Literatura científica selecionada sobre o tema "PLA-PVDF"

The aim of this study was to investigate the ecotoxicity of polyvinylidene difluoride (PVDF) and polylactic acid (PLA) microplastics (MPs) in two marine zooplankton: the crustacean Artemia franciscana and the cnidarian Aurelia sp. (common jellyfish). To achieve this goal, (i) MP uptake, (ii) immobility, and (iii) behavior (swimming speed, pulsation mode) of crustacean larval stages and jellyfish ephyrae exposed to MPs concentrations (1, 10, 100 mg/L) were assessed for 24 h. Using traditional and novel techniques, i.e., epifluorescence microscopy and 3D holotomography (HT), PVDF and PLA MPs were found in the digestive systems of the crustaceans and in the gelatinous tissue of jellyfish. Immobility was not affected in either organism, while a significant behavioral alteration in terms of pulsation mode was found in jellyfish after exposure to both PVDF and PLA MPs. Moreover, PLA MPs exposure in jellyfish induced a toxic effect (EC50: 77.43 mg/L) on the behavioral response. This study provides new insights into PLA and PVDF toxicity with the potential for a large impact on the marine ecosystem, since jellyfish play a key role in the marine food chain. However, further investigations incorporating additional species belonging to other trophic levels are paramount to better understand and clarify the impact of such polymers at micro scale in the marine environment. These findings suggest that although PVDF and PLA have been recently proposed as innovative and, in the case of PLA, biodegradable polymers, their effects on marine biota should not be underestimated.

Abstract In the present work, we studied the effect of adding PZT nanoparticles to PVDF-HFP/PLA matrix on piezoelectric properties of blend-based nanocomposites. Polyvinylidene fluoride hexafluoro-propylene /Polylactic acid /Lead titanate zirconate (PVdF-HFP/PLA/PZT) films nanocomposites were prepared by solvent casting technique using different percentages of PZT Nano fillers. The different samples were characterized by Polarized optical microscope (POM), Fourier transformed infrared (FTIR) and Thermogravimetric analysis (TGA). POM images indicate uniform distribution of PZT Nano fillers in the PVdF-HFP/PLA matrix. FTIR analysis reveals the appearance of β-phase in nanocomposites and the enhancement of their piezoelectric properties. These electroactive nanocomposites thin films are a potential candidate for the piezoelectric Nano generators, energy storage devices and energy harvesting applications.

In this study, small amplitude oscillatory shear tests are applied to investigate the rheological responses of polylactide/poly(vinylidene fluoride) (PLA/PVDF) blends and to correlate their viscoelastic properties with the morphological evolutions during processing. Although the analysis of the elastic moduli reveals some changes as a function of blend composition and processing time, the weighted relaxation spectra are shown to be more useful in detecting changes. The analysis demonstrates that when PVDF, i.e., the more viscous phase, is the matrix, the blend relaxes cooperatively and only a single relaxation peak is observed. By contrast, blends with highly concentrated morphologies do not fully relax, showing instead an upward increasing trend at longer times. This outcome is attributed to the broad distribution of highly concentrated droplets with a high probability of droplet–droplet contacts. Dynamic mechanical analysis (DMA) reveals that crystalline segmental motions attributed to the α-relaxation of PVDF at around 100 °C are restricted by the highly concentrated morphology of the 50/50 PLA/PVDF blend processed for 10 min. Relaxation analyses of the blends via dynamic oscillatory shear tests and DMA are shown to be powerful tools for investigating small microstructural changes in immiscible polymer blends.

Polylactic acid (PLA) is one of the most widely used materials for fused deposition modeling (FDM) 3D printing. It is a biodegradable thermoplastic polyester, derived from natural resources such as corn starch or sugarcane, with low environmental impact and good mechanical properties. One important feature of PLA is that its properties can be modulated by the inclusion of nanofillers. In this work, we investigate the influence of SiC and ZnO doping of PLA on the triboelectric performance of PLA-based tribogenerators. Our results show that the triboelectric signal in ZnO-doped PLA composites increases as the concentration of ZnO in PLA increases, with an enhancement in the output power of 741% when the ZnO concentration in PLA is 3 wt%. SiC-doped PLA behaves in a different manner. Initially the triboelectric signal increases, reaching a peak value with enhanced output power by 284% compared to undoped PLA, when the concentration of SiC in PLA is 1.5 wt%. As the concentration increases to 3 wt%, the triboelectric signal reduces significantly and is comparable to or less than that of the undoped PLA. Our results are consistent with recent data for PVDF doped with silicon carbide nanoparticles and are attributed to the reduction in the contact area between the triboelectric surfaces.

