Polytetrafluoroethylene homopolymers

Gangal SV (1985) Polytetrafluoroethylene, homopolymer of tetrafluoroethylene. In Mark HF, Bikales NM, Overberger CG, Menges G (eds) Encyclopedia of polymer science and engineering, vol 16.Wiley,NewYork,p 577... 

Gangal, S.V. Polytetrafluoroethylene, homopolymers of tetrafluoroethylene. In Encyclopedia of Polymer Science and Engineering, 2nd Ed. John Wiley Sons New York, 1989 Vol. 16, 577-600. 

Additional studies comprise various forms of polyethylene (CH2)j , such as oriented homopolymer (7,46). Other examples include polytetrafluoroethylene homopolymer and models (7,47-50) poly(ethylene terephthalate) and the related polymers poly(butylene terephthalate) and poly(ethylene naphthalate) (51-53) and electrochemically polymerized thin films such as poly(3-methyl thiophene) (54) and polyp5urole (55). This is not intended to be a comprehensive list, but only an indication of the wide range of applications possible with nexafs spectroscopy. 

Tetrafiuoroethylene-hexafluoropropylene copolymers (sometimes called fluor-inated ethylene-propylene (FEP) copolymers) appeared on the market in 1956. The essential feature of the commercial copolymers is that the proportion of hexafluoropropylene is such that they are truly thermoplastic whilst retaining other properties similar to those of polytetrafluoroethylene homopolymer. 

Gangal SV. Polytetrafluoroethylene, homopolymers of tetrafluoroethylene. 2nd ed. Encyclopedia of polymer science and engineering, 16. New York John Wiley and Sons 1989. p. 577-600. 

Gangal, S. V., Polytetrafluoroethylene, Homopolymers of Tetrafluoroethylene, in Encyclopedia of Polymer Science and Engineering, 2 ed., 16 577-600, John Wiley Sons, New York, 1989. 

In this paper we examine electron diffraction fiber patterns of the homopolymer polytetrafluoroethylene (-CF2 CF2-)n PTFE, in which the resolution is sufficient to yield much more accurate values of layer line heights than were available from the previous x-ray diffraction experiments (1) on the crystal structure of Phase II, the phase below the 19°C transition (2). On the basis of x-ray data, the molecule was assigned the conformation 13/6 or thirteen CF2 motifs regularly spaced along six turns of the helix. This is equivalent to a 132 screw axis. The relationship between the molecular conformation and the helical symmetry has been studied by Clark and Muus (3) and is illustrated in Figure 1. The electron diffraction data of high resolution enabled us to determine if this unusual 13-fold symmetry was exact or an approximation of the true symmetry. We have also... 

The structure of polyvinylidene fluoride chain, namely, alternating CH2 and CF2 groups, has an effect on its properties which combine some of the best performance characteristics of both polyethylene (-CH2-CH2-)n and polytetrafluoroethylene (-CF2-CF2-)n. Certain commercial grades of PVDF are copolymers of VDF with small amounts (typically less than 6%) of other fluorinated monomers, such as HFP, CTFE, and TFE. These exhibit somewhat different properties than the homopolymer. 

Perfluoroalkylvinyl ethers form an important class of monomers in that they are used as comonomers for the modihcation of the properties of homofluoropolymers in addition to their broad nse in copolymers with TFE and other monomers. They are capable of snppressing the crystallization of PTFE efficiently, which imparts usefnl mechanical properties to lower molecular weight of polytetrafluoroethylene polymers. Copolymers of PAVEs and tetrafluoroethylene are thermally stable as PTEE homopolymers. Commercially significant monomers are perfluoropropylvinyl ether and perflnoromethylvinyl ether (PMVE), used for the production of a variety of perflnoroalkoxy resins. 

Polytetrafluoroethylene (Teflon, PTFE, Fluon, Fluoroflex, Polytef, TFE). A thermoplastic homopolymer composed of lot chains of —CFj— units. Colorl to grey powder, flakes or... 

Transition Temperature - This is a temperature (19°C for 100% homopolymer of tetrafluoro-ethylene) at which the unit crystalline cell of polytetrafluoroethylene changes from triclinic to hexagonal. 

