Polytetrafluoroethylen PVDF properties

Examples of fluoroplastics include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), ethylene—chlorotrifluoroethylene (ECTFE), ethylene—tetrafluoroethylene (ETFE), poly(vinylidene fluoride) (PVDF), etc (see Fluorine compounds, organic). These polymers have outstanding electrical properties, such as low power loss and dielectric constant, coupled with very good flame resistance and low smoke emission during fire. Therefore, in spite of their relatively high price, they are used extensively in telecommunication wires, especially for production of plenum cables. Plenum areas provide a convenient, economical way to run electrical wires and cables and to interconnect them throughout nonresidential buildings (14). Development of special flame-retardant low smoke compounds, some based on PVC, have provided lower cost competition to the fluoroplastics for indoors application such as plenum cable, Riser Cables, etc. 

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. 

PVDF is the third most widely used fluoropolymer, after polytetrafluoroethylene (PTFE) and fluorinated ethylene-propylene (FEP). The worldwide consumption of PVDF was approximately 15,000 metric tons in 2001 and is growing at an annual rate of 6-8%. PVDF applications have been expanded over the past 40 years because of its unique physical properties, and have over 30 years of proven and field performance data on thermal, chemical, radiation, and weathering applications. PVDF applications include, but are not limited to, chemical processing of pipes and components, semiconductor, architectural finishes and coatings, electrical plenum, cable jacketing. 

Asymmetric and composite membranes commercially known as HYFLON AD are obtained from copolymers of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-l,3-dioxole (TTD) these membranes show a high hydrophobic character with contact angles to water greater than 120° (Arcella et al. 1999). Hydrophobic membranes from copolymers of polytetrafluoroethylene (PTFE) and polyvinylidenefluoride (PVDF) were prepared by a phase inversion process (Feng et al. 2004) these membranes exhibit excellent mechanical properties and good hydrophobicity (contact angle to water of about 87°). 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), polytetrafluoroethylene (PTFE), polyvinylidine fluoride (PVdF), and polyvinyl chloride (PVC). Nonwoven fabrics have not been able to compete with microporous films in lithium-ion cells. This is primarily because of the inadequate pore-size structure and difficulty in making thin (<25 pm) nonwoven fabrics with acceptable physical properties. However, nonwoven separators have been used in button cells and bobbin cells when thicker separators and low discharge rates are acceptable. 

Inappropriate matching of the physicochemical properties of the binder with the carbon material may influence dramatically upon the electroactive area via blocking of the SPE film or simply decreasing the electroactive surface area. Another point to be considered is the cost of the binders. For example, fluoropolymers such Nafion, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are commonly used as binder in electrode preparation in the field of lithium-ion batteries or fuel cells. However, the curing process has to be soft in most cases... 

Many high-performance polymer fibres are used in filter media to meet various specific requirements in diverse filtration applications. Filters made from fluoropol-ymer (Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), and Per-fluoroalkoxy alkane (PFA)) fibres, and membranes have inherent, chemical-resistant, and flame-retardant properties, and they are widely employed to filter aggressive chemicals and acids in the manufacture of wafers and microchips in the microelectronics industry. Ethylene ChloroTriFluoroEthylene (E-CTFE) melt blown fabrics have a unique ability to coalesce difficult liquids and can withstand the piranha effect in filtering ozone enriched ultrapure water. Polyphenylene sulfide (PPS) fibres are also chemical resistant, stand high temperature, and are suitable for making baghouse filters. Eilter media made from other high-performance polymer fibres, such as polyamide-imide, polyetherimide (PEI), Polyimide P84 fibre,polyetheretherke-tone, and liquid crystal polymers also appear in the filtration and separation market. 

In another example,1 1 a problem with poor physical properties of molded fluoroplastics was overcome. Transfer molded material was found to have low modulus of elasticity above 150°C and prone to irreversible cold flow. The solution involved embedding a metal or plastic insert as a core material in the mold. The choice of the core material depended on the end use performance requirements. An engineering plastic core was found preferable examples included polyetherether ketone (PEEK), polyphenylene sulfide (PPS), and polyether imide (PEI). Polytetrafluoroethylene bearers were placed in the mold to keep the core material away from the walls of the mold. No special cavity modifications were required. Any hot-melt fluoroplastic could be molded surrounding the insert examples include PVDF, FEP, ETFE, PFA, ECTFE, and PCTFE. 

Recently, PVDF has become a more popular material to produce hydrophobic membranes through phase inversion processes, mainly for membrane contactor and MD applications. It is preferred to other more hydrophobic polymers, such as polypropylene and polytetrafluoroethylene, because of its excellent combination of properties and its solubility in common organic solvents. Furthermore, the excellent thermal stability of PVDF has made it interesting as a membrane material in a wide range of industrial applications. In addition, unlike other crystalline polymers, PVDF exhibits thermodynamic compatibility with other polymers, such as poly(methyl methacrylate) (PMM A), over a wide range of blend compositions, which can be useful in the fabrication of membrane with desired properties. PVDF can be further chemically modified to obtain specific functions. In addition, it can be cross-linked when subjected to electron beam radiation or gamma radiation. 

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