Jose Luis Acosta

Ionic conductive polymer systems based on polyether and polyphosphazene blends

Several polymer electrolytes have been obtained, based on binary blends of polyethylene oxide (PEO), polypropylene oxide, and polyphosphazene by means of solvation with lithium triflate. The different samples were studied both as to their microstructure and for their electrical properties, either through the determination of their respective glass transition temperatures and melting enthalpies or by means of complex impedance spectroscopy. When comparing the results obtained for the synthesized binary systems with those known for PEO, the former systems prove to possess a better dimensional stability and a higher conductivity than PEO in itself.

The effect of interfacial adhesion and morphology on the mechanical properties of polypropylene composites containing different acid surface treated sepiolites

The study of the microstructure of polymeric composites and its relationship to mechanical properties, are of great importance. In the present study vv8 have carried out a study of the microstructure of polymeric composites of polypropylene and different sepiolites treated with organic acids, in order to determine the mesophase produced around We filler particles and its relationship with the mechanical properties of the composites. This study was made using scanning electron microscopy, differential Scanning calorimetry and mechanical tests.

Acid/base characterization of sepiolite by inverse gas chromatography

SummaryThe surface properties of sepiolite were investigated by inverse gas chromatography. It is shown that the value of the dispersive component change uniformly with temperature, while the values obtained for the parameters KA and KD indicate an acidic character for the sepiolite surface.

Electrical and morphological studies of polymeric composites based on carbon black

Conventional polymers, polypropylene and polystyrene, containing carbon black as conductor additive, were prepared. Impedance complex-plane analysis is used in order to characterize the composites obtained. Microstructure studies indicate that carbon black affects the size but not the geometrical morphology. The electrical conductivity of polypropylene composites is higher than polystyrene, and is correlated to the microstructural and wettability properties of these polymer matrices.

Dynamic mechanical properties of binary and ternary blends based on PVDF

SummaryA universally accepted criterion when assessing blend compatibility is the existence of a single glass transition temperature, which changes as a function of blend composition. Differential scanning calorimetry and dynamic mechanical strain spectra are powerful tools in the study of polymer relaxation in the glass transition zone. In this research both techniques are employed to determine the glass transition temperatures of a series of polymer blends based on polyvinylidene fluoride. In the light of the data obtained further thought is given to the discrepancies between the results obtained with one and the other method, as well as to the compatibility of the experimental blends.

Morphological properties of composite solid polymer electrolytes based on polyethylene oxide

Morphological properties of polymer electrolytes based on blends of polyethylene oxide and a perfluorinated polyphosphazene solvated with LiCF 3 SO 3 with and without the addition of dispersed γ-LiAlO 2 are reported. The effect exerted on the morphology of the complex electrolytes by the addition of a plasticizer-like propylene carbonate has also been studied. Results indicate the incorporation of γ-LiAlO 2 leads to changes on the morphology of the complex electrolyte, as verified by X-ray diffraction analysis. The major effect observed by plasticizer addition was a decrease on the crystallinity of the system together with a displacement of the T g towards lower temperatures.

Crystallization, thermal behavior, and compatibility of poly(ethylene oxide)/poly(propylene oxide) blends

Isothermal and nonisothermal crystallization kinetics of different poly(ethylene oxide)/poly(propylene oxide) blends were investigated by means of differential scanning calorimetry (DSC). Glass transition temperature of quenched samples have also been reported. Phase morphologies and poly(ethylene oxide) spherulite growth rates were analyzed by polarizing light transmission microscopy. Results show morphological changes along with regime transitions of poly(ethylene oxide) crystal growth. Kinetic analyses of the data suggest that, although the blend behaves as a noncompatible, phase-separated system, there exists a certain degree of interaction between polymer chains.

Conductivity study on semicrystalline and amorphous polymers filled with conducting additives

SummaryPolymeric conducting composites were obtained on the basis of polypropylene and polystyrene and conducting fillers (iron, copper and carbon black). The materials obtained by means of physical blends of the components were characterized through complex impedance diagrams. The respective data provided evidence of the fact that the conduction mechanism of such composites depends both on the chemical and structural properties of the polymeric matrix and on the nature of the conducting additive.

Prediction of polymer-solute thermodynamic parametersχ;12 and Ω;1∞; from inverse gas chromatography data. Application to poly(propylene oxide)-solute system

SummaryThe solvation equation has been applied to the solubility of 13 probes in poly(propylene oxide). It has been shown that log Vg0 values can be predicted with reasonable precision using this equation, while the results are not so good for predicting thermodynamic parameters. The high values found when applying regression analysis to the independent parameter c, indicates that parameters exist with a marked effect on retention but not included in the equation.

Effect of sepiolite on glass transition temperature and melting behaviour of semicrystalline polymer blends

SummaryThermal analysis of blends poly(vinylidene fluoride) (PVF2) with poly(methyl methacrylate) (PMMA) or polystyrene (PS) filled with sepiolite was carried out to examine the effects of the filler on properties such as melting behaviour and glass transition temperature. For the compatible PVF2/PMMA system, the presence of the filler did not cause any substantial changes in the thermal behaviour of the blend. In the non-compatible PVF2/PS system, some compatibilization is achieved in the blend, indicated by PVF2 melting point depression as well as by a shift of the glass transition of the homopolymers in the blend.