CAS 9002-84-0 EINECS/ELINCS 204-126-9 Synonyms Poly (ethylene tetrafluoride) Polytef Polytetrafluoroethene Polytetrafluoroethylene resin PTFE (INCI) Tetrafluoroethene homopolymer Tetrafluoroethylene polymer Tetrafluoroethylene polymers Tetrafluoroethylene resin Classification Thermoplastic homopolymer Definition Polymer of tetrafluoroethylene Emprkal (CiF,),... 

Tetrafluoroethene. See Tetrafluoroethylene Tetrafluoroethene homopolymer. See Polytetrafluoroethylene Tetrafluoroethylene CAS 116-14-3 UN 1081 (DOT)... 

Polyethylene is an example of a homopolymer, which is a polymer made up of only one type of monomer. Other homopolymers that are synthesized by the radical mechanism are Teflon, polytetrafluoroethylene (Figure 25.2) and poly(vinyl chloride) (PVC) ... 

The commercial copolymers have physical properties similar to those of polytetrafluoroethylene but with somewhat greater impact strength. Comparative values for some properties are given in Table 7.1. The copolymers also have similar excellent electrical insulation properties and chemical resistance. The maximum service temperature for the copolymers is about 60 deg C lower than that for the homopolymer under equivalent conditions. The temperature range of useful performance is from about —80°C to 200°C. Tetrafluoro-ethylene-hexafluoropropylene copolymers are used for various electrical and corrosion resistant mouldings, coatings and wire covering. 

The analysis of heat capacity of a given homopolymer thus starts with the evaluation of the experimental crystalline and amorphous heat capacities over as wide a temperature range as possible. For amorphous polymers, the glassy and liquid heat capacities are directly measurable. For crystallizing polymers, the crystalline and amorphous heat capacities may have to be extrapolated, as illustrated in the polyethylene example in Fig. 5.17. Only in rare cases are almost completely crystalline polymers samples available (as for example, for polyethylene, polytetrafluoroethylene, polymeric selenium, and polyoxymethylene). 

The application of the ATHAS has not only produced a large volume of heat capacity data on solid and liquid homopolymers, helpful in the determination of the integral thermodynamic functions, but is also of help in the separation of nonequilibrium enthalpy and heat capacity effects. Figure 5.23 shows two typical examples. At the top, the measured and computed heat capacities of polytetrafluoroethylene are reproduced. As in the case of the polyoxides, it is also possible to predict heat capacities of all less fluorinated polyethylenes. The measured sample was almost completely crystalline, but... 

The simplest systems to start with are the high m.wt. homopolymers of the fluoroethylenes for which complications due to branching, end groups, etc., are minimal. In this section, we therefore outline the results from studies on polyethylene (high density), polyvinyl fluoride, polyvinylidene fluoride, polyvinylene fluoride, polytrifluoroethylene and polytetrafluoroethylene. 

Mattem et al carried out laser mass spectrometry on polytetrafluoroethylenes. They found a fragmentation mechanism common to each fluoropolymer yields structurally relevant ions indicative of the orientation of monomer units within the polymer chain. A unique set of structural fragments distinguished the positive ion spectra of each homopolymer, allowing identification. 

This book is the second of two volumes about fluoropolymers. The division of the volumes is based on the processing techniques of commercial fluoropolymers. Volume One covers the homopolymers of tetrafluoroethylene (TFE) or polytetrafluoroethylene plastics, which are processed by nontraditional techniques. The extremely high melt viscosity of TFE homopolymers precludes its processing by conventional melt processing methods such as injection molding and melt extrusion. The copolymers of TFE and other fluorocarbon polymers, which are processed by melt-processing methods, have been covered in Volume Two. This book is devoted to exploring the various perflu-orinated and partially fluorinated copolymers of tetrafluorethylene and chlorotrifluoroethylene. Polymers of vinyl fluoride and vinylidene fluoride that are, for the most part, melt-processible have been discussed in the second volume. 

Homopolymers of polytetrafluoroethylene are completely linear without detectable branehes, which is contrary to polyethylene. 

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