ARTICLE pubs.acs.org/IECR
Preparation and Properties of Multiwall Carbon Nanotubes/ Polystyrene-Block-Polybutadiene-Block-Polystyrene Composites Shigeki Inukai,*,† Ken-ichi Niihara,† Toru Noguchi,† Hiroyuki Ueki,‡ Akira Magario,‡ Eisuke Yamada,§ Shinji Inagaki,§ and Morinobu Endo|| †
Research Center for Exotic Nano Carbon Project, Shinshu University 4-17-1 Wakasato, Nagano-shi 380-8553, Japan Nissin Kogyo Co., Ltd. 801 Kazawa, Tomi-shi, Nagano 386-8505, Japan § Department of Applied Chemistry, Aichi Institute of Technology, 1247 Yachigusa Yakusa-cho, Toyota-shi, Aichi, 470-0392, Japan Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano-shi 380-8553, Japan
)
‡
ABSTRACT: We prepared poly(styrene-b-butadiene-b-styrene) (SBS) matrix composites in which multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed, and their morphologies, thermal properties, and mechanical properties were investigated. The incorporation of MWCNTs into the SBS matrices improved their thermal and mechanical properties with appropriate flexibility. The MWCNT/SBS composites did not flow above 100 °C, and showed surprising improvements in terms of their creep properties. The results indicated the possibility of broadening their use in high temperature applications, and of significantly improving permanent strain, which are currently the main demerits of TPE. These drastic improvements in the various properties of MWCNT/SBS composites were assumed to have been caused by the formation of a three-dimensional structure at the interfacial phase of the SBS matrix along the MWCNTs, which we designated as a “cell structure”.
1. INTRODUCTION Since carbon nanotubes (CNTs) were discovered by Endo1 and Iijima,2 they have been viewed as attractive functional fillers for producing novel composites due to their high mechanical strength, outstanding thermal and electrical conductivities, and capability for electron emission. Many studies have been carried out on CNT/resin composites3 and CNT/metal composites.4 On the other hand, there have been only a few studies dealing with CNT/soft material composites.5,6 This is because it is rather difficult to disperse the CNTs homogeneously into soft materials and to form an interfacial soft material phase that is strongly bound to the CNTs. Bokobza reviewed multiwall carbon nanotube (MWCNT)/ elastomer composites.5 According to her review, the mechanical properties of the MWCNT/elastomer composites showed more significant improvements than those brought about when CNTs were introduced into a matrix, which were minimal with regard to their expected potential based on the properties of the nanotubes themselves, because of the great difficulty of dispersing CNTs homogeneously. Recently, it was reported that high-shear processing induced homogeneous dispersion of MWCNTs in TPE.6 However, the mechanical properties of the composite were not significantly improved because of the low CNT content (below 5 wt %) in the composite. In our previous paper, the polarity and free radical content were used along with the flexibility and viscoelasticity of elastomer molecules to prepare composites in which various CNTs were uniformly dispersed in an elastomer in a controlled manner. Rubber matrix composites in which a high content of MWCNTs were homogeneously dispersed (above 16 wt %) possessed high stiffness and strength, and displayed appropriate flexibility and extremely high electron emission capability.7,8 These outstanding r 2011 American Chemical Society
properties were assumed to have arisen from the three-dimensional structure formed by the CNTs and the interfacial rubber region bound to them. We named this system “cellulation”.9,10 In this paper, TPEs, which are very advantageous in terms of both resource conservation and energy-saving due to their ease of recycling after use, were used as matrices for forming MWCNT composites. The MWCNT/TPE composites were prepared using an open-two-roll mill, and their mechanical and thermal properties and morphologies were investigated. We clarified the relationship between their outstanding properties and their structures.
