The aim of this paper is the characterization of a carbon felt (Le Carbone Lorraine, RVC 4002) to be used as three-dimensional electrode. A wide group of very different techniques were used in the physical and structural characterization of this material. Both, structural (porosity, mean pore radius, specific surface area, tortuosity) and physical properties (permeability, electrical resistance) were determined by using mercury porosimetry, adsorption isotherm analysis, a filamentary analog procedure and liquid permeametry (pressure drop method). The results obtained from the modelling of the hydrodynamic behaviour, from previous work, were also applied here. The carbon felt studied was found to have a porosity around 0.98, a specific surface area of 22100-22700 m -1 , 2.7 10 -3 Ω m electrical resistivity and a tortuosity between 5 and 6. The comparison of these results with those found in the literature for other similar materials, used as three-dimensional electrodes, highlights the attractions of this
Thermoplastic polyurethane (TPU) adhesives containing nanosilicas with different specific surface area and silanol group content were prepared and characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TGA), X-ray diffraction, plate-plate rheology, dynamical-mechanical-thermal analysis (DMTA), transmission electron microscopy (TEM), and strain-stress test. Adhesive strength was obtained from T-peel tests of PVC/polyurethane adhesive joints.Formation of agglomerates of nanosilica particles within the polyurethane matrix were favoured by increasing the silanol content likely due to stronger hydrogen bond interactions between the silanol groups on the nanosilica over those between the polyurethane and the nanosilica. As a consequence, inter-urethane bonds formation rather than ester-urethane bonds were favoured, leaving the soft segment chains more free to interact between them. Thus, addition of nanosilica favoured the phase segregation in the thermoplastic polyurethane. The increase in specific surface area and silanol content in the nanosilica, generally enhanced the degree of phase separation in the polyurethane, being less marked for nanosilicas with more than 200 m 2 /g and 0.60 mmol SiOH/g silica . On the other hand, the addition of the nanosilica improved the tensile strength and elongation at break, and the viscoelastic properties of the polyurethane. The immediate adhesive strength of PVC/polyurethane adhesive joints increased in the filled adhesives and it was determined by the rheological properties of the polyurethane-nanosilica mixtures. By increasing the time after joint formation, the crystallization of the polyurethane was produced giving higher adhesive strength and although a cohesive failure in the PVC was always obtained, a slight though progressive increase in joint strength was found with the passage of time with the ordering of the three systems (PU-0.45, PU-0.60 and PU-0.90) remaining unchanged with the PU-0.60 system the stronger and the PU-0.90 system the weaker. This is in agreement with the trends in the viscoelastic and mechanical properties of the filled adhesives. r
Abstract-Ethylene vinyl acetate (EVA) material containing 20 wt% vinyl acetate (EVA20) was treated with corona discharge to improve its adhesion to polychloroprene adhesive. Several experimental variables in the corona discharge treatment of EVA20 were considered: corona energy, type of electrode, and number of consecutive treatments. Advancing contact angle measurements (water, 25 ± C) showed an increase in the wettability of EVA20 after treatment with corona discharge, which corresponds to an increase in the O / C ratio on the treated surface. The higher the corona energy (i.e. the higher discharge power and longer treatment times), the greater the degree of surface oxidation. Peel strength values of the joints produced with EVA20 using a polychloroprene adhesive containing 5 wt% isocyanate increased from 1.5 kN / m (as-received EVA20) to 4.3 kN/ m (corona-treated EVA20). A mixed (adhesional C cohesive in EVA20) locus of failure was obtained in all adhesive joints produced with corona discharge-treatedEVA20. Finally, the number of consecutive corona discharge treatments and the surface area of the electrode (spherical versus hook-shaped electrode) did not greatly in uence the adhesion of EVA20 to polychloroprene adhesive.
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