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Type: article × Publisher: Amsterdam [u.a.] : Elsevier × Subject: Electrical conductivity ×

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Now showing 1 - 3 of 3
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    Liquid sensing: Smart polymer/CNT composites
    (Amsterdam [u.a.] : Elsevier, 2011) Villmow, T.; Pegel, S.; John, A.; Rentenberger, R.; Pötschke, P.
    Today polymer/carbon nanotube (CNT) composites can be found in sports equipment, cars, and electronic devices. The growth of old and new markets in this area has been stimulated by our increased understanding of relevant production and processing methods, as well as the considerable price reduction of industrial CNT grades. In particular, CNT based electrically conductive polymer composites (CPCs) offer a range of opportunities because of their unique property profile; they demonstrate low specific gravity in combination with relatively good mechanical properties and processability. The electrical conductivity of polymer/CNT composites results from a continuous filler network that can be affected by various external stimuli, such as temperature shifts, mechanical deformations, and the presence of gases and vapors or solvents. Accordingly, CNT based CPCs represent promising candidates for the design of smart components capable of integrated monitoring. In this article we focus on their use as leakage detectors for organic solvents.
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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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    Electrically conductive and piezoresistive polymer nanocomposites using multiwalled carbon nanotubes in a flexible copolyester: Spectroscopic, morphological, mechanical and electrical properties
    (Amsterdam [u.a.] : Elsevier, 2022) Dhakal, Kedar Nath; Khanal, Santosh; Krause, Beate; Lach, Ralf; Grellmann, Wolfgang; Le, Hai Hong; Das, Amit; Wießner, Sven; Heinrich, Gert; Pionteck, Jürgen; Adhikari, Rameshwar
    Nanocomposites of multiwalled carbon nanotubes (MWCNTs) with poly(butylene adipate-co-terephthalate) (PBAT), a flexible aromatic–aliphatic copolyester, were prepared by melt mixing followed by compression moulding to investigate their spectroscopic, morphological, mechanical and electrical properties. A comparison of the Fourier transform infrared (FTIR) spectra of the neat polymer matrix and the composites showed no difference, implying a physical mixing of the matrix and the filler. A morphological investigation revealed the formation of a continuous and interconnected MWCNT network embedded in the polymer matrix with partial agglomeration. Increasing Martens hardness and indentation modulus and decreasing maximum indentation depth with increasing filler concentration demonstrated the reinforcement of the polymer by the MWCNTs. A volume resistivity of 4.6 × 105 Ω cm of the materials was achieved by the incorporation of only 1 wt.-% of the MWCNTs, which confirmed a quite low percolation threshold (below 1 wt.-%) of the nanocomposites. The electrical volume resistivity of the flexible nanocomposites was achieved up to 1.6 × 102 Ω cm, depending on the filler content. The elongation at the break of the nanocomposites at 374% and the maximum relative resistance changes (ΔR/R0) of 20 and 200 at 0.9 and 7.5% strains, respectively, were recorded in the nanocomposites (3 wt.-% MWCNTs) within the estimated volume resistivity range. A cyclic strain experiment shows the most stable and reproducible ΔR/R0 values in the 2%–5% strain range. The electrical conductivity and piezoresistivity of the investigated nanocomposites in correlation with the mechanical properties and observed morphology make them applicable for low-strain deformation-sensing.