Faika F. Hanna

Studies on the dielectric behavior of silica-filled butyl rubber vulcanizates after cyclic deformation

Abstract The broadband dielectric spectroscopy (10−3–106 Hz) is used to study the effect of stress-strain cycles on the dielectric properties of butyl rubber vulcanizates filled with silica. The influence of chemical modification of the surface of the silica by silane coupling agent (Si69) also was investigated. In addition Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were carried out. Dielectric investigations of the samples were done after stress-strain cycles with maximum elongation 26%, 40%, 60%, and 80% from elongation at break, respectively. It was found that the dielectric properties recovered after storage at room temperature for about one year.

Dielectric properties of some ternary mixtures of normal alcohols and aliphatic diols with heptane

Abstract The static permittivity has been investigated for the ternary mixtures of 1,6-hexanediol/n-dodecanol/heptane, 1,2-ethanediol/n-dodecanol/heptane, and 1,6-hexanediol/n-hexanol/heptane. In addition, the static properties of pure n-hexanol and binary solutions of n-hexanol, cyclohexanol and n-heptanol in n-heptane have been studied together with the binary mixture hexanediol/hexanol. The results are discussed. Broadband dielectric relaxation spectra (at 20 to 40 °C) are reported for the three ternary systems. The concentration of the polar substances ranges from alcohol mole fraction x = 0.1 to 1. The dependence of relaxation parameters on concentration and temperature of the ternary mixtures is discussed.

Full band spectroscopic studies on the molecular mobility of diluted alcohols

Abstract Static permittivity has been determinded for pure n-decanol and cyclohexanol and their solutions in cyclohexane up to very dilute solutions, the dipole moment is found to decrease with the increase in concentration to a minimum, then it increases continuously. At a certain concentration range, no effect of temperature on the measured dipole moments could be observed, within the observed temperature interval. The dielectric loss was measured in the frequency range from o.1 GHz to 670 GHz. The data are analysed in several Debye and Frohlich terms and the results are discussed.

On the distribution of potential wells and its relation to collision-induced dipole moments in nonpolar solvents. - Part I.

Abstract The relaxation times of some rigid polar molecules in three non-polar solvents of different molecular geometries (and different collision induced dipole moments) are studied. There is some relationship to be observed between the arbritary distribution of surrounding potential wells and the dipole moments measured in the various solvents.

Dielectric relaxation of polar molecules in mixtures of non-polar solvents.

Abstract The relaxation times of some rigid polar molecules are studied in very diluted mixtures of heptane-carbontetrachloride and heptanedecaline, Exponential relation between relaxation time and a characteristic length of the polar solute (r eff ) is found. The structure factor of the mixture which contains the contributions of both solvents cannot be composed by adding the features of each component only. Furthermore, the measured collision times seem not to follow a simple sum rule.

Dipolar orientation mechanisms for dilute mixtures of alcohols in non-polar solvents

In this study the aliphatic alcohol n-hexanol is impregnated by a small amount of a diol-type alcohol, and the influence of the latter on the formation of heteroclusters is studied. Cooperative generation of hydrogen-bonded heteroclusters in equilibrium with the common quaternary clustered monoalcohol, together with its mean lifetimes and librational motions, are discussed. The dependence on concentration of the binary mixture, its temperature and the physical parameters of the solvent are discussed.