Polyvinylidene fluoride
Encyclopedia : P : PO : POL : Polyvinylidene fluoride
| Polyvinylidene fluoride | |
|---|---|
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| General | |
| Systematic name | poly-1,1-difluoroethene |
| Other names | polyvinylidene fluoride |
| Molecular formula | -(CH2CF2)n- |
| SMILES | ? |
| Appearance | transparent solid |
| CAS number | |
| Properties | |
| Density and phase1,2 | 1.76 g/cm3 (110 lb/ft3), solid |
| Solubility in water | not soluble in water |
| Melting point4 | 134–169 °C (273–336 °F, 407-442 K) |
| Thermal conductivity4 | 0.18 W m-1 K-1 |
| Coefficent of expansion4 | 0.18×10-6 K-1 (0.10×10-6 °F-1) |
| Yield strength4 | 15–35 MPa (2.2–5.0 kpsi) |
| Elongation at rupture4 | 200%–750% |
| Modulus of elasticity | 350–1100 MPa (50–160 kpsi)4 E1= 2.56GPa, E2= 2.6GPa (Vinogradov, 2002) |
| Poisson ratio | ν21~0.1, ν31~0.8 (Tasaka, 1981) |
| Volume resistivity4 | ≥ 1x1012 Ω·m |
| Piezoelectric constants | d33=20 pC/N, d31= -5 to -16 pC/N, d32= -3 to -5 pC/N |
| Structure | |
| Crystal structure | mm2 (Kawaii, 1969) |
| Dipole moment | 2.1 D (Zhang, 2002) |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | ? |
| NFPA 704 | |
| Flash point | ? °C |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties | n = ?, εr = 9 to 11. 3 |
| Related compounds | |
| Related compounds | PVC, PTFE, P(VDF-TrFE) |
| References | |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
PolyVinylidine DiFluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer. It is also known as KYNAR®.
PVDF is very expensive; its use generally reserved for applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat. It is available as piping products, sheet, plate and an insulator for premium wire. It can be injection molded and welded and is commonly used in the chemical, semiconductor, medical and defense industries.
When poled, PVDF is a ferroelectric polymer, exhibiting efficient piezoelectric and pyroelectric properties. These characteristics make it useful in sensor and battery applications.
PVDF has a glass transition temperature (Tg) of about -35oC and is typically 50-60% crystalline. To give the material its piezoelectric properties, it is mechanically stretched to orient the molecular chains and then poled under tension. PVDF exists several forms: alpha (TGTG'), beta (TTTT), and gamma (TTTGTTTG') phases, depending on the chain conformations as trans (T) or gauche (G) linkages.
Copolymers
Copolymers of PVDF are also used in piezoelectric and electrostrictive applications. One of the most commonly-used copolymers is P(VDF-TrFE), usually available in ratios of about 50-50 wt% and 65-35 wt% (equivalent to about 56-44 mol% and 70-30 mol%).History
In 1969, the strong piezoelectricity of PVDF was observed by Kawai et al. The piezoelectric coefficient of poled thin films of the material were reported to be as large as 6-7 pCN-1, 10 times larger than that observed in any other polymer.See also
References:- Kawai, H., (1969). Jpn. J. Appl. Phys, 8, p975.
- 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.
- Vinogradov, A., Schwartz, M. (Ed.), (2002). "Piezoelectricity in Polymers", Encyclopedia of Smart Materials, Volumes 1-2, John Wiley & Sons, 780-792.
- Tasaka, S., Miyata, S., (1981). Ferroelectrics, 32 (1), 17-23.
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