Processable 3-nm thick graphene platelets of high electrical conductivity and their epoxy composites

Abstract

<span lang="EN-US" style="font-family: &quot;Calibri&quot;,&quot;sans-serif&quot;; font-size: 10.5pt; mso-bidi-font-size: 11.0pt; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: &quot;Times New Roman&quot;; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;"><font color="#000000">Graphene platelets (GnPs) are a class of novel 2D nanomaterials owing to their very small thickness (similar to 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 G(1c) from 0.204 +/- 0.03 to 1: 422 +/- 0: 24 kJ m(-2), while the same fraction of unmodified GnPs increased G(1c) 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 degrees C.</font></span