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Phase transition and anomalous rheological behaviour of polylactide/graphene nanocomposites
journal contribution
posted on 2018-02-15, 00:00 authored by Sima Kashi, R K Gupta, T Baum, N Kao, S N BhattacharyaPolylactide (PLA) nanocomposites with graphene nanoplatelet (GNP) contents of 0–15 wt% were prepared and characterised in terms of rheology and electrical conductivity. As expected for rigid nanofillers, GNP incorporation significantly enhanced the viscoelastic properties of the nanocomposites. Furthermore, above a certain GNP concentration the liquid-like melt flow behaviour changed into a solid-like behaviour. However, this rheological percolation threshold was found to decrease from near 9 wt% at 180 °C to below 6 wt% at 220 °C, detected and measured by Van Gurp-Palmen plots and Winter-Chambon method, respectively. It was also found that the viscoelastic properties of some of the nanocomposites increased with increasing temperature, which is in contrast to the rheology of ideal polymeric melts. The Electrical percolation threshold of the PLA/GNP system, which is determined by a sudden increase in DC conductivity and is indicative of establishment of interconnected conductive structures of GNPs within the matrix, was observed to be between 6 and 9 wt% GNPs. Morphological studies also showed physical contact between the platelets at 9 wt% while at 6 wt% they were still separated by the PLA matrix. These observations challenge the attribution of rheological percolation threshold to the formation of a percolating network of only filler particles within the matrix. A percolating network consisting of both polymer chains and filler particles might be the reason for the temperature dependency of rheological percolation threshold in the PLA/GNP system.
History
Journal
Composites Part B: EngineeringVolume
135Pagination
25 - 34Publisher DOI
ISSN
1359-8368Publication classification
C1 Refereed article in a scholarly journalUsage metrics
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No categories selectedKeywords
Science & TechnologyTechnologyEngineering, MultidisciplinaryMaterials Science, CompositesEngineeringMaterials ScienceRheological percolationTemperature effectViscoelastic propertiesElectrical conductivityGraphenePoly lactideNanocompositeENHANCED MECHANICAL-PROPERTIESGRAPHENE NANOPLATELETSTHERMAL-STABILITYPOLYPROPYLENE NANOCOMPOSITESCARBON NANOTUBESTHERMOMECHANICAL PROPERTIESPHYSICAL GELATIONMELT RHEOLOGYCOMPOSITES
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