Synthesis and process optimization of electrospun PEEK-sulfonated nanofibers by response surface methodology

In this study electrospun nanofibers of partially sulfonated polyether ether ketone have been produced as a preliminary step for a possible development of composite proton exchange membranes for fuel cells. Response surface methodology has been employed for the modelling and optimization of the electrospinning process, using a Box-Behnken design. The investigation, based on a second order polynomial model, has been focused on the analysis of the effect of both process (voltage, tip-to-collector distance, flow rate) and material (sulfonation degree) variables on the mean fiber diameter. The final model has been verified by a series of statistical tests on the residuals and validated by a comparison procedure of samples at different sulfonation degrees, realized according to optimized conditions, for the production of homogeneous thin nanofibers

Fire phenomena of rigid polyurethane foams

Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and water-blown polyurethane (PUR) as well as pentane-blown polyisocyanurate polyurethane (PIR) foams with densities ranging from 30 to 100 kg/m3. Thermophysical properties were studied using thermogravimetry (TG); flammability and fire behaviour were investigated by means of the limiting oxygen index (LOI) and a cone calorimeter. Temperature development in burning cone calorimeter specimens was monitored with thermocouples inside the foam samples and visual investigation of quenched specimens’ cross sections gave insight into the morphological changes during burning. A comprehensive investigation is presented, illuminating the processes taking place during foam combustion. Cone calorimeter tests revealed that in-depth absorption of radiation is a significant factor in estimating the time to ignition. Cross sections examined with an electron scanning microscope (SEM) revealed a pyrolysis front with an intact foam structure underneath, and temperature measurement inside burning specimens indicated that, as foam density increased, their burning behaviour shifted towards that of solid materials. The superior fire performance of PIR foams was found to be based on the cellular structure, which is retained in the residue to some extent

Electrically Conductive Membranes Obtained by Simultaneous Electrospinning and Electrospraying Processes

Electrically conductive polyurethane nanostructured membranes have been prepared combining the electrospinning of polymer nanofibers (NFs) with the electrospraying of pristine multiwall carbon nanotubes (MWCNTs) in simultaneous processes. In order to have a better understanding of the distribution of MWCNTs on the surface of the membranes, the optimization of the electrospraying process has been carried out and the distribution of MWCNTs has been evaluated using image texture analysis techniques. Large membranes with a volume resistivity typical of electrostatic discharge materials with a MWCNTs concentration less than 0.3% wt (0.01 mg/cm2) have been obtained and characterized with morphological (SEM and TEM) and spectroscopic (UV-Vis, Raman) techniques

Effect of dual functional ionic liquids on the thermal degradation of poly(vinyl chloride)

The short-term thermal stability of PVC on addition of functional ionic liquids (ILs) based on phosphonium and pyridinium cations, and a docusate anion, was studied using FTIR, TGA-MS and TGA-FTIR. The thermal stability of PVC plasticized with these ILs is reduced and the activation energy for thermal degradation for the first step of PVC degradation lowered, relative to neat PVC. This feature is not dependent on the thermal stability of the IL itself, as their addition to neat PVC did not result in increased thermal stability of the resin. Analysis of the gases evolved during thermal degradation showed that there is no variation in the mechanism of PVC degradation in the presence of ILs, the only difference observed is that HCl is evolved at lower temperatures for PVC-ILs samples. The ILs had no effect on the second step of the thermal degradation of PVC. The decrease in the thermal stability of PVC-ILs is associated with two different effects: firstly, the anion weakens the C-H bond while the cation forms complexes and weakens the C-Cl bond; second, the IL interaction with the polymer chains partly substitutes the interaction between the polymer chain and heat stabilizers (e.g. stearates) added to the PVC compound. In this way, the latter tends to be expelled from the bulk polymer, thus not being available for PVC stabilization at high temperature. Heat stabilizer migration is related to the solvating power of the ILs: the higher the solvating power, the higher the migration of heat stabilizer, the lower the thermal stability of the polymer

