Fluoropolymers vinyl fluoride

Many vinyl monomers were reported to have been grafted onto fluoropolymers, such as (meth)acrylic acid and (meth)acrylates, acrylamide, acrylonitryl, styrene, 4-vinyl pyridine, N-vinyl pyrrolidone, and vinyl acetate. Many fluoropolymers have been used as supports, such as PTFE, copolymers of TFE with HFP, PFAVE, VDF and ethylene, PCTFE, PVDF, polyvinyl fluoride, copolymers ofVDF with HFP, vinyl fluoride and chlorotrifluoroethylene (CTFE). The source of irradiation has been primarily y-rays and electron beams. The grafting can be carried out under either direct irradiation or through the use of preliminary irradiated fluoropolymers. Ordinary radical inhibitors can be added to the reaction mixture to avoid homopolymerization of functional monomers. 

The fluoropolymer family consists of polymers produced from alkenes in which one or more hydrogens have been replaced by fluorine. The most important members of this family are polytetrafluoroethylene (PTFE) (XLVII), polychlorotrifluoroethylene (PCTFE) (XLVIII), poly(vinyl fluoride) (PVF) (XLIX), poly(vinylidene fluoride) (PVDF) (L) copolymers of... 

The major commercial fluoropolymers are made by homopolymerization of tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE),vinyhdene fluoride (VF2), and vinyl fluoride (VF), or by co-polymerization of these monomers with hexafluoropropylene (HFP), perfluoro(propyl vinyl ether) (PPVE), per-fluoro(methyl vinyl ether) (PMVE), or ethylene. The polymers are formed by free-radical polymerization in water or fluorinated solvents. 

Fluoro-substituted Polymers. The fluoropolymers were between the first to be studied by the XPS technique because the substitution of F atom(s) in the -CH.-CH - unit induced very large modifications in the XPS core level spectra (shifts up to 8eV) that were easy to detect and interpret. The XPS valence band spectra of similar compounds, namely poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVF2), poly(trifluoroethylene) (PVF3), and poly(tetrafluoroethylene) (PTFE) (26, 27, 28) are also expected to reflect the induction of such strong electronic effects at the valence molecular level. 

The volume of commercial fluorine containing polymers is not large when compared with other polymers, such as poly(vinyl chloride). Fluoropolymers, however, are required in many important applications. The main monomers are tetrafluoroethylene, trifluorochloroethylene, vinyl fluoride, vinylidine fluoride, and hexafluoropropylene. 

In the addition to homo-PVF2, a large number of copolymers have also been synthesized which allow to optimize the mechanical properties of fluoropolymers. Most common are copolymers with vinyl fluoride, trifluoroethylene, tetrafluoroethylene, hexafiuoropropy-lene, hexafluoroisobutylene, chlorotrifluoroethylene, and pentafiuoro-propene [521,535, 559-562]. Copolymerization with nonfluorinated monomers is possible [563] in principle but has not yet found commercial use. Fluorocarbon monomers that can help to retain or enhance the desirable thermal, chemical, and mechanical properties of the vinylidene structure are more interesting comonomers. Copolymerization with hexafluoropropylene, pentafluoropropylene, and chlorotrifluoroethylene results in elastomeric copolymers [564]. The polymerization conditions are similar to those of homopoly(vinylidene fluoride) [564]. The copolymers have been well characterized by x-ray analysis [535], DSC measurements [565], and NMR spectroscopy [565,566]. 

In this chapter, we describe a variety of methodologies for applying multidimensional NMR (mostly 2D- and some 3D-NMR) for the characterization of fluoropolymers. Space limitations preclude a comprehensive survey of the literature. Instead, a few of the primary methodologies are described involving combined use of multidimensional NMR methods for structure elucidation. Then, a selected group of papers were reviewed to illustrate the applications of these methodologies to the characterization of some of the most common classes of fluoropolymers, including homo- and copolymers with poly(vinylidene fluoride), fluorinated polyethers, fluori-nated ionomers, poly(vinyl fluoride) and its copolymers, and polytetrafluoroethylene (PTFE) and its copolymers. 

