title: Processable 3-nm thick graphene platelets of high electrical conductivity and their epoxy composites.
abstract: Graphene platelets (GnPs) are a class of novel 2D nanomaterials owing to their very small thickness (∼3 nm), high mechanical strength and electric conductivity (1460 S cm(-1)), and good compatibility with most polymers as well as cost-effectiveness. In this paper we present a low-cost processing technique for producing modified GnPs and an investigation of the electrical and mechanical properties of the resulting composites. After dispersing GnPs in solvent N-methyl-2-pyrrolidone, a long-chain surfactant (Jeffamine D 2000, denoted J2000) was added to covalently modify GnPs, yielding J2000-GnPs. By adjusting the ratio of GnPs to the solvent, the modified GnPs show different average thickness and thus electrical conductivity ranging from 694 to 1200 S cm(-1). To promote the exfoliation and dispersion of J2000-GnPs in a polymeric matrix, they were dispersed in the solvent again and further modified using diglycidyl ether of bisphenol A (DGEBA) producing m-GnPs, which were then compounded with an epoxy resin for the development of epoxy/m-GnP composites. A percolation threshold of electrical volume resistivity for the resulting composites was observed at 0.31 vol%. It was found that epoxy/m-GnP composites demonstrated far better mechanical properties than those of unmodified GnPs of the same volume fraction. For example, m-GnPs at 0.25 vol% increased the fracture energy release rate G1c from 0.204 ± 0.03 to 1.422 ± 0.24 kJ m(-2), while the same fraction of unmodified GnPs increased G1c to 1.01 ± 0.24 kJ m(-2). The interface modification also enhanced the glass transition temperature of neat epoxy from 58.9 to 73.8 °C.
authors.affiliation: School of Engineering, University of South Australia, Mawson Lakes, SA5095, Australia. Mawson Institute, University of South Australia, SA5095, Australia.
authors.forename: Qingshi
authors.initials: Q
authors.lastname: Meng
authors.forename: Jian
authors.initials: J
authors.lastname: Jin
authors.forename: Ruoyu
authors.initials: R
authors.lastname: Wang
authors.forename: Hsu-Chiang
authors.initials: HC
authors.lastname: Kuan
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kawashima
authors.forename: Andrew
authors.initials: A
authors.lastname: Michelmore
authors.forename: Shenmin
authors.initials: S
authors.lastname: Zhu
authors.forename: Chun H
authors.initials: CH
authors.lastname: Wang