Composites science and technology

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COMPOSITES SCIENCE AND TECHNOLOGY
Composites Science and Technology 67 (2007) 2965–2972 www.elsevier.com/locate/compscitech

Effects of silane functionalization on the properties of carbon nanotube/epoxy nanocomposites
Peng Cheng Ma a, Jang-Kyo Kim
a

a,*

, Ben Zhong Tang

b

Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay,Kowloon, Hong Kong, PR China b Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China Available online 13 May 2007

Abstract The effects of silane functionalization of multi-wall carbon nanotubes (CNTs) on properties of CNT/epoxy nanocomposites are investigated in this work. Epoxy-based nanocomposites reinforced with CNTs with andwithout functionalization were prepared. The properties of nanocomposites were characterized extensively using the scanning electronic microscopy (SEM), electrical conductivity measurement, thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA), three-point bending test and fracture toughness measurement. The results showed that grafting silane molecules onto the CNT surface improvedthe dispersion of CNTs in epoxy along with much enhanced mechanical and thermal properties as well as fracture resistance of nanocomposites compared to those containing CNTs without functionalization. The electrical conductivity of nanocomposites decreased due to the wrapping of CNTs with non-conductive silane molecules. These findings confirmed the improved interfacial interactions arising fromcovalent bonds between the functionalized CNTs and epoxy resin. Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: A. Polymer–matrix composites (PMCs); B. Electrical properties; B. Thermal properties; B. Mechanical properties; Carbon nanotubes (CNTs)

1. Introduction With unique structural and transport properties, such as excellent strength, modulus, electrical and thermal conductivities alongwith a low density, carbon nanotubes (CNTs) have attracted much interest as the reinforcement for polymer–matrix composites [1–3]. The CNT/polymer nanocomposites hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. The potential of employing CNTs as reinforcements has, however, been severely limited because of the difficulties associated withdispersion of entangled CNTs during processing and the poor interfacial interactions between CNTs and polymer. To ensure effective reinforcements for polymer composites, proper dispersion and good interfacial

Corresponding author. Tel.: +86 852 23587207; fax: +86 852 23581543. E-mail address: mejkkim@ust.hk (J.-K. Kim). 0266-3538/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.compscitech.2007.05.006

*

bonds between CNTs and polymer–matrix have to be guaranteed [4]. Epoxy resin-based CNT nanocomposites have been extensively investigated in view of their potential applications in the electronics, aerospace and automotive industries [5–7]. However, there is no consensus regarding the efficiency of CNTs in improving the certain properties of nanocomposites: forexample, the mechanical properties of epoxy resin were enhanced with less than 1 wt% of CNT [8,9], whereas negligible improvement or even adverse effects were reported on the mechanical properties owing to CNTs [10,11]. These discrepancies are thought to be attributed to the fact that there were large differences in the degree of entanglement and dispersion of CNTs in the resin, as well as ininterfacial adhesion between the CNT and the matrix because the CNTs were not properly functionalized in many of the above studies. This paper is part of a large project on the development of CNT functionalization techniques for improved dispersion and interfacial interactions with polymer resins, and

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P.C. Ma et al. / Composites Science and Technology 67 (2007) 2965–2972

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