Assessing the sustainability of nanomanufacturing products and processes has been difficult to achieve using conventional approaches mainly due to an inadequate inventory, large process-to-process variation, and a dearth of relevant toxicology data for nanomaterials. Since these issues are long term in nature, it is required to create hybrid methodologies that can work towards filling the existing gaps. Merging thermodynamic techniques such as the exergy analysis with environmental assessments can help make better, more informed choices while providing an opportunity for process improvement by enabling to correctly quantify efficiency loss through the waste stream, and by locating the exact areas for improvement. A preliminary technique that utilizes environmental assessment feedback during the process design along with an exergy analysis is presented. As a test case, an environmental assessment aided by an exergy analysis was carried out on the electrospinning process for producing polyvinylidene fluoride nanofibers. The areas of greatest concern, both from an environmental as well as a thermodynamic point of view, have been found to be the high energy consumption and the complete loss of solvent during the process of electrospinning. Interestingly, exergy consumption is significantly higher for fibers with a smaller (

Lors de ce travail nous avons étudié les modifications de HDPE, PVF, PVDF et PTFE par des plasmas O2 et N2. Nous nous sommes focalisés sur l’effet des ions et des neutres. Nous constatons dans tous les cas une modification de la composition des échantillons, cette modification de composition est accompagnée d’une modification de l’énergie de surface. Les traitements plasma greffent de nouvelles fonctions polaires (oxygénées ou azotées) à la surface des échantillons, responsables de l’augmentation de l’énergie de surface. Le PTFE traité par plasma O2 présente lui un comportement particulier. Il est possible de greffer de faibles quantités d’oxygène à sa surface et d’augmenter faiblement son énergie de surface lors de traitements de courte durée à faibles puissances. Les traitements de plus fortes puissances érodent fortement la surface du PTFE sans y greffer de fonctions oxygénées. Les surfaces obtenues sont extrêmement rugueuses et leur énergie de surface est fortement diminuée, nous obtenons des surfaces de type ultra-hydrophobes. Les résultats obtenus lors des traitements plasma ont été comparés à ceux obtenus dans le cas de traitements par des ions O2+/O+ ou N2+/N+. Ceci nous a permis de mettre en évidence une différence de réactivité des échantillons face aux différents traitements. Cette différence de réactivité nous permet de conclure que les ions ne sont pas l’espèce principale responsable de la modification de nos échantillons lors des traitements plasma. Nous avons également pu mettre en évidence une différence de réactivité entre les différents échantillons. Le HDPE, PVF et PVDF ont des réactivités semblables alors que le PTFE est beaucoup plus résistant aux modifications, nous pensons que ceci est dû à la structure entièrement fluorée du PTFE. Nous avons également étudié la résistance de nos échantillons à l’adsorption de protéines dans le cadre d’une étude sur la biocompatibilité. Nous avons pu montrer que les échantillons de PTFE rendu ultra hydrophobe, après traitement par plasma O2 de haute puissance, présentent une bonne résistance à l’adsorption de protéines. Cette caractéristique est intéressante pour la synthèse de matériaux biocompatibles.

Many industrial processes handling organic solvents produce volatile organic compounds (VOCs). These VOCs not only cause environmental pollution, but also represent an economic loss. VOC removal and recovery have become a big issue that needs to be addressed. Traditional techniques for VOCs removal include carbon adsorption, condensation, and absorption, and none is efficient enough to meet every need. Membrane separation has emerged as an excellent alternative or complementary technology for VOC separation. Separation of VOCs from nitrogen by composite hollow fiber membranes is studied in this thesis. Microporous hollow fiber membranes were spun from polyvinylidene fluoride (PVDF) using the phase inversion method, and the hollow fibers were coated with a thin layer of poly(ether block amide) (PEBA), thereby forming composite membranes. PVDF was chosen as the substrate material because of its excellent thermal and chemical stabilities and good mechanical strength, and PEBA was selected as the active separating layer because of its good permselectivity and film forming properties. In PEBA polymer, the hard polyamide blocks provide high mechanical strength, and the soft polyether blocks provide flexibility and elasticity. This study is focused on the preparation and characterization of PEBA/PVDF composite hollow fiber membranes. The membranes were tested for the removal of representative VOCs including hexane, heptane and cyclohexane, which are the main components of gasoline, and dimethyl carbonate (DMC), ethanol, methanol, and methyl t-butyl ether (MTBE) that are the oxygenates and octane number enhancers of gasoline. The separation of gasoline vapor from nitrogen was also investigated. It was found that the PEBA/PVDF composite hollow fiber membranes are effective for the separation of hydrocarbon vapors from nitrogen. The effects of hollow fiber membrane preparation conditions on the membrane performance were studied, and the separation performance of the composite hollow fiber membranes at various operating conditions (e. g. feed concentration, operating temperature) was evaluated.

