Nonlinear Loading Effects in Oxide-filled Polyester Nanocomposites Observed by IR-spectroscopy and Lifetime Positron Spectroscopy

Abstract

Impact of nanosized oxide particles of titania (rutile) (TiO 2) and silica-titania fumed compound on physical properties related to inner structure of a styrene-cross-linked polyester resin have been experimentally studied. The IR-spectroscopy and the positron annihilation lifetime spectroscopy (PAL) were used to study the electronic polarizability of interatomic bonds and the positron annihilation processes with increasing the filler loading. All the nanocomposites show unmonotonous variations in the IR-absorption lines and the positron annihilation parameters. Three lifetime components, namely τ 1 , τ 2 , and τ 3 with intensities I 1 , I 2 , and I 3 have been determined. The lifetime loading dependences exhibit non-monotonous lowering within the low loading range (C m ≤ 5%) with the minima values at C m ∼ 1.5 % for the unfilled resin and the nanocomposites. The free-volume portion f v (in %) in a polymer matrix decreases droningly for the nanocomposites with STO-particles upon loading while for the TiO 2-nanocomposites it increases non-monotonously. The parameters describing the supramolecular structure of the nanocomposites have been calculated using the fractal approach. Some correlations between loading-dependent PAL-properties and underlying alterations in the resin's supramolecular structure have been discussed.