Fluoropolymers hexafluoropropylene

Curve fitting may be carried out either in a "free manner or using constraints. Generally, the use of physically realistic contraints results in a fit that is more physically acceptable. Typical examples of the use of constraints would be the fixing of the Zpj/i to 2pi/2 ratio in an overlapping doublet from a simple element such as sulfur or phosphorus, at least initially, and to. set equal the linewidths of the two components. Alternatively, where different chemical forms of the same element are known to be present in certain ratios, that information could be included in the fit. For example, in the curve-fitted carbon l.v spectrum of the fluoropolymer hexafluoropropylene-vinylidene fluoride shown in Fig. 4, the areas of the three components of the hexatluoropylene block, namely CFj, CF2 and CF. are equal. The CF> and CH2 components of the vinylidene fluoride monomer are also of equal intensity, and a very satisfying fit is found. 

In addition to the fluoroplastics and fluororubbers already described other fluoropolymers have been marketed. Polymers of hexafluoropropylene oxide are marketed by Du Pont (Krytox). These materials have a low molecular weight (2000-7000) and are either oils or greases. The oils are uses as lubricants, heat transfer fluids and non-flammable oils for diffusion pumps. The greases are also used as lubricants. They have good heat and oil resistance but it is said that explosions may result from contact with the surfaces aluminium or magnesium cuttings. 

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]... 

Peduoropolyethers, which constitute special class of fluoropolymer, are useful as lubricants,1 elastomers,2 and heat-transfer fluids under demanding conditions. Several commerical products are available, which are generally prepared by ring-opening polymerization of hexafluoropropylene oxide or by the random copolymerization oftetrafluoroethylene and hexafluoropropylene with oxygen under ultraviolet irradiation.3 Direct fluorination of hydrocarbon ethers has been reported4 but must be done very slowly under carefully controlled... 

Fluoropolymers are used for the manufacture of coatings for frying pans, pots, fryers and other cooking equipment and utensils. Polytetrafluoroethylene with a melting point of approximately 327 °C is mostly used but polymer mixtures with perfluoro-alkylvinyl ether and hexafluoropropylene can also be used. 

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. 

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). 

Polytetrafluoroethylene (PTFE Teflon) was discovered accidently by PlunkettCZ nd commercialized by DuPont in the 1940 s. This polymer has a solubility parameter of about 6H and a high melting point of 327°C and is not readily moldable. Poly-chlorotrifluoroethylene (CTFE, Kel-F), the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF, Kynar), the copolymer of tetrafluoroethylene and ethylene (ETFE), the copolymer of vinylidene fluoride and hexafluoroisobutylene (CM-1), perfluoroalkoxyethylene (PFA) and polyvinyl fluoride (PVF, Tedlar) are all more readily processed than PTFE. However, the lubricity and chemical resistance of these fluoropolymers is less than that of PTFE. 

Fluoropolymer elastomers (or Viton, a registered trademark of the DuPont Performance Elastomer LLC) consist of hexafluoropropylene (HFP), vinylidene fluoride (VDF), and tetrafluoroethylene. The 3M Corporation uses the trade name Fluorel. The structures of each of these monomers are shown in Figure 8.14. The fluorine content of these terpolymers is typically around 70% for Viton. Four basic types of this material are shown in Table 8.8 however, Viton Extreme comprises more types. 

Vinylidene Fluoride Hexafluoropropylene Copolymer - Thermoplastic copolymer of vinylidene fluoride and hexafluoropropylene. Has better thermal stability, antistick, dielectric, and antifriction properties, and chemical resistance, but lower mechanical strength at room temperature and creep resistance, compared to incompletely fluorinated fluoropolymers. Processing by conventional thermoplastic techniques is difficult due to its high melt viscosity. Uses include chemical apparatus, containers, films, and coatings. Also called TAM... 

Fluoropolymers (e.g., copolymers of vinylidene fluoride and hexafluoropropylene) and silicone-based (e.g., poly-dimethylsiloxanes) additives are often referred to as processing aids, preventing melt-fracture, for example, the so-called sharkskin. Fluoropolymers are applied in concentrations between 0.01% and 0.1%. 

