Polyvinylidene fluoride

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Polyvinylidene fluoride
Names
IUPAC name
Poly(1,1-difluoroethylene) [1]
Other names
Polyvinylidene difluoride; poly(vinylene fluoride); Kynar; Hylar; Solef; Sygef; poly(1,1-difluoroethane)
Identifiers
ChEBI
ChemSpider
  • None
ECHA InfoCard
 100.133.181 Edit this at Wikidata
MeSH polyvinylidene+fluoride
Properties
−(C2H2F2)n−
Appearance Whitish or translucent solid
Melting point 177 °C (351 °F)
Insoluble
Structure
2.1 D[2]
Related compounds
Related compounds
PTFE
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive

vinylidene difluoride
. Its chemical formula is (C2H2F2)n.

PVDF is a specialty plastic used in applications requiring the highest purity, as well as resistance to solvents, acids and hydrocarbons. PVDF has low density 1.78 g/cm3 in comparison to other fluoropolymers, like polytetrafluoroethylene.

It is available in the form of piping products, sheet, tubing, films, plate and an insulator for premium wire. It can be injected, molded or welded and is commonly used in the chemical, semiconductor, medical and defense industries, as well as in

closed-cell foam, used increasingly in aviation and aerospace applications, and as an exotic 3D printer filament. It can also be used in repeated contact with food products, as it is FDA-compliant and non-toxic below its degradation temperature.[3]

As a fine powder grade, it is an ingredient in high-end paints for metals. These PVDF paints have extremely good

gloss and color retention. They are in use on many prominent buildings around the world, such as the Petronas Towers in Malaysia and Taipei 101
in Taiwan, as well as on commercial and residential metal roofing.

PVDF membranes are used in western blots for the immobilization of proteins, due to its non-specific affinity for amino acids.

PVDF is also used as a binder component for the carbon electrode in

supercapacitors
and for other electrochemical applications.

Names

PVDF is sold under a variety of brand names including KF (

Kureha), Hylar (Solvay), Kynar (Arkema
) and Solef (Solvay).

Production

Properties

In 1969, strong

N: 10 times larger than that observed in any other polymer.[4]

PVDF has a

thermal camera
sensors.

Unlike other popular piezoelectric materials, such as lead zirconate titanate (PZT), PVDF has a negative d33 value. Physically, this means that PVDF will compress instead of expand or vice versa when exposed to the same electric field.[7]

Thermal

PVDF resin has been subjected to high-heat experiments to test its thermal stability. PVDF was held for 10 years at 302 °F (150 °C), and following measurements indicated no thermal or oxidative breakdown occurred [citation needed]. PVDF resin has been recorded stable up to 707 °F (375 °C).[8]

Chemical compatibility

PVDF exhibits an increased chemical resistance and compatibility among thermoplastic materials. PVDF is considered to have excellent / inert resistance to:[citation needed]

  • strong acids, weak acids,
  • ionic, salt solutions,
  • halogenated compounds,
  • hydrocarbons,
  • aromatic solvents,
  • aliphatic solvents,
  • oxidants,
  • weak bases.

Chemical sensitivity

PVDF, similar to other fluoropolymers, exhibits chemical sensitivity, in general, with the following chemical families:

  • strong bases, caustics,
  • esters,
  • ketones.[9]

Intrinsic properties and resistance

Polyvinylidene fluoride expresses inherent resistance characteristics in certain high-focus applications. Namely these are: ozone oxidation reactions, nuclear radiation, UV damage, and microbiological, fungus growth.[citation needed] PVDF's resistance to these conditions is fairly distinctive among thermoplastic materials. PVDF's carbon and fluoride elemental stability contributes to this resistance, as well as the polymeric integration of PVDF during its processing.[citation needed]

Processing

PVDF may be synthesized from the gaseous

anion form as a processing aid by solubilizing monomers.[10] Compared to other fluoropolymers, it has an easier melt
process because of its relatively low melting point of around 177 °C.

Processed materials are typically in the non-piezoelectric alpha phase. The material must either be stretched or annealed to obtain the piezoelectric beta phase. The exception to this is for PVDF

thin films
(thickness in the order of micrometres). Residual stresses between thin films and the substrates on which they are processed are great enough to cause the beta phase to form.

In order to obtain a piezoelectric response, the material must first be poled in a large electric field. Poling of the material typically requires an external field of above 30 megavolts per metre (MV/m). Thick films (typically >100 µm) must be heated during the poling process in order to achieve a large piezoelectric response. Thick films are usually heated to 70–100 °C during the poling process.

A quantitative defluorination process was described by mechanochemistry,[11] for safe eco-friendly PVDF waste processing.

Applications

PVDF piping used to carry ultrapure water

PVDF is a thermoplastic that expresses versatility for applications similar to other thermoplastics, particularly fluoropolymers. PVDF resin is heated and handled for use in extrusion and injection molding to produce PVDF pipes, sheets, coatings, films, and molded PVDF products, such as bulk containers. Common industry applications for PVDF thermoplastics include:[9]

  • chemical processing,
  • electricity, batteries and electronic components,
  • construction and architecture,
  • healthcare and pharmaceutics,
  • biomedical research,
  • ultra-pure applications,
  • nuclear waste handling,
  • petrochemical, oil and gas,
  • food, beverage processing,
  • water, wastewater management.