Construction and demolition waste: evaluation of quantification methods

Neste trabalho, estimou-se a gerão dos resíduos de construção e demolição por dois métodos de quantificação, um indireto e outro direto, considerando-se a produção advinda dos agentes informais e formais. O método indireto considerou a área construída das edificações (construção) e transformação dos pontos de ligação de água e luz instalados (reforma). O método direto identificou a geração advinda de agentes informais e formais nos pontos de disposição finais em diferentes regiões do município, empregando-se o conceito de balanço de massa. Não é possível quantificar a geração de resíduos de construção e demolição dos agentes informais (reformas) por meio de dados indiretos relacionados Às transformações dos pontos de água no município. Há indícios de que as transformações dos pontos de energia elétrica sejam um indicador indireto mais preciso, podendo evitar a dispendiosa quantificação direta.In this paper, construction and demolition waste generation was estimated by two quantification methods, one direct and other indirect, regarding informal and formal generators. Construction area and transformation of the points of water and energy were applied for indirect quantification method. For the direct one, volume of dumping areas associated with informal and formal generators in different regions of municipality were quantified and the mass balance was applied. Indirect quantification of informal generators by transformation points of water is not precise. There are evidences that transformation points of energy can be more precise, avoiding costly direct construction and demolition waste quantification method

Produção de concretos autoadensáveis com alto teor de ar incorporado e propriedades mecânicas para fins estruturais

O uso de concreto autoadensável já é bastante difundido na construção civil, sendo utilizado principalmente em elementos esbeltos e/ou com altas taxas de armadura. Ainda assim, os efeitos combinados de autoadensabilidade com determinadas estratégias modificadoras das propriedades dos concretos são pouco conhecidos. Esse é o caso observado com o aditivo incorporador de ar. Dessa forma, o presente trabalho busca avaliar a influência da incorporação de ar no comportamento de concretos autoadensáveis mantendo propriedades mecânicas adequadas para uso estrutural. Algumas premissas de interesse foram definidas com base na utilização do material para a execução de paredes de concreto moldadas no local. Assim, foram produzidos dois traços de concreto autoadensável, sem incorporação de ar, com classes de resistência C25 e C40 e, a partir de cada um deles, foram produzidos outros dois traços modificados com aditivo incorporador de ar, variando o teor de ar incorporado, em um total de seis misturas cujas propriedades foram avaliadas tanto no estado fresco quanto no estado endurecido. Os resultados obtidos foram muito satisfatórios, considerando que dois dos traços de concreto autoadensável com incorporação de ar apresentaram propriedades mecânicas adequadas para utilização com função estrutural, apesar do alto teor de ar incorporado.Palavras-chave: Concreto autoadensável. Aditivo incorporador de ar. Autoadensabilidade. Resistência à compressão

Is raw better? A multiple DNA barcoding approach (full and mini) based on mitochondrial and nuclear markers reveals low rates of misdescription in sushi products sold on the Italian market

New dietary habits have favored an ever growing popularity of Eastern country cooking style and in particular of sushi. Even though the Reg. (EU) 1379/2013 does not apply to restaurants and caterers, the Reg. (EU) 1169/2011 establishes that all the information they provided to the final consumer have to meet the transparency requirements as regards the description of the ingredients used for the preparation of food. The present study aimed at performing a molecular based survey to identify the seafood species used in the sushi preparations at the retail level. A total of 185 samples were collected from sushi venues and supermarkets and DNA barcoding, followed by a pairwise divergence and Neighbor Joining clustering analysis, was applied in order to verify the information declared at purchase. Rather than to a proper training of Food Business Operators working at the catering level, the low mislabeling rate found in this study (3.4%) could be ascribed to the standardization of the products sold in ethnic restaurants. In fact, the common practice of proposing standardized menus always relying on the same species of fish could limit the risk of mislabeling occurrence

Polyether Single and Double Crystalline Blends and the Effect of Lithium Salt on Their Crystallinity and Ionic Conductivity

