Mechanical properties of PVDF

Figure 3.116 Effect of y-rays on the mechanical properties of PVDF.i ...

Refer to Table 3.15 for the physical and mechanical properties of PVDF. It is a tluoropolymer resin (one that is not fully fluorinated). As such it is resistant... 

Livi et al. demonstrated that the use of perfluoroalkylimidazolium as surfactant agent of MMT (1%) allows a dramatic increase of mechanical properties with a strain at break of 250% compared to 30% for neat PVDF [73], The impaet of MMT modification by the imidazolium IL on the structuration as well as on the mechanical properties of PVDF is shown in Figure 24.3. 

Like ETFE, PVDF readily cross-links as a result of exposure to radiation. Radiation (gamma rays) has a modest effect on the mechanical properties of PVDF. 

Nevertheless, mechanical stability of electrospun PVDF-based fibrous membranes is inherently weak to withstand the strong tension during battery assembly process, which severely restricts their practical applications. Chemical modification by grafting or crosslinking with functional reagents has been proved as an effective approach to improve the mechanical property of PVDF [25]. Kader et al. reported the preparation of electrospun poly(vinylidene fluoride)-graft-poly(tert-butyl... 

P. Sukitpaneenit and T.S. Chung, Molecular elucidation of morphology and mechanical properties of PVDF hollow fiber membranes from aspects of phase inversion, crystallization and rheology. Journal of Membrane Science 340 (2009) 192-205. 

Sukitpaneenit, P. and T.-S. Chung. 2009. Molecular Elucidation of Morphology and Mechanical Properties of PVDF Hollow Fiber Membranes from Aspects of Phase Inversion, Crystallization and Rheology. Journal of Membrane Science 340(1/2) 192-205. doi 10.1016/j.memsci.2009.05.029. 

Malmongea,L.E do Carmo Langianoa,S. Marques Cordeiroa,J. M. Capparelli Mattosob, L. H. and Malmongea, J. A., Thermal and mechanical properties of PVDF/PANI blends. Mater. Res., 13(4), 465-470 (2010). 

In order to anticipate problems and to interpret observations under the extreme conditions of shock compression, it is necessary to consider structural and electronic characteristics of PVDF. Although the phenomenological piezoelectric properties of PVDF are similar to those of the piezoelectric crystals, the structure of the materials is far more complex due to its ferroelectric nature and a heterogeneous mixture of crystalline and amorphous phases which are strongly dependent on mechanical and electrical history. 

To overcome the poor mechanical properties of polymer and gel polymer type electrolytes, microporous membranes impregnated with gel polymer electrolytes, such as PVdF. PVdF—HFP. and other gelling agents, have been developed as an electrolyte material for lithium batteries.Gel coated and/ or gel-filled separators have some characteristics that may be harder to achieve in the separator-free gel electrolytes. For example, they can offer much better protection against internal shorts when compared to gel electrolytes and can therefore help in reducing the overall thickness of the electrolyte layer. In addition the ability of some separators to shutdown... 

Figure 6. Mechanical properties of films of PMMA-PVdF blends...

Jin et al. (65) used poly(vinylidene fluoride) (PVDF) as a compatibilizer to assist dispersion of CNTs in PMMA. Multi-walled carbon nanotubes were first coated with PVDF and then melt-blended with PMMA. Poly(vinylidene fluoride) served as an adhesive to improve wetting of CNTs by PMMA and to increase the interfacial adhesion resulting in improved mechanical properties of MWCNT-PMMA composites. 

Ferroelectric composites are alternatives to standard piezoelectric and pyroelectric ceramics such as lead zirconate titanate (PZT) and BaHOs (BT). They combine the strong ferroelectric and dielectric properties of ceramics with the easy processing and good mechanical properties of polymers. Dispersion of micrometer-sized ferroelectric particles in an electrically passive epoxy matrix was first published by Furukawa et al. [1976] and later extended to ferroelectric matrices such as poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-3-fluoroethylene) (PVDF-TrFE) [Hsiang et al., 2001 Hilczer et al., 2002 Gimenes et al., 2004 Lam et al., 2005 Beloti et al., 2006]. However, the necessity of miniaturization of electronic components and... 

The properties of PVDF homopolymers and copolymers are sensitive to the chemical composition, molecular mass characteristics, and molecular architecture. These attributes are dictated by the polymerization method and ingredients, the method of isolation, and the thermal/mechanical history during isolation and subsequent processing. 

The newest market for KYNAR resins is perhaps the most exciting and most challenging. This is the KYNAR Piezo Film. By definition, a piezo electric material is one that can change polarization in response to mechanical stress. The CH - CF repeat unit was found to exhibit the strongest piezo electric and pyro electric activity of all known polymers. This property was first reported in 1969 based on experiments using KYNAR PVDF. Since that time the piezo and pyro electric properties of PVDF have been the subject of many publications. 

Recently, PVDF has been intensively studied by many authors as a polymer matrix for ceramic nanopowders such as BaTiOs [212,214-216], PbTiOs [217], CaCOs [218], and Pb(Zro.5TiOo.5)03 [215] because they combine the excellent ferroelectric properties of ceramics with the flexible mechanical properties of the polymer. The PVDF polymer composites with electroactive ceramic nanoparticles were prepared by sol-gel processes [214,217], a natural adsorption action between the nanosized BaTiOs and PVDF particles, and then a hot press process [216]. 

PVDF nanocomposites based on ammonium-, pyridinium-, imidazolium-, or phosphonium-modified MMT have been prepared by melt intercalation [57,64-73]. The influence of the modified clays on the morphologies and their consequence on the physical properties have been investigated. XRD and TEM analyses evidence different morphologies as a function of the nature of the surfactant. An exfoliated structure is obtained with ammonium-, pyridinium-, and imidazolium-treated MMT, while phosphonium IL-modified MMT leads to a partially exfoliated morphology. The mechanical properties of nanocomposites are higher than the neat PVDF. However, the influence of thermostable ILs on mechanical properties is limited. In fact, the storage modulus of the neat PVDF and the PVDF nanocomposites remains the same whatever be the nature of the IL intercalant. Nevertheless, the elongation at break increases (-1-175%) with 5wt.% of pyridinium-treated MMT compared to h-200% of strain at break obtained for ammonium-modified MMT. Recently,... 

PVDF was discovered by Dr. Heiji Kawai in 1969 [32]. Although PVDF is a piezoelectric system, it is a ferroelectric cum piezoelectric material as explained earlier, with a Curie point of 103 °C. PVDF possesses various phases such as a, p, y, and 5, among which p-phase has the most responsive piezoelectric properties. Compared with all ferroelectric polymers, PVDF has a dielectric constant with a reasonable chemical and mechanical durability [4,32]. In general, the physical properties of PVDF make it the most valuable material for application in sensors. 

Partially fluorinated fluoroplastics can be cross-linked to improve the mechanical properties of shaped articles such as wire insulation. For example, the aerospace industry requires wire and cable that can withstand abrasion and cutting in addition to flammability. Cross-linking a fluoropolymer like ETFE, ECTFE, or PVDF enhances its mechanical properties. For example, actual cross-linking is accomplished by incorporating a cross-linking agent in ETFE after the extrusion of the insulation, followed by irradiation.fi l... 

---