Electrical conductive behavior of polymer composites prepared with aqueous graphene dispersions

Graphene was produced from graphite powder using the three best known water-based conversion approaches. The first two are based on chemical oxidation methods, only differing in the reduction process, either by the use of hydrazine or by thermal expansion, respectively. The third one is based on long-term ultrasonic exfoliation. Water/surfactant solutions were prepared with these three nanofillers and latex technology concept was applied for the preparation of conductive graphene/polystyrene composites with well-dispersed graphene platelets. The samples were characterized with respect to filler properties and morphology, and their influences on electrical conductive properties of the composites were compared. Microscopic studies showed that both reduction processes lead to agglomeration/wrinkling of the platelets, even though they yield composites with high conductivity and low percolation threshold. Although mechanical ultrasound exfoliation of graphite produces less defective multi-layer graphene, these platelets have a smaller lateral size and their composites exhibit a higher percolation threshold. Differences in electronic transport behavior were observed, which suggest direct contact transport competing with tunneling.