2. EXPERIMENTAL METHODS Materials. A thermoplastic elastomer, poly(styrene-b-butadiene-b-styrene) (SBS TR2787 with Mw 120 000 and 30 wt % polystyrene), used as a matrix, was supplied by JSR Co., Ltd. The CNTs were multiwall carbon nanotubes (MWCNTs) with an average diameter of 18 nm, which were supplied by ILJIM Nanotech Co., Ltd. The carbon black (CB) used for comparison was ISAF carbon black with a mean diameter of 22 nm, which was supplied by Tokai Carbon Co., Ltd. Preparation of MWCNTs/SBS Composites. The specified quantity of the MWCNTs was gradually mixed into 50 g of SBS in a 6-in. open-two-roll mill at a mill opening of 0.5 mm and at a relatively high temperature of 6065 °C to prepare composites containing MWCNTs at 1, 3, 5, 6.5, 9, 13, 17 wt %, respectively. Received: December 2, 2010 Accepted: May 6, 2011 Revised: April 18, 2011 Published: May 06, 2011 8016
dx.doi.org/10.1021/ie102380t | Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research
ARTICLE
Dynamic Mechanical Analysis (DMA). Measurements of dynamic viscoelasticity were performed using a DMA2980 (TA Instruments). The storage modulus (E0 ), the loss modulus (E00 ), and the loss tangent (tanδ) of the specimens (width ∼2 mm, thickness ∼1 mm, and length ∼20 mm) were measured in air in the range from 120 °C to 300 °C at a chuck gap of 10 mm, a frequency of 1 Hz, and a dynamic tensile strain (0.2%. The temperature was raised at a rate of 3 °C/min.
3. RESULTS AND DISCUSSION 3.1. Morphological Characterization of MWCNT/SBS Composites. SEM images of the MWCNTs in their raw powder form
Figure 1. SEM images of MWCNT raw materials: (a) 300, (b) 50 000.
For homogeneous and uniform dispersion of the MWCNTs, the mixture was subjected to 10 passes through the mill, where the nip was tightened to 0.1 mm at a relatively low temperature of 2025 °C. The compounds that were obtained were hot-pressed at 120 °C for 1 h to form sheets with a thickness of 1 mm. For comparison, CB/SBS composites were prepared by the same procedure as that described above. Field-Emission Scanning Electron Microscopy (FE-SEM) Observation. The fracture surfaces of the sheet samples were observed by JSM7400-F (JEOL Co., Ltd.). Transmission Electron Microscopy (TEM) Observation. Ultrathin sections were ultramicrotomed using a diamond knife at 100 °C with a Leica Ultra cut UCT. To observe the microphase-separated structure of the SBS, SBS ultrathin sections were stained by OsO4 vapor for 1 h. The TEM experiments were carried out on a JEM-2200FS (JEOL Co., Ltd.) operated at 200 kV. Tensile Test. Tensile tests were carried out using an Orientec RTA-100 at 23 °C with a tension speed of 100 mm/min. The tensile specimens (ISO 37, dumbbell shaped specimen type 3) were punched out from 1 mm thick sheet samples. Creep Property Measurement. Creep tests were carried out by means of a thermal mechanical analyzer (TMA 6100, SII). The specimens (width ∼2 mm, thickness ∼1 mm, and length ∼20 mm) were measured at a chuck gap of 10 mm in air at 70 °C, with a constant tensile stress of 150 KPa.
