as a class of materials are fairly new; all of them have been produced since 1930’s. The rest of this chapter primarily covers fluorocarbon gases and liquids. A short explanation of commercial fluoropolymers rounds off the Chapter.
2.1 Fluorine and Fluorochemicals
Organic fluorine compounds rarely occur naturally in contrast to bromine and chlorine products. The most famous naturally existing organic fluorine-containing compound is probably monofluoroacetic acid (FCH2COOH). This compound is found in a South African plant called “Gifblaar,” which is known to be so poisonous that ingesting only a half of its leaf is enough to kill a cow. In 2003, a Chinese research group discovered fluorine-containing compounds from the extract of a marine sponge called Phakellia fusca. Another example of a naturally occurring organic fluorine containing compound is called nucleocidin. Even the presence of elemental fluorine has been reported in fluorspar (CaF2) containing radioactive uranium [2].
None of the rare natural organic compounds are useful as a source for C-F bonds for commercial production of chemicals. The easiest route to produce carbon fluorine (C-F) bond is via hydrofluoric acid (HF). Acid grade fluorspar (CaF2) is combined with sulfuric acid to produce HF and calcium sulfate. Chloroform is produced by and chlorination of methane. Catalytic reaction of HF and CHCl3 produces CHClF2, which is the starting point for producing many fluorocarbons.
2.2 Fluorocarbons
Development of fluorine chemistry allowed economically viable fluorinated chemicals and polymers to be produced during the first half of 20th century. The first commercial fluorine products of any kind go back to 1930’s, developed to meet the evolving industrial needs for compounds such as new refrigerants. The traditional agents used in refrigeration included ammonia, carbon dioxide, sulfur dioxide, hydrocarbons and methyl chloride. These refrigerants suffered from shortcomings including toxicity, flammability, instability and poor efficiency in the refrigeration cycle. Consequently, the challenges in the development of new agents consisted of the following characteristics:
1 Non-flammable
2 Good thermal stability
3 Low toxicity
4 Atmospheric boiling point of -40°C to 0°C
5 Refrigeration cycle efficiency
Some of the early patents described methods using rather exotic compounds to produce fluorocarbons [3, 4]. Simpler preparation methods have been described for the reaction of hydrofluoric acid with halocarbons (chlorine and bromine) using a catalyst [5].
Fluorocarbon in this book refers an acyclic alkane hydrocarbon in which all or some of hydrogen atoms have been replaced with fluorine (Table 2.1). An acyclic alkyl has the general formula CnH2n+1. Some chlorine or bromine atoms may also be present in the molecule. Depending on the structure of chemical compound, fluorocarbon consists of chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), hydrofluorocarbon (HFC) and hydrofluoroolefin (HFO). All except HFO have been the targets for obsolescence under Montreal Protocol and its amendments. Major fluorocarbon applications include refrigerants, blowing, agents (foam), solvents, aerosol propellants and fire extinguishers.
Chlorofluorocarbons contain Carbon and some combination of Fluorine and Chlorine atoms. They were the original fluorocarbons developed in the 1930’s. Hydrochlorofluorocarbons contain Hydrogen, Chlorine, Fluorine, and Carbon atoms; they were quickly developed and commercialized after the enactment of the Montreal Protocol. Hydrofluorocarbons contain Hydrogen, Fluorine, and Carbon (no chlorine) known as the third generation of fluorocarbons.
Hydrobromofluorocarbons contain Hydrogen, Bromine, Fluorine, and Carbon atoms. Perfluorocarbons contain Fluorine, Carbon, and Bromine atoms, and some contain Chlorine and/or Hydrogen atoms.
Table 2.1 Examples of various acyclic alkane fluorocarbons.
| Compound | Chemical formula | Form |
| Hexane | CH3-CH3 | Alkane |
| Perfluorohexane | CF3-CF3 | Perfluorinated |
| 2-bromo-2-chloro-1,1,1- trifluoroethane (Halothane) | CF3-CHBrCl | Fluorobromochlorinated |
| 1,2-dichloro-1,1,2-trifluoroethane | CClF2-CHClF | Hydrochlorofluorocarbon |
| 1,1,2-Trifluoroethane | CHF2-CH2F | Hydrofluorocarbon |
Hydrobromofluorocarbons contain Hydrogen, Bromine, Fluorine, and Carbon atoms. Perfluorocarbons contain Fluorine, Carbon, and Bromine atoms, and some contain Chlorine and/or Hydrogen atoms.
To avoid repeating the rather long chemical names of fluorocarbons a system has been devised to use codes for each of them. Oak Ridge National Laboratory [6] has provided the designations of fluorocarbon codes (Section 2.2.1).
2.3 Designations for Fluorocarbons
Fluorocarbon compounds are designated by a combination of letters and numbers (e.g., CFC-11, HCFC-142b). In the latter example, the lower-case b refers to an isomer. It has no relationship to the chemical formula (C2H3F2Cl), rather it designates a particular structural arrangement of the atoms in the molecule. For example, HCFC-142b identifies the isomer in which all three hydrogen atoms are attached to the same carbon atom, and the structural formula is written as CH3CF2Cl. By contrast, HCFC-142 (without the b) refers to an arrangement in which one carbon atom is attached to two hydrogen atoms and one chlorine atom, while the other carbon atom is attached to the third hydrogen atom and two fluorine atoms (CH2ClCHF2).
To find the number, given the chemical formula: consider the number as consisting of 3 digits: a, b, and c. For 2-digit numbers (e.g., CFC-11) one digit is zero (e.g., CFC-011).
a is the number of carbon atoms minus 1;
b is the number of hydrogen atoms plus 1;
c is the number of fluorine atoms.
| For CFCl3: | a = the number of carbon atoms (1) minus 1 = 0 |
| b = the number of hydrogen atoms (0) plus 1 = 1 | |
| c = the number of fluorine atom = 1 |
and the compound is CFC-011, or CFC-11.
Similarly:
CCl2F2 is CFC-012
C2Cl3F3 is CFC-113
To find
