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Item type:Publication, Access status: without files , Charakterisierung der Dispersionsgüte von Carbon Nanotubes in Polymer-Nanokompositen(Wiley-VCH, 2011-06-01); ; ; ; Pegel, SvenA practical overview of possibilities and limits to characterize the state of dispersion of carbon nanotubes (CNT) in polymer based nanocomposites is given. The most important and widely available methods are discussed with practical employment in mind. One focus is the quantitative characterization of the state of dispersion in solid samples using microscopy techniques such as optical microscopy or transmission electron microscopy. For dispersions of CNTs in aqueous media, solvents or monomers a sedimentation analysis is presented. This way dispersability and dispersion state of CNTs can be assessed. Indirect methods such as electrical conductivity measurements and rheological tests, dynamic differential scanning calorimetry and mechanical test are discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Publicationtype: Journal Article11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Comparison of rheological and electrical percolation phenomena in carbon black and carbon nanotube filled epoxy polymersEpoxy nanocomposite suspensions including multi-wall carbon nanotubes (MWCNTs) and carbon black (CB) were produced and investigated by means of combined rheological and electrical analysis. The rheological percolation behaviour was compared to the electrical percolation behaviour. Due to similar dynamic agglomeration mechanisms the difference between the rheological and the electrical percolation threshold in the cured state is identical for MWCNT and CB filled systems. Non-covalent matrix-nanoparticle interactions in uncured epoxy suspensions are negligible since the onset of electrical and rheological percolation in the uncured state coincidence. Furthermore, the electrical percolation threshold in the cured state is always lower than in the uncured state because of the high tendency of CB and MWCNTs to form conductive networks during curing. The difference between rheological and electrical percolation threshold is dependent on the curing conditions. Thus, the rheological percolation threshold can be considered as an upper limit for the electrical percolation threshold in the cured state. Due to the formation of co-supporting networks multi-filler (MWCNTs and CB) suspensions exhibit a similar rheological behaviour as the binary MWCNT suspensions. For both types of suspensions a rheological percolation threshold of around 0.2 and 0.25 wt% was determined. Conversely, the binary CB nanocomposites exhibit a four-times higher percolation threshold of about 0.8 wt%. The difference between the binary MWCNT suspension and the ternary CB/MWCNT suspension in storage shear modulus at high filler concentrations (~0.8 wt%) turns out to be less than expected. Thus, synergistic effects in network formation are already present in the epoxy suspension and get more pronounced during curing.Publicationtype: Journal Article12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Glass-fibre-reinforced composites with enhanced mechanical and electrical properties - Benefits and limitations of a nanoparticle modified matrixNanoparticles and especially carbon nanotubes (CNTs) provide a high potential for the modification of polymers. They are very effective fillers regarding mechanical properties, especially toughness. Furthermore, they allow the implication of functional properties, which are connected to their electrical conductivity, into polymeric matrices. In the present paper, different nanoparticles, as fumed silica and carbon black, were used to optimise the epoxy matrix system of a glass-fibre-reinforced composite. Their nanometre-size enables their application as particle-reinforcement in FRPs produced by the resin-transfer-moulding method (RTM), without being filtered by the glass-fibre bundles. Additionally, an electrical field was applied during curing, in order to enhance orientation of the nanofillers in z-direction. The interlaminar shear strengths of the nanoparticle modified composites were significantly improved (+16%) by adding only 0.3 wt.% of CNTs. The interlaminar toughness GIc and GIIc was not affected in a comparable manner. The laminates containing carbon nanotubes exhibited a relatively high electrical conductivity at very low filler contents, which allows the implication of functional properties, such as stress-strain monitoring and damage detection.Publicationtype: Journal Article23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multiwall carbon nanotube/epoxy composites produced by a masterbatch processA masterbatch process based on a minicalander (three-roller mill) and a vacuum dissolver was developed in order to produce multiwall carbon nanotube/epoxy composites with loading fractions of 0.5, 1.0, and 2.0 wt.%. TEM and SEM analyses were performed to investigate the dispersion results. A contrast imaging in the SEM backscattering mode revealed a homogeneous distribution of carbon nanotubes in the whole volume of the material. Furthermore, an interesting correlation was found to exist between the network structure formed by the nanotubes in the epoxy matrix and the appearance of fracture surface of the nanocomposites. Furthermore, the nanocomposites exhibited an electrical conductivity in the regime of some 10-2 S/m.Publicationtype: Journal Article21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Production and properties of glass fibre-reinforced polymer composites with nanoparticle modified epoxy matrixIncreasing the mechanical performance, e.g. strength, toughness and fatigue properties of composites is the objective of many ongoing research projects. Nanoparticles, e.g. carbon nanotubes (CNTs) and fumed silica provide a high potential for the reinforcement of polymers. Their size in the nanometre regime make them suitable candidates for the reinforcement of fibre reinforced polymers, as they may penetrate the reinforcing fibre-network without disturbing the fibre-arrangement. In this work, glass fibre-reinforced epoxy composites with nanoparticle modified matrix systems were produced and investigated. GFRPs containing different volume fractions of the nanofillers were produced via resin transfer moulding. Matrix dominated mechanical properties of the GFRP laminates could be improved by the incorporation of nanoparticles. The addition of only 0.3 wt.% CNTs to the epoxy matrix increased the interlaminar shear strength from 33.4 to 38.7 MPa (+16%). Furthermore, the application of electrically conductive nanoparticles enables the production of conductive nanocomposites. This offers a high potential for antistatic applications and the implementation of functional properties in the composite structures. The effects of different filler types and volume fractions on the electrical properties of the GFRPs were investigated. GFRPs containing 0.3 wt.% of CNTs, for example, exhibit an anisotropic electrical conductivity. Furthermore, an electrical field was applied to the composites during curing. The effects on the resulting electrical and mechanical properties are discussed.Publicationtype: Conference Paper24