Fluoroplastics partially fluorinated

The era of fluoropolymers began with the serendipitous discovery of PTFE by Roy Plunkett of DuPont Companywhile conducting research to find new refrigerants. A number of fluoroplastics have been developed since the discovery of PTFE. They are divided into two classes of perfluorinated and partially fluorinated polymers. Perfluorinated fluoropolymers... 

Partially fluorinated fluoropolymers confain hydrogen (H) or other atoms such as chlorine, in addition to fluorine and carbon. The mosf significanf are homopolymers and copolymers of vinylidene fluoride (VDF). There are also copolymers and homopolymers of CTFE, alfhough some have elastomeric properties. Other significant fluoroplastics include ETFE and PVF. 

Perfluorinated fluoroplastics have higher creep tendency than partially fluorinated fluoropol5miers. Polytetrafluoroethylene, comprised of 100% tet-rafluoroethylene monomer, has the highest tendency to exhibit cold flow. Copolymers of tetrafluoroeth-ylene containing small amounts (0.1% by weight) of certain other fluorinated monomers, also referred to as modifiers, have significantly lower creep. These modifiers form pendent groups in the polymer chain. 

Table 3.50. Impact Strength (J/m) of Partially Fluorinated Fluoroplastics Measured by Notched Izod ASTM D256P i-P ...

Fluoropolymers are semicrystalline polymers most do not exhibit glass transition in the conventional sense during which all crystalline structures are converted to the amorphous. The glass transitions of fluoroplastics have been described as molecular relaxation (conformational disorder) that takes place in the amorphous phase of the polymer. These temperatures are also called second order transitions their value depends on the technique and the frequency of energy addition to the polymer sample. Table 3.61 presents these temperatures and melting points of perfluorinated and partially fluorinated fluoroplastics. 

Appendix II Permeation Properties of Partially Fluorinated Fluoroplastics... 

The fluoroplastic materials are divided into two groups fully fluorinated fluorocarbon polymers such as PTFE, FEP, and PPA called perfluoropoly-mers, and the partially fluorinated pol)nners such as ETFE, PVDF, and ECTFE that are called fluoropol)nners. The pol)uneiic characteristics within each group are similar, but there are important differences between the groups as will be seen later. 

Traditionally, a fluoropolymer or fluoroplastic is defined as a polymer consisting of carbon (C) and fluorine (F). Sometimes these are referred to as per-fluoropolymers to distinguish them from partially fluorinated polymers, fluoroelastomers, and other polymers that contain fluorine in their chemical structure. For example, fluorosilicone and fluoroacrylate polymers are not referred to as fluoropolymers. The monomers used to make the various fluoropolymers are shown in Figure 9.1. 

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. 

Perfluorocyclobutane (PFCB) polyaryl ethers are one such class of partially fluorinated polymers which combine the processability and durability of engineering thermoplastics with the optical, electrical, thermal, and chemical resistant properties of traditional fluoroplastics. Developed originally at The Dow Chemical Company" in Freeport, TX, PFCB polymers are prepared by the radical mediated thermal cyclopolymerization of trifluorovinyl ethers (Figure 1) and have, to date, provided a variety of thermoplastic and thermosetting materials possessing a tunable range of... 

The present chapter covers information published by resin manufacturers about the commercially available grades of melt processible fluoropolymers. The first two polymers are perfiuorinated resins, followed by partially fluorinated polymers ethylene-tetrafiuoro-ethylene and ethylene chlorotrifiuoroethylene, andpoly-vinylidene fluoride and polyvinylfiuoride, and finally concluding with fluoroplastics polymerized in supercritical carbon dioxide. Commercially available resins have been classified by type, grade, and manufacturer. Properties of commercial grades have been presented in this chapter based on the literature published by the manufacturers. 

Tables 6.31 and 6.33 show dimensions and properties of partially fluorinated fluoroplastic films. These films are available with different surface finishes such as one side polished, Haircell, or dull. Films with both sides polished or matte are also available.

Table 6.31. Dimensions of Partially Fluorinated Fluoroplastic Films Made by Westlake Plastics Company S ...

In this section, foaming techniques are covered based on the fluoropolymer type, beginning with perfluoroplastics. Next, foaming of partially fluorinated fluoropolymers are reviewed, combining ETFE and ECTFE and separately covering PVDF. Technological reviews are based primarily on patents and publications that focus on potentially commercial methods of foaming fluoroplastics. 

The moduli of fluoropolymers are a function of a number of variables, most important of which is the composition of the pol)mier and more specifically the presence or absence of hydrogen in the polymer. Other variables are those affecting the other mechanical properties of these plastics. They include testing temperature, molecular weight, and crystallinity, which affect the modulus of these plastics disregarding of the re-gime/type of measurements. Perfluoropolymers have lower moduli than partially fluorinated fluoroplastics. An increase in the fluorine content of the fluoroplastic increases the modulus. 

Perfluorinated fluoroplastics have higher creep tendency than partially fluorinated fluoropolymers, due to their extreme neutrality and consequently weak in-termolecular interactions. Polytetrafluoroethylene,... 

Partially fluorinated fluoropolymers (PVDF, ETFE, ECTFE) are much more resistant to electron beam and y-radiation than perfluorinated fluoroplastics. Table 13.47 provides mechanical property data for ECTFE as a fiinction of Co radiation (y-rays). Figure 13.108 shows the effect ofy-rays on the break elongation and yield strength of PVDF. Exposure of... 

Partially fluorinated fluoroplastics can be cross-linked to improve the mechanical properties of shaped articles such as wire insulation. For example, the aerospace industry requires wire and cable that can withstand abrasion and cutting in addition to flammability. Cross-linking a fluoropolymer like ETFE, ECTFE, or PVDF enhances its mechanical properties. For example, actual cross-linking is accomplished by incorporating a cross-linking agent in ETFE after the extrusion of the insulation, followed by irradiation.fi l... 

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