Browsing by Author "Battisti, Andrea"
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Item Open Access Conductive Carbon Nanotube Thermosetting Polyester Nanocomposites(Cranfield University, 2009) Battisti, Andrea; Partridge, Ivana K.; Skordos, Alexandros A.A commercial unsaturated polyester resin has been used in combination with commercial multiwalled carbon nanotubes (MWNTs) to study the effects of this nanofiller on the electrical properties of the mix in the liquid state, during the cure and in the solid state. The level of addition of the nanotubes ranged from 0.05 to 0.3 wt%. The dispersion of the filler particles in the matrix was carried out combining triple roll milling, horn sonication and high shear mixing. Qualitative optical and electronic microscopy characterisation supports the development of novel techniques for real-time quantitative assessments of dispersion quality. Fitting of shear dependent viscosity, measured between 0.1 and 100 s-1, to Carreau's model has been shown to provide an indicator of the state of nanotube dispersion in the mixture. Additionally, liquid electrical conductivity measurements offer the option of on-line monitoring, providing a promising tool for process optimisation. The formation of an effective conductive network of nanotubes during the cure was investigated by combining impedance spectroscopy measurements and equivalent circuit modelling with two parallel RC circuit in series with each other. This allows in-situ observation of the key phenomenon responsible for the electrical conductivity of the nanocomposite, namely the filler re-aggregation during cure. Optimisation of dispersion and cure parameters results in a nanocomposite showing conductive behaviour in the solid state, achieving DC conductivity of 0.13 S/m at 0.30 wt% loading. The percolation threshold was estimated to occur at 0.026 wt% filler loading. The conductivity achieved is comparable to state-ofthe-art epoxy thermosetting nanocomposites based on use of carbon nanotubes of equivalent quality. Successful laboratory scale trials demonstrated the suitability of the materials in copper electroplating and resistance heating. An industrial scale up trial of a 40 kg batch was carried out, using the dispersion and the monitoring techniques developed in the study.Item Open Access Dielectric monitoring of carbon nanotube network formation in curing thermosetting nanocomposites(Iop Publishing Ltd, 2009-01-01T00:00:00Z) Battisti, Andrea; Skordos, Alexandros A.; Partridge, Ivana K.This paper focuses on monitoring of carbon nanotube (CNT) network development during the cure of unsaturated polyester nanocomposites by means of electrical impedance spectroscopy. A phenomenological model of the dielectric response is developed using equivalent circuit analysis. The model comprises two parallel RC elements connected in series, each of them giving rise to a semicircular arc in impedance complex plane plots. An established inverse modelling methodology is utilized for the estimation of the parameters of the corresponding equivalent circuit. This allows a quantification of the evolution of two separate processes corresponding to the two parallel RC elements. The high frequency process, which is attributed to CNT aggregates, shows a monotonic decrease in characteristic time during the cure. In contrast, the low frequency process, which corresponds to inter-aggregate phenomena, shows a more complex behaviour explained by the interplay between conductive network development and the cross-linking of the polymer.Item Open Access Monitoring dispersion of carbon nanotubes in a thermosetting polyester resin(Elsevier Science B.V., Amsterdam., 2009-08-01T00:00:00Z) Battisti, Andrea; Skordos, Alexandros A.; Partridge, Ivana K.The paper concerns the initial steps in the preparation of carbon nanotube containing nanocomposites of an isophthalic unsaturated polyester resin, prior to cure. Developments in the nature of the rheology of the liquid samples were monitored as a function of the level of energy introduced via ultrasonic horn mixing and related to microscopic observations. On-line sampling, coupled with off-line viscosity measurements, is compared with on-line measurements of electrical resistivity of the mixture, in terms of the relative suitability of these techniques for real-time monitoring of nanofiller dispersion in the liquid mixtures. The shear thinning parameter, N, derived from fitting Carreau model to the shear viscosity data, appears to provide a good qualitative indicator of the state of nanotube dispersion in the sample.Item Open Access Percolation threshold of carbon nanotubes filled unsaturated polyesters(Elsevier Science B.V., Amsterdam., 2010-04-01T00:00:00Z) Battisti, Andrea; Skordos, Alexandros A.; Partridge, Ivana K.This paper reports on the development of electrically conductive nanocomposites containing multi-walled carbon nanotubes in an unsaturated polyester matrix. The resistivity of the liquid suspension during processing is used to evaluate the quality of the filler dispersion, which is also studied using optical microscopy. The electrical properties of the cured composites are analysed by AC impedance spectroscopy and DC conductivity measurements. The conductivity of the cured nanocomposite follows a statistical percolation model, with percolation threshold at 0.026 wt.% loading of nanotubes. The results obtained show that unsaturated polyesters are a matrix suitable for the preparation of electrically conductive thermosetting nanocomposites at low nanotube concentrations. The effect of carbon nanotubes reaggregation on the electrical properties of the spatial structure generated is discussed.