Teflon chemical structures

Fig. 2.5.9 COSY spectra acquired at 600 MHz with an eight-coil probe along with the chemical structures of the compounds used. Each sample was a 10 mM solution in D20 loaded into the coil via the attached Teflon tubes, with the samples being (A) sucrose, (B) galactose, (C) arginine, (D) chloroquine, (E) cysteine, (F) caffeine, (G) fructose and (H)...

PFIB is a chemical 2 of the CWC and therefore contained in Schedule 2 A. Its chemical structure is shown in Figure 24.1. PFIB is produced by thermal decomposition of Teflon, and has high inhalation toxicity characterized by pulmonary edema. PFIB has been characterized in more detail in an ASA Newsletter (Patocka and Bajgar, 1998). Therapy is symptomatic. 

When interpreting the results, however, it is important to bear in mind the possibility that the thermal effects observed are influenced by the interaction of the container material and the sample. If the chemical structure indicates this possibility, these first runs should be followed by further tests using chemically inert sample containers. The variety ranges today from pure glass containers, those with gold or Teflon coating to pure carbon containers. The use of such containers, however, is usually accompanied either by pressure or temperature measuring constraints. 

For a further comparison of the free volume of polymers with different Tg values and different chemical structures, we show in Figure 11.11 the fractional hole free volume h calculated from PVT experiments employing the S-S equation of state. Polymers denoted as conventional (hydrogen polymers and others) have hole fractions ranging up to 0.15, while at 606 K Teflon AF2400 has a value of A = 0.374. 

Two of these are under extensive investigation and are currently being studied for gas separation on a pilot scale. These are DuPonfs 2,2-bistrifluoromethyl-4,5-difluoro-l,3-dioxole/tetrafluorethylene copolymer (Teflon AF 2400 ) and poly(4-methyl-2-pentyne) (PMP). All three polymers, PTMSP, PMP and Teflon AF2400, are glassy with glass transition above 230°C and have a very high fractional free volume (FFV). Figure 7.4 shows the chemical structure and fractional free volume of these three polymers. 

Fig. 7.4 Chemical structure and fractional free volume of PTMSP, PMP and Teflon AF2400.

The chemical composition of such treated surfaces, shown by XPS, does not present any oxygen atoms the Ois peak is not detected anymore. Therefore, a fluo-rinated layer whose elemental composition corresponds to a Teflon-like structure covers the entire LDPE surface (Table 2). Since the ratio between fluorine and carbon atomic concentrations does not increase with the plasma parameters, i.e. a plateau value is rapidly obtained, so the observed increase of contact angle is mostly induced by the increase of the surface roughness. 

It is also possible for material abraded from one surface to transfer to the other surface in a chemical sense and in a physical sense. Research on friction between Teflon and aluminum surfaces, for example, has revealed the formation of a certain amount of aluminum trifluoride on the aluminum surface, a condition made possible only by chemical reaction between the aluminum metal and heat-induced breakdown products of the perfluorinated chemical structure of the Teflon surface. 

FIGURE 16.1 Chemical structures of monomers (I) and (II) and their copolymers with tetrafluoroethylene Teflon AF and Hyflon AD. 

FLUOROCARBON An organic compound having fluorine atoms in its chemical structure, an inclusion that usually lends stability to plastics. Teflon is a fluorocarbon. 

Figure 4.2 Chemical structures of (a) Teflon AF, (b) Flyflon AD, and (c) CYTOP.

To avoid the formation of the crystalline phase, introduction of aliphatic rings into the main chain, which causes it to become twisted, is an effective method. The most well-known amorphous perfluorinated polymers are Teflon AF, Hyflon AD, and CYTOP, developed by DuPont, Solvay Chemicals, and AGC, respectively. The chemical structures of these three polymers are shown in Figure 4.2. They have excellent clarity, solubility in some fluorinated solvents, thermal and chemical durability, low water absorption, and low dielectric properties. In particular, their high transparencies arise from the cyclic structures that exist in the polymer main chains. Teflon AF is a copolymer of 2,2-bis(trifluoromethyl)-4,5-difluoro-... 

It is similar to Teflon, to which sulfonic acid groups are attached. The acid molecules are fixed to the polymer and cannot leak out, but the protons of these acid groups are free to migrate through the membrane. The chemical structure of Nafion is in Fig. 2.2. 

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