are shown in Figure 1. The low magnification image in Figure 1a shows that the MWCNTs form aggregates with dimensions ranging from a few micrometers to a few hundreds of micrometers. From the high magnification image shown in (b), it can be seen that the MWCNT aggregates consist of complicated intertwined MWCNTs (such as fiber balls) with extremely high aspect ratios. It would appear to be extremely difficult to unravel these complicated structures of MWCNT fibers and to disperse them uniformly and homogeneously into a matrix, considering that the size of the MWCNTs is of the order of nanometers. SEM images of the tensile fractured surfaces of 9 wt % MWCNT/SBS composite and TEM images of cross section of 9 wt % MWCNT/SBS composite are shown in Figures 2 and 3, respectively. The shiny white regions in Figure 2 correspond to the MWCNTs. The MWCNTs exist in an isolated state and do not form into the intertwined fiber balls that are present in the raw powder (see Figure 1a). In addition, no holes where MWCNTs had been pulled out from the SBS matrix or cracked interfaces between the MWCNTs and the SBS matrix were observed (see Figure 2). These results indicated that the MWCNTs could be fractured simultaneously with the SBS, and that the level of adhesion between the SBS and the MWCNTs was strong. From a detailed TEM image (see Figure 3a and b), we confirmed that the individual MWCNTs disperse uniformly and homogeneously into the SBS matrix. And Figure 3 (c) shows the TEM image ofa stained cross section of 9 wt % MWCNT/SBS composite. The black regions and the white regions in Figure 3c correspond to the polybutadiene (PB) phase and the polystyrene (PS) phase, respectively. Figure 3c indicates that the MWCNTs exist not only in the PB phase but also in the PS phase. To accomplish the homogeneous dispersion of the CNTs within the matrix rubber, the authors developed a milling process at low temperature to obtain enhanced elasticity and shear force, and succeeded in the development of extremely high performance rubber reinforced with MWCNTs.10 We mention here the “elasto-milling” method, which is capable of realizing the homogeneous dispersion of the CNTs into the matrix rubber. This process allows (i) the elastomer molecules of the matrix to fill the voids created by the physically intermingled nanotubes, thus effectively breaking their intrinsic agglomeration during the mixing process, (ii) the rubber matrix to exhibit good “wet ability” with carbon nanotubes, and (iii) the rubber matrix to display extreme elasticity. Below we detail the use of this method to systematically achieve these three requirements. During the preparation of the composites that were used in this study, the viscous flow of the SBS was enhanced by inducing a temperature rise at the time when the MWCNTs were added to 8017
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research
ARTICLE
Figure 2. SEM images of the fracture surface of the 9 wt % MWCNT/SBS composites: (a) 2000, (b) 20 000.
Figure 3. TEM images of cross section of the 9 wt % MWCNT/SBS composites: (a) no stain, (b) magnification of panel (a), (c) with stain, arrows indicate the MWCNTs.
the mixture, during which period SBS molecules with lowered viscosity entered the gaps between the MWCNTs in a cohesive group. Due to the van der Waals interactions, improvement of the wetting between the MWCNTs and the SBS can be achieved. In the tight-milling process that was used for the homogeneous dispersion, the compound experienced a strong shearing force. We should note here that the rubber elasticity of SBS is the highest among TPEs. The compound becomes very distorted by the large shearing force when it passes through the rollers, but the recovery force of the rubber immediately restores it after passing through the rollers. The MWCNTs can be extracted from the
cohesive group, thread by thread, by virtue of this plastic kneading process, which involves repeated distortion and recovery, and are then homogenously dispersed. It is thought that the MWCNTs are homogenously dispersed into the matrix because the three requirements mentioned above are systematically met. 3.2. Mechanical and Thermal Properties of The Composite Materials. Table 1 lists the values for 100% tensile stress (σ100), 300% tensile stress (σ300), tensile strength (TB), and elongation at break (EB) obtained from the tensile testing of various composites. Figures 4 show the relationship between filler content and the values of σ100 and σ300 for various composites. 8018
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research
ARTICLE
Table 1. Tensile Properties of MWCNT/SBS Composites and CB/SBS Composites item
a
MWCNT/SBS composites
CB/SBS composites
contents [wt%]
σ100 [MPa]a
σ300 [MPa]b
TB [MPa]c
EB [%]d
σ100 [MPa]a
σ300 [MPa]b
TB [MPa]c
EB [%]d
0
2.1
3.0
30
840
2.1
3.0
30
840
1
2.2
3.1
36
850
2.1
3.0
33
850
3
2.3
3.8
36
850
2.1
3.0
34
850
5
3.1
5.5
37
850
2.2
3.1
34
830
6.5
3.5
7.0
38
820
2.2
3.0
37
820
9
4.0
7.4
40
830
2.1
3.3
40
850
13
4.3
7.7
39
790
2.3
3.6
38
840
17
6.0
37
720
2.4
4.4
35
820
11
σ100: tensile stress at 100% strain. b σ300: tensile stress at 300% strain. c TB: tensile stress at break. d EB: elongation at break.
