Graphene was synthesized through two-step method. In the first step, graphene oxide (GO) was synthesized from purified graphite via modified Hummers method. Because graphene oxide poorly dispersed in aqueous solution at pH 7, the surface treatment by adjusting pH of solution for repulsive charge and homogeneous colloid solution before reducing GO with hydrazine was studied in this research. The colloidal stability of graphene oxide in aqueous solution was measured by UV-VIS spectroscopy in term of spectrum absorption and the zeta- potential technique was used for detecting surface change of particle. Then, the chemical reduction of graphene oxide to graphene sheet was done by using hydrazine hydrate. The physical properties of particle were characterized by Raman spectroscopy, SEM, TEM and AFM technique. The functional group and thermal stability of particle were characterized via FTIR, TG/DTA respectively. Graphene sheet was then mixed with epoxy, poly[(phenyl glycidyl ether)-co-formaldehyde] at 1-3 wt% loading for steady state measurement and 5-9 wt% loading for oscillatory measurement. The rheological properties of epoxy-graphene suspension were studied by cone and plate fixture. The rheological flow model was fitted in Casson model. The solid and liquid like behavior of suspension was detected from strain sweep and frequency sweep technique.
