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Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

CHINAGLIA, Dante Luis; GREGORIO JR., Rinaldo; STEFANELLO, Josiani Cristina; ALTAFIM, Ruy Alberto Pisani; WIRGES, Werner; WANG, Feipeng; GERHARD, Reimund
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
100.24799%
The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N-dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt % at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films. (C) 2009 Wiley Periodicals...

Response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate membrane

TEIXEIRA, L. N.; CRIPPA, G. E.; GIMENES, R.; ZAGHETE, M. A.; OLIVEIRA, P. T. de; ROSA, A. L.; BELOTI, M. M.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
69.59199%
This study investigated the response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT) membrane. Osteoblastic cells were cultured in osteogenic conditions either on P(VDF-TrFE)/BT or polytetrafluoroethylene (PTFE) for up to 14 days. At 7 and 14 days, the mRNA expression of Runt-related transcription factor 2 (RUNX2), Type I collagen (COL I), Osteopontin (OPN), Alkaline phosphatase (ALP), Bone sialoprotein (BSP), and Osteocalcin (OC), key markers of the osteoblastic phenotype, and of Bcl2-associated X protein (Bax), B-cell CLL/lymphoma 2 (Bcl-2), and Survivin (SUR), associated with the control of the apoptotic cell death, was assayed by real-time PCR. In situ ALP activity was qualitatively evaluated by means of Fast red staining. Surface characterization was also qualitatively and quantitatively assayed in terms of topography, roughness, and wettability. Cells grown on P(VDF-TrFE)/BT exhibited a significantly higher mRNA expression for all markers compared to the ones on PTFE, except for Bcl-2, which was not detected for both groups. Additionally, Fast red staining was noticeably stronger in cultures on P(VDF-TrFE)/BT at 7 and 14 days. At micron-and submicron scale...

In vitro biocompatibility of poly(vinylidene fluoride-trifluoroethylene)/barium titanate composite using cultures of human periodontal ligament fibroblasts and keratinocytes

TEIXEIRA, L. N.; CRIPPA, G. E.; TRABUCO, A. C.; GIMENES, R.; ZAGHETE, M. A.; PALIOTO, D. B.; OLIVEIRA, P. T. de; ROSA, A. L.; BELOTI, M. M.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
69.59199%
The mm of this work was to evaluate the biocompatibility of poly(vinylidene fluoride-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT) membrane to be used in guided tissue regeneration (GTR) Fibroblasts from human periodontal ligament (hPDLF) and keratinocytes (SCC9) were plated on P(VDF-TrFE)/BT and polytetrafluorethylene membranes at a cell density of 20.000 cells well(-1) and Cultured for up to 21 days Cell morphology, adhesion and proliferation were evaluated in hPDLF and keratinocytes, while total protein content and alkaline phosphatase (ALP) activity were assayed only for hPDLF Using a higher cell density. real-time polymerase chain reaction (PCR) was performed to assess the expression of typical genes of hPDLF, such as periostin, PDLs17, S100A4 and fibromodulin, and key phenotypic markers of keratinocytes, including involucrin, keratins 1. 10 and 14 Expression of the apoptotic genes bax, bcl-2 and Survivin was evaluated for both cultures hPDLF adhered and spread more oil P(VDF-TrFE)/BT, whereas keratinocytes showed a round shape on both membranes. hPDLF adhesion was greater oil P(VDF-TrFE)/BT at 2 and 4 h, while keratinocyte adhesion was similar for both membranes. Whereas proliferation was significantly higher for hPDLF on P(VDF-TrFE)/BT at days 1 and 7. no signs of keratinocyte proliferation could be noticed for both membranes Total protein content was greater on P(VDF-TrFE)/BT at 7...