To prepare PSSA-grafted fluoropolymers, poly(vinylidene fluoride-co-hexafluoropropylene), poly (ethylene-co-tetrafluoroethylene) and poly(tetrafluoroethylene-co-hexafluoropropylene) were used as base polymers. Each polymer was molded into a film (200-300 pm thick) and irradiated with y-ray at room temperature at the rate of 6.8 kGyh using a cobalt-60 source to obtain a total absorbed dose of 50 kGy. The irradiated film was immersed in nitrogen-purged styrene at 70°C for 8 h for... 

Coating is one of the important uses of fluoropolymers, since it enables them to exhibit their characteristics on the surface of a substrate. Some of the conventional fluoropolymers such as polytetrafluoroethylene [9002-84-0] (PTFE), tetrafluo-roethylene-hexafluoropropylene copolymer [25067-11-2] (FEP), and ethylene-tetrafiuoroethylene copolymer [25038-71-5] (ETFE) have been used as antistick or anticorrosive coatings. Only poly(vinylidene fluoride) [9002-58-1] (PVDF) has so far been used in paints. The major difficulties in employing thermoplastic fluoropolymers in paints and coatings result from their poor solubility in organic solvents and... 

Chem. Descrip. Tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer disp. with ionic emulsifier Uses Fluoropolymer for coating heat-sensitive substrates such as polyester fabrics in low temp, fabric composites Features Useful for applies, requiring performance and flexibility Properties Cone, water disp. sp.gr. 1.95 melt flow 35-60 (265 C/5 g) m.p. 140-150 C 50% solids Dyneon THV 400 G [Dyneon]... 

Chem. Descrip. Tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymer disp. with ionic emulsifier Uses Fluoropolymer for molded parts, extruded films, tubes, profiles, and wire coatings... 

Hexafluoropropylene/vinylidene fluoride/ tetrafluoroethylene teipolymer, Viton A-100 Viton A-200 fluoroelastomer, tank coatings Hexafluoropropylene/vinylidene fluoride/ tetrafluoroethylene terpolymer fluoroelastomer, tank solution coatings Viton A-100 Viton A-200 fluoroelastomer, thin film Fluordatex 200 fluoropolymer modifier Dynasylan F 8815 fluoropolymer, coatings Dyneon THV 220A Teflon PTFE 30 Teflon TE-3667N... 

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. 

If one of the fluorine atoms on TEE is replaced with a trifluoromethyl group (—CF3), then the new monomer is called hexafluoropropylene (HEP). Polymerization of monomers HEP and TEE yields a fluoropolymer, fluorinated ethylene propylene, called FEP. The number of HEP groups is typically 13% by weight or less and its stmcture is shown in Figure 9.57. The CAS number for FEP is 25067-11-2. 

In blends, fluoropolymers are used in small quantities to enhance throughput, reduce the frictional properties, and increase the wear resistance. Blends comprising 0.3-50 wt% of a low molecular weight PTFE (T , < 350 °C) with engineering resin showed improved antifriction properties (Asai et al. 1991). LLDPE generally exhibits sharkskin melt fracture, but the use of fluoropolymer additives, such as the copolymer of vinyUdene fluoride and hexafluoropropylene, can help to eliminate the extrusion instability (Hatzikiriakos and Migler 2005). 

Melt fracture in polyethylene products can be avoided by adding a fluoropolymer, traditionally a copolymer of hexafluoropropylene and vinylidene fluoride, with trifluoromethyl side groups. The copolymer may be accompanied by other polymers or additives. There can be interaction between hexafluoropropylene and certain fimctional groups, such as amines, causing discoloration. 

Uses. The variety of fluoropolymers and fluoroelastomers incorporating VDF in the main chain is extensive. The commercially important thermoplastic copolymers are based upon hexafluoropropylene HFP (10,11) chlorotrifluoroethy-lene (CTFE) (12,13) and co- or ter-polymers with tetrafluoroethylene (14). Telomer-ization of VDF to form fluorinated oligomers by radical addition has been reviewed (15). 

Fluoropolymers are unique amongst polymers in respect of their chemical and thermal stability, biocompatibility, water resistance and superb dielectric properties, having a dielectric constant of 2.1. Other members of the Teflon family include a polymer of tetrafluoroethylene and hexafluoropropylene (FEP) and a polymer of tetrafluoroethylene and perfluorovinylether (PEA). The 327 °C melting point of PTFE is reputed to be one of the highest in organic polymer chemistry. The melting points of FEP and PEA are 260 C and 305 °C, respectively. 

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]. 

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