Melt mixing of polycarbonate with multi-walled carbon nanotubes in miniature mixers

Abstract

MWNT mixtures with PC were prepared in three different miniature mixers at 265°C and 50 rpm for 6 min by the master batch dilution method. One mixer is a 4.5 cm3 DACA microcompounder (DACA Instruments) consisting of two conical co-rotating screws with a bypass, allowing the material to circulate for defined periods. The other two miniature mixers are custom-built in our lab: the 2.2 cm3 APAM and the 3 cm3 MBM. The volume resistivity for the nanocomposites obtained from the APAM and the MBM showed a similar trend for different MWNT compositions. The electrical percolation concentration for the nanocomposites prepared in the APAM and the MBM is between 0.50 wt.-% (or 0.34 vol.-%) and 0.75 wt.-% (or 0.52 vol.-%) MWNT, and it is between 0.75 wt.-% (or 0.52 vol.-%) and 1.00 wt.-% (or 0.69 vol.-%) for the DACA microcompounder. Rheological characterization indicates that the microstructure of PC/MWNT composites prepared from the miniature mixers changes at a concentration of 0.38 wt.-% for the APAM and the MBM and 0.50 wt.-% for the DACA where an interconnected network is formed. TEM micrographs show that there are some small aggregates in the nanocomposites obtained from the APAM, fewer aggregates from the MBM, and least from the DACA. AFM analysis suggests that the length of nanotubes is reduced from 0.57 μm to 0.38-0.42 μm after they were melt mixed in the three mixers. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.