Many industrial processes handling organic solvents produce volatile organic compounds (VOCs). These VOCs not only cause environmental pollution, but also represent an economic loss. VOC removal and recovery have become a big issue that needs to be addressed. Traditional techniques for VOCs removal include carbon adsorption, condensation, and absorption, and none is efficient enough to meet every need. Membrane separation has emerged as an excellent alternative or complementary technology for VOC separation. Separation of VOCs from nitrogen by composite hollow fiber membranes is studied in this thesis. Microporous hollow fiber membranes were spun from polyvinylidene fluoride (PVDF) using the phase inversion method, and the hollow fibers were coated with a thin layer of poly(ether block amide) (PEBA), thereby forming composite membranes. PVDF was chosen as the substrate material because of its excellent thermal and chemical stabilities and good mechanical strength, and PEBA was selected as the active separating layer because of its good permselectivity and film forming properties. In PEBA polymer, the hard polyamide blocks provide high mechanical strength, and the soft polyether blocks provide flexibility and elasticity. This study is focused on the preparation and characterization of PEBA/PVDF composite hollow fiber membranes. The membranes were tested for the removal of representative VOCs including hexane, heptane and cyclohexane, which are the main components of gasoline, and dimethyl carbonate (DMC), ethanol, methanol, and methyl t-butyl ether (MTBE) that are the oxygenates and octane number enhancers of gasoline. The separation of gasoline vapor from nitrogen was also investigated. It was found that the PEBA/PVDF composite hollow fiber membranes are effective for the separation of hydrocarbon vapors from nitrogen. The effects of hollow fiber membrane preparation conditions on the membrane performance were studied, and the separation performance of the composite hollow fiber membranes at various operating conditions (e. g. feed concentration, operating temperature) was evaluated.

To identify the dynamic model of the treadmill, this study uses the piezoelectricity material (Po1yviny-lidene fluoride, PVDF) to measure the force under treadmill. With this dynamic model, the ground reaction force (GRF) can be derived from the PVDF sensors. The reliability and precision of the GRF results are verified by replacing the PVDF with the traditional load cell (Force measurement devices). To verify the accuracy of treadmill model, this study acquires three different types of GRF signals (marking time, walking and running) from ten subjects. For the marking time case, the correlation coefficients between the actual and predicated GRF signals are approximately 0.98. This study also demonstrates that the proposed model can provide sufficient bandwidth for the walking and running GRF signals. Finally, via comparing the average GRF profile, inter-personal differences of the GRF signal can be observed. Among the three tested locomotion patterns, the marking time GRF has the highest similarity whereas the running GRF signals has the largest variability.

The pyroelectric ceramic thin films and detectors based on PbTiO3[abbreviated to PT] that exhibit a low dielectric constant and a high pyroelectric coefficient, which were fabricated by a sol-gel method in this thesis. The (PVDF/PT) pyroelectric bilayer thin films with low leakage current were deposited on PbTiO3/Pt/SiO2/Si substrates by the spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of the spin coating and drying processes to obtain the desired thickness of PbTiO3 thin film. By changing the concentrations of PVDF solutions (0.6M~1.0M) and thickness of PVDF thin films (50nm~580nm), the effects of various processing parameters on the bilayer thin films growth and the response of pyroelectric infrared detector device are studied. Experimental results reveal that the thickness of PVDF thin films will influence strongly on dielectricity, ferroelectricity, leakage current and pyroelectricity of (PVDF/PT) bilayer thin films. With the increase of the thickness of PVDF thin films, the relative dielectric constant of (PVDF/PT) bilayer thin films decrease from 63 to 20. The tan£_ increases from 0.00152 to 0.0024, leakage current decreases from 1.54x10-6 A/cm2 to 3.86x10-7 A/cm2, Ec decreases from 70.7 KV/cm to 35 KV/cm, Pr decreases from 6.29 £gC/cm2 to 1.14 £gC/cm2, and £^ decreases from 22.5x10-9 C/cm2K to 6.8 x10-9 C/cm2K with an increase of the thickness of PVDF thin film. In addition, the results also show that the largest figure of merit Fv is 1.31x10-10 Ccm/J as the thickness of PVDF thin film is 80nm. With the increase of the thickness of PVDF thin film, the figure of merit Fm decreases from 2.26x10-8 Ccm/J to 1.07x10-8 Ccm/J. The voltage responsivities (Rv) measured at 20 Hz decrease from 1383 V/W to 804 V/W and the specific detectivities (D*) measured at 100Hz decrease from 2.72x107 cmHz1/2/W to 1.71x107 cmHz1/2/W. From the result of D*/J, the result shows the device possesses the best property as the thickness of the PVDF thin film is 165nm. Therefore, the (PVDF/PT) bilayer thin film with the thickness 165nm of PVDF thin film is the most suitable for the applications of pyroelectric thin film IR detectors.

