Spatial statistics of carbon nanotube polymer composites

Dispersion, distribution, and alignment of carbon nanotubes (CNT) in polycarbonate (PC) composites are quantified by means of statistical analysis of transmission electron microscopy (TEM) images. The analysed images originate from samples with 0.875 and 2 wt% CNT, processed by compression and injection moulding, respectively. The composites exhibit different microstructures with different electrical properties, depending on the processing parameters. By means of stereological approaches for projections of three dimensional fibre systems the CNT contents within the TEM samples are estimated. The tendency of CNT clustering as well as characteristic distances between the CNT and CNT clusters are quantified by evaluation of morphological functions. Furthermore, a correlation function is introduced to obtain a quantitative measure of CNT clustering within the isotropic compression moulded samples. For the injection moulded samples the correlation function is used to derive local orientation factors. The results underline that clustering of CNT can enhance and alignment of tubes can reduce electrical conductivity.