Ethylene tetrafluoroethylene copolymer structure

Polyvinylidene fluoride (PVDF) and Ethylene tetrafluoroethylene copolymer (ETFE) can be considered as diluted PTFE s, which in their structure and their properties... 

Figure 8. XPS valence band spectra for two ethylene-tetrafluoroethylene copolymers (top) alternating structure (Twttom block structure.

Isomerism is a term covering different molecular conformation effects. We will not speak here again on the type of information that can be gained on the alternating or block structure of copolymers, as was explained above for an ethylene-tetrafluoroethylene copolymer. For homopolymers, we will distinguish various categories ... 

Alternating ethylene-tetrafluoroethylene copolymer (ETFE) having a 50/50 comonomer composition crystallizes in two polymorphic forms. An orthorhombic form, stable at room temperature, and a disordered hexagonal form, stable at high temperatures. The crystal structures of both forms have been studied and the structural disorder present in both forms have been analyzed as a function of the composition [250-256]. 

Ethylene-tetrafluoroethylene copolymer (Tefzel/ETFE) is structurally similar to Teflon, possessing also a high chemical resistance. This material has proved excellent for sealing surfaces and in applications involving aggressive solvents. Tefzel is also used in threaded materials, particularly in low-voltage lines and adapters. However, the polymer can be degraded or swollen by chlorinated solvents. 

The film condensation. The ions, electrons and energetic neutrals induce chemical and structural modifications of the growing sputtered films. This fact has been shown recently in the case of rare gas interactions on ethylene-tetrafluoroethylene copolymers . During the deposition these interactions eliminate fluorine atoms and also small fragments to form cross links, unsaturated and free radicals in the deposited polymer. These free radicals and un-... 

The phase transition in an ethylene-tetrafluoroethylene alternating copolymer from the orthorhombic to the hexagonal structure is a result of the generation and propagation of conformational collective defects (182). 

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... 

C. ESCA Studies of Structural Details. Copolymers of ethylene/ tetrafluoroethylene. So far we have shown how a consideration of the detailed structure of the C core levels of certain copolymers may be used to obtain information on composition. A further example which also illustrates the utility of ESCA for providing structural data is provided by studies of copolymers of ethylene and tetra-fluoroethylene. Fig. 3 shows the C and Fjs levels for a series of samples of varying bulk composition. From the ESCA data, the copolymer compositions may be calculated in two independent ways. Firstly, from the relative ratios of the high to low binding energy peaks in the C g spectrum attributable to F2 and H2 type environments respectively. Secondly, from the overall C /F intensity ratios taken in conjunction with data obtained from the study of the homopolymers previously discussed. The results are tabulated in Table 7. 

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]... 

Fluorinated ethylene-propylene (FEP) is a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). It has a branched structure containing units of -CF2-CF2- and -CF2-CF (CF3)-. It retains most of the favorable properties of PTFE but its melt viscosity is low enough for conventional melt-processing. The introduction of HFP reduces the melting point of polytetrafluoroethylene from 325°C (617°F) to about 260°C (500°F).26... 

The compilation of such data constituted a firm basis that was used to study a specific and more complicated system the elucidation of the electronic structure of a copolymer of ethylene (48%) and tetrafluoroethylene (52%) whose synthesis was conducted in order to maximize the alternating sequences. The valence band spectrum of such a compound (Figure 8) was found very similar to the one measured e.g. for poly(vinylidene fluoride). But, by looking to the fine details of the spectrum, by simulating the valence band of a block copolymer (by addition of PE and PTFE spectra), and by comparison with model calculations, it was possible to show that the C-C band width and the distance F2s-top of the C-C band were characteristic of an ethylene-tetrafluoro-ethylene copolymer with dominant alternant structure (28). 

ETFE is an alternating copolymer of ethylene and tetrafluoroethylene by duPont imder the tradename of Tefzel and has the following structural formula ... 

Scheme 2 Chemical structures of a poly(perfluorosulfonic acid) b sulfonated polystyrene (SPS) c sulfonated polystyrene-fc-(ethylene-co-butylene)-fc-sulfonated polystyrene (SSEBS) d sulfonated polystyrene-fc-(isobutylene)-fc-sulfonated polystyrene (SSIBS) e poly(ethylene-co-tetrafluoroethylene)-g-polystyrene sulfonic acid (ETFE-g-PSSA) f poly(vinylidene fluoride)-g-polystyrene sulfonic acid (PVDF-g-PSSA) g poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)-g-polystyrene sulfonic acid (FEP-g-PSSA) h sulfonated trifluorostyrene-trifluorostyrene copolymer (PTFSSA)...

Non-modified thermoplastic ETFE is a copolymer existing of approximately 25% ethylene and 75% tetrafluoroethylene. Figure 6.28 shows the structural formula of both monomer units of ETFE. 

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