Melt Mixing of Polycarbonate with Multi‐Walled Carbon Nanotubes in Miniature Mixers

Abstract

Summary: 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.Effect of MWNT content on volume resistivity of PC/MWNT obtained from different microcompounders.magnified imageEffect of MWNT content on volume resistivity of PC/MWNT obtained from different microcompounders.

Low Electrical Percolation Threshold of Silver and Copper Nanowires in Polystyrene Composites

“…The molecular weight of the polymer, alignment and dispersion of the nanotubes, mixing method, and surface tension between the nanotubes and polymer matrix have been recognized as critical factors influencing the electrical and mechanical properties of polymer nanocomposites prepared by solution-processing or melt-mixing. [10,12,[53][54][55][56][57][58][59] For instance, using both experimental data and simulations of anisotropic and isotropic nanocomposites, Winey and co-workers showed that a slight anisotropy in the nanocomposites produces enhanced electrical conductivity. [54] In the work reported here, individual dispersion as well as aggregation and segregation of high-aspect-ratio silver and copper nanowires have contributed to the formation of electrically conductive networks at low concentrations of metal in the PS matrix.…”

Masterbatch-based multi-walled carbon nanotube filled polypropylene nanocomposites: Assessment of rheological and mechanical properties

“…Importantly, the dispersion of MWNT in masterbatches should be ascertained, the dilution process has to be carried out under appropriate processing conditions to distribute the filler and avoid masterbatch aggregates in the nanocomposites. There are reports in the literature which examine the dilution of MWNT containing masterbatches [30][31][32][33][34][35][36][37][38][39][40][41]. However, literature survey reveals that, reports on the detailed investigations on the properties of MWNT/PP masterbatches are limited [42,43] when compared to the studies of nanocomposites prepared by direct incorporation of MWNT in PP [16][17][18][19][20][21][22]27] and this prompted us to take up this work.…”

Influence of dry grinding in a ball mill on the length of multiwalled carbon nanotubes and their dispersion and percolation behaviour in melt mixed polycarbonate composites

“…For the fractured composites, PC was dissolved in THF and aspect ratio distributions of the partially broken nanotubes are shown. Lin et al [17] determined the MWCNT lengths after melt dilution of a PC based masterbatch using SFM whereby a relatively harsh solvent and ultrasound treatment was used to extract the nanotubes from the PC matrix. Using different small scale mixers a comparable shortening of the nanotubes from 10-15 µm to 0.4 -0.6 µm were measured.…”