Tuning the localization of functionalized MWCNTs in SAN/PC blends by a reactive component

The influence of the reactive component (N-phenylmaleimide styrene maleic anhydride) on the blend morphology, the localization of functionalized multiwalled carbon nanotubes (MWCNTs), and the electrical resistivity of MWCNT filled blend systems of polycarbonate (PC) and poly(styrene-co-acrylonitrile) (SAN) was investigated. SAN, PC, amino-functionalized MWCNTs (Nanocyl™ NC3152) and the reactive component (RC) were melt mixed in a DSM Xplore microcompounder using different mixing sequences. The RC containing maleic anhydride (MA) groups is miscible with SAN and is assumed to act as linking agent to the functionalized MWCNTs. The morphology of the SAN/PC blends was studied depending on the concentration of the RC. Thereby co-continuous morphologies were found for all blends with 40. wt.% SAN and 60. wt.%. PC. In all nonmodified blends the MWCNTs were localized within the PC phase. After the addition of RC the MWCNTs migrated completely into the miscible SAN-RC phase. Consequently, the electrical resistivities of the blends changed in dependence on the localization. Whereas the SAN/PC/MWCNT blends showed low electrical resistivity values, much higher values were found for SAN-RC/PC/MWCNT blends. This was assigned to a coupling or strong interaction of MA groups to the nanotubes disturbing electrical contacts and percolation between them. The occurrence of the MWCNT migration from PC towards SAN was found to be dependent on the concentrations of RC and MWCNTs. By adapting that ratio and the mixing strategy, the localization of the carbon nanotubes in the blend phases can be tuned. The investigations indicated that MWCNTs once coupled with the RC remain in the SAN-RC phase. Thus, a chemical reaction or strong interactions seem to be the driving forces for localization of the MWCNTs in the SAN-RC blend phase.