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Influence of compounding parameters on the Electrical properties of polystyrene-carbon nanotube nanocomposites

: Sathyanarayana, S.; Olowojoba, G.; Weiss, P.; Hübner, C.; Henning, F.

Beckwith, S.W. ; Society for the Advancement of Material and Process Engineering -SAMPE-:
SAMPE 2012. Conference & Exhibition. CD-ROM : Baltimore, MD, May 21 - 24, 2012
ISBN: 978-1-934551-12-7
Society for the Advancement of Material and Process Engineering (Conference and Exhibition) <2012, Baltimore/Md.>
Fraunhofer ICT ()

Polystyrene (PS) composites containing 1, 2, 3, 5, and 7.5 wt.% Multiwalled carbon nanotubes (MWCNT) were processed on a compounding extruder using varying operating conditions such as screw speed, throughput and temperature with an optimal screw configuration. Extrudates were compression molded into plates and volume resistivity measurements were carried out on both the extruded strands and compression molded plates. Electrical percolation threshold decreased from 2-3 wt.% CNT loading to 1-2 wt.% when the processing speed was increased from 500 rpm to 1100 rpm. A 2 wt.% sample processed at 1100 rpm showed a resistivity drop by 11 orders of magnitude compared to a sample processed at 500 rpm due to substantial reduction in the undispersed MWCNT area fractions (or better dispersion) which arises as a result of higher specific mechanical energy input. Volume resistivities of the compression molded samples were lower than that of the strand samples. Significant variations in resistivities are found in strand samples up to 3 wt.% MWCNT with different processing parameters while very little changes are observed in the compression molded specimens. Statistical analysis of dispersion qualities in terms of area fraction of undispersed MWCNT agglomerates was performed to correlate the morphology with specific mechanical energy inputs, resulting dispersions and measured resistivities. Melt resistance measurements were carried out during processing which served as a process monitoring tool in addition to being an indicator of offline composite resistivities while processing. This helps in process optimization and also provides insight into optimal parameters for processing of an unknown conductive composite system.