The applications of membrane technologies have dramatically increased during the last few decades due to technology improvement and cost reduction. Membrane applications can be found in water and wastewater treatment, pharmaceutical industry, chemical processing industry, food industry, etc. However, the membrane technology faces two major challenges: membrane fouling and membrane lifetime. During the membrane filtration process, membrane fouling caused by natural organic matter (NOM) is an inevitable phenomenon, and physical cleaning or chemical cleaning are required for recovering the performance of membrane. As a result of these cleaning processes, membrane lifetime is shortened. For this reason, it is necessary to improve membrane's fouling resistance and lifetime in order to apply membrane technology in large-scale facilities. This dissertation focuses on improving the fouling resistance and flux performance of polyvinyl chloride (PVC) membrane and polyvinylidene fluoride (PVDF) membrane. Specifically, it is comprised of four parts. First, I prepared PVC membranes by adding different amounts of amphiphilic copolymer (Pluronic F 127) into PVC casting solutions. I optimized the performance of PVC membranes by changing the amount of Pluronic F127 used in the casting solution. The results show that with the increase of Pluronic F 127 content, the pore size and pore density both decrease. Moreover, the membrane surface becomes more hydrophilic as indicated by lower contact angles. In addition, the PVC membrane exhibits remarkable antifouling characteristics after adding Pluronic F 127. Second, I synthesized PVDF membranes by adding PVDF graft poly(ethylene glycol) methyl ether methacrylate (PEGMA) (PVDF-g-PEGMA) as additive in casting solutions via the phase inversion method. The synthesized PVDF membranes have unique pillar-like structures on surfaces, which gives the PVDF membrane a defect-free feature and allows it to generate high flux under low pressure. Third, I investigated the forming mechanism of the pillar-like structure from aspects of solvent and additive. Finally, I investigated the influence of PEGMA dose on the performance of PVDF membranes. I changed the amount of PEGMA used in the casting solution and compared the performance of the synthesized PVDF membranes. To summarize, this dissertation has deepened our understanding of how to improve the fouling resistance and flux performance of PVC membranes and PVDF membranes by using amphiphilic copolymer. In addition, the PVDF membrane I synthesized has unique pillar-like structures that give it defect-free and high flux properties. Overall, the results of this study provide valuable information for PVC and PVDF membrane synthesis for large-scale production.

Orientador: Fernando Rogério de Paula / Resumo: Neste trabalho foi realizado um estudo das propriedades morfológicas e fotocatalíticas de fibras de PVDF/TiO2 sem e com adsorções de partículas de prata na superfície das fibras. Os resultados demonstraram que os parâmetros: taxa de injeção de 76 μl/min, distância de trabalho de 25 cm, velocidade do coletor 400 rpm e pressão de 0,26 MPa foram os parâmetros ideais para produção de fibras de PVDF/TiO2. As mantas obtidas com essa pressão apresentaram fibras dispersas com baixa rugosidade e diâmetros próximos a 600 nm. Estas fibras apresentaram a melhor propriedade fotocatalítica, sendo a incorporação de 0,50 g de TiO2 a que apresentou maior eficiência degradando 91% do corante em 40 minutos. A difratometria de raios-X das fibras de PVDF/TiO2 identificou picos característicos da fase cristalográfica anatase e rutilo referente ao TiO2 e a fase β correspondente ao PVDF. Visando melhorar a eficiência fotocatalítica das fibras de PVDF/TiO2 foram incorporadas nas superfícies das mesmas, partículas de prata. A deposição promoveu um aumento na atividade fotocatalítica, a manta que sofreu um banho na solução de AgNO3 com concentração 58,9 mmol/L degradou 95 % do corante em 20 minutos, apresentando uma melhora significativa quando comparada com a mesma manta sem incorporação de prata que degradou 50 % no mesmo período de tempo. A presença de partículas de prata, nas superfícies das fibras, foi comprovada por difratometria de raios-X e EDS. / Abstract: In this work a study of the morphological and photocatalytic properties of PVDF/TiO2 fibers with and without adsorptions of silver particles on the surface of the fibers was carried out. The results showed which the parameters: injection rate of 76 μl/min, work distance of 25 cm, collector speed 400 rpm and pressure of 0.26 MPa were the ideal parameters for the production of PVDF/TiO2 fibers. The blankets obtained with this pressure presented dispersed fibers with low roughness and diameters close to 600 nm. These fibers had the best photocatalytic properties, being the incorporation of 0.50 g of TiO2, which presented higher efficiency, degrading 91% of the dye in 40 minutes. The X-ray diffraction of PVDF/TiO2 fibers identified characteristic peaks of the anatase and rutile crystallographic phase related to TiO2 and the β phase corresponding to PVDF. In order to improve the photocatalytic efficiency of the PVDF/TiO2 fibers, silver particles were incorporated into the surfaces thereof. The deposition promoted an increase in the photocatalytic activity, the blanket that was bathed in the AgNO3 solution with a concentration of 58.9 mmol / L degraded 95% of the dye in 20 minutes, presenting a significant improvement when compared to the same blanket without incorporation of silver degraded 50% over the same period. The presence of silver particles on the surfaces of the fibers was confirmed by Xray diffraction and EDS. / Mestre

