Characterization of the hierarchical structures of a dry nanopowder in a polymer matrix by X-ray scattering techniques

There are many material properties benefits that can be realized by adding nano-sized filler particles to a polymeric resin, such as improvements in strength, modulus and optical transparency. However, the relative amount of improvement is highly dependent on the degree of particle dispersion or homogeneity within the nanocomposite. In this study, a commercially available dry titania nanopowder with a mean primary particle diameter of approximately 30 nm was mixed into an epoxy resin/hardener system to produce nanocomposite samples. Processing techniques such as ultrasonication and particle surface modification were used to produce nanocomposites with varying degrees of particle mixture homogeneity. The extent of nanoparticle dispersion was characterized by a combination of small-angle X-ray scattering and ultra-small-angle X-ray scattering. The measurement length scale ranged between 1 nm and several micrometres. Both measurement techniques provided information on the size distribution of primary particles, aggregates or particle agglomerates in the polymer nanocomposites, depending on the length scale (q region) of interest. Using this combination of processing and characterization techniques, a decrease in average particle cluster size of two orders of magnitude was observed between samples of varying particle mixture homogeneity.