Low-cost air quality sensors (LCSs) are becoming more ubiquitous as individuals and communities seek to reduce their exposure to poor air quality. Compact, efficient, and aesthetically designed sensor housings that do not interfere with the target air quality measurements are a necessary component of a low-cost sensing system. The selection of appropriate housing material can be an important factor in air quality applications employing LCSs. Three-dimensional printing, specifically fused deposition modeling (FDM), is a standard for prototyping and small-scale custom plastics production because of its low cost and ability for rapid iteration. However, little information exists about whether FDM-printed thermoplastics affect measurements of trace atmospheric gasses. This study investigates how five different FDM-printed thermoplastics (ABS, PETG, PLA, PC, and PVDF) affect the concentration of five common atmospheric trace gasses (CO, CO2, NO, NO2, and VOCs). The laboratory results show that the thermoplastics, except for PVDF, exhibit VOC off-gassing. The results also indicate no to limited interaction between all of the thermoplastics and CO and CO2 and a small interaction between all of the thermoplastics and NO and NO2.

The growing popularity of quasi-solid-state supercapacitors inevitably leads to the unrestricted consumption of commonly used petroleum-derived polymer electrolytes, causing excessive carbon emissions and resulting in global warming. Also, the porosity and liquid electrolyte uptake of existing polymer membranes are insufficient for well-performed supercapacitors under high current and long cycles. To address these issues, poly(lactic acid) (PLA), a widely applied polymers in biodegradable plastics is employed to fabricate a renewable biocomposite membrane with tunable pores with the help of non-solvent phase inversion method, and a small amount of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is introduced as a modifier to interconnect with PLA skeleton for stabilizing the porous structure and optimizing the aperture of the membrane. Owing to easy film-forming and tunable non-solvent ratio, the porous membrane possesses high porosity (ca. 71%), liquid electrolyte uptake (366%), and preferable flexibility endowing the GPE with satisfactory electrochemical stability in coin and flexible supercapacitors after long cycles. This work effectively relieves the environmental stress resulted from undegradable polymers and reveals the promising potential and prospects of the environmentally friendly membrane in the application of wearable devices.

