共查询到20条相似文献,搜索用时 0 毫秒
1.
Fangming Du John E. Fischer Karen I. Winey 《Journal of polymer science. Part A, Polymer chemistry》2003,41(24):3333-3338
A coagulation method providing a better dispersion of single-walled carbon nanotubes (SWNTs) in a polymer matrix was used to produce SWNT/poly(methyl methacrylate) (PMMA) composites. Optical microscopy and scanning electron microscopy showed an improved dispersion of SWNTs in the PMMA matrix, a key factor in composite performance. Aligned and unaligned composites were made with purified SWNTs with different SWNT loadings (0.1–7 wt %). Comprehensive testing showed improved elastic modulus, electrical conductivity, and thermal stability with the addition of SWNTs. The electrical conductivity of a 2 wt % SWNT composite decreased significantly (>105) when the SWNTs were aligned, and this result was examined in terms of percolation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3333–3338, 2003 相似文献
2.
Cheol Park John Wilkinson Sumanth Banda Zoubeida Ounaies Kristopher E. Wise Godfrey Sauti Peter T. Lillehei Joycelyn S. Harrison 《Journal of Polymer Science.Polymer Physics》2006,44(12):1751-1762
While high shear alignment has been shown to improve the mechanical properties of single‐wall carbon nanotube (SWNT)‐polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field‐induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high‐resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1751–1762, 2006 相似文献
3.
Jin Ho Kang Cheol Park Sharon E. Lowther Joycelyn S. Harrison Chan Eon Park 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):2532-2538
Compliant electrodes to replace conventional metal electrodes have been required for many actuators to relieve the constraint on the electroactive layer. Many conducting polymers have been proposed for the alternative electrodes, but they still have a problem of poor thermal stability. This article reports a novel all- organic actuator with single wall carbon nanotube (SWCNT) films as an alternative electrode. The SWCNT film was obtained by filtering a SWCNT solution through an anodized alumina membrane. The conductivity of the SWCNT film was about 280 S/cm. The performance of the SWCNT film electrode was characterized by measuring the dielectric properties of NASA Langley Research Center – Electroactive Polymer (LaRC-EAP) sandwiched by the SWCNT electrodes over a broad range of temperature (from 25 to 280 °C) and frequency (from 1 kHz to 1 MHz). The all-organic actuator with the SWCNT electrodes showed a larger electric field-induced strain than that with metal electrodes, under identical measurement conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2532–2538, 2008 相似文献
4.
Cheol Park Jae‐Woo Kim Godfrey Sauti Jin Ho Kang Conrad S. Lovell Luke J. Gibbons Sharon E. Lowther Peter T. Lillehei Joycelyn S. Harrison Negin Nazem Larry T. Taylor 《Journal of Polymer Science.Polymer Physics》2012,50(6):394-402
Although many metal decorated nanotubes and nanowires appear in the literature, well‐dispersed metal decorated nanotube polymer composites have rarely been reported because of the excessive density mismatch between the decorated nanotubes and polymer matrix. Here, we report a novel method to prepare well‐dispersed, highly functional, metallized nanotube polymer composites (MNPCs) that possess remarkably improved electrical conductivity and mechanical toughness. The MNPCs are prepared by supercritical fluid impregnation of an organometal compound into a premade well‐dispersed single wall carbon nanotube‐polymer composite film. The infused precursor preferentially migrates towards the nanotubes to undergo spontaneous reduction and form nanometer‐scale metal particles leading to an increase in the conductivity of the MNPC films. The environmentally friendly supercritical fluid impregnation process significantly improved the toughness of the composite films, regardless of the presence of metal. Additional functionality can be imparted into the resulting MNPC by infusing other precursors such as magnetic and catalytic metal compounds. © 2011 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys, 2012 相似文献
5.
M Wang J Zhu W Zhu B Zhu J Liu X Zhu Y Pu P Sun Z Zeng X Li D Yuan S Zhu G Pezzotti 《Angewandte Chemie (International ed. in English)》2012,51(36):9123-9127
The dielectric constant and electrical conductivity of a composite of two insulators, poly(1,1-difluoroethylene) (yellow) and K(2) CO(3) (white), increased dramatically near the percolation threshold?f(c) (f=concentration of K(2) CO(3) ). This intriguing phenomenon can be interpreted in terms of interface percolation caused by the formation of chemically activated interfaces. 相似文献
6.
