle size and processed by powder metallurgy techniques. 
Fine powder resins are prepared by dispersion polymerization and 
coagulation by high-speed agitation. The fine powder resins consisting 
of uniform particles of 0.2 mm diameter are mixed with a lubricant such 
as kerosene and processed by a cold extrusion method called paste 
extrusion. The third form of PTFE is an aqueous dispersion. The 
dispersion products are processed by latex processing techniques (dip 
coating or spray coating) followed by baking at high temperature which 
causes coalescence into a continuous film.
Manufacturers of PTFE resins include Ausimont (Algoflon and Halon), 
Daikin Kogyo (Polyflon), Du Pont (Teflon), Hoechst (Hostaflon), ICI 
(Fluon), and the Soviet Union (Ftoroplast). The People's Republic of 
China also manufactures PTFE products.
production
Polymerization. Tetrafluoroethylene must be polymerized with great care 
to avoid thermal decomposition of the monomer, which can 
disproportionate explosively to carbon and carbon tetrafluoride:
CF2=CF2   ¾®    C + CF4   D H = –316.4 kJ/mol
This reaction, which generates the same explosive force as gun powder, 
can be initiated by hot spots formed during polymerization. Because of 
the high heat of polymerization of TFE and the excellent insulating 
qualities of the polymer, hot spots can develop if mixing is not 
adequate or polymerization is not controlled. Therefore, equipment and 
polymerization vessels must be adequately barricaded to prevent injury 
or death in the event of monomer decomposition. Polymerization in 
storage vessels can be prevented by the addition of inhibitors such as 
terpenes, mercaptans, or amines. However, these must be completely 
removed from the TFE before use.
Tetrafluoroethylene is polymerized in aqueous medium by two different 
processes. In the first, little or no dispersing agent is employed and 
vigorous agitation produces a coagulated granular resin. In the second 
procedure, a fluorinated surfactant is employed and agitation is very 
mild, producing small spherical particles dispersed in the aqueous 
medium. In the latter process, coagulation of the dispersion is avoided 
until after polymerization is completed. Subsequent precipitation of 
the particles produces fine powder resins which are converted to 
finished products by paste extrusion. The dispersion can also be 
concentrated and stabilized by addition of a nonionic surfactant. These 
stabilized aqueous dispersions can be applied by spray or dip coating.