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Espumas de PLA/Amido e PLA/Amido/Sepiolita (SEP) com distintas composições foram produzidas. As amostras foram caracterizadas pelas seguintes técnicas: i) microscopia eletrônica de varredura (MEV); ii) medidas de densidade (ρ); iii) calorimetria diferencial exploratória (DSC), iv) análise mecânica (flexão e tração); v) análise térmica dinâmico mecânica (DMTA); vi) testes in vivo. Nas imagens de MEV, tanto nos precursores quanto nas espumas, a interface entre as fases foi eminentemente física com duas fases distintas e houve ocorrência de lacunas entre elas, sendo que um aumento no tamanho das lacunas foi observado nas espumas. Observou-se que nas amostras com SEP ocorreu uma maior geração de células com menores dimensões e mais compactas. Isto demonstra que a SEP apresentou, assim como os grânulos de amido, o comportamento de agente de nucleação. Nas medidas de ρ os menores valores ocorreram com as amostras originárias do autoclave e do banho de glicerina, respectivamente. Essas diminuições foram consistentes com a expansão da matriz de PLA observada nas imagens de MEV. Nas medidas de DSC, em geral, a adição do amido ao PLA implicou no aumento da Xc. Tal efeito sucedeu-se devido a interface entre o amido e o PLA ser mais energética, o que facilitou a formação de cristais na matriz de PLA. Nos compósitos contendo SEP, em geral, maiores valores de Xc foram observados quando comparados com as blendas de PLA/amido nas mesmas proporções de materiais. Esse comportamento provavelmente está associado ao efeito da SEP como agente nucleante no PLA. Na análise mecânica, tanto no ensaio de flexão quanto no de tração, com o aumento do conteúdo de amido nas blendas menores foram a resistência e a deformação máxima, bem como a tensão e a deformação de ruptura. Adicionalmente, o mesmo comportamento de diminuição foi mantido para os compósitos com a SEP. No entanto, no ensaio de tração, essas amostras apresentaram medidas com valores maiores do que o das blendas. Nos resultados observados via DMTA, em geral, a adição do amido e da SEP diminuíram a rigidez da matriz PLA, ou seja, valores de E' menores nas blendas e nos compósitos do que nas amostras de PLA puro. No estudo in vivo, aprovado pela Comissão de Ética no Uso de Animais da FCT/UNESP, Presidente Prudente, São Paulo, Brasil (processo nº 02/2014), foram utilizados 18 ratos machos da linhagem Wistar (Rattus novergicus, variedade albina, Rodentia, Mammalia) com idade de 120 dias, obtidos junto à Universidade do Oeste Paulista (UNOESTE). Os animais foram submetidos a processo cirúrgico para a implantação das amostras e após 40 semanas, contadas a partir da data da cirurgia de implantação, as amostras foram removidas. Para a análise da morfologia estrutural das amostras e tecidos removidos, medidas de MEV e microscopia ótica (MO) foram realizadas, respectivamente. Observou-se pela técnica de MEV que as superfícies das amostras pós implante apresentaram um padrão de recobrimento por tecido biológico com morfologia capsular. Nas fotomicrografias obtidas pela MO estruturas como fibras musculares, tecido adiposo (TA) e conjuntivo denso (TCD) foram observados. Além disso, em algumas fotomicrografias foram observados poucos pontos focais de infiltrado inflamatório. Próximo ao tecido muscular foi observada a presença de TA permeado de TCD, caracterizando como um tecido capsular.
Foams of PLA/Starch and PLA/Starch/Sepiolite (SEP) with different compositions were produced. The following techniques were used in the samples characterization: i) scanning electron microscopy (SEM); ii) density (ρ) measures; iii) differential scanning calorimetry (DSC), iv) mechanical analysis (flexion and traction); v) dynamic mechanical thermal analysis (DMTA); vi) in vivo test. In the SEM images, in both foams and precursors, the interface between the phases was eminently physic with two distinct phases with gaps between them, and an increase in size of the gaps was observed in the foam. It was observed that in the samples with SEP occurred greater generation of smaller cell and more compact. This demonstrates that SEP presented, as well as the starch granules, the nucleating agent behavior. In ρ measures the lowest values were found in samples originating from the autoclave and glycerine bath, respectively. These decreases were consistent with the expansion of PLA matrix observed in the SEM images. In the DSC measurements in general, the starch addition to PLA resulted in increased Xc. This effect happened because the interface between starch and PLA be more energetic, which facilitated the crystals formation in the PLA matrix. In composites containing SEP, generally larger Xc values were observed when compared with the PLA/starch blends in the same proportions materials. This behavior is probably related to the effect of the SEP as a nucleating agent in the PLA. In the mechanical analysis, flexion and traction, with increasing starch content in the blends lower resistance and maximum deformation as the tension and rupture deformation were obtained. Additionally, the same decrease in performance was maintained for composites SEP. However, in the tensile test, these samples showed values greater than the blends. In the results observed via DMTA, in general, the addition of starch and SEP resulted in a stiffness decrease of PLA matrix, that is, E' lower values for blends and composites when compared with pure PLA samples. In the in vivo study, approved by the Ethics Committee on Animal Use the FCT/UNESP, Presidente Prudente, São Paulo, Brazil (process No. 02/2014), 18 rats Wistar (Rattus norvegicus, albino variety, Rodentia, Mammalia) were used with age of 120 days, obtained from the Universidade do Oeste Paulista (UNOESTE). The animals underwent surgical procedure for samples implantation, after 40 weeks counted from the implantation surgery date, the samples were removed. For structural analysis of removed samples and tissues SEM morphology measurements and optical microscopy (OM) were performed respectively. It was observed by SEM technique that the surfaces of post-implant samples showed a pattern coating by biological tissue with capsular morphology. In the photomicrographs obtained by OM, structures such as muscle fibers; adipose tissue (AT) and dense connective (TDC) were observed. Furthermore, in photomicrographs were observed in some few focal inflammatory infiltrate. Next to the muscle tissue was observed the presence of AT permeated by the TDC, featuring as capsular tissue.
Foams of PLA/Starch and PLA/Starch/Sepiolite (SEP) with different compositions were produced. The following techniques were used in the samples characterization: i) scanning electron microscopy (SEM); ii) density (ρ) measures; iii) differential scanning calorimetry (DSC), iv) mechanical analysis (flexion and traction); v) dynamic mechanical thermal analysis (DMTA); vi) in vivo test. In the SEM images, in both foams and precursors, the interface between the phases was eminently physic with two distinct phases with gaps between them, and an increase in size of the gaps was observed in the foam. It was observed that in the samples with SEP occurred greater generation of smaller cell and more compact. This demonstrates that SEP presented, as well as the starch granules, the nucleating agent behavior. In ρ measures the lowest values were found in samples originating from the autoclave and glycerine bath, respectively. These decreases were consistent with the expansion of PLA matrix observed in the SEM images. In the DSC measurements in general, the starch addition to PLA resulted in increased Xc. This effect happened because the interface between starch and PLA be more energetic, which facilitated the crystals formation in the PLA matrix. In composites containing SEP, generally larger Xc values were observed when compared with the PLA/starch blends in the same proportions materials. This behavior is probably related to the effect of the SEP as a nucleating agent in the PLA. In the mechanical analysis, flexion and traction, with increasing starch content in the blends lower resistance and maximum deformation as the tension and rupture deformation were obtained. Additionally, the same decrease in performance was maintained for composites SEP. However, in the tensile test, these samples showed values greater than the blends. In the results observed via DMTA, in general, the addition of starch and SEP resulted in a stiffness decrease of PLA matrix, that is, E' lower values for blends and composites when compared with pure PLA samples. In the in vivo study, approved by the Ethics Committee on Animal Use the FCT/UNESP, Presidente Prudente, São Paulo, Brazil (process No. 02/2014), 18 rats Wistar (Rattus norvegicus, albino variety, Rodentia, Mammalia) were used with age of 120 days, obtained from the Universidade do Oeste Paulista (UNOESTE). The animals underwent surgical procedure for samples implantation, after 40 weeks counted from the implantation surgery date, the samples were removed. For structural analysis of removed samples and tissues SEM morphology measurements and optical microscopy (OM) were performed respectively. It was observed by SEM technique that the surfaces of post-implant samples showed a pattern coating by biological tissue with capsular morphology. In the photomicrographs obtained by OM, structures such as muscle fibers; adipose tissue (AT) and dense connective (TDC) were observed. Furthermore, in photomicrographs were observed in some few focal inflammatory infiltrate. Next to the muscle tissue was observed the presence of AT permeated by the TDC, featuring as capsular tissue.

