Establishment, morphology and properties of carbon nanotube networks in polymer melts

Abstract

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

Shear induced electrical behaviour of conductive polymer composites

“…It was found, that the resistance shows an oscillating response as well, where the frequency of the electrical oscillations is twice as fast the frequency of the deformation. This finding was also confirmed qualitatively by Alig et al [2] and Zeiler et al [12] for polycarbonate filled with carbon nanotubes. Zeiler et al [12] measured the oscillating electrical conductivity for different strain amplitudes and for different molar masses of the matrix polymer.…”

“…The electrical properties of polymers are dramatically influenced by the incorporation of conductive fillers, such as carbon black or carbon nanotubes [1,2]. To produce conductive polymer composites for industrial applications, melt processing techniques such as extrusion or injection moulding are usually used.…”

Morphology and electrical properties of injection-molded PP carbon-based nanocomposites

“…The formation of a conductive network in the internal core leads to a conductive path, which can explain the before discussed electrical properties [16]. Consequently, it is possible to conclude that the skin layers, covering the external regions, are characterized by a low conductivity, while the core region already becomes conductive at low filler content.…”

Influence of processing history on the mechanical properties and electrical resistivity of polycarbonate – multi-walled carbon nanotubes nanocomposites

“…Detailed work by Alig and co-workers has shed light on the mechanisms of the formation of the CNT network in the matrix melt [1]. Zeiler et al found that the network formation is enhanced by a matrix of lower molar mass and at higher temperature [2].…”