Impact of nanosized oxide particles of titania (titanium dioxide, rutile) and silica-titania fumed compound on structure relaxation processes in nanocomposites of an orthophtalic unsaturated styrene cross-linked polyester resin has been experimentally studied using the thermal desorption mass spectroscopy, the dielectric spectroscopy, and the positron annihilation lifetime spectroscopy. All the nanocomposites showed unmonotonous variations in the thermal resistance, the dielectric permittivity and losses, and the annihilation rates for both positrons and ortho-positronium atoms with increasing filler's loading. The nanoparticle-loading effects can be explained on the assumption that the oxide particles embedded into a cross-linked polyester resin induce rearrangements in its structure. Several mechanisms of particle-polymer interface interaction compete simultaneously and thus promote the alterations in molecular structure of the nanocomposites. The mechanisms may include both chemical and electrostatic fastening of polyester chains and styrene cross-links to the active surface sites, the destruction of the styrene cross-links, and redistribution of electron density in polymers. The features of the loading effects observed in the different nanocomposites can be ascribed to distinctions in both of active surface sites and intrinsic dielectric properties of the filling oxide particles.
Concentration effects of a high-reactive-surface nanosized SiO2 filler on structure and dielectrical properties of a styrene-cross-linked polyester resin have been experimentally studied. Thermal desorption mass-spectroscopy, IR-spectroscopy, dielectric spectroscopy, and positron annihilation lifetime spectroscopy were used to determine an atomic content of thermal destruction products, IR-reflection spectra, complex dielectric permittivity, and a nature of positron traps as function of filler content in the polymer matrix. Interaction between active surface centers of SiO2-nanoparticles and atoms of polyester chains and styrene molecules gives the non-monotonous influence on the structure of polyester chains, macromolecule polarity, dielectric parameters and the number of positronium nanotraps.
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