Orientador: Carlos José Leopoldo Constantino
Banca: Antonio José Félix de Carvalho
Banca: Neri Alves
Banca: Hermann Bremer Neto
Banca; Rebeca Delatore Simões
O Programa de Pós Gradução em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi
Abstract: Foams of PLA/Starch and PLA/Starch/Sepiolite (SEP) with different compositions were produced. The following techniques were used in the samples characterization: i) scanning electron microscopy (SEM); ii) density (ρ) measures; iii) differential scanning calorimetry (DSC), iv) mechanical analysis (flexion and traction); v) dynamic mechanical thermal analysis (DMTA); vi) in vivo test. In the SEM images, in both foams and precursors, the interface between the phases was eminently physic with two distinct phases with gaps between them, and an increase in size of the gaps was observed in the foam. It was observed that in the sampleswith SEP occurred greater generation of smaller cell and more compact. This demonstrates that SEP presented, as well as the starch granules, the nucleating agent behavior. In ρ measures the lowest values were found in samples originating from the autoclave and glycerine bath, respectively. These decreases were consistent with the expansion of PLA matrix observed in the SEM images. In the DSC measurements in general, the starch addition to PLA resulted in increased Xc. This effect happened because the interface between starch and PLA be moreenergetic, which facilitated the crystals formation in the PLA matrix. In composites containing SEP, generally larger Xc values were observed when compared with the PLA/starch blends in the same proportions materials. This behavior is probably related to the effect of the SEP as a nucleating agent in the PLA. In t... (Complete abstract click electronic access below)
Resumo: Espumas de PLA/Amido e PLA/Amido/Sepiolita (SEP) com distintas composições foram produzidas. As amostras foram caracterizadas pelas seguintes técnicas: i) microscopia eletrônica de varredura (MEV); ii) medidas de densidade (ρ); iii) calorimetria diferencial exploratória (DSC), iv) análise mecânica (flexão e tração); v) análise térmica dinâmico mecânica (DMTA); vi) testes in vivo. Nas imagens de MEV, tanto nos precursores quanto nas espumas, a interface entre as fases foi eminentemente física com duas fases distintas e houve ocorrência de lacunas entre elas, sendo que um aumento no tamanho das lacunas foi observado nas espumas. Observou-se que nas amostras com SEP ocorreu uma maior geração de células com menores dimensões e mais compactas. Isto demonstra que a SEP apresentou, assim como os grânulos de amido, o comportamento de agente de nucleação. Nas medidas de ρ os menores valores ocorreram com as amostras originárias do autoclave e do banho de glicerina, respectivamente. Essas diminuições foram consistentes com a expansão da matriz de PLA observada nas imagens de MEV. Nas medidas de DSC, em geral, a adição do amido ao PLA implicou no aumento da Xc. Tal efeito sucedeu-se devido a interface entre o amido e o PLA ser mais energética, o que facilitou a formação de cristais na matriz de PLA. Nos compósitos contendo SEP, em geral, maiores valores de Xc foram observados quando comparados com as blendas de PLA/amido nas mesmas proporções de materiais. Esse comportamento provavelm... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor

