A controllable electrical percolation behaviour of conductive polymer composite is desirable for industrial applications, allowing industry to produce composite systems that are robust against differing processing conditions. In order to control and modify the electrical percolation behaviour of conductive polymer composites (CPC), a comprehensive understanding between the morphology of filler network and conductive network, conduction mechanism and the final electrical properties is needed. This project comprises three main aspects: the influence of filler morphology, hybrid fillers with different morphology and orientation of fillers on the electrical properties of composites. Single filler with different morphology - carbon black (CB), carbon nanotube (CNT) and graphene nanoplatelet (GNP) filled polycarbonate composites were fabricated by melt mixing. Conductive atomic force microscopy were used to characterize the conductive network in the composites and provided quantitively analysis of the volume fraction of percolated filler in the composites. It was revealed that these three types of composites demonstrated different percolation behaviour in term of percolation threshold and percolating rate. The key factors for conductive network formation can be ascribed to dispersion and aspect ratio of filler. Additionally, electron conduction via tunnelling effect and geometric contact between filler was studied by impedance spectroscopy using equivalent circuit. Binary hybrid filler composites with CB and CNT, GNP and CNT, CB and GNP as well as ternary hybrid composites at various ratios were fabricated to investigate the morphology of hybrid filler network and the resultant electrical percolation behaviour. It was found that the percolation threshold (Pc) of the hybrid composite mainly depended on the micro-agglomerate and nano-aggregate of fillers, while the transition rate of the hybrid composite was mainly governed by the filler with a more gradual transition, indicating that the percolation threshold (Pc) and transition rate can be independently controlled. Hence, it was found that through selection of the hybrid fillers, one can control the percolation threshold, exponent of the percolation curve and ultimate electrical conductivity within an over-arching parameter window. CNT composites were prepared by injection moulding to study the influence of filler orientation on electrical conductivity. It was revealed by conductive atomic force microscopy (CAFM) that the formation of conductive network is highly dependent on the orientation of CNT cluster. A laminated skin-core structure of filler orientation and electrical conductivity were found, resulting in the anisotropic electrical conductivity of injection moulded composites.
Date of Award | 31 Dec 2023 |
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Original language | English |
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Awarding Institution | - The University of Manchester
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Supervisor | Ian Kinloch (Supervisor) & Mark Bissett (Supervisor) |
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- Conductive Atomic Force Microscopy
- Carbon Black
- Carbon Nanotube
- Composite
- Electrical properties
- Polymer
- Graphene
Electrical Properties of Nanocarbon Polymer Composites
Lin, K. (Author). 31 Dec 2023
Student thesis: Phd