Estudo das propriedades físicas de blendas de PVDF/Látex visando aplicação como biomaterial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução

Pós-graduação em Ciência dos Materiais - FEIS

Estudo das propriedades térmicas e mecânicas de blendas de PVDF/PANI

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise modal de uma estrutura do tipo viga utilizando materiais piezelétricos (PVDF) como sensores

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fabricação, caracterização e aplicações do compósito PZT/PVDF

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fabrication and Characterization of PZT-PAni/PVDF Based Nanocomposite

This work presents the preparation and characterization of PZT ceramic obtained by the polymeric precursor method (PPM). The influence of the synthesis method on the grain size and the morphology are also object of study. The fabrication and characterization of composite films with 0-3 connectivity, immersing nanoparticles of PZT into the non-polar poly(vinylidene fluoride) -PVDF as the polymer matrix were presented. For comparison there are results obtained with composite samples made of ceramic particles unrecovered and recovered with a conducting polymer, the polyaniline (PAni).

Fabricação de membranas fibrosas de compósito PVDF/TIO2 pelo método de fiação por sopro em solução

Pós-graduação em Ciência dos Materiais - FEIS

Obtenção e caracterização de mantas fibrosas de poli(fluoreto de vinilideno) (PVDF) com poli(o-metoxianilina) (POMA) pela técnica de "Solution Blow Spinning"

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tenacizzazione di laminati compositi mediante l'utilizzo di nanofibre in PVDF

Analisi riguardante la tenacizzazione della matrice di laminati compositi. Lo scopo è quello di aumentare la resistenza alla frattura di modo I e, a tal proposito, sono stati modificati gli interstrati di alcuni provini tramite l’introduzione di strati, di diverso spessore, di nanofibre in polivinilidenfluoruro (PVDF). La valutazione di tale metodo di rinforzo è stata eseguita servendosi di dati ottenuti tramite prove sperimentali svolte in laboratorio direttamente dal sottoscritto, che si è occupato dell’elaborazione dei dati servendosi di tecniche e algoritmi di recente ideazione. La necessità primaria per cui si cerca di rinforzare la matrice risiede nel problema più sentito dei laminati compositi in opera da molto tempo: la delaminazione. Oltre a verificare le proprietà meccaniche dei provini modificati sottoponendoli a test DCB, si è utilizzata una tecnica basata sulle emissioni acustiche per comprendere più approfonditamente l’inizio della delaminazione e i meccanismi di rottura che si verificano durante le prove. Quest’ultimi sono illustrati servendosi di un algoritmo di clustering, detto Fuzzy C-means, tramite il quale è stato possibile identificare ogni segnale come appartenente o meno ad un determinato modo di rottura. I risultati mostrano che il PVDF, applicato nelle modalità esposte, è in grado di aumentare la resistenza alla frattura di modo I divenendo contemporaneamente causa di un diverso modo di propagazione della frattura. Infine l’elaborato presenta alcune micrografie delle superfici di rottura, le quali appoggiano i risultati ottenuti nelle precedenti fasi di analisi.

Influence of additives on the performance of a PVDF membrane

The field of use of membranes is wide and ranges from the automotive industry to biomedical uses. Many formulations and compositions find a niche where they are able to improve efficiency, running cost and quality of the product. The aim of this research is to expand GVS’s product portfolio introducing a new membrane formulation. A series of additives were researched and evaluated, adding them to the membrane solutions, which were then cast and characterised using techniques like Scanning Electron Microscopy (SEM), poroscopy, FT-IT ATR and measurements like Water Break Through (WBT), Air Flow (AF), thickness. This study ultimately focused on one additive, which effect on the membranes was studied in various compositions. Interesting insights were also collected on the stability of the polymer solutions over time, which was found to change the membrane properties significantly, mainly affecting airflow and water breakthrough. Properties of the membranes were studied to find possible correlations to the amount of additive. The additive seems however to change the membrane porometry considerably depending on the time of immersion in the water bath. A new procedure to yield uniform unsupported polymeric membranes for tensile tests was developed. The additive was found to reduce elongation at break and decrease tensile strength of the membranes, possibly hinting toward plasticization of the product.

Scaffold piezoelettrici in PVDF/PCL per la rigenerazione del tessuto nervoso periferico

Le lesioni del sistema nervoso periferico, causate da eventi traumatici o da patologie degenerative, costituiscono un danno che può portare alla perdita di specifiche funzionalità motorie o sensoriali. In questi casi, la terapia chirurgica è necessaria per riparare la perdita di continuità assonale. Il gold standard operatorio attuale è costituito dal trapianto nella sede lesionata di un nervo da donatore o dallo stesso soggetto affetto dal danno. Recentemente, un approccio basato su tecniche di ingegneria dei tessuti propone l’impianto di biomateriali modellati come condotti che favoriscano la rigenerazione assonale. Ne è un esempio chiaro un recente lavoro di ricerca, nel quale Cheng et al. propongono una strategia basata sull’impiego di scaffold piezoelettrici prodotti attraverso una tecnica di "casting annealing displacement " che utilizza Polivinilidenfluoruro (PVDF) e Policaprolattone (PCL). Confrontando in vitro scaffold in PCL, in PVDF e PCL/PVDF, in particolare analizzandone le proprietà piezoelettriche e quelle meccaniche, si rilevano i vantaggi della copolimerizzazione. Questi risultati di interesse vengono inoltre confermati dai risultati funzionali ottenuti con l’impianto in vivo in topi con una lesione di 15 mm al nervo sciatico.

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

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, Inc. J Appl Polym Sci 116: 785-791, 2010

Local piezoelectric response of single poly(vinylidene fluoride) electrospun fibers

It is shown that electrospun poly(vynilidene fluoride) nanofibers are fully poled right after preparation and show b-phase contents of 70%, therefore being able to be implemented into electroactive devices without further processing steps. Further,the local piezoelectric properties of individual electrospun fibers have been studied by piezoresponse force microscopy. Piezoelectric response, polarization switching, and nanoscale patterning of the fibers have been demonstrated.

Osteoblast, fibroblast and in vivo biological response to poly(vinylidene fluoride) based composite materials

Electroactivematerials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidenefluoride),PVDF,have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.

Effect of fiber alignment in gelled electrospun membranes based on poly(vinylidene fluoride) for battery applications

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of 272 nm and a degree of porosity of 87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li+. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.