Kolos Molnár Gábor Szebényi Beáta Szolnoki György Marosi László Mihály Vas Andrea Toldy 《先进技术聚合物》2014,25(9):981-988
The potential of carbonized electrospun nanofiber mats to render epoxy resin composites for aircraft applications electrically and thermally more conductive was investigated. The effect of carbon nanotube inclusion both inside the carbon nanofiber and in the epoxy resin matrix material was studied, in order to reveal any synergistic effects of multilevel presence of nanosized reinforcements on the conductivity and mechanical properties. The carbon nanotube inclusion into the carbonized nanofibers increased the electrical conductivity of the samples by 20–50% and the thermal conductivity by approximately three times leading to a higher value than that of the conventional composites. The preparation of layered composites with a conductive upper layer containing nonwoven carbon nanofabric and a load bearing lower layer with conventional unidirectional carbon fiber reinforcement can offer a cost‐effective and weight‐saving solution for the replacement of metal meshes in structural aircraft composites. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Several kinds of polymer composites with carbonaceous fillers such as carbon black (CB), vapor‐grown carbon fiber (CF), and carbon nanotube (CNT) are prepared by a gelation/crystallization process or a melt mixing method. The electrical phenomena, changes of electrical conductivities with different filler's type, filler's concentration and temperatures, and the mechanism of electron transport in these carbon‐filled polymer composites are directly influenced by the geometric grain shape and aggregating morphology of the fillers dispersed in the polymer matrix. For the composites of CB and CF, long‐range macroscopic conduction are governed by the percolation phenomenon, the conduction is behaved through the conductive path formed by the conductors' contacting, and the thermal expansion changes the physical dimensions of the entire electrical network and leads to the changes in the electrical phenomenon. Microscopic conduction between conductive elements is influenced by the tunneling barrier or tunneling voltage, which varies with the temperature change, explaining the apparent observation of the temperature dependence of the composites. In comparison with fillers of CB and CF, the CNT performs unique electric properties for their nonspherical geometry and morphology as a three‐dimensional network (high structures), which has been visually proved by SEM photos in our former research, leading to the percolation threshold lower than 1% in the volume fraction and much less temperature dependence in its composites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1037–1044, 2007 相似文献
8.
The mechanical properties and morphology of multiwall carbon nanotube (MWNT)/polypropylene (PP) nanocomposites were studied as a function of nanotube orientation and concentration. Through melt mixing followed by melt drawing, using a twin screw mini‐extruder with a specially designed winding apparatus, the dispersion and orientation of MWNTs was optimized in PP. Tensile tests showed a 32% increase in toughness for a 0.25 wt % MWNT in PP (over pure PP). Moreover, modulus increased by 138% with 0.25 wt % MWNTs. Transmission electron microscopy and scanning electron microscopy demonstrated qualitative nanotube dispersion and orientation. Wide angle X‐ray diffraction was used to study crystal morphology and orientation by calculating the Herman's orientation factor for the composites as function of nanotube loading and orientation. The addition of nanotubes to oriented samples causes the crystalline morphology to shift from α and mesophase to only α phase. Furthermore, the addition of nanotubes (without orientation) was found to cause isotropization of the PP crystal, and drawing was shown to improve crystal orientation through the orientation factor. In addition, differential scanning caloriometry qualitatively revealed little change in overall crystallinity. In conclusion, this work has shown that melt mixing coupled with melt drawing has yielded MWNT/PP composites with a unique combination of strength and toughness suitable for advanced fiber applications, such as smart fibers and high‐performance fabrics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 864–878, 2006 相似文献
9.
Weawkamol Leelapornpisit Minh‐Tan Ton‐That Florence Perrin‐Sarazin Kenneth C. Cole Johanne Denault Benoit Simard 《Journal of Polymer Science.Polymer Physics》2005,43(18):2445-2453
The effect of different concentrations of single‐walled carbon nanotubes (SWNTs) on the nonisothermal crystallization kinetics, morphology, and mechanical properties of polypropylene (PP) matrix composites obtained by melt compounding was investigated by means of X‐ray diffraction, differential scanning calorimetry, optical and scanning electron microscopy, and dynamic mechanical thermal analysis. Microscopy showed well‐dispersed nanotube ropes together with small and large aggregates. The modulus was found to increase by about 75% at a level of 0.5 wt % nanotubes. The SWNTs displayed a clear nucleating effect on the PP crystallization, favoring the α crystalline form rather than the β form. The crystallization kinetics analysis showed a significant increase in activation energy on incorporating nanotubes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2445–2453, 2005 相似文献
10.