Caracterização de uma microválvula fabricada usando o polímero piezoelétrico poli(fluoreto de vinilideno) (PVDF) integrada a saída de um microbocal sônico; Characterization of a microvalve using the piezoelectric polymer poly(viniyidene fluoride) (PVDF) integrated to a micronozzle end

Wiederkehr, Rodrigo Sérgio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/12/2007 PT
Relevância na Pesquisa
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Este trabalho descreve a seqüência de fabricação de uma microválvula piezoelétrica posicionada na saída de um microbocal sônico. A técnica usada para fabricar os microbocais foi o jateamento utilizando pó de alumina e o substrato usado foi de vidro. As microválvulas são atuadores fabricados com o polímero poli(fluoreto de vinilideno) (PVDF) que é um material piezoelétrico. Os microbocais têm um formato convergente-divergente com diâmetro na entrada de 1 mm e com diâmetro na garganta em cerca de 240 microns. O atuador foi fabricado no modo bimorfo (duas folhas do polímero coladas com polarização opostas) com dimensões de 3 mm de largura por 6 mm de comprimento. Ambas as folhas do polímero são recobertas por um filme condutor de 200 nm de espessura usados como eletrodos. Aplicando uma voltagem entre os eletrodos uma folha expande enquanto a outra contrai gerando um movimento vertical do atuador. O movimento vertical pode ser maior ou menor dependendo do valor da tensão aplicada. Os dispositivos foram testados usando uma linha de gás, aplicando tensões DC e AC nos eletrodos do atuador. Para controle, também foram realizadas medidas em bocais sem atuadores. No caso onde foram aplicadas tensões DC nos atuadores...

Estudo da viabilidade de aplicação do polímero piezelétrico fluoreto de polivinilideno (PVDF) entre osso cortical e placa de osteossíntese para estimulação de crescimento ósseo.; Study of the viability of the piezoeletric poly(vinylidene fluoride) (PVDF) polymer application between cortical bone and osteosynthesis plate for growth bone simulation.

Paschoal, André Luís
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/05/2003 PT
Relevância na Pesquisa
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O uso de biomateriais para acelerar reparos de fraturas ósseas tem aumentado nos últimos anos. Neste estudo, as propriedades piezelétricas do fluoreto de polivinilideno foram utilizadas com a finalidade de mimetizar os potenciais bioelétricos associados à deformação óssea, que são diminuídos quando ocorre fratura óssea. Estudos histomorfométricos foram efetuados para verificar a influência do polímero. Testes de biocompatibilidade e de esterilização permitiram avaliar os riscos da utilização do polímero como material de implante. O polímero piezelétrico associado à placa de osteossíntese resultou em uma maior quantidade de matriz óssea mineralizada na lesão quando comparado ao implante da placa sem o polímero.; The use of biomaterials to promote accelerated bone fracture repair has been improved in the recent years. In the present study, the piezoelectric properties of poly(vinylidene fluoride) were used with the aim of mimetizing bioelectrical potentials associated to bone strain which decrease when a bone fracture occurs. Histomorphometric studies were accomplished to verify the influence of the polymer. Biocompatibility and sterilization tests assessed any risk related to the use of a polymer as an implantable material. The piezoelectric polymer associated to an osteosynthesis plate resulted in a larger amount of mineralized bone matrix in the lesion when compared to a plate implanted without the polymer.

Modificação de poli(fluoreto de vinilideno) induzida por radiação gama para aplicação como compósito ionomérico de metal-polímero; Poly(vinylidene fluoride) modification induced by gamma irradiation for application as ionic polymer-metal composite

Ferreira, Henrique Perez
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/07/2011 PT
Relevância na Pesquisa
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Foi estudada a enxertia de estireno induzida por radiação gama em filmes de poli(fluoreto de vinilideno) (PVDF) com espessura de 0,125 mm com doses entre 1 e 100 kGy em presença de soluções de estireno/N,Ndimetilformamida (DMF) (1:1, v/v) e estireno/tolueno (1:1, v/v) com taxa de dose de 5 kGy.h-1 por meio do método simultâneo de irradiação sob atmosfera de nitrogênio e em temperatura ambiente, usando raios gama de uma fonte de Co- 60. Depois de enxertados, os polímeros foram sulfonados em soluções de ácido clorossulfônico/1,2-dicloroetano (2 e 10 %). Os filmes foram caracterizados antes e depois de cada modificação com o cálculo do Grau de enxertia, (DOG), espectrometria no infravermelho (FT-IR), microscopia eletrônica de varredura (MEV), calorimetria exploratória diferencial (DSC) e termogravimetria (TG/DTG). Os resultados do grau de enxertia mostraram que a enxertia aumenta com o aumento da dose e varia enormemente de acordo com o solvente utilizado, com enxertias cerca de 20 vezes maiores quando do uso da DMF em relação ao do tolueno. Foi possível confirmar a enxertia do estireno por FT-IR graças ao aparecimento de novos picos característicos e por TG/DTG e DSC por meio das alterações do comportamento térmico dos materiais enxertados/sulfonados. Os materiais sulfonados ainda foram caracterizados por suas capacidades de troca iônica (IEC)...

Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

Chinaglia, Dante Luis; Gregorio, Rinaldo; Stefanello, Josiani Cristina; Pisani Altafim, Ruy Alberto; Wirges, Werner; Wang, Feipeng; Gerhard, Reimund
Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: Artigo de Revista Científica Formato: 785-791
ENG
Relevância na Pesquisa
100.24799%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N-dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt % at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films. (C) 2009 Wiley Periodicals...

Response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate membrane

Teixeira, L. N.; Crippa, G. E.; Gimenes, R.; Zaghete, M. A.; Oliveira, P. T. de; Rosa, A. L.; Beloti, M. M.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 151-158
ENG
Relevância na Pesquisa
69.59199%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); This study investigated the response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT) membrane. Osteoblastic cells were cultured in osteogenic conditions either on P(VDF-TrFE)/BT or polytetrafluoroethylene (PTFE) for up to 14 days. At 7 and 14 days, the mRNA expression of Runt-related transcription factor 2 (RUNX2), Type I collagen (COL I), Osteopontin (OPN), Alkaline phosphatase (ALP), Bone sialoprotein (BSP), and Osteocalcin (OC), key markers of the osteoblastic phenotype, and of Bcl2-associated X protein (Bax), B-cell CLL/lymphoma 2 (Bcl-2), and Survivin (SUR), associated with the control of the apoptotic cell death, was assayed by real-time PCR. In situ ALP activity was qualitatively evaluated by means of Fast red staining. Surface characterization was also qualitatively and quantitatively assayed in terms of topography, roughness, and wettability. Cells grown on P(VDF-TrFE)/BT exhibited a significantly higher mRNA expression for all markers compared to the ones on PTFE, except for Bcl-2, which was not detected for both groups. Additionally...

Efeito das condições de preparação na condutividade elétrica de blendas de poli(fluoreto de vinilideno) e poli(o-metoxianilina)

Malmonge, Luiz Francisco; Mattoso, Luiz Henrique C.
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica Formato: 72-78
POR
Relevância na Pesquisa
69.753506%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Neste trabalho estudou-se o efeito das condições de preparação na condutividade elétrica de blendas condutoras de poli(fluoreto de vinilideno) (PVDF) com poli(o-metoxianilina) (POMA). A condutividade elétrica e a qualidade dos filmes produzidos dependem significativamente do solvente, dopante e das condições de preparação das blendas. Filmes flexíveis e auto-sustentáveis da blenda PVDF/POMA dopada com o ácido p-tolueno sulfônico (TSA) foram obtidos em condições otimizadas. Estes apresentam condutividade elétrica em uma larga faixa (10-12 - 10-2 S/cm), onde para baixos teores de POMA-TSA (<2,0% em massa) já se atinge alto valor de condutividade (10-7 S/cm), não sendo definida uma composição mínima para percolação.; In this work, the effect of preparation conditions on the properties of conductive blends of poly (vinylidene fluoride) (PVDF) and poly(o-methoxyaniline) (POMA) was studied. The quality and conductivity of the films produced depend significantly on the solvent, dopant and preparation conditions of the blends. Flexible...

Phase transition in poly(vinylidene fluoride) investigated with micro-Raman spectroscopy

Constantino, CJL; Job, A. E.; Simoes, R. D.; Giacometti, J. A.; Zucolotto, V; Oliveira, O. N.; Gozzi, G.; Chinaglia, D. L.
Fonte: Soc Applied Spectroscopy Publicador: Soc Applied Spectroscopy
Tipo: Artigo de Revista Científica Formato: 275-279
ENG
Relevância na Pesquisa
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The phase transition from the non-polar a-phase to the polar beta-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of alpha-PVDF were subjected to stretching under controlled rates at 80 degrees C, while the transition to P-PVDF was monitored by the decrease in the Raman band at 794 cm(-1) characteristic of the a-phase, along with the concomitant increase in the 839 cm-1 band characteristic of the P-phase. The alpha ->beta transition in our PVDF samples could be achieved even for the sample stretched to twice (2 X -stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the a-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques...

