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Author: Müller, Michael T. × Version: acceptedVersion ×

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    The influence of matrix viscosity on MWCNT dispersion and electrical properties in different thermoplastic nanocomposites
    (Oxford : Elsevier Science, 2012) Socher, Robert; Krause, Beate; Müller, Michael T.; Boldt, Regine; Pötschke, Petra
    Composites of MWCNTs having each three different levels of matrix viscosity with five different polymers (polyamide 12, polybutylene terephthalate, polycarbonate, polyetheretherketone and low density polyethylene) were melt mixed to identify the general influence of matrix viscosity on the electrical properties and the state of MWCNT dispersion. Huge differences in the electrical percolation thresholds were found using the same polymer matrix with different viscosity grades. The lowest percolation thresholds were always found in the composites based on the low viscosity matrix. The state of primary MWCNT agglomerate dispersion increased with increasing matrix viscosity due to the higher input of mixing energy. TEM investigations showed nanoagglomerated structures in the low viscosity samples which are obviously needed to achieve low resistivity values. The effect of nanotube shortening was quantified using two different viscosity grades of polycarbonate. Due to the higher mixing energy input the nanotube shortening was more pronounced in the high viscosity matrix which partially explains the higher percolation threshold. © 2011 Elsevier Ltd. All rights reserved.
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    Improvement of carbon nanotube dispersion in thermoplastic composites using a three roll mill at elevated temperatures
    (Barking : Elsevier, 2013) Pötschke, Petra; Krause, Beate; Buschhorn, Samuel T.; Köpke, Ulf; Müller, Michael T.; Villmow, Tobias; Schulte, Karl
    The paper reports the effect of using of a three roll mill as additional dispersion step after twin-screw melt extrusion of nanocomposites containing thermoplastic polymers and multiwalled carbon nanotubes. The three roll milling technology was adapted to elevated temperatures of up to 180 °C and examples are shown for its use in processing of different pre-compounded thermoplastic polymer composites based on polypropylene, polycaprolactone and ethylene-vinyl acetate. The aim is to enhance the state of dispersion achieved by the previous melt extrusion step. In particular, depending on the state of dispersion before three roll milling and the adapted conditions, like number of runs and gap sizes, a reduction of number and size of remaining primary nanotube agglomerates was found. This was studied using light microscopy. The resulting improvements in mechanical properties were assessed and could be attributed to the improved dispersion. In some cases agglomerate free samples could be achieved after the three roll milling process. © 2012 Elsevier Ltd.