Abstract

Epoxy nanocomposites reinforced with carbon nanotubes have found their path through a wide range of applications in aerospace, automotive, and electronics packaging industries. This is due to the superior properties provided by carbon nanotubes such as enhancing mechanical strength and chemical resistance as well as thermal and electrical conductivity. However, epoxy composites have proved to be vulnerable to different environmental conditions such as humidity and temperature, and the role of carbon nanotubes in leading the extent of changes of their properties have been a subject of research in several studies. This research brought into focus the electrical properties of multi-walled carbon nanotube (MWCNT) reinforced epoxy nanocomposites exposed to humid environments. For this purpose, different concentrations of multi-walled carbon nanotubes were added to epoxy, and a wide range of conductivities were obtained. The nanocomposite was immersed in water, and its water uptake, alongside the changes in thickness and electrical resistivity were measured and analyzed. The water saturation level, regardless of the type and content of MWCNT or the temperature, remained unchanged. The diffusivity in a constant temperature was influenced by two factors of MWCNT attraction and MWCNT crowd. The electrical resistivity of the polymer increased with water uptake, and samples with higher MWCNT content showed less sensitivity to water absorption. Changes in the electrical resistivity were explained through a resistivity model. The increase in electrical resistivity was significantly higher with a faster swelling. This conclusion resulted from a comparative experiment conducted on MWCNT reinforced silicone rubber nanocomposite immersed in engine oil. Finally, desorption behaviour of the epoxy nanocomposites was investigated. It was found that weight gain is recoverable at an elevated temperature, while a constant increase in electrical resistivity resides in the nanocomposite.