Figure 4. Relationship between filler content and the values of σ100 and σ300 for various composites.
Figure 5. Creep test (70 °C, 150 kPa) for MWCNT/SBS composites and CB/SBS composites.
As shown in Figure 4, the values of σ100 and σ300 for the MWCNT/SBS composites increased with increasing content of the MWCNTs. In contrast, the values of σ100 and σ300 for the CB/SBS composite did not increase until 13 wt % of CB. When the content of CB reaches 16 wt %, the values of σ100 and σ300 increased slightly. This was caused by the high aspect ratio of the MWCNTs and the uniform and homogeneous dispersion of the MWCNTs into the SBR matrix, along with the very strong adhesion between the SBS and MWCNTs. The values of TB for the MWCNT/SBS composites and the CB/SBS composites were enhanced without reducing their EB values from 1 to 9 wt % content of filler. When the content of filler exceeds 9 wt %, the values of TB and EB of the MWCNT/SBS composites and the CB/SBS composites respectively tended to reduce. However, the reductions in their flexibilities were not so large. From the above-mentioned result, it was shown that the stiffness of the MWCNT/SBS composites was higher than the stiffness of the CB/SBS composites, without significantly reducing their flexibilities.
One weak point of TPEs is a large permanent strain that is related to the heat resistance. If this could be improved by filling with MWCNTs, then TPEs could be used in a wider range of applications. Creep testing of various composites was carried out as a way of determining their heat resistance. Figure 5 shows the results of the creep tests. As shown in Figure5, the initial strain (ε0) and the creep rate (εC) of the neat SBS and of the 17 wt % CB/SBS composite turned out to be too large. In addition, because the creep-strain reached a machine limit, the creep strain of the neat SBS could not be measured in a period of 50 min, and the creep strain of the 17 wt % CB/SBS composite could not be measured in less than 140 min. However, the values of both ε0 and εC for the 17 wt % MWCNT/SBS composite remained low. These results suggested that the MWCNT/SBS composites had high heat resistance and were resistant against collapse of the composite matrix. The possibility of significantly improving the resilience of the SBS composites was therefore demonstrated. The temperature dependence of the storage modulus (E0 ) and the loss tangent (tanδ) for the various composites are shown in 8019
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research
Figure 6. Temperature dependence of storage moduli for MWCNT/ SBS composites and CB/SBS composites.
Figures 6 and 7. Tables 2 and 3 list the peak temperature and the peak value of tanδ and the loss modulus (E00 ) for various composites. The value of E0 for the neat SBS decreased at around 90 °C under increasing process temperature, and displayed a rubbery plateau region. In addition, the value of E0 dropped at around 70 °C and could not be measured by the flow. The values of E0 for the MWCNT/SBS composites showed the same tendency as the values of E0 for SBS, but the values of E0 for the rubbery plateau region were greatly enhanced by filling with MWCNTs. This result accords with the increases in tensile stress seen in the tensile tests. In particular, the value of E0 at room temperature for the 17 wt % MWCNT/SBS composite showed a very high value of more than 200 MPa. The tanδ temperature dispersion curve of the neat SBS showed two peaks with changes in the value of E0 . The two peaks are at around 91 and 88 °C respectively. The peak at lower temperature and the peak at higher temperature can be attributed to the glass transition of the PB phase and the glass transition of the PS phase, respectively. The temperatures of those peaks are assumed to be the glass transition temperature (Tg). This double peak indicates that the neat SBS forms a phase-separation structure. The value of Tg for the PB phase of the MWCNT/SBS composites was essentially unchanged from those with MWCNTs contents of between 1 and 9 wt %. When the content of MWCNTs exceeds 13 wt %, the value of Tg for the PB phase of the MWCNT/SBS composites shifts slightly to higher temperature, with a decrease in the peak value. The values of Tg for the PS phase of the MWCNT/SBS composites shifted to higher temperature with increasing content of MWCNTs, and the peak value decreased with increasing content of MWCNTs. When the content of MWCNTs exceeded 13 wt %, the peak of the Tg curve for the PS phase started to display a “shoulder” shape. The peak temperature of E00 for the MWCNT/SBS composites shifted to higher temperature with increasing content of the MWCNTs, as did tanδ, while the peak values of E00 increase with increasing content of MWCNTs. In addition, it is thought that interfacial
ARTICLE
Figure 7. Loss tangents (tanδ) for MWCNT/SBS composites and CB/ SBS composites.
