Variation of the physicochemical and morphological characteristics of solvent casted poly(vinylidene fluoride) along its binary phase diagram with dimethylformamide

Poly(vinylidene fluoride), PVDF, films and membranes were prepared by solvent casting from dimethylformamide, DMF, by systematically varying polymer/solvent ratio and solvent evaporation temperature. The effect of the processing conditions on the morphology, degree of porosity, mechanical and thermal properties and crystalline phase of the polymer were evaluated. The obtained microstructure is explained by the Flory-Huggins theory. For the binary system, the porous membrane formation is attributed to a spinodal decomposition of the liquid-liquid phase separation. The morphological features were simulated through the correlation between the Gibbs total free energy and the Flory-Huggins theory. This correlation allowed the calculation of the PVDF/DMF phase diagram and the evolution of the microstructure in different regions of the phase diagram. Varying preparation conditions allow tailoring polymer 2 microstructure while maintaining a high degree of crystallinity and a large β crystalline phase content. Further, the membranes show adequate mechanical properties for applications in filtration or battery separator membranes.

Tailoring poly(vinylidene fluoride-co-chlorotrifluoroethylene) microstructure and physicochemical properties by exploring its binary phase diagram with dimethylformamide

Poly(vinylidene fluoride-co-chlorotrifluoroethylene), PVDF-CTFE, membranes were prepared by solven casting from dimethylformamide, DMF. The preparation conditions involved a systematic variation of polymer/solvent ratio and solvent evaporation temperature. The microstructural variations of the PVDF-CTFE membranes depend on the different regions of the PVDF-CTFE/DMF phase diagram, explained by the Flory-Huggins theory. The effect of the polymer/solvent ratio and solvent evaporation temperature on the morphology, degree of porosity, β-phase content, degree of crystallinity, mechanical, dielectric and piezoelectric properties of the PVDF-CTFE polymer were evaluated. In this binary system, the porous microstructure is attributed to a spinodal decomposition of the liquid-liquid phase separation. For a given polymer/solvent ratio, 20 wt%, and higher evaporation solvent temperature, the β-phase content is around 82% and the piezoelectric coefficient, d33, is - 4 pC/N.

Plastic-damage smeared crack model to simulate the behaviour of structures made by cement based materials

This work proposes a constitutive model to simulate nonlinear behaviour of cement based materials subjected to different loading paths. The model incorporates a multidirectional fixed smeared crack approach to simulate crack initiation and propagation, whereas the inelastic behaviour of material between cracks is treated by a numerical strategy that combines plasticity and damage theories. For capturing more realistically the shear stress transfer between the crack surfaces, a softening diagram is assumed for modelling the crack shear stress versus crack shear strain. The plastic damage model is based on the yield function, flow rule and evolution law for hardening variable, and includes an explicit isotropic damage law to simulate the stiffness degradation and the softening behaviour of cement based materials in compression. This model was implemented into the FEMIX computer program, and experimental tests at material scale were simulated to appraise the predictive performance of this constitutive model. The applicability of the model for simulating the behaviour of reinforced concrete shear wall panels submitted to biaxial loading conditions, and RC beams failing in shear is investigated.

Sustainability education in PBL education: the case study of IEM-UMINHO

Sustainability-related skills are becoming more and more relevant for a proficient and professional engineering practice. Industrial engineers in particular, given their broad field of intervention and being at the heart of industrial activity, hold a great deal of potential and responsibility in providing and delivering best industrial practices, that support enhanced industrial systems and products. Therefore making a real contribution in generating wealth and income for all the companies’ stakeholders, including local communities, as well as adding up to more sustainable ecosystems. Previous work by the authors focused on studying the inclusion of this subject on the education of industrial engineers, especially through active-learning methodologies, as well as presenting results on the use of one such approach. The study conducted tried to identify the impacts on sustainability learning using a given specific activity, i.e. a workshop on industrial ecology, held in the 2014/2015 academic year on the Integrated MSc degree on Industrial Engineering and Management at the University of Minho, Portugal. The study uses content analysis of student teams’ reports for two consecutive academic years. The former did not include one such workshop, while the latter did. The Fink taxonomy was used in the discussion of results and reflection. The study outcomes aimed at supporting decision making on worthiness of investment on similar education instruments for sustainability competency development. Some results of the study highlight that: (1) the workshop seem to globally have a positive contribution on the sustainability learning; (2) a number of dimensions of the Life cycle design strategy wheel was developed, but the approach was not broadly used, (3) There was a mismatch on the workshop schedule; (4) students enjoy the workshop; (5) a clearer endorsement on relevance of this aspect is required. Suggestions for future work are also issued.

Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) lithium-ion battery separator membranes prepared by phase inversion

Separator membranes based on poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) were prepared by solvent casting technique based on its phase diagram in N,Ndimethylformamide (DMF) solvent. The microstructure of the PVDF-CTFE separator membranes depends on the initial position (temperature and concentration) of the solution in the phase diagram of the PVDF-CTFE/DMF system. A porous microstructure is achieved for PVDF-CTFE membranes with solvent evaporation temperature up to 50 ºC for a polymer/solvent relative concentration of 20 wt%. The ionic conductivity of the separator depends on the degree of porosity and electrolyte uptake, the highest room temperature value being 1.5 mS.cm-1 for the sample with 20 wt% of polymer concentration and solvent evaporation temperature at 25 ºC saturated with 1 mol L-1 lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) in propylene carbonate (PC). This PVDF-CTFE separator membrane in Li/C-LiFePO4 half-cell shows good cyclability and rate capability, showing a discharge value after 50 cycles of 92 mAh.g-1 at 2 C, which is still 55% of the theoretical value. PVDF-CTFE separators are thus excellent candidates for high-power and safety lithium-ion batteries applications.

Implementação de técnicas e princípios de produção lean no processo de pré-confeção de uma indústria de cablagens

Dissertação de mestrado em Engenharia Industrial

Implementação de ferramentas Lean numa empresa de componentes para calçado

Dissertação de mestrado em Engenharia Industrial

Balanceamento e redefinição de layouts de células de costura de uma empresa da indústria automóvel

Dissertação de mestrado integrado em Engenharia e Gestão Industrial

Análise e melhoria da produtividade numa empresa do sector de componentes de automóveis

Dissertação de mestrado integrado em Engenharia e Gestão Industrial

Controlador com FPGA para um motor-in-wheel CA de fluxo axial

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores

Controlo de qualidade e inspeção visual por imagem: definição de uma aplicação para registo de alterações e avaliação de desempenho

Dissertação de mestrado em Engenharia e Gestão da Qualidade

Estudo numérico sobre o reforço de pilares de betão armado com cantoneiras e presilhas metálicas: análise paramétrica e modelo de cálculo

Dissertação de mestrado integrado em Engenharia Civil

Promoção da motivação e da autonomia com recurso às tecnologias de informação e comunicação em alunos normovisuais e em alunos com deficiência visual

Relatório de estágio de mestrado em Ensino de Informática

Análise técnica - económica da produção de energia em sistemas de abastecimento de água: caso do aproveitamento de fins múltiplos dos socorridos

Dissertação de mestrado integrado em Engenharia Civil

Zebrafish embryos as in vivo model for toxicity evaluation: screening of nanoparticle formulations DODAB:MO and DODAC:MO

Dissertação de mestrado em Molecular Genetics