TEM image of a nanoclay platelets in an
epoxide resin

The general consensus is that the greatest stumbling block to large-scale production and commercialisation of polymer nanocomposites (PNCs) is achieving good dispersion of the nanoparticles in the matrix, which is hindered by the lack of reliable measurement methods for assessing, and thus controlling dispersion.

The inclusion of small concentrations of nanoparticles in polymers (typically <5 wt%) can significantly enhance mechanical and physical properties of PNCs. Dispersion of nanoparticles during mixing is problematic with poor mixing resulting in particle agglomeration (i.e. particle clustering), which subsequently limits the potential for property enhancement. A key step towards meeting the goal of large-scale production and commercialisation of PNCs is the availability of a reliable in-situ measurement technique for production and in-service inspection capable of quantitatively characterising particle loading and dispersion. Non-invasive optical and image processing techniques are being developed at NPL that are capable of discriminating between different particle loadings and levels of dispersion.

The techniques, based on optical diffraction and diffusion mechanisms, are optical coherence tomography (OCT), Fraunhofer wavefront correlation (FWC) and oscillatory photon correlation spectroscopy (Os-PCS). It is intended to produce a bench top demonstrator within the next 2-3 years that could be commercialised for use for production and/or in-service inspection. The methods have been applied to nanoclay reinforced epoxy PNCs with the intention of extending the use of these methods to semi-transparent and opaque PNCs (e.g. carbon nanotube based systems).