Fabrication and properties of aligned multiwalled carbon nanotube-reinforced epoxy composites
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A method to fabricate continuous and aligned multiwalled carbon nanotube (CNT)/epoxy composites is presented in this paper. CNT/epoxy composites were made by infiltrating an epoxy resin into a stack of continuous and aligned multiwalled CNT sheets that were drawn from super-aligned CNT arrays. By controlling the amount and alignment of the continuous multiwalled CNT sheets, a CNT/epoxy composite with high content of well-dispersed CNTs can be obtained. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results show that the thermal stability of these CNT/epoxy composites was not affected by the addition of CNTs. The mechanical properties and electrical properties of the CNT/epoxy composites were dramatically improved compared to pure epoxy, suggesting that the CNT/epoxy composites can serve as multifunctional materials with combined mechanical and physical properties.
I. INTRODUCTION
Carbon nanotube (CNT)/epoxy composites have been widely investigated in the last decade since CNT/ thermosetting resin composites were first fabricated by Ajayan et al. in 1994.1 CNTs are considered to be the ideal reinforcing materials for making polymer composites due to their large specific surface area and aspect ratio, high tensile strength and Young’s modulus,2,3 and superior thermal4 and electrical properties.5 However, the mechanical and physical properties of CNT polymer composites are much lower than the predicted values. For example, the tensile modulus of CNT/epoxy composites was only improved from 3.1 to 3.71 GPa with 5 wt% multiwalled nanotubes (MWNTs), corresponding to 20% improvement.6 The critical issues for achieving desirable properties of the CNT/polymer composites are to introduce a high content of CNTs with uniform dispersion and controlled alignment throughout the polymer matrix and improve CNT/epoxy interface properties.7 High-strength epoxy resins are commonly used polymers in the formation of CNT/polymer composites that can serve as multifunctional materials with light weight, high strength, and high electrical conductivity for many industrial applications, such as aircrafts and electronics products. Depending on the chemical compositions and
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0356 J. Mater. Res., Vol. 23, No. 11, Nov 2008
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curing kinetics of the epoxy resins, it is possible to vary their mechanical properties such as Young’s modulus, strength, and hardness, and physical properties such as thermal conductivity and electrical conductivity. Epoxy resins start in a liquid form to facilitate dispersion of CNTs. Afterward, the mixture of CNTs and epoxy resins is cured when a hardener or agent is added to form a solid-state CNT/epoxy composite. There are many methods to disperse CNTs in epoxy resins for preparing CNT/ epoxy composites, such as blending,6,8–10 solution mixing,11,12 and buckypaper-based processing.13,14 Blending is a direct method to mix CNTs with epoxy re
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