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Subject: Agglomeration × WGL Institute: IPF ×

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Now showing 1 - 4 of 4
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    Dispersability and particle size distribution of CNTs in an aqueous surfactant dispersion as a function of ultrasonic treatment time
    (New York, NY [u.a.] : Pergamon Press, 2010) Krause, Beate; Mende, Mandy; Pötschke, Petra; Petzold, Gudrun
    The dispersability of carbon nanotubes (CNTs) was assessed by studying the sedimentation of CNTs dispersed in aqueous surfactant solutions at different ultrasonication treatment times using a LUMiSizer® apparatus under centrifugal forces. Different commercially available multiwalled CNTs, namely Baytubes® C150P, Nanocyl™ NC7000, Arkema Graphistrength® C100, and FutureCarbon CNT-MW showing quite different kinetics were compared. In addition, the particle size distributions were analyzed using dynamic light scattering and centrifugal separation analysis. The best dispersabilities were found for Nanocyl™ NC7000 and FutureCarbon CNT-MW; to prepare stable dispersions of Baytubes® C150P or Graphistrength® C100 five times the energy was needed. As a result of the centrifugal separation analysis, it was concluded that Nanocyl™ NC7000 and Baytubes® C150P were dispersed as single nanotubes using ultrasonic treatment whereas small agglomerates or bundles are existing in dispersions containing FutureCarbon CNT-MW and Graphistrength® C100. © 2010 Elsevier Ltd. All rights reserved.
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    Establishment, morphology and properties of carbon nanotube networks in polymer melts
    (Amsterdam [u.a.] : Elsevier, 2012) Alig, I.; Pötschke, P.; Lellinger, D.; Skipa, T.; Pegel, S.; Kasaliwal, G.R.; Villmow, T.
    As for nanofillers in general, the properties of carbon nanotube (CNT) -polymer composites depend strongly on the filler arrangement and the structure of the filler network. This article reviews our actual understanding of the relation between processing conditions, state of CNT dispersion and structure of the filler network on the one hand, and the resulting electrical, melt rheological and mechanical properties, on the other hand. The as-produced rather compact agglomerates of CNTs (initial agglomerates, >1 μm), whose structure can vary for different tube manufacturers, synthesis and/or purification conditions, have first to be well dispersed in the polymer matrix during the mixing step, before they can be arranged to a filler network with defined physical properties by forming secondary agglomerates. Influencing factors on the melt dispersion of initial agglomerates of multi-walled CNTs into individualized tubes are discussed in context of dispersion mechanisms, namely the melt infiltration into initial agglomerates, agglomerate rupture and nanotube erosion from agglomerate surfaces. The hierarchical morphology of filler arrangement resulting from secondary agglomeration processes has been found to be due to a competition of build-up and destruction for the actual melt temperature and the given external flow field forces. Related experimental results from in-line and laboratory experiments and a model approach for description of shear-induced properties are presented.
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    An updated micromechanical model based on morphological characterization of carbon nanotube nanocomposites
    (Oxford [u.a.] : Elsevier, 2017) Talò, Michela; Krause, Beate; Pionteck, Jürgen; Lanzara, Giulia; Lacarbonara, Walter
    By leveraging on extensive morphological analysis of carbon nanotube nanocomposites, an update of the Eshelby-Mori-Tanaka method is proposed for a more accurate estimation of the nanocomposites effective elastic response. The experimental results are employed to overcome the main modeling limitations inherent in most common micromechanical theories, such as the perfect dispersion of the nanofiller and the uniformity of the nanofiller's aspect ratio within the nanocomposite. The actual variability of the CNTs aspect ratio and the CNTs degree of dispersion are experimentally measured and introduced in the proposed model by averaging the Eshelby tensor over the actual CNT lengths distribution and by accounting for the effective CNT volume fraction. The effects of the nanofiller morphology on the mechanical response of three different thermoplastic nanocomposites with low- and high-aspect ratio CNTs are explored, and monotonic tensile tests are performed to validate the predictions of the proposed model. A good agreement is found between the predicted nanocomposites elastic moduli and the experimental data.
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    Influence of the hydrophobicity of polyelectrolytes on polyelectrolyte complex formation and complex particle structure and shape
    (Basel : MDPI AG, 2011) Mende, M.; Schwarz, S.; Zschoche, S.; Petzold, G.; Janke, A.
    Polyelectrolyte complexes (PECs) were prepared by structural uniform and strongly charged cationic and anionic modified alternating maleic anhydride copolymers. The hydrophobicity of the polyelectrolytes was changed by the comonomers (ethylene, isobutylene and styrene). Additionally, the n -/n + ratio of the molar charges of the polyelectrolytes and the procedure of formation were varied. The colloidal stability of the systems and the size, shape, and structure of the PEC particles were investigated by turbidimetry, dynamic light scattering (DLS) and atomic force microscopy (AFM). Dynamic light scattering indicates that beside large PEC particle aggregates distinct smaller particles were formed by the copolymers which have the highest hydrophobicity (styrene). These findings could be proved by AFM. Fractal dimension (D), root mean square (RMS) roughness and the surface profiles of the PEC particles adsorbed on mica allow the following conclusions: the higher the hydrophobicity of the polyelectrolytes, the broader is the particle size distribution and the minor is the swelling of the PEC particles. Hence, the most compact particles are formed with the very hydrophobic copolymer.