Molecular Structure
Perfluorocarbons are linear, cyclic, or polycyclic compounds derived from hydrocarbons by replacement of all hydrogen atoms with fluorine atoms. Strictly speaking, perfluorocarbons are fluorocarbons containing carbon and fluorine atoms only, while perfluorochemicals (PFC's) include perfluorocarbon derivatives that may carry different substitutions, such as hydrogen, oxygen, nitrogen atoms, or halogens other than fluorine...
Stability.
Due to the strong carbon-fluorine bond, low polarizability and high electronegativity of fluorine, which enhances the CC bond energy in the backbone, and the shielding effect of fluorine atoms, who's dense electron cloud forms a protective electron coating, PFC's are thermally stable and chemically and biologically inert. However, PFC's use a long retention time (they can be eliminated only through the lungs.)