© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.3.4.5 Chemical Inertness of Teflon

Teflon is inert to chemical attack, being unaffected by ozone, elemental fluorine, boiling nitric acid or aqua regia, concentrated sulfuric acid, or strong oxidizing agents such as potassium permanganate [1406]. Reducing agents such as hydrogen or carbon do not affect it even at temperatures as high as 1000 ^oC [1406]. Fluorocarbons are attacked only by hot metals such as molten sodium [858]. Some of the chemical stability of fluorine derivatives must be attributed to the impossibility of expansion of the octet of fluorine and the inability of water to coordinate to fluorine or carbon as the first step in hydrolysis [858]. Also, C-F bonds are among the strongest covalent bonds known. Fluorine atoms are larger than hydrogen atoms, so the F atoms effectively shield the carbon atoms from attack much better than the H atoms in hydrocarbons. Since the C-F bond is very polar, the carbon can be considered to be effectively oxidized (whereas the C-H bond is only slightly polar, so the carbon is not nearly as reduced), so there is no tendency for oxidation by oxygen [858]. Teflon can be heated in air without burning [1406] up to 450-500 ^oC [1310]. When pyrolyzed, fluorocarbons tend to split at C-C rather than C-F bonds [858]. This is because carbon-carbon bonds are much weaker than carbon-fluorine bonds. In fluorocarbons, C-C bond energies are approximately 80 kcal/mole, while C-F bond energies are 115 kcal/mole. Since it takes less energy to break C-C bonds than C-F bonds, fluorocarbons will split at the C-C bonds.

Teflon is a chemically inert [1197, 1310, 1378], bioinactive [1183], nonabsorbable [1196] implant material. It is relatively stable in the tissues and is not readily dissolved or digested by the host [1033]. Teflon particles are indigestible by macrophages and Kupffer cells [1391], and bulk Teflon is not cytotoxic [1190]. As noted elsewhere in this Section there can be some biocompatibility problems with traditional medical fluorocarbon-based surfaces, but atomically smooth surfaces of this type have yet to be rigorously investigated.

Last updated on 30 April 2004