An organic solvent soluble and high electrical conductivity, for example, 55.43 S/cm, polyaniline (PANI), was synthesized by a novel method. In this two steps process, a noncovalent approach was initially developed by functionalization of multiwalled carbon nanotubes (MWNTs) using calcium lignosulfonate (LsCa) via self‐assembly to result MWNTs‐LsCa. Then, the MWNT‐LsCa was employed as a template to lead anilinium monomers directly aligned on the surface to start the polymerization of PANI. The noncovalent modification of MWNTs avoided their agglomeration effectively to allow them doped in PANI at the molecular level. The obtained novel PANI/MWNTs‐LsCa presented excellent solubility and high conductivity. The recorded scanning electron microscopy photographs revealed that the MWNTs‐LsCa was wrapped with PANI chains that caused the crystal orientation improvement. In this article, a related scheme on resulting in the high conductivity of PANI/MWNTs‐LsCa was showed and described. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2036–2046, 2009 相似文献
11.
M. Arai M. Kanamaru T. Matsumura Y. Hattori S. Utsumi T. Ohba H. Tanaka C. M. Yang H. Kanoh F. Okino H. Touhara K. Kaneko 《Adsorption》2007,13(5-6):509-514
Single wall carbon nanotube (SWCNT), which has bundle structure and entangled structure, was untangled and cut by sonication
in hydrogen peroxide (H2O2) solution. The untangled state of SWCNT was examined by SEM, TEM, Raman spectroscopy and N2 adsorption. It was confirmed that the surface area of sonicated nanotubes strongly depended on the sonication time. The BET
specific surface area (SSA) of nanotubes sonicated for 3 h was maximum. The SSA decreased at 6 h or more of sonication time.
These results indicated that the bundle structure was untangled and the cap of SWCNT was opened. Thus, N2 molecules can access the most efficiently inside of the SWCNT sonicated for 3 h. On the contrary, the sonication treatment
for 6 h or more decomposed the nanotubes to produce amorphous carbon, evidenced by TEM and SEM observation; the amorphous
carbon blocked the open pore sites such as the internal pore spaces and interstitial pores. 相似文献
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Karl W. Putz Cynthia A. Mitchell Ramanan Krishnamoorti Peter F. Green 《Journal of Polymer Science.Polymer Physics》2004,42(12):2286-2293
Dynamic mechanical analysis, nuclear magnetic resonance, and thermogravimetric analysis experiments were performed on pure poly(methyl methacrylate) and on in situ polymerized single-walled carbon nanotube (SWNT)/PMMA nanocomposites. The addition of less than 0.1 wt % SWNT to PMMA led to an increase in the low-temperature elastic modulus of approximately 10% beyond that of pure PMMA. The glass-transition temperature and the elastic modulus at higher temperatures of the nanocomposites remained unchanged from those of pure PMMA. These changes were associated with excessive cohesive interactions between the large-surface area nanotubes and PMMA and were not due to changes in the microstructural features of the polymer during synthesis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2286–2293, 2004 相似文献
14.
A. Andreescu Adriana Savin Rozina Steigmann Nicoleta Iftimie E. Mamut R. Grimberg 《Journal of Thermal Analysis and Calorimetry》2008,94(2):349-353
This paper presents a model for evaluation of effective thermal conductivity for the composites with carbon nanotubes (CNT)
having log-normal function of distribution of CNT, with direct effect over depolarization factor. The CNT are considered having
cylindrical shape with L/d ratio very high. The model parameters are calculated in function of the data from literature. The influence of volume fraction
of reinforced materials, of the aspect ratio of the particles included and of the ratio of the two thermal conductivities
is presented. 相似文献
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16.
D. Sordi C. De Ruijter S. Orlanducci S. J. Picken E. J. R. Sudhölter M. L. Terranova L. C. P. M. de Smet T.J. Dingemans 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1079-1087
The focus of this study is on incorporating pendant sulfonate groups along the backbone of a liquid crystalline polyester (LCPE) with the aim to improve the dispersion of single wall carbon nanotubes (SWNTs) and nanodiamonds (NDs). Two LCPE matrices, one sulfonated (LCPE‐S) and one nonsulfonated reference polymer (LCPE‐R), were successfully synthesized via a melt condensation method using aromatic and aliphatic AB, AA, and BB‐type monomers. Upon the introduction of SWNT and ND particles, the glass transition temperature (Tg) of the sulfonated LCPE increased from 21.5 °C to 41.0 °C and 41.9 °C, for SWNTs and NDs, respectively. When sulfonate groups were absent, a decrease in Tg was observed. The storage modulus (E′) followed a similar trend, i.e., E′ increased from 1.3 GPa to 5.2 GPa and 3.4 GPa, upon the addition of NDs and SWNTs. The LCPE‐S showed a lower thermal stability due to the loss of sulfonate groups, i.e. the 5% weight loss temperature (T) is ~280 °C for LCPE‐S vs. 333 °C for LCPE‐R. The decomposition temperature increased somewhat upon addition of the nanoparticles. The ability of dispersing carbon‐based nanostructures combined with an accessible melt processing window makes sulfonated LCPs attractive matrices towards preparing nanocomposites with improved thermal and mechanical properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
17.