A study by Bruch [9] is a classic example of the use of F homonuclear 2DJ spectroscopy for the study of fluoropolymers. Scalar couplings of poly(vinyl fluoride)... 

The commercial production of polymers containing fluorine is very small compared to the output of many other synthetic polymers. Nevertheless, several fluoropolymers are used in various important specialized applications. The principal commercial fluoropolymers at the present time are the homopolymers of tetrafluoroethylene (I), chlorotrifluoroethylene (II), vinyl fluoride (III) and vinylidene fluoride (IV) and vinylidene fluoride-chlorotrifluoroethylene, vinyli-dene fluoride-hexafluoropropylene (V) and tetrafluoroethylene-hexafluoropro-pylene copolymers. These materials, together with a few other fluoropolymers of interest, form the contents of this chapter. 

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. 

The other major monomers, in addition to TFE, are chlorotrifluoroethylene (CTFE, CC1F=CF2), vi-nylidene fluoride (VDF, CFj CHj) and vinyl fluoride (VF, CH2=CHF). These monomers are polymerized and copolymerized by different methods to produce commercial fluoropolymers. TFE, CTFE, and VDF have associated families of polymers and copolymers. Only one commercial VF polymer is known (Tedlar by DuPont). 

Poly(vinyl fluoride) is included, although it shows greater similarities to poly(vinyl chloride) than to the other fluoropolymers. It also should be mentioned that a wide variety of fluoropolymer elastomers is used under extreme conditions of temperature and chemical environment. 

The commercially important fluorocarbon polymers are poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly[tetrafluoroethylene-co-(perfluoroaJkylvinyl ether)] (PFA), and amorphous fluoropolymer (AF), typically copolymers of tetrafluoro-ethylene and fluorinated dioxole. The second group of fluoropolymers includes modified poly(tetrafluoroethylene-co-ethylene) (ETFE), poly(vinylidene fluoride) (PVDF) (sometimes referred to as PVF2), and copolymers of vinylidene fluoride, poly(chlorotrifluoroethylene) (PCTFE), poly(chlorotrifluorethylene-co-ethylene) (E/CTFE) and poly(vinyl fluoride) PVF. 

Since PTFE was first synthesized more than 50 years ago, fluoropolymers have been produced by radical polymerization and copolymerizaton processes, but without any functional groups, for several reasons. First, the synthesis of functional vinyl compounds suitable for radical polymerization is much more complicated and expensive in comparison with common fluoroolefins. In radical polymerization of one of the simplest possible candidates—perfluorovinyl sulfonic acid (or sulfonyl fluoride—there was not enough reactivity to provide high-molecular-weight polymers or even perfluorinated copolymers with considerable functional comonomer content. Several methods for the synthesis of the other simplest monomer—trifluoroacrylic acid or its esters—were reported,1 but convenient improved synthesis of these compounds as well as radical copolymerization with TFE induced by y-irradiation were not described until 1980.2... 

In this entry, fluoropolymer means a polymer that consists of partially or fully fluorinated olefinic monomers, such as vinylidene fluoride (CH2=CF2) and tetrafluor-oethylene (CF2=CF2). Commercial fluoropolymers include homopolymers and copolymers. Homopolymers contain 99wt.% or more one monomer and lwt.% or less of another monomer according to the convention by American Society for Testing Materials. Copolymers contain 1 wt.% or more of one or more comonomers. The major commercial fluoropolymers are based on tetrafluoroethylene, vinylidene fluoride, and to a lesser extent chlorotrifluoroethylene. Examples of comonomers include perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoro-propyl vinyl ether (PPVE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), and perfluorobutyl ethylene (PFBE). 

Commercial fluoropolymers are based on tetrafluo-roethylene, vinylidene fluoride, and, to a lesser extent, chlorotrifluoroethylene. Examples of comonomers include perfluoromethyl vinyl ether, perfluoroethyl... 

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