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1.
The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.  相似文献   

2.
Poly(vinyl chloride) (PVC)/acrylonitrile–butadiene rubber (NBR) were mixed with multiwalled carbon nanotubes (MWCNTs) and silicon carbide (SiC) to prepare microwave‐absorbing composites. The complex permittivity, direct‐current (dc) conductivity, microwave‐absorbing performance, morphology, and mechanical properties of the composites were studied. The real and imaginary parts of the permittivity of the composites increased with increasing MWCNT content. The premixing of the MWCNTs with PVC was more beneficial to the dispersion of MWCNTs; this led to a higher dc conductivity and permittivity and better microwave‐absorbing performance than the premixing of MWCNTs with NBR for the PVC/NBR/MWCNT composites. The PVC/NBR/MWCNT composites had a minimum reflection loss (RLmin) of ?49.5 dB at the optimum thickness of 1.96 mm. The efficient microwave absorption of the PVC/NBR/MWCNT composites was due to a high dielectric loss and moderate permittivity. The incorporation of SiC into the PVC/NBR/MWCNT composites increased the real and imaginary parts of permittivity of the composites. When the SiC content was 70 phr, RLmin decreased to ?34.9 dB at a thickness of 3 mm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

3.
Adding conductive carbon fillers to insulating thermoplastic resins increases composite electrical conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity and still allow the material to be molded into a bipolar plate for a fuel cell. In this study, various amounts of three different carbons (carbon black, synthetic graphite particles, and carbon nanotubes) were added to polypropylene resin. The resulting single‐filler composites were tested for electrical resistivity (1/electrical conductivity). The effects of single fillers and combinations of the different carbon fillers were studied via a factorial design. The percolation threshold was 1.4 vol % for the composites containing only carbon black, 2.1 vol % for those containing only carbon nanotubes, and 13 vol % for those containing only synthetic graphite particles. The factorial results indicate that the composites containing only single fillers (synthetic graphite followed closely by carbon nanotubes and then carbon black) caused a statistically significant decrease in composite electrical resistivity. All of the composites containing combinations of different fillers had a statistically significant effect that increased the electrical resistivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

4.
Polyaniline (PANI)/multiwalled carbon nanotube (MWNT) composites with a uniform tubular structure were prepared from in situ polymerization by dissolving amino‐functionalized MWNT (a‐MWNT) in aniline monomer. For this the oxidized multiwalled nanotube was functionalized with ethylenediamine, which provided ethylenediamine functional group on the MWNT surface confirmed by Fourier‐transform infrared spectra (FT‐IR). The a‐MWNT was dissolved in aniline monomer, and the in situ polymerization of aniline in the presence of these well dispersed nanotubes yielded a novel tubular composite of carbon nanotube having an ordered uniform encapsulation of doped polyaniline. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanotubes were coated with a PANI layer. The thermal stability and electrical conductivity of the PANI /MWNTs composites were characterized by thermogravimetric analysis (TGA) and conventional four‐probe method respectively. Compared with pure PANI, the electrical conductivity and the decomposition temperature of the MWNTs/PANI composites increased with the enhancement of MWNT content in PANI matrix. POLYM. COMPOS., 34:1119–1125, 2013. © 2013 Society of Plastics Engineers  相似文献   

5.
In recent times, there is an increasing need for effective control of electromagnetic pollution, which can avoid excessive radiation effects on the human body. Microwave absorption materials are attracting wide research interests to reduce electromagnetic pollution due to the rapid development of electronic equipment. In this study, Nitrile butadiene rubber (NBR)/ethylene propylene diene monomer rubber (EPDM) were mixed with multiwalled carbon nanotubes (MWCNT) to prepare microwave absorbing materials. The distribution of fillers, AC conductivity, complex permittivity, and microwave absorption performance of the composites were systematically investigated. It found that the AC conductivity, both real and imaginary parts of the permittivity were significantly improved in the composite with the increasing ratio of MWCNT contents. The NBR/EPDM/MWCNT composites with eight parts per hundred concerning with rubber (phr) MWCNT had a minimum reflection loss (RLmin) of −48.1 dB at the optimum thickness of 2.07 mm. Importantly, the adding sequence of MWCNT and plasticizer dioctyl phthalate (DOP) to the rubber matrix is found to play an important role in determining the distribution of fillers and the structure of polymer blends. The composite with plasticizer added before MWCNT exhibited a better impedance matching and as a result, achieved a good microwave absorption performance.  相似文献   

