Ethylene-tetrafluoroethylene , chain

Ethylene-Tetrafluoroethylene Copolymer. Ethylene-tetralluoroethylene copolymer consists of linear chains in which the repeating unit is... 

The negative expansivity along the chain direction (a[j) seems to be a universal phenomenon with planar zigzag chains as it is exhibited by a variety of polymers of different chemical compositions, i.e. PE [37,38,60], ethylene tetrafluoroethylene alternating copolymer [61], PET [36], nylon 6 [39, 40], poly (vinyl alcohol) [62] and poly diacetylene... 

This polymerization process is used with gaseous monomers such as ethylene, tetrafluoroethylene, and vinyl chloride. The monomer is introduced under pressure into a reaction vessel containing a polymerization initiator. Once polymerization begins, monomer molecules diffuse to the growing polymer chains. The resulting polymer is obtained as a granular solid. 

Feng et al. tested SIMS as an analytical technique for distinguishing between two polymers having an identical composition and a similar chain sequence structure ethylene-tetrafluoroethylene (ETFE) copolymer and poly(vinylidene fluoride) (PVDF) [142]. The positive ToF-SIMS spectra, obtained under 8 kV Cs" bombardment, showed that ETFE generates Q, C2, C3, C4, and C5 ions, while PVDF only produces Ci, C2, and C3 ions. These results clearly imply that sequence structure can significantly influence the positive SIMS spectra of... 

The melt processible fluoroplastics are often desired due to the cost benefits of melt extrusion over paste extrusion. FEP, PEA and specially formulated melt processible perfluoroplastics are used in many of these applications however, in some of these applications, perfluoroplastics may not be the ideal choice. In cases where high cut-through resistance and better tensile properties are required, it is often desirable to employ a partially fluorinated polymer such as ETFE (ethylene-tetrafluoroethylene). ETFE is the copolymer of ethylene and TEE [16] that normally includes an additional termonomer to increase the flexibility required in commercial applications [17]. The increased physical and electronic interactions of the ETFE polymer chain are responsible for the comparatively enhanced physical properties. Additionally, the partially fluorinated polymers may be cross-linked to further improve physical properties. These benefits, however, are obtained at the expense of the unique properties of perfluoroplastics discussed in the Introduction and Overview. 

The equimolar copolymer of ethylene and tetrafluoroethylene is isomeric with poly(vinyhdene fluoride) but has a higher melting point (16,17) and a lower dielectric loss (18,19) (see Fluorine compounds, organic-poly(VINYLIDENE fluoride)). A copolymer with the degree of alternation of about 0.88 was used to study the stmcture (20). Its unit cell was determined by x-ray diffraction. Despite irregularities in the chain stmcture and low crystallinity, a unit cell and stmcture was derived that gave a calculated crystalline density of 1.9 g/cm. The unit cell is befleved to be orthorhombic or monoclinic (a = 0.96 nm, b = 0.925 nm, c = 0.50 nm 7 = 96%. 

Temperature dependence (related to the temperature dependence of the conformational structure and the morphology of polymers) of the radiation effect on various fluoropolymers e.g., poly (tetrafluoroethylene-co-hexafluoropropylene), poly(tetrafluoroethylene-co-perfluoroalkylvinylether), and poly(tetrafluoroethylene-co-ethylene) copolymers has been reported by Tabata [419]. Hill et al. [420] have investigated the effect of environment and temperature on the radiolysis of FEP. While the irradiation is carried out at temperatures above the glass transition temperature of FEP, cross-linking reactions predominate over chain scission or degradation. Forsythe et al. [421]... 

Bryant has calculated the changes in free energy for various reaction steps of the polymerization of tetrafluoroethylene. He concluded (1) that the initiation and propagation are about twice as favorable for tetrafluoroethylene as the analogous reactions for ethylene, (2) that termination by combination is more favorable than disproportionation, and (3) that chain-transfer to monomer and to polymer are less likely than the combination of radicals. 

Fluorinated ethylene propylene (FEP), a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), is essentially PTFE with an occasional methyl side group attached. The methyl groups have effect as defects in crystallites and therefore reduce the melting point. These side groups also impede the slipping of the polymer chains past each other, thus reducing the cold flow. 

There followed a very important series of papers coocenung the emulsifier-free system (Machi et al., 1978, I9 9a-d)- The equipment used was a modification of that used eailier, but the tetrafluoroethylene pressure was continuously recorded with the use of a strain gauge. In the first paper of the series (Machi er cl., 1978) the rate of polymerization was shown to be proportional to the 1.0 and 1.3 powers of the dose rate and the initial pressure, respectively. The activation energies were 0.8 above and —5.2 kcal/mol below 70°C. There was a maximum in the molecular weights at about the same temperature. This behavior is reminiscent of the behavior of ethylene and was again attributed to the increased mobility of the growing chains above the maximum temperature. The very low mobility would also account for the first-order dependence of the rate on the dose rate below 70 C. As before, n-hexadecane proved to be an excellent inhibitor of polymerization in the gas phase. Particle sizes in the range of 0.1-0.2 microns were obtained. 

This plastic is a partially fluorinated straight-chain polymer with a very high molecular weight. It is produced by free-radical polymerization mechanism in a solvent or a hybrid (a solvent/aqueous mixture) media, using an organic peroxide initiator. Copolymerization of tetrafluoroethylene and ethylene (CH2=CH2, molecular weight 28, CAS number 74-85-1) proceeds by an addition mechanism. 

Fluorinated ethylene propylene (FEP) is produced by copolymerization of tetrafluoroethylene and hexafluoropropylene, and consists of predominantly linear chains. 

With copolymerisation the long-chain molecules are created. In a chemical reaction the two monomer units ethylene and tetrafluoroethylene are linked together. Catalysts crack the carbon compound of the macromolecules and hence additional monomer units can link. The product of copolymerisation is an aqueous solution. 

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