regions were formed by an interaction between the polarity of the unsaturated bond of the PB phase and the MWCNTs, and an interaction between the benzene ring of the PS phase and the graphene layer of MWCNT (This is thought about from Figure 3b), because the value of E0 for the MWCNT/SBS composites in the rubbery plateau region is increased by filling with MWCNTs. When the neat SBS is at a temperature higher than 120 °C, the value of E0 could not be measured because of the flow. However, the flow-region of the MWCNT/SBS composites could be moved to higher temperature by filling with MWCNTs, and the value of E0 could be measured up to 300 °C. The value of E0 shows a tendency to increase above approximately 200 °C, and this suggests that a cross-linking reaction occurs in these samples. It is known that oxidative degradation of the neat SBS is caused by an auto-oxidation reaction of the polybutadiene at temperatures higher than 200 °C. In addition, the surfaces of the MWCNTs include many functional groups because the heat treatment of the nanotubes occurs at lower temperature. When the temperature is higher than 200 °C, because the functional groups on the MWCNTs surfaces contain trapped radicals that occur during oxidative degradation, it is believed that a crosslinking reaction can occur because the samples became “resin like” after the tests. The value of tanδ rises due to the flow of the polystyrene phase from around 200 °C, but the values decrease with increasing content of MWCNTs, and a new peak appears at around 160 °C. On the other hand, for the 17 wt % CB/SBS composite, the value of E0 in the rubbery plateau region was enhanced by filling with CB as well as with the MWCNT/SBS composites. However, the effects of reinforcing the 17 wt % CB/ SBS composite on the values of E0 were the same as on the 5 wt % CNT/SBS composite, and were much smaller than that of the 17 wt % MWCNT/SBS composite. It is necessary to increase the contents of CB to obtain E0 values of more than 200 MPa in CB/ SBS composites, and the composites then lose their flexibility. In addition, the values of E0 could be not measured by the flow as well as the pure SBS in the higher temperature region. 8020
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research
ARTICLE
Table 2. Loss Tangents (tanδ), Peak Temperature (°C), and Peak Value of MWCNT/SBS and CB/SBS Composites item contents [wt%]
MWCNT/SBS composites tanδ peak [°C]
CB/SBS composites
tanδ peak value
tanδ peak [°C]
0
90.7
88.4
0.573
0.593
1
90.7
88.4
0.554
0.592
3
90.7
88.5
0.447
0.521
5
90.7
88.5
0.428
0.496
6.5
90.8
88.7
0.417
0.462
9
91.1
89.3
0.376
0.441
13
89.7
92.9
0.341
0.394
17
89.8
92.9
0.273
0.364
tanδ peak value
90.7
88.4
0.573
0.593
90.8
87.5
0.544
0.592
91.1
87.3
0.482
0.592
91.3
87.0
0.381
0.579
Table 3. Loss Moduli (E00 ), Peak Temperature (°C), and Peak Value (MPa) of MWCNT/SBS and CB/SBS item contents [wt%]
MWCNT/SBS composites E00 peak [°C]
CB/SBS composites
E00 peak value [MPa]
0
94.5
67.3
315
6.2
1 3
94.3 94.0
67.1 68.0
359 384
6.6 7.1
5
94.4
68.1
421
7.9
6.5
94.9
70.3
446
8.9
9
95.1
70.9
479
12
13
92.5
71.5
508
16
17
92.7
72.0
443
21
E00 peak [°C]
E00 peak value [MPa]
94.5
67.3
315
6.2
94.5
64.2
335
6.4
94.7
61.8
386
8.9
94.9
57.7
426
11
Figure 8. Schematic diagram of the “cellulation model” formed in CNTs/elastomers composites: (a) percolation, (b) partial “cellular structure”, and (c) three-dimensional “celluar structure”.