Effect of low contents of a polyaniline derivative on the crystallization and electrical properties of blends with PVDF

Rocha, I. S.; Mattoso, L. H. C.; Malmonge, L. F.; Gregório Júnior, R.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 1219-1224
ENG
Relevância na Pesquisa
69.753506%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The effect of low levels of poly(o-methoxyaniline) (POMA) on the crystallization, morphology, and electrical characteristics of blends with poly(vinylidene fluoride) (PVDF) were studied by infrared spectroscopy, AC electrical measurements, and optical microscopy. Undoped POMA has a strong effect in increasing the alpha-phase and decreasing the beta-phase content of PVDF in blends crystallized from solution. For blends melt crystallized, doped POMA promotes much greater homogeneity than undoped POMA. Interestingly, doped POMA promotes the nucleation and growth of unringed PVDF spherulites, whereas undoped POMA hinders it. The doping state of the POMA was also extremely important in determining the electrical behavior of the blend. (C) 1999 John Wiley & Sons, Inc.

ELECTROACTIVE BLENDS OF POLY(VINYLIDENE FLUORIDE) AND POLYANILINE DERIVATIVES

Malmonge, L. F.; Mattoso, LHC
Fonte: Butterworth-heinemann Ltd Publicador: Butterworth-heinemann Ltd
Tipo: Artigo de Revista Científica Formato: 245-249
ENG
Relevância na Pesquisa
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The conditions for processing and doping of blends of poly(o-alkoxyaniline)s and poly(vinylidene fluoride) were investigated. Flexible, free-standing and stretchable films of blends of various compositions were obtained by casting. A low percolation threshold was observed with the onset of conductivity at low polyalkoxyaniline contents (i.e. 5%). Interestingly, these blends displayed electrochromism with colour changes similar to those of the parent conducting polymer, as observed from cyclic voltammetry measurements. This behaviour is seen even for low contents of the conducting polymer, indicating that a continuous conducting pathway, which is capable of exchanging charge, is formed within the insulating matrix.

MORPHOLOGY OF POLY(VINYLIDENE FLUORIDE) AND POLY(O-METHOXYANILINE) BLENDS

Malmonge, L. F.; Mattoso, LHC
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 123-124
ENG
Relevância na Pesquisa
69.8529%
Blends of poly(o-methoxyaniline) - POMA - and poly(vinylidene fluoride) - PVDF - of various compositions were prepared from organic solvent solutions. Flexible, free-standing and stretchable films were obtained by casting, which were characterized by conductivity measurements, electron microscopy and differential scanning calorimetry. As expected, the blends conductivity increases with increasing contents of the conducting polymer. The onset of the conductivity at low contents of conducting polymer indicates a low percolation threshold for the blends. Despite the presence of the conductive host, the blends displayed the crystalline spherulitic morphology and the beta-phase characteristic of pure PVDF. This morphology appears to be destroyed, however, if the film is stretched by zone-drawing.

Thermal analysis of conductive blends of PVDF and poly(o-methoxyaniline)

Malmonge, L. F.; Mattoso, L. H C
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 8387-8391
ENG
Relevância na Pesquisa
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The thermal behavior of blends of poly(vinylidene fluoride), or PVDF, and poly(o-methoxyaniline) doped with toluene sulfonic acid was studied by thermogravimetic analysis, electrical conductivity measurements, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Blends with thermal and electrical conductivity stabler than the conductive polymer alone were obtained. Nevertheless, degradation occurs after a long period of time (500 h) at high temperatures. The possible association of the conductivity decay with dopant loss, degradation and structural and morphological changes of the blend is discussed. (C) 2000 Elsevier Science Ltd.; The thermal behavior of blends of poly(vinylidene fluoride), or PVDF, and poly(o-methoxyaniline) doped with toluene sulfonic acid was studied by thermogravimetic analysis, electrical conductivity measurements, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Blends with thermal and electrical conductivity stabler than the conductive polymer alone were obtained. Nevertheless, degradation occurs after a long period of time (500 h) at high temperatures. The possible association of the conductivity decay with dopant loss, degradation and structural and morphological changes of the blend is discussed.