Pan Du Yanmao Shi Ping Wu Yaoming Zhou Chenxin Cai 《Frontiers of Chemistry in China》2007,2(4):369-377
It was reported that carbon nanotube (CNT) was functionalized with the electroactive Nile blue (NB), which is a phenoxazine
dye, by a method of adsorption to form a NB-CNT nanocomposite. The NB-CNT nanocomposite was characterized by several spectroscopic
techniques, for example, Ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared (FTIR), Raman spectroscopy
and scanning electron microscopy (SEM) etc., and the results showed that NB could rapidly and effectively be adsorbed on the
surface of CNT with a high stability without changing the native structure of NB and the structure properties of CNT. Moreover,
it was shown that the dispersion ability of CNT in aqueous solution had a significantly improvement after CNT functionalized
with NB even at a level of high concentration, for example, 5 mg of NB-CNT per 1 mL of H2O. The NB-CNT/ glasssy carbon (GC) electrode was fabricated by modifying NB-CNT nanocomposite on the GC electrode surface
and its electrochemical properties were investigated by cyclic voltammetry. The cyclic voltammetric results indicate that
CNT can improve the electrochemical behavior of NB and greatly enhance its redox peak currents. While the NB-CNT/GC electrode
exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of (−0.422±0.002) V (versus
SCE, 0.1 mol/L PBS, pH 7.0), which was almost independent on the scan rates, for electrochemical reaction of NB monomer; and
the redox peak potential of NB polymer located at about −0.191 V. The experimental results also demonstrated that NB and CNT
could synergistically catalyze the electrochemically oxidation of NADH (β-nicotinamide adenine dinucleotide, reduced form) and NB-CNT exhibited a high performance with lowing the overpotential of
more than 560 mV. The NB-CNT/GC electrode could effectively sense the concentration of NADH, which was produced during the
process of oxidation of substrate (e.g. ethanol) catalyzed by dehydrogenase (e.g. alcohol dehydrogenase). The presented method
for functionalization of CNT had several advantages, such as rapid and facile CNT functionalization, easy electrode fabrication
and high electrocatalytic activity, etc., and could be used for fabrication electrochemical biosensor on the basis of dehydrogenase.
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Translated from Acta Chimica Sinica, 2007, 65(1): 1–9 [译自: 化学学报] 相似文献
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Jin Ho Kang Cheol Park Jonathan A. Scholl Amy H. Brazin Nancy M. Holloway James W. High Sharon E. Lowther Joycelyn S. Harrison 《Journal of Polymer Science.Polymer Physics》2009,47(10):994-1003
A systematic study of the effect of single wall carbon nanotubes (SWCNTs) on the enhanced piezoresistive sensitivity of polyimide nanocomposites from below to above percolation was accomplished. The maximum piezoresistive stress coefficient (Π) of 1.52 × 10?3 MPa?1 was noted at just above the percolation threshold concentration (Φ ~ 0.05 wt %) of SWCNT. This coefficient value exceeds those of metallic piezoresistive materials by two orders of magnitude (4.25 × 10?5 MPa?1 for aluminum). The high piezoresistive characteristics appear to originate from a change in the intrinsic resistivity of the composite caused by the variation of the tunneling distance between conducting inclusions (SWCNTs) under compression or tension. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 994–1003, 2009 相似文献
20.
G. Chakraborty S. Ghatak A. K. Meikap T. Woods R. Babu W. J. Blau 《Journal of Polymer Science.Polymer Physics》2010,48(15):1767-1775
Polyaniline/multiwalled carbon nanotube (PANI/MWNT) composites were prepared by in situ polymerization. Scanning electron microscope, X‐ray diffraction, Fourier transform infrared, Uv‐Visible spectroscopy, Fluorescence spectrophotometry were done to characterize the PANI/MWNT composites. Thermal stability was measured by thermogravimetry analysis. The thermal stability of PANI/MWNT composites becomes higher than PANI. Electrical transport properties of different PANI/MWNT composites were investigated in the temperature range 77 ≤ T ≤ 300 K with and without magnetic field up to 1 T. The dc resistivity of PANI/MWNT composites shows different behavior compared to the sample without MWNT. The room temperature dc magnetoconductivity of the samples is negative; however, its sign changes to positive by lowering the temperature, which has been explained by hopping type charge transport. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1767–1775, 2010 相似文献