In this work, blends of Poly(ethylene oxide), PEO, and poly(1,6-hexanediol), PHD, were prepared in a wide composition range. They were examined by Differential Scanning Calorimetry (DSC), Polarized Light Optical Microscopy (PLOM) and Wide Angle X-ray Scattering (WAXS). Based on the results obtained, the blends were partially miscible in the melt and their crystallization was a function of miscibility and composition. Crystallization triggered phase separation. In blends with higher PEO contents both phases were able to crystallize due to the limited miscibility in this composition range. On the other hand, the blends with higher PHD contents display higher miscibility and therefore, only the PHD phase could crystallize in them. A nucleation effect of the PHD phase on the PEO phase was detected, probably caused by a transference of impurities mechanism. Since PEO is widely used as electrolyte in lithium batteries, the PEO/PHD blends were studied with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), and the effect of Li-salt concentration was studied. We found that the lithium salt preferentially dissolves in the PEO phase without significantly affecting the PHD component. While the Li-salt reduced the spherulite growth rate of the PEO phase within the blends, the overall crystallization rate was enhanced because of the strong nucleating effect of the PHD component. The ionic conductivity was also determined for the blends with Li-salt. At high temperatures (>70 °C), the conductivity is in the order of ~10−3 S cm−1, and as the temperature decreases, the crystallization of PHD was detected. This improved the self-standing character of the blend films at high temperatures as compared to the one of neat PEO.This work has received funding from Basque Government through grant IT1309-19

Considerações sobre a eficiência de misturas de concreto de cimento Portland com base no conceito de empacotamento de partículas

O concreto é o material de construção mais utilizado e nos últimos anos, estudos têm sido desenvolvidos em busca de materiais com desempenho mecânico e durabilidade superior. Com a finalidade de abranger a realidade das obras civis no que se refere à produção in loco do concreto convencional e de alta resistência, diversos métodos de dosagem são propostos. Apesar de esses métodos permitirem obter a proporção ideal entre os materiais constituintes da mistura de concreto, é possível otimizar a composição aplicando-se o conceito de empacotamento de partículas. Diante disso, o presente estudo tem por objetivo avaliar a eficiência do empacotamento de partículas de misturas de concretos de cimento Portland amplamente utilizados na prática da construção civil, obtidas por métodos de dosagem tradicionais. Para isso, foram produzidos três traços de concreto utilizando o método de dosagem tradicional IPT/EPUSP, sendo dois para concretos com classe de resistência convencional e um de alta resistência. Conhecendo a proporção e a distribuição granulométrica dos materiais constituintes desses concretos, o coeficiente de distribuição de cada mistura foi determinado considerando o modelo de empacotamento de Alfred. Posteriormente, mantendo-se o mesmo coeficiente de distribuição, as misturas de concretos foram otimizadas aplicando o conceito de empacotamento de partículas, sendo determinadas as propriedades físicas e mecânicas dos concretos. No processo de otimização, verificouse lacunas entre as distribuições granulométricas dos materiais constituintes normalmente considerados na produção dos concretos, caracterizando uma deficiência quanto ao empacotamento. Com relação as propriedades do concreto no estado endurecido, as misturas otimizadas apresentaram, em geral, propriedades físicas e mecânicas superiores aos concretos de referência.  Palavras-chave: Concreto, Método de dosagem, Empacotamento de partículas, Modelo de Alfred, Coeficiente de distribuição

Produção de concreto autoadensável incorporado com resíduo da indústria de cerâmica vermelha

Nos últimos anos, observa-se uma crescente utilização de adições minerais na produção de cimento Portlande de concretos com o intuito de melhorar as propriedades físicas, mecânicas e de durabilidade desses materiais,além dos benefícios econômicos e ambientais, já que essas adições geralmente são resíduos ou subprodutosindustriais. Considerando que a indústria de cerâmica vermelha do Brasil gera uma elevada quantidade deresíduos no processo de produção, existe um passivo ambiental e um custo elevado relacionados a esses resíduos.Uma alternativa de aproveitamento consiste na sua utilização como adição mineral na produção de cimentoPortland e concreto. Assim, o presente trabalho avalia a utilização de resíduos de cerâmica vermelhana produção de concreto autoadensável. Além das propriedades de autoadensabilidade no estado fresco, foramdeterminadas as propriedades físicas e mecânicas no estado endurecido. Os resultados demonstram que omaterial possui um grande potencial para utilização na produção de concreto autoadensável, inclusive aquelesde alta resistência.Palavras-chave: resíduo; cerâmica vermelha; adição mineral; cimento composto; concreto autoadensável