La potentialité des films PLA produits par extrusion et étirés uniaxialement par MDO à partir des grades industriels a été investiguée pour la récupération d’énergie vibratoire par effet piézoélectrique. Une technique de caractérisation du coefficient piézoélectrique plus adaptée aux films polymères a été testée et validée sur un film piézoélectrique commercial de PVDF, puis utilisée pour évaluer le coefficient piézoélectrique d14 des films PLA. Une étude physico-chimique a été menée afin de comprendre les relations entre les observables piézoélectriques des films PLA et les modifications structurales (orientation moléculaire, cristallinité et nature des phases cristallines) apportées par les conditions d’élaboration des films. Un banc de test de récupération d’énergie reposant sur l’application des déformations de traction dynamiques a été utilisé pour évaluer la capacité des PLAs à convertir des vibrations mécaniques en énergie électrique. Une comparaison avec du PVDF commercial a été réalisée. Un modèle électro-mécanique équivalent a été développé et a permis de décrire l’évolution de la puissance électrique récupérée en fonction des conditions de sollicitations mécaniques pour différents grades de PLA ainsi que pour le PVDF. Ce modèle étant validé, a été utilisé pour prédire l’effet de la variation des différents paramètres intrinsèques (qualités mécaniques et piézoélectriques des polymères) et extrinsèques (conditions de sollicitations mécaniques et adaptation d’impédance électrique). Enfin, pour de futures applications, nous avons évalué la potentialité du PLA (sous forme de film ou de textile) pour des applications comme capteur de déformation, de force dynamique et de chocs mais aussi pour l’émission et la réception ultrasonore
The potentiality of PLA films produced by extrusion and uniaxial stretching by MDO of industrial grades has been investigated for the energy harvesting by piezoelectric transformation. A piezoelectric coefficient characterization technique suitable for polymer films was tested and validated on a commercial PVDF piezoelectric film. It was then used to evaluate the d14 coefficient of PLA films. A study on the effect of structural parameters of the PLAs on their piezoelectric behaviour was carried out. An energy recovery test bench based on the application of dynamic tensile strains was used to assess the capability of PLAs to convert mechanical vibrations into electrical energy. A comparison with commercial PVDF was carried out. An equivalent electro-mechanical model was developed and made it possible to describe the evolution of power as a function of mechanical stress conditions for different grades of PLA as well as for PVDF. This model, was used to predict the effect of the variation of the various intrinsic parameters (mechanical and piezoelectric qualities of polymers) and extrinsic (characteristics of the vibratory source and electrical impedance matching). Finally, for future applications, we evaluated the potentiality of PLA (in film or textile form) for applications as a dynamic deformation, dynamic force and shock sensor and also for ultrasonic emission and reception

In this study, the polymer-based humidity sensors were investigated for humidity sensing applications. The key advantages of polymers that have garnered this attraction are their lightweight, easy preparation, and low cost of both materials and fabrication process. Different techniques are used to enhance the surface morphology and sensitivity of polymeric films, which include synthesis of nanocomposites, copolymerization techniques, and blending of polymers. The incorporation of nanoparticles to the polymer matrix improves the electrical and mechanical properties of the polymeric film. We have investigated different polymer nanocomposites based humidity sensors on enhancing the sensitivity of the sensor, on achieving faster response and recovery time and lower hysteresis loss as compared to the polymeric humidity sensors. In the first phase, we investigated the PLA-TiO2 nanocomposite for humidity sensing applications. We have optimized the concentration of TiO2 in the PLA-TiO2 nanocomposite and apply acetone for the surface treatment of the sensing film. In the second phase, we studied the PVDF-TiO2 nanocomposite-based humidity sensor, achieved a linear response of the sensor, and optimized the concentration of PVDF. In the third phase, we incorporated the BaTiO3 nanoparticles within optimized PVDF and studied the dielectric property of the nanocomposite film. PVDF-BaTiO3 sensors show a smaller hysteresis response. In the 4th phase, we blend the PVDF with SPEEK polymer; the optimized concentration of SPEEK improves the sensitivity of the humidity sensors at a lower humidity level.