(162c) Characterization of the Dispersion of Nanoparticles in a Polymer Matrix

There are many emerging applications where it is necessary to disperse nanoparticles into a viscous matrix, such as a polymer. These dispersed particle systems are mainly used to enhance or improve the properties of the composite material, such as conductivity, strength, energetics, wear resistance, optical properties and others. One of the main reasons for using nanoparticles is the large surface to volume ratio. The large surface area increases the number of particle-matrix interactions, thus increasing the effects on the overall material properties. It has been demonstrated that a well dispersed system generally yields more desirable composite properties. Particle agglomerates decrease material performance by the inclusion of voids that act as preferential sites for crack initiation and failure. Particles, especially in the nano regime (less than 100nm) tend to agglomerate, or cluster, due to the dominant intermolecular van der Waals interactions between them.

The objective of this research is to quantify the three-dimensional interparticle spacing of nanoparticles in a glassy polymer matrix. The arrangement and size distribution of 0.5 wt% titania particles (30 nm) in an epoxy matrix have been characterized by static light scattering measurements and transmission electron microscopy. The nanocomposites were processed either by shear mixing only, ultrasonication with shear mixing or surface treated coupled with both ultrasonication and shear mixing. Particle cluster sizes of 0.1, 0.25, and 1.3 μm were estimated using the Mie Theory applied to the light scattering intensity fluctuations. A dispersion index of 0.13, 0.23 and 0.31 was estimated for the 0.10, 0.25 and 1.3 μm diameter particle composites, respectively. The technique demonstrates that light scattering is an effective method of estimating the dispersion of nanoparticles in a solid, polymeric matrix.