In electronics / electricity

PVDF is commonly used as insulation on electrical wires, because of its combination of flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat resistance. Most of the narrow 30-gauge wire used in wire wrap circuit assembly and printed circuit board rework is PVDF-insulated. In this use the wire is generally referred to as "Kynar wire", from the trade name.

The piezoelectric properties of PVDF are exploited in the manufacture of

outer Solar System.[12]

PVDF is the standard binder material used in the production of composite electrodes for lithium-ion batteries.

N-methyl-2-pyrrolidone (NMP) is mixed with an active lithium storage material such as graphite, silicon, tin, LiCoO2, LiMn2O4, or LiFePO4 and a conductive additive such as carbon black or carbon nanofibers. This slurry is cast onto a metallic current collector, and the NMP is evaporated to form a composite or paste electrode
. PVDF is used because it is chemically inert over the potential range used and does not react with the electrolyte or lithium.

In biomedical science

In the biomedical sciences, PVDF is used in

western blotting). PVDF is resistant to solvents and, therefore, these membranes can be easily stripped and reused to look at other proteins. PVDF membranes may be used in other biomedical applications as part of a membrane filtration device, often in the form of a syringe filter or wheel filter. The various properties of this material, such as heat resistance, resistance to chemical corrosion, and low protein binding properties, make this material valuable in the biomedical sciences for preparation of medications as a sterilizing filter, and as a filter to prepare samples for analytical techniques such as high-performance liquid chromatography
(HPLC), where small amounts of particulate matter can damage sensitive and expensive equipment.

PVDF transducers have the advantage of being dynamically more suitable for modal testing than semiconductor piezoresistive transducers and more compliant for structural integration than piezoceramic transducers. For those reasons, the use of PVDF active sensors is a keystone for the development of future structural-health monitoring methods, due to their low cost and compliance.[14]

In high-temperature processes

PVDF is used as piping, sheet, and internal coatings in high-temperature, hot acid, radiation environment applications due to PVDF's resistance characteristics and upper temperature thresholds. As piping, PVDF is rated up to 248 °F (120 °C). Examples of PVDF uses include nuclear reactor waste handling, chemical synthesis and production, (sulfuric acid, common), air plenums, and boiler service pipe.

Other uses

PVDF is used for specialty monofilament fishing lines, sold as fluorocarbon replacements for nylon monofilament. The surface is harder, so it is more resistant to abrasion and sharp fish teeth. Its refractive index is lower than nylon, which makes the line less discernible to sharp fish eyes. It is also denser than nylon, making it sink faster towards fish.[15]

Other forms

Copolymers

The copolymer Poly(vinylidene fluoride-co-hexafluoropropylene) or PVDF-HFP is used as a co-polymer in the blades of artificial turf.[16]

Copolymers of PVDF are also used in piezoelectric and electrostrictive applications. One of the most commonly used copolymers is P(VDF-trifluoroethylene), usually available in ratios of about 50:50 and 65:35 by mass (equivalent to about 56:44 and 70:30 molar fractions). Another one is P(VDF-tetrafluoroethylene). They improve the piezoelectric response by improving the crystallinity of the material.

While the copolymers' unit structures are less polar than that of pure PVDF, the copolymers typically have a much higher crystallinity. This results in a larger piezoelectric response: d33 values for P(VDF-TFE) have been recorded to be as high as −38

p C/N[17] compared to −33 pC/N in pure PVDF.[18]

Terpolymers

dielectric constant of ~50.[21]

See also

References

  1. ^ "poly(vinylene fluoride) (CHEBI:53250)". Retrieved 14 July 2012.
  2. ^ Zhang, Q. M., Bharti, V., Kavarnos, G., Schwartz, M. (Ed.), (2002). "Poly (Vinylidene Fluoride) (PVDF) and its Copolymers", Encyclopedia of Smart Materials, Volumes 1–2, John Wiley & Sons, 807–825.
  3. ^ "PVDF (Polyvinylidene fluoride, Tecaflon ®, Solef®, Kynar®) | Plastics International".
  4. S2CID 122316276
    .
  5. ISSN 0079-6700
    .
  6. S2CID 205976678
    .
  7. PMID 28773798
    .
  8. ^ "Physical and Mechanical Properties". Arkema, Inc. Innovative Chemistry.
  9. ^ a b "PVDF Performance & Characteristics Data" (PDF). Plastic Pipe Solutions.
  10. PMID 16433330
    .
  11. doi:10.1002/app.1663
    .
  12. S2CID 129795884
    . Retrieved 17 August 2023.
  13. ISSN 1364-0321
    .
  14. S2CID 136758382
    .
  15. ^ Seaguar history — Kureha America, Inc. manufacturer's site. Archived 20 June 2010 at the Wayback Machine
  16. ^ McMenemy, Jeff (10 December 2021). "Portsmouth to test for PFAS in new turf field. Is it dangerous? City says no. Others disagree". Portsmouth Herald. Retrieved 30 December 2021.
  17. doi:10.1063/1.364300
    .
  18. doi:10.1080/00150198608245016
    .
  19. doi:10.1063/1.1358847
    .
  20. doi:10.1021/ma062800l
    .
  21. S2CID 120322803
    .
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