Development and modelling of electrically conductive composite materials

The electrical conductivity of polymers can be increased by the addition of conductive fillers, including various forms of carbon fibers, carbon black, and graphite. The resulting composites can be used in applications where metals have typically been the materials of choice. The advantages of using these materials include lighter weight, resistance to corrosion, and the ability to be readily adapted to the needs of a specific application. The possible applications for electrically conductive resins include electromagnetic and radio frequency interference (EMI/RFI) shielding for electronic devices and electrostatic dissipation (ESD).; A more efficient materials design can be achieved through the use of electrical conductivity models. The use of accurate models aid in the understanding of the mechanisms that control conductivity in these composites, and provide insight into the properties important to achieving desired conductivity levels. In addition, the use of models can reduce costly experimental work, as well as the consumption of materials, through the ability to target a desired conductivity level for the composite based on a set of calculations.; The first objective of this project was to analyze single-filler conductive resins in order to propose an electrical conductivity model for the development of conductive carbon-polymer composites. The second objective was to uncover any synergistic effects present due to the combination of fillers. A 2 3 factorial design analysis of three conductive fillers in polycarbonate and nylon 6,6 was performed to accomplish this task. In these projects, the through-plane and in-plane electrical conductivity were measured. In addition, optical microscopy and image analysis were also performed in order to determine structural parameters of the composite, such as length and orientation of the conductive carbon fillers.; The results of the factorial design analysis showed that the combination of conductive fillers indeed produced a positive synergistic effect in the electrical conductivity measurements. Additionally, the electrical conductivity results were modelled using an updated literature model and a newly-formulated model accounting for surface energy and structural parameters of the composite materials.