Rheological Characterisation of Graphene filled Isotropic Conductive Adhesives

Isotropic Conductive Adhesives (ICAs) offer a viable alternative to traditional tin/lead soldering methods, which are restricted by regulations such as the European Union’s Restriction of Hazardous Substances Directive (RoHS). The synthesis of graphene oxide (GO) was carried out through Huang's method, followed by reduction using hydrazine as per Stankovich's approach, resulting in reduced graphene oxide (RGO) that accumulated into a solid aggregate. The synthesized RGO particles were manually dispersed in DGEBA epoxy resin and subjected to rheological flow and oscillatory tests using an Anton Paar MCR301 rheometer. The rheological tests revealed that neat (unmixed) epoxy behaves as a Newtonian fluid, while the addition of RGO fillers from 1 to 4 by weight percentage (%) increases viscosity due to particle interference with the flow. Higher filler concentrations, particularly at 4%, resulted in more significant changes, indicating that the rheological properties are strongly influenced by filler content and distribution. In contrast, the graphite sample showed minimal viscosity change due to smoother flow, underscoring the impact of particle shape and alignment on fluid behaviour. The liquid matrix was found to be very stable and resistant to shear-induced destruction, exhibiting Newtonian-like behaviour at filler loadings below 4% by weight. However, at a 4% loading, the material displayed a stepwise rheological transformation, characterized by strong thixotropic behaviour.