C. del Río

Carbon black effect on the microstructure of incompatible polymer blends

Abstract This work reports on a study of the effects exerted by carbon black (CB) on the microstructure of the incompatible polymer blend polyvinylidene fluoride/polyamide (PVDF/PA) by means of calorimetric and dynamic mechanical determinations of the glass transition temperatures, as well as the isothermal crystallization kinetics. The results demonstrate partial polymer compatibilization to take place in the PVDF-rich phase, as a consequence of an improvement in component adhesion at the CB–PVDF interface. In addition, CB is shown to modify the isothermal crystallization kinetic parameters.

Determination of the interaction parameter of partially or totally compatible systems through glass transition temperature measurements

Abstract A compatibility study was conducted on the system poly(vinylidene fluoride)/polystyrene in the presence of carbon black, metallic copper, YBaCuO ceramics and poly(vinyl acetate). From T g measurements the volume fractions of the respective minority polymer in either phase were calculated, and applying an expression proposed by Kim and Burns, the Flory-Huggins polymer-polymer interaction parameters χ 12 were determined. The results show that a greater portion of polystyrene is dissolved in the poly(vinylidene fluoride)-rich phase than vice versa, the dissolution level being a function of the nature of the third component added to the blend.

Extrinsic conducting and superconducting polymer systems. III. Electrical properties of PVDF/PS blends containing copper, carbon black, and YBaCuO fillers

In this work, the electrical characterization of three extrinsic polymeric conducting systems was carried out using complex impedance spectroscopy. These systems were obtained by the incorporation of conducting fillers (carbon black and metallic copper), on the one hand, and, on the other hand, by blending with a superconducting ceramic (YBaCuO). The experimental results prove that the electrical characteristics of these systems vary as a function of the nature of the filler added. In the case of metallic copper, the resulting composites posses a conductivity which is intermediate between insulating materials and semiconductors. When carbon black is incorporated in concentration above 10%, the composites may be considered as metalliclike from the point of view of conductivity. Finally, when the filler is YBaCuO, the low conductivity values obtained are indicative of insulating materials regardless of their composition.

Effect of compatibility on dielectric relaxation and on the microstructure of semicrystalline polymer blends

Abstract Polyvinylidene fluoride, polystyrene, polyvinyl acetate and their blends were investigated using dielectric measurements at different temperatures and frequencies in order to study the effect of compatibility on the glass transition temperature of these polymer systems. Isothermal crystallization kinetic studies were performed in order to determine the microstructure and the morphology of the samples.

Elastomeric conducting systems based on ethylene–propylene–norbornene composites

This work reports the preparation and structural and electrical characterizations of composites consisting of ethylene–propylene–norbornene, polypropylene, and carbon black (CB) blends, comparing the data obtained from crosslinked and noncrosslinked samples. Structural analysis provided evidence of the reinforcing effect of CB on the properties when present in the initial system, as well as of the excellent conducting properties of CB composites. This, together with their mechanical properties and their extraordinary processing ease, makes them suited as bipolar plates in fuel cells based on polymeric electrolyte.

Electrical and electrochemical characterization of petrol cokes for lithium-ion cells

Several cokes and graphites have been electrically and electrochemically characterized. The process of electrochemical lithium ion insertion into these materials has been analyzed for the purpose of assessing their performance as electrodes in advanced batteries and as potential candidates to substitute for lithium metal. The results obtained prove the process of electrochemical lithium ion insertion into cokes and graphites to be strongly influenced both by the ordered structure of the starting material and by the nature of the anion of the lithium salt, which is used as electrolyte.

Extrinsic conducting and superconducting polymer systems. IV. Superconducting properties of YBaCuO composites based on PVDF/PS/carbon black and PVDF/PS/copper polymer systems

In this work, the critical temperature (Tc) of a series of polymeric superconducting systems is determined which, sintered or not, are obtained through the incorporation of the superconducting ceramic YBaCuO into two extrinsic conducting polymer systems: PVDF/PS/carbon black and PVDF/PS/copper. In addition, the diamagnetic characteristics of these systems are studied on the basis of susceptibility measurements as a function of temperature. As regards the unsintered systems and according to the experimental results, copper-based composites can be termed as insulating materials and the samples with the highest carbon black content as reaching metalliclike conductivities. In no case, however, is an abrupt leap in conductivity observed as a function of temperature, indicating the superconducting nature of these systems from an electrical point of view. On the contrary, magnetic susceptibility measurements as a function of temperature detect in all cases a superconducting transition, i.e., a shift in the critical temperature range, bringing it close to that of pure YBaCuO (≈100 K). After sintering, the samples retained their original shape as well as reasonable mechanical properties. The electrical conductivity study confirmed the absence of superconductivity as a consequence of polymer combustion during sintering and thereby implying the disappearance of the orthorhombic phase of YBaCuO, which X-ray evidence proved to be accountable for superconductivity in this ceramic material.

Conductivity studies of solid polymer electrolytes based on polyethers and polyphosphazene blends

In this work, electrical characteristics of several polymer electrolytes based on polyether and polyphosphazene blends are reported by means of complex impedance spectroscopy. In addition, a statistical analysis was conducted applying a mathematical model to a previously designed pattern to the purpose of gaining insight into the effect exerted on the conductivity of the electrolyte by the portion of each component in the blend. Evidence was obtained to prove that the dependence of conductivity on blend composition adjusts to a reduced cubic model, whose regression coefficients are determined in this work.