Determination of the crystallinity of polyvinylidene fluoride

Gal'perin, Ye.L.; Kosmynin, B.P.; Smirnov, V. K.

doi:10.1016/0032-3950(70)90133-4

Cited by 14 publications

(7 citation statements)

References 14 publications

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“…In the case of the electrospun nanofibers, the bands at ca 840 and 1278 cm −1 which correspond to the β phase are well outlined with respect to the cast film. In addition, γ phase related bands appear at ca 1225 and 811 cm −1 for the cast sample . Taking into account that the band at 840 cm −1 is an indicator of trans chains longer than TT, while the 1274 cm −1 peak stands for much longer trans sequences, the FTIR spectra corroborate the improvement of the β phase formation in the electrospun nanofibers.…”

Section: Resultssupporting

confidence: 59%

On the electrospinning of PVDF: influence of the experimental conditions on the nanofiber properties

Cozza

Monticelli

Marsano

et al. 2012

Polymer International

147

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The characteristics of poly(vinylidene fluoride) (PVDF) nanofibers, prepared by applying the electrospinning technique from N,N‐dimethylformamide/acetone mixtures, were studied by varying the experimental conditions. The nanofiber morphology was assessed by scanning electron microscopy, while wide angle X‐ray diffraction and infrared spectroscopy were performed to study the crystallinity. The influence of the electrospinning conditions, such as kind of solvent mixture, polymer concentration, voltage tension, airflow and humidity, on nanofiber morphology was studied. In particular, the latter parameter, generally not considered, was found to modify the electrospun mat structure in a relevant way. Generally, the above technique turns out to be capable of strongly affecting the polymorphism of the polymer, namely β phase formation was higher in the electrospun mats compared with cast films, which displayed a non‐polar α crystal phase. As far as the influence of the electrospinning conditions on PVDF crystal structure is concerned, modification of the experimental parameters did not affect the α/β ratio. Nevertheless, comparing the behavior of two commercial PVDF samples with similar molecular masses, our results show that the polymer which forms a higher content of β phase in its cast films allowed electrospun mats characterized by almost complete formation of β phase to be obtained. Copyright © 2012 Society of Chemical Industry

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Section: Resultssupporting

confidence: 59%

On the electrospinning of PVDF: influence of the experimental conditions on the nanofiber properties

Cozza

Monticelli

Marsano

et al. 2012

Polymer International

147

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“…2θ = 12°−20°, ,, these features are not expected to significantly contribute to the diffractograms of the blends with PVDF due to the low level of crystallinity of Nafion and its low composition in the blend. The diffractogram of pure PVDF contains characteristic reflections due to the α-form crystallites, specifically the reflections due to the (110), (020), (100), and (120) crystal planes located at 27.0°, 20.4°, 18.8°, and 18.2° 2θ, respectively. , A similar diffraction pattern is observed when PVDF is melt crystallized in the presence of Na + -form Nafion with the exception of a reflection at 2θ = 18.8° which may be attributed to the γ-crystal polymorph. In the blend of PVDF with TBA + -form Nafion, the characteristic reflections of the α-form at 27.0° 2θ have almost completely disappeared, and only two broad reflections at 18.8° and 20.5° are present.…”

Section: Resultsmentioning

confidence: 63%

“…In agreement with the FTIR results, these reflections are more characteristic of a mixture of the γ-and β-polymorphic forms of PVDF. 47,56,57 With respect to the effect of these blends on the formation of polymorphic crystalline domains in the PVDF, previous studies have shown that melt crystallization of PVDF in the presence of PMMA can alter the crystal morphology of PVDF from the R-form to the β-or γ-crystal forms. 9 While no satisfactory explanation was given for this phenomenon, it has been reported that the crystal growth rate of PVDF in the presence of PMMA is significantly reduced relative to that of pure PVDF.…”

Section: Resultsmentioning

confidence: 99%

Blends of a Perfluorosulfonate Ionomer with Poly(vinylidene fluoride): Effect of Counterion Type on Phase Separation and Crystal Morphology

Landis

Moore

2000

Macromolecules

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The type of counterion present in the Nafion component of a blend with poly(vinylidene fluoride) (PVDF) is shown to affect phase separation and the crystalline polymorphism of the PVDF component. Nafion neutralized with an alkali metal counterion, Na + , results in blends displaying largescale phase separation upon heating to temperatures above the melting point of PVDF. In contrast, when the Nafion counterion is changed to a larger tetrabutylammonium counterion (TBA + ), the melt is homogeneous, and with the exception of the PVDF crystallites, large-scale phase separation is not observed after the blend is cooled to room temperature. For the blends containing Na + -form Nafion, the crystalline morphology of the PVDF component develops in predominately the R crystal form, similar to pure PVDF crystallized from the melt. However, for blends containing TBA + -form Nafion, the PVDF component crystallizes with a higher content of the β-and/or γ-crystal forms. This effect of counterion type on the phase separation behavior and crystal morphology is attributed to the strength of the electrostatic crosslinks within the Nafion component. Strong electrostatic cross-links induce gelation of the Nafion component leading to phase separation at elevated temperatures, whereas weak electrostatic cross-links provide a free-flowing melt that allows for a more favorable mixing with the PVDF component and is thus capable of influencing the crystallization process.

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“…The techniques which have been reported to yield this crystal phase include the following: crystallization from the melt at high temperatures and pressures;8,9 annealing the a phase at high temperatures and pressures;8 various atmospheric-pressure thermal treatments of both the a2,10,11 and 8W phases; high-temperature crystallization from the melt at atmospheric pressure;12 and crystallization from dimethyl sulfoxide, dimethylacetamide (DMA), and dimethylformamide solutions. [13][14][15] The y phase very readily undergoes a crystal-crystal phase transition to the 8 phase when mechanically deformed.2,8,9 Thus, Hasegawa et al 3 used unoriented samples to determine their proposed structure for the y phase. According to Hasegawa et al,3 the 7-phase chain conformation is identical with that in the 8 phase, that is, a nearly all-trans backbone.…”

mentioning

confidence: 99%

The Crystal Structure of the γ Phase of Poly(vinylidene fluoride)

Weinhold¹,

Litt²,

Lando³

1980

Macromolecules

171

109

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The crystal structure of the y phase of poly(vinylidene fluoride) (PVF2) was determined by X-ray diffraction techniques. Oriented specimens of the y phase were obtained by high-temperature drawing of films of ultrahigh molecular weight PVF2 cast from dimethylacetamide solution. The unit cell of the y phase was found to be orthorhombic with dimensions a = 0.497, b = 0.966, and c = 0.918 nm. The chain conformation is approximately TTTGTTTG'. Individual chains with this conformation possess a net electrical dipole and pack such that the unit cell is polar. The chains pack in a statistical parallel-antiparallel manner, which can be modeled by a hypothetical four-chain unit cell belonging to space group C2cm.Four crystal forms of poly(vinylidene fluoride) are known. The a phase, or phase II, is the form produced

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Determination of the crystallinity of polyvinylidene fluoride

Cited by 14 publications

References 14 publications

On the electrospinning of PVDF: influence of the experimental conditions on the nanofiber properties

On the electrospinning of PVDF: influence of the experimental conditions on the nanofiber properties

Blends of a Perfluorosulfonate Ionomer with Poly(vinylidene fluoride): Effect of Counterion Type on Phase Separation and Crystal Morphology

The Crystal Structure of the γ Phase of Poly(vinylidene fluoride)

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