Effects of thermal treatment on phase transitions and on the mechanical relaxation in poly(vinylidene fluoride)

Alves, Neri; Cardoso, C. X.; Job, A. E.; Giacometti, J. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 263-266
ENG
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This work reports on the effects from thermal treatment in poly(vinylidene fluoride), PVDF, obtained with differential scanning calorimetry (DSC) and dynamic thermal analysis (DMA) measurements. It is shown that in successive DMA measurements performed with one sample the α relaxation peak almost disappears while the γ′ peak appears. The α relaxation peak, at ∼100°C in DMA measurements, is attributed to the preferential orientation of chains in the amorphous phase while the γ′ relaxation peak, at ∼50°C, is related to the thermal treatment to which the sample was submitted.

Poly(vinylidene fluoride) and copolymers as porous membranes for tissue engineering applications

Pereira, J. Nunes; Ribeiro, S.; Ribeiro, C.; Gombek, C. J.; Gama, F. M.; Gomes, A. C.; Patterson, D. A.; Lanceros-Méndez, S.
Fonte: Elsevier BV Publicador: Elsevier BV
Tipo: Artigo de Revista Científica
Publicado em /07/2015 ENG
Relevância na Pesquisa
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Poly(vinylidene fluoride) (PVDF) and its main copolymers - poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), and poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE) - were processed by solvent casting at room temperature in the form of porous membranes. Copolymer membranes showed higher degree of porosity than PVDF, the average pore size being larger for P(VDF-TrFE) than for P(VDF-HFP) and PVDF. All membranes show high hydrophobicity with water contact angles in the range 94° to 115°, and electroactive beta phase contents above 90%. The adhesion and proliferation of both C2C12 myoblast and MC3T3-E1 pre-osteoblast cells on the membranes were investigated. It is demonstrated that PVDF membranes promote higher cell proliferation while P(VDF-HFP) membranes show the lowest proliferation for both kinds of cell. The proliferation on P(VDF-TrFE) membranes is cell dependent, higher for MC3T3-E1 cells but lower for C2C12 cells, related to the effect of the highly porous structure on the preferred morphology of each cell type, as the higher pore size and porosity of the P(VDF-TrFE) membrane induce cell elongation, which is preferred just by the C2C12 muscle cells.; Funded by FEDER funds through the “Programa Operacional Fatores de Competitividade e COMPETE” and by national funds arranged by FCT Fundação para a Ciência e a Tecnologia...

Clay nanoparticles effects on performance and morphology of poly(vinylidene fluoride) membranes

Morihama,A. C. D.; Mierzwa,J. C.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
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In this study, a comparison between neat poly(vinylidene fluoride) (PVDF) membrane and composite (PVDF-Nanoclay and PVDF-PVP-Nanoclay) membranes is presented. All membranes were synthesized by the phase inversion process, using 18% PVDF, n-methylpyrrolidone as solvent and water as the non-solvent. Demineralized water cross-flow permeation tests were conducted to evaluate the membranes performance. Scanning electron microscopy (SEM) images of the membranes surface and cross-section and water contact angle measurements were used to estimate additives effects on membranes morphology. The results indicate that dopant addition affected membrane permeate flux and morphology. The 4% nanoclay composite membrane resulted in the highest ultrapure water permeability (0.9130 m³.m-2.h-1.MPa-1), lower hydraulic resistance (3.27´10+12.m-1), lower contact angle (87.1º) and highest surface porosity (0.95%). Furthermore, it was verified that the membrane surface porosity increased with increasing clay nanoparticles concentrations. It was observed that the morphology of the membranes with clay nanoparticle addition is characterized by a thin surface layer, with macro-pores, a thin bottom layer, which has a sponge-like structure with micro-pores and a thick intermediate layer...