3.3. Mechanism of Reinforcement by MWCNT. It is considered that the unique and extraordinary properties of the MWCNT/SBS composites, which are not observed in the CB/ SBS composites, were derived from the structures that were formed in the composites. When SBS is dipped into a solvent such as THF for a long time, it dissolves. However, in the THF immersion test, MWCNT/SBS composites containing more than 6.5 wt % of MWCNTs did not dissolve, and the specimens became swollen and “pudding-like” in consistency. In addition, from measurements of the weight of the gel that remained, 0.7 g of interfacial substance per 1 g of MWCNTs was obtained from the composites containing 17 wt % of MWCNTs. In our previous
paper, we reported some outstanding properties of elastomer rubber matrix composites in which MWCNTs were dispersed homogeneously. These phenomena were assumed to have been caused by the “cellulation” of the MWCNT/elastomer rubber composites, and we therefore proposed the “cellulation model”.9,10 In this model, MWCNT/elastomer rubber composites were considered to have an internal structure in which the elastomer rubber matrices were divided into nanosized units by interfacial regions bound to the MWCNTs. With these regions functioning as cell walls, the elastomer matrices were assumed to be confined in the “cells”. We proposed a schematic diagram of the “cellular 8021
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
Industrial & Engineering Chemistry Research structure” model formed in MWCNTs/elastomers composites illustrated in Figure 8. First, when the amount of MWCNTs is very low (below 5 wt %), an electrically conductive network of carbon nanotubes forms in the matrix (shown in Figure 8a). When the content of MWCNTs reaches 11 wt %, partial “cellulation” takes place (shown in Figure 8b). Finally, when the amount of MWCNTs added exceeds 16 wt %, the cells are homogeneously distributed, thus forming three-dimensional networks (shown in Figure 8c). This reinforcing mechanism is entirely different from that of conventional rubber based composites that use carbon black as a filler, in which carbon black and other fillers are dispersed in the matrix discontinuously. On the other hand, for complete “cellulation” to occur, a continuous three-dimensional structure containing tough and flexible MWCNTs networks that are bound by the rubber must be formed. Because this continuous three-dimensional structure bears the load in the composite, it is thought that the MWCNT/elastomer rubber composites can exhibit outstanding properties that are not observed in composites reinforced by conventional fillers such as CB. The swelling phenomenon observed in the THF immersion test was assumed to have been caused by trapping in the matrix by the interfacial region. This result indicated that the MWCNT/SBS composites form a cellular structure, similar to other MWCNT/elastomer rubber composites.
