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Author: Pötschke, Petra × Subject: Materials forming × Subject: Nanotubes × Subject: Polymers ×

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    Influence of mixing conditions on carbon nanotube shortening and curling in polycarbonate composites
    (Melville, NY : AIP, 2017) Krause, Beate; Carval, J.; Pötschke, Petra
    Polycarbonate composites containing multiwalled carbon nanotubes (MWCNTs, 0.2-2.0 wt%) were melt mixed in small scale at different conditions of screw speed and mixing time to vary the specific mechanical energy (SME) input between 0.4 and 4.0 kWh/kg. Next to the electrical properties of compression molded plates and the MWCNT macrodispersion also the nanotube length and shape were analyzed. For this, the matrix of the composites with 0.75 wt% MWCNT loading was dissolved and the remaining nanotubes were investigated using TEM. It was found that with increasing SME input the number of remaining CNT agglomerates decreases. The MWCNT length decreased from initially about 1.4 micrometers towards 350 nanometers at a SME of 4 kWh/kg and the mean curling values were also reduced. The electrical percolation threshold increases with SME from about 0.4 wt% to 0.6 wt%.
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    Thermal conductivity of hybrid filled HDPE nanocomposites
    (Melville, NY : AIP, 2017) Müller, M. T.; Krause, Beate; Kretzschmar, B.; Jahn, I.; Pötschke, Petra
    In this study composite materials based on high-density polyethylene (HDPE) with fillers containing nanostructures were prepared using melt mixing. Vapour Grown Carbon Fibers (VGCF), multiwalled carbon nanotubes (MWCNT) of the types Baytubes® C150P and Nanocyl™ NC7000, anthracite powder, microsilica, organoclay and expanded graphite (EG) as well as mixtures of these fillers were used. The amount and mixing ratios of the hybrid filled systems have been varied to determine their effects on the achievable level of thermal conductivity as measured on compression molded plates. The filler dispersion and phase adhesion were studied using scanning electron microscopy. When limiting the maximum filler content to 10 wt%, the highest enhancement in thermal conductivity by 166% was found for VGCF followed by a 1:1 filler combination of VGCF with EG (148%).