Correlation between morphological properties and ionic conductivity in an electrolyte based on poly(vinylidene fluoride) and poly (2-hydroxyethyl methacrylate)

J. S.,Lívio Bruno; Patricio,Patrícia S. de O.; Matencio,Tulio; Oréfice,Rodrigo L.
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2014 EN
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Materials based on a mixture of poly(vinylidene fluoride) (PVDF), poly(2-hydroxyethyl methacrylate) (PHEMA) and LiClO4 were produced to evaluate their ionic behavior and morphological structure to determine if they can be used as an electrolyte in electrical devices. FTIR chemical analysis results indicated the presence of interactions between PVDF, PHEMA and LiClO4. MDSC results showed that the transition temperatures of the polymers shifted to higher temperatures for systems containing high concentrations of each polymer. SEM images indicated that there was some miscibility between the polymers especially for the 25 and 75 wt. % compositions. In terms of the electrical performance, the ionic conductivity level of the electrolyte could be controlled by changing the composition of the system.

Fabrication and characterisation of an electrospun tubular 3D scaffold platform of poly(vinylidene fluoride-co-hexafluoropropylene) for small-diameter blood vessel application

Ahmed, F.; Roy Choudhury, N.; Dutta, N.K.; Zou, L.; Zannettino, A.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
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In this research, nanofibrous 3D tubular (~4-mm-diameter tube) scaffolds of poly (vinylidene fluoride-co-hexafluoropropylene) were fabricated by electrospinning. The role of surface charge in the success of these scaffolds for potential small-diameter artificial vascular grafts has been investigated using streaming potential study. Prior to endothelial cell culture, surface properties such as wettability and the surface charge of these tubular scaffolds were evaluated using unmodified and fibrinogen-adsorbed surfaces to understand their interaction with surrounding environment. The tubular scaffolds constructed using electrospinning show similar mechanical properties such as tensile strength and elastic modulus as those of native vessels. Whilst endothelial cell proliferation on unmodified tubes, as analysed by scanning electron microscopy, was found to be moderate, a simple process of dynamic fibrinogen adsorption was seen to enhance the endothelialisation of these tubular grafts. The high negative zeta potential values, high strength, robustness and structural reliability of the scaffolds represent them to be promising biomaterials for vascular graft applications.; Furqan Ahmed, Namita Roy Choudhury, Naba K. Dutta, Linda Zou & Andrew Zannettino; Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/09205063.2014.968018.

Investigations on compatibilized and uncompatibilized blends of poly(vinylidene fluoride) and poly(ethylene oxide)

Kulkarni, Pranita
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
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This thesis describes the investigation of compatibilized and uncompatibilized blends of Poly(vinylidene fluoride) (PVDF) and Poly(ethylene oxide) (PEO). Poly(vinyl acetate) (PVAc) was used a compatibilizer for the system. Modeling of crystallization exotherms, high -temperature phase behavior and partitioning of the components in the above blend systems are considered in detail. Only blends having PVDF as the continuous phase are studied. The crystallization behavior as observed by differential scanning calorimetry (DSC) of PVDF seemed unchanged upon blending with PEO for both compatibilized and uncompatibilized systems. However, PEO showed a significant depression in its crystallization temperature when blended with PVDF. As the concentration of PEO increased above 10%, two distinct crystallization peaks were observed. Optical microscopy revealed that at lower concentrations, PEO, is segregated into domains that are -10 micron in diameter. These domains nucleate at very low temperatures, yet grow nearly instantaneously once nucleated. As the concentration of PEO increases, somewhere between 10 to 20 wt %, larger PEO domains of about 100 micron size are formed that crystallize at a temperature close to that of pure PEO. High temperature optical microscopy images suggested that PEO and PVDF are incompatible in the molten state. The studies on PVDF/PEO/PVAc blends performed by using DSC and HATRFTIR revealed that PVAc acts as a diluent for the PEO phase. There was no appreciable change in the crystallization behavior of PVDF. The compatibilizer increased the degree of supercooling for PEO crystallization and made the domain size distribution for the PEO domains more or less uniform. A model based on modifying the Avrami equation to handle samples of finite thickness was developed. The model was shown to work well for DSC exotherms of pure PEO. The present model does neither takes into account finite domain size of the crystallizing element nor the domain size distribution of the discontinuous phase. Further investigations regarding the domain size distribution and modifications in the existing model to account for domain size must be undertaken to obtain a good fit between actual data and model predictions.