4. CONCLUSIONS In this study, the following results became obvious from investigations into the morphology and the mechanical properties and viscoelasticity of MWCNT/SBS composites. From SEM observations of the composites, it was shown that MWCNTs can be extracted thread-by-thread from a cohesive group and can be homogenously dispersed into an SBS matrix by using an “elasto-milling” method. In addition, it was shown that very good adhesion could be achieved between the SBS and the MWCNTs. From tensile tests that were carried out on the composites, it was shown that the stiffness of the composites could be greatly enhanced without significantly reducing their flexibility by filling with MWCNTs. From creep tests that were carried out on the composites, it was shown that the values of both ε0 and as εC for the composites remained low when they were filled with MWCNTs. These results suggested that SBS composites filled with MWCNTs should exhibit high heat resistance. From DMA analyses of the composites, it was shown that the values of E0 for the rubbery plateau region of the composites were greatly enhanced by filling with MWCNTs. In addition, it was shown that the flow of the composites in the high temperature region could be inhibited by filling with MWCNTs. The results of the DMA and creep tests indicated the possibility of relieving some of the restrictions on the use of TPE in high temperature applications and of significantly improving permanent strain, which are currently the main demerits of TPE. It was assumed the dramatic improvements that were observed in many of the properties of MWCNT/SBS composites were induced by a three-dimensional structure that forms at the interfacial phase of the SBS matrix along the MWCNTs, which has become known as a “cell structure”.9,10
ARTICLE
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT We thank Ms. Shiori Hara and Mr. Naoki Oyaidu (Aichi Institute of Technology) for valuable assistance. This work was partly supported by a project of ‘‘Carbon Nanofiber Composite Materials’’ performed under the Focus 21 program by the New Energy and Industrial Technology Department Organization (NEDO) under the Ministry of Economy, Trade, Industry (METI) in Japan, and Exotic Nanocarbons, Japan Regional Innovation Strategy Program by the Excellence Japan Science and Technology Agency. ’ REFERENCES (1) Oberlin, A.; Endo, M.; Koyama, T. Filamentous Growth of Carbon Through Benzene Decomposition. J. Cryst. Growth 1976, 32, 335. (2) Iijima, S. Helical Microtubules of Graphitic Carbon. Nature 1991, 354, 56. (3) Lau, A. K. T.; Hui, D. The Revolutionary Creation of New Advanced Materials-Carbon Nanotube Composites. Composites, Part B 2002, 33B, 263. (4) Noguchi, T.; Magario, A.; Fukazawa, S.; Shimizu, S.; Beppu, J.; Seki, M. Carbon Nanotube/Aluminium Composites with Uniform Dispersion. Mater. Trans. 2004, 45, 602. (5) Bokobza, L. Multiwall Carbon Nanotube Elastomeric Composites: A review. Polymer 2007, 48, 4907. (6) Li, Y.; Shimizu, H. High-Shear Processing Induced Homogenous Dispersion of Pristine Multiwalled Carbon Nanotubes in A Thermoplastic Elastomer. Polymer 2007, 48, 2203. (7) Yanagi, H.; Kawai, Y.; Kita, T.; Fujii, S.; Hayashi, Y.; Magario, A.; Noguchi, T. Carbon Nanotube/ Aluminum Composites As A Novel Field Electron Emitter. Jpn. J. Appl. Phys. 2006, 45, L650. (8) Noguchi, T.; Magario, A.; Ueki, H.; Beppu, J.; Seki, M.; Iwabuki, H.; Nagata, K.; Endo, M. Viscoelasticity and Cellulation for Carbon Nanotube/elastomer Composites. Polym. Prepr. Jpn. 2006, 55, 3404. (9) Noguchi, T.; Inukai, S.; Ueki, H.; Magario, A.; Endo, M. Mechanical Properties of MWCNT/Elastomer Nanocomposites and the Cellulation Model. SAE World Congress Tech. Pap. 2009, 01, 0606. (10) Endo, M.; Noguchi, T.; Ito, M.; Takeuchi, K.; Hayashi, T.; Kim, Y. A.; Wanibuchi, T.; Jinnai, H.; Terrones, M.; Dresselhaus, M. S. Extreme-Performance Rubber Nanocomposites for Proving and Excavating Deep Oil Resources Using Multi-Walled Carbon Nanotubes. Adv. Funct. Mater. 2008, 18, 3403.
8022
dx.doi.org/10.1021/ie102380t |Ind. Eng. Chem. Res. 2011, 50, 8016–8022