Blends of poly(vinylidene fluoride) (PVDF) and polyamide 6 (N6) are interesting for both scientific studies and commercial exploitation. PVDF is known to be miscible with polymers produced from monomers containing carbonyl side groups, eg. polyethyl acrylate, polyacrylamide etc., but is not miscible with polymers containing carbonyl groups in the main chain, ego polyamides, polyester, etc. Although complete miscibility of the blend components is not always necessary, strong physical interactions between the two components are needed in order to obtain a compatible blend, i.e. one which exhibits good mechanical properties. An investigation was carried out to explore the possibility to compatibilise blends of PVDF and N6 using y-radiation to graft acid groups on either polymer and subsequently ionomerizing these with zinc cations. Graft copolymer type of compatibilizer was produced when the acid functionalized PVDF (grafted PVDF) was blended with N6 or acid functionalized N6 (grafted N6). Fourier transform infrared analysis has confirmed the occurance of reactions between acid groups in the grafted PVDFand amine groups in the N6. The compatibility of the PVDF/N6 blends was found to increase with increasing amount of carboxylic acid groups in the two polymers. This was accompanied by an increase in Tg of the N6 phase in blend, which became more pronounced when both components were grafted. Tensile test and solvent resistance experiments were carried out to relate the compatibization of the blend to the improvement in mechanical properties. Ionomerization of the functionalized polymers with zinc cations was performed in order to study the effect on compatibility of the blend. The neutralization of the acid groups in either polymer in the blend by addition of zinc acetyl acetonate was found to suppress the chemical reaction with the amine end groups in the N6 phase, and to cause a reduction in the T g and a reduction in crosslinking of the N 6 phase. However when both polymers were grafted, the crystallinity of the N6 phase was restored, which was accompanied by an increase in Tg.

Abstract: Poly (vinylidene fluoride) (PVDF), thanks to its versatile properties, finds many applications ranging from water purification membranes (thermal and chemical stability) to electronic devices (piezoelectric, pyroelectric and ferroelectric properties). Block copolymers of PVDF with other polymers further expand its properties and, consequently, its applications. Toward this line, my thesis investigates the synthesis, molecular characterization and properties of novel PVDF-based copolymers mainly with poly(tert-butyl acrylate) (PtBuA), poly(methyl methacrylate) (PMMA) and polystyrene (PSt). To prepare the block copolymers a living polymerization is needed, which is compatible with the VDF and the comonomer (tBuA, MMA, St). For this purpose, we used iodine transfer polymerization (ITP) with the difunctional chain transfer agent (CTA) C4F8I2. Difunctional macroinitiator (I-PVDF-I) was first obtained by ITP of VDF monomer with C4F8I2, followed by addition of the comonomer tBuA, MMA or St to afford the triblock copolymers poly(tert-butyl acrylate)-block-poly(vinylidene fluoride)-block-poly(tert-butyl acrylate) (PtBuA-b-PVDF-b-PtBuA), poly(methyl methacrylate)-block-poly(vinylidene fluoride)-block-poly(methyl methacrylate) (PMMA-b-PVDF-b-PMMA) and polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PSt-b-PVDF-b-PSt). The structure of all intermediates and final products were characterized by Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC). The microstructure and polymorphism of all triblock copolymers, characterized by XRD, shown that the PVDF in the first two copolymers exhibits the electroactive β-phase, while in the third copolymer there is the coexistence of α- and γ-phases. Linear PVDF homopolymers, using the free radical and IT polymerizations, were prepared for comparison purposes. All linear polymers possess the α-phase. The thesis is divided into the following five chapters: 1. Introduction, where the scope of this thesis is given with a brief background on PVDF; 2. Literature Review, where a summary of previously published works on PVDF synthesis and polymorphism is presented; 3. Experimental Section, where detailed procedures and characterization methods are given; 4. Results and Discussion, where outcomes of successful experiments are discussed; and 5. Conclusion and Perspective, where the outcomes of this work are summarized and perspective are discussed.