Enhanced thermal and mechanical properties of carbon nanotube composites through the use of functionalized CNT-reactive polymer linkages and three-roll milling
Introduction
Polymer composites containing conducting fillers such as carbon black [1], carbon fiber, and metal fiber have been extensively investigated for various applications such as structural reinforcement, electromagnetic interference shielding, electronic packaging, radar absorption, heating element construction and high-charge storage capacitors [2], [3], [4], [5], [6], [7]. An enhancement in the mechanical properties has also been observed in the composites, facilitated through load transfer from a low elastic modulus (E) polymer matrix to a high E filler [8]. However, there is a limit to the impregnation of polymers with traditional filler material as the structural strength of these composites begin to breakdown (embrittlement) when the loading is increased significantly. Consequently, high aspect ratio fillers which favor reinforcement and electrical properties/percolation at lower volume fractions are desirable. Carbon nanotubes (CNTs) offer an attractive option in this regard, primarily due to their extremely large aspect ratio, which could be as high as 106, coupled with a large interfacial area >1300 m2/g [9]. Additionally, the CNT surfaces and interfaces can be functionalized and made to interact in a desirable manor with the polymer matrix groups [10]. However, there are still several challenges to the utilization of CNTs as filler. Aggregation and bundling can lead to non-uniform dispersion and poor reproducibility. Furthermore, designing a process that is amenable to large scale production is troublesome when high nanotube loading volume fractions are used [11].
The aim of this work is to present a method to enhance the thermal and mechanical properties of polymer composites containing homogeneously dispersed CNTs for practical usage. Enhanced nanotube polymer interface bonding is achieved, through mutual localized chemical reactions between functional groups on the CNTs and groups on the polymer. Homogeneous dispersion is further facilitated through an effective mixing process. Measurements are presented to show that the thermal and mechanical properties of such functionalized CNT/polymer composites, at identical CNT weight fractions, are superior to those using pristine nanotubes.
Section snippets
Experimental
For fabrication of the CNT composites, epoxy consisting of epoxy medium (Sigma 45345), DDSA (2-Dodecenylsuccinic anhydride), NMA (Nadic methyl anhydride) and DPM-30 (2,4,6-Tris dimethylaminomethyl phenol) was purchased from Sigma Aldrich and both pristine and carboxyl (COOH) functionalized multiwalled carbon nanotubes (MWCNTs) having 8–15 nm outer diameter and 20–50 μm length were purchased from Cheap-tube Inc. To ensure effective mixing and dispersion of the entangled CNTs within the polymer
Results and discussion
To maximize composite performance for a given CNT wt%, the nanotubes must be separated and then evenly dispersed within the polymer matrix. This was achieved using premixing and three-roll milling regardless of CNT type (COOH-CNT or pristine CNT), the results of which are shown Fig. 1(a)–(c). In both Fig. 1(b) and (c), a 5 wt% CNT loading is depicted. Through three-roll milling, shear force created by three horizontally positioned rolls rotating in opposite directions and at different speeds
Conclusions
It has been shown that the use of localized chemical reactions, between functional groups on CNTs and corresponding group in a polymer matrix, combined with three-roll milling, de-bundling and dispersing by applying a shear force, help enhance the thermal and mechanical properties of CNT composites. Such a method can be used to reliably produce uniform CNT composites. Consequently, the interfacial bonding and load transfer of composites can be enhanced enabling superior E and thermal properties
Acknowledgement
This research is the part of the result carried out by support of the naval institute for ocean research in Republic of South Korea.
References (20)
- et al.
The relation between compressive strength of carbon/epoxy fabrics and micro-tow geometry with various bias angles
Compos Struct
(2006) - et al.
Effect of CNT functionalization on crack resistance of a carbon/epoxy composite at a cryogenic temperature
Composites Part A
(2012) - et al.
Specific surface area of carbon nanotubes and bundles of carbon nanotubes
Carbon
(2001) - et al.
Highly conductive multiwall carbon nanotube and epoxy composites produced by three-roll milling
Carbon
(2009) Aspects of dynamic mechanical analysis in polymeric composites
Compos Sci Technol
(1993)- et al.
Superior electromagnetic interference shielding and dielectric properties of carbon nanotube composites through the use of high aspect ratio CNTs and three-roll milling
Org Electron
(2013) - et al.
Functionalisation effect on the thermo-mechanical behaviour of multi-wall carbon nanotube/epoxy-composites
Compos Sci Technol
(2004) - et al.
Improved mechanical properties of carbon nanotube/polymer composites through the use of carboxyl-epoxide functional group linkages
Polymer
(2010) - et al.
Electromagnetic interference (EMI) shielding effectiveness of PP/PS polymer blends containing high structure carbon black
Macromol Mater Eng
(2008) - et al.
Enhanced dielectric constants and shielding effectiveness of, uniformly dispersed, functionalized carbon nanotube composites
Appl Phys Lett
(2009)
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