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Grégório, Rinaldo; Ueno, Eri

doi:10.1023/a:1004689205706

Cited by 479 publications

(278 citation statements)

References 11 publications

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“…8a, there is a remarkable enhancement of the peak intensity at 2h of 20.60 o , demonstrating the increase of b Fig. 8b, while the band intensity at 840 and 510 cm -1 associated with b phase is boosted, a new band at 472 cm -1 attributed to oriented b phase appears [30,53], thus confirming the XRD result. As derived from the DSC result, the crystallinity, F(b), and X(b) of the annealed membrane are increased from 29.81, 70, and 12.52 % to 37.96, 76, and 17.31 %, respectively.…”

Section: Annealing Effectsupporting

confidence: 72%

Surface characteristics and blood compatibility of PVDF/PMMA membranes

Wang

et al. 2012

J Mater Sci

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Poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) membranes have important applications as biomaterials. In this study, PVDF/PMMA with varying ratios is blown into membranes, the surface property and blood compatibility of which are thoroughly investigated. Membrane surface characteristics including composition and topography exert considerable influence on the blood compatibility. Introduction of PMMA disturbs PVDF crystallization, however, favors the b phase crystal formation. PVDF content, crystallization ability, and surface enrichment have decisive effects on the membrane surface composition. Meanwhile, with increased PMMA fraction, the membrane surface roughness is also increased, and subsequently results in decreased hemocompatibility. While the membranes with PMMA content lower than 30 wt% show good blood compatibility, those with higher PMMA fraction exhibit obvious platelet adhesion to the surface. Thermal annealing promotes the formation of b phase PVDF and generates much smoother surface, thus endowing the membranes with greatly enhanced blood compatibility. These results show the prospect for optimization of processability, surface property, and blood compatibility of PVDF/PMMA membranes through facile modulation of PMMA content and fabrication process.

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Section: Annealing Effectsupporting

confidence: 72%

Surface characteristics and blood compatibility of PVDF/PMMA membranes

Wang

et al. 2012

J Mater Sci

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“…7,22 The piezoelectric properties of the polarized PVDF films significantly depended on the b-phase content. 10,14 The d 33 values of the films prepared with both dies after cold drawing to two different draw ratios are reported in Table III. Table III shows that the d 33 values of the PVDF films prepared with the two-channel die were higher than those obtained from the sample prepared with the slit die with the same draw ratio.…”

Section: Resultsmentioning

confidence: 99%

“…The b form consists of parallel packing of the polymer chains in all-trans conformations, and thus, it shows a large spontaneous lattice polarization. [9][10][11] The polar b phase is the most desirable crystalline form for PVDF because it provides better pyroelectric and piezoelectric properties. Although the most common polymorph of PVDF is the a form, which is directly produced by the cooling of the melt, PVDF films consisting of b crystals are usually prepared by the drawing of samples having a crystals at temperatures below 1008C and stretching ratios of 3-5.…”

Section: Introductionmentioning

confidence: 99%

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Sobhani

Razavi‐Nouri

Yousefi

2007

J of Applied Polymer Sci

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This study was devoted to the effect of extensional flow during film extrusion on the formation of the b-crystalline phase and on the piezoelectric properties of the extruded poly(vinylidine fluoride) (PVDF) films after cold drawing. The PVDF films were extruded at different draw ratios with two different dies, a conventional slit die and a two-channel die, of which the latter was capable of applying high extensional flow to the PVDF melt. The PVDF films prepared with the two-channel die were drawn at different temperatures, strain rates, and strains. The optimum stretching conditions for the achievement of the maximum b-phase content were determined as follows: temperature ¼ 908C, strain ¼ 500%, and strain rate ¼ 0.083 s À1. The samples prepared from the dies were then drawn under optimum stretching conditions, and their b-phase content and piezoelectric strain coefficient (d 33 ) values were compared at equal draw ratios. Measured by the Fourier transform infrared technique, a maximum of 82% b-phase content was obtained for the samples prepared with the two-channel die, which was 7% higher than that of the samples prepared by the slit die. The d 33 value of the two-channel die was 35 pC/N, which was also 5 pC/N higher than that of the samples prepared with the slit die.

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“…The maximum dielectric constant values of pure PVDF and binary composite film are found at 10 7 Hz, denoted as a c relaxation [19,20]. Many researches [21][22][23] have reported the glass transition relaxation of PVDF at 10 7 Hz which relates to the micro-Brownian motions of the main chain backbone of PVDF. This phenomenal is found in our results for both cases; pure PVDF and binary composite film, but there is a difference at the value causes by the presence of Ba-PCH in PVDF.…”

Section: Dielectric Relaxation Studymentioning

confidence: 99%

Increment of dielectric constant in binary composite based on PVDF/clay system

Bunnak

Laoratanakul

Bhalla

et al. 2015

J Mater Sci: Mater Electron

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Binary composite films, with 10 wt% of barium doped porous clay heterostructure (Ba-PCH) in polyvinylidene difluoride, were fabricated by using mechanical mixing (Brabender) and hot pressing methods. The grain morphology of the composite films, as investigated by using the field emission scanning electron microscope, exhibits some agglomeration of Ba-PCH particles. The dielectric properties, as functions of frequency and temperature, were measured using a network analyzer. The dielectric constant of the composite film exhibits strong frequency and temperature dependence. The sharp drop of the dielectric constant is resulted, when temperature is decreased below the glass transition temperature of the polyvinylidene difluoride. The relaxation behaviors are analyzed carefully using the Arrhenius law and the other possible mechanisms and the study indicated that the dielectric behavior in these composite films is highly dominated by the electronic polarizability contributions.

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Untitled

Cited by 479 publications

References 11 publications

Surface characteristics and blood compatibility of PVDF/PMMA membranes

Surface characteristics and blood compatibility of PVDF/PMMA membranes

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Increment of dielectric constant in binary composite based on PVDF/clay system

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