6.
Poly(phenylene sulfide) (PPS)/multiwalled carbon nanotubes (MWNTs) conductive composites were prepared through the simple mixing of PPS granules with MWNT powder and subsequent compression. The electrical properties as a function of MWNT loading clearly showed a low percolation threshold of about 0.22 vol % and a high critical exponent value of 3.55 for composites prepared by this method. A comparison study with composites prepared via melt mixing was also carried out, where a random dispersion of MWNTs was achieved. There existed a striplike morphology of MWNTs in the PPS matrix and MWNTs were selectively located in strips caused by compression. The effects of temperature and pressure on the conductivity of the PPS/MWNT composites as prepared via simple mixing and compression are discussed. In addition, the conductivity also showed a dependence on the flow direction of the compression, with higher conductivity in the direction parallel to the flow direction than in the direction perpendicular to the flow direction. So the relationship of the processing and morphological properties was investigated in detail. The possible conductive mechanisms of conventional melt blending and preparation via sample mixing and compression are also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

7.
Conductive network formation and its dynamic process for multiwalled carbon nanotubes (MWNTs) and carboxyl‐tethered MWNT (MWNT‐COOH) filled poly(vinylidene fluoride)(PVDF) systems were investigated. Based on real‐time tracing the variation of electrical resistivity of systems with isothermal treatment time, the conductive network formation was evaluated. It was found that the conductive network formation was temperature and time dependent. The percolation time, characterized at a certain annealing time where the electrical resistivity started to decrease drastically, decreased with the increase of the filler concentration or the annealing temperature. However, the values of the percolation time and the activation energy of conductive network formation for the PVDF/MWNT‐COOH system were higher than those of the PVDF/MWNT system, indicating that the interaction between MWNTs and PVDF molecules played an important role in the conductive network formation of the composites. Furthermore, a modified thermodynamic percolation model was proposed to predict the percolation time of PVDF/MWNT composites. It was found that the calculated results fit the experimental data very well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

8.
Cyclo-olefin copolymer (COC) composites containing different amounts of nickel (Ni) and/or nickel-coated carbon (NiC) hybrid fillers were prepared, and their morphological, rheological, mechanical, dielectric, and X-band microwave absorption properties were examined. Rheological percolation thresholds for Ni and NiC fillers were determined to be in the range of 45 to 60 and 60 to 75 phr, respectively. Both fillers caused no significant increase in melt viscosity at low shear rates. The minimum filler concentrations to obtain acceptable reflection loss (RL) values (RL < −10 dB) were determined as 60 and 45 phr for the Ni and NiC series of samples, respectively. The minimum RL value (RLmin) and the broadest absorption bandwidth were determined as −52.5 dB and 8.2 to 12.5 GHz, respectively, for the composite sample containing 75 phr of Ni, whereas a similar performance could be obtained by the sample containing 45 phr of NiC. Considerable enhancement in the RLmin value could not be provided by the use of hybrid NiC fillers; however, the absorption bandwidth was enlarged, and the minimum sample thicknesses to obtain an acceptable absorption bandwidth were reduced significantly.  相似文献   

9.
Multiwalled carbon nanotubes (MWNT) were successfully functionalized with phthalazinone‐containing diamine (DHPZDA) groups by the amidation reaction. The morphologies and structures of the DHPZDA‐functionalized MWNT (MWNT‐DHPZDA) were characterized by scanning electron microscope, Fourier transform infrared, and Raman spectroscopy, revealing that the DHPZDA were covalently attached onto the surface of MWNT, and the weight gain due to the functionalization was determined by thermogravimetric analysis. The MWNT‐DHPZDA/poly(phthalazinone ether sulfone ketone)s (PPESK) composites with different filler content were prepared by the solution‐mixing method. MWNT‐DHPZDA can be uniformly dispersed in the matrix and the strong interfacial adhesion between two constituents was found, which resulted in obvious enhancements of the mechanical properties. For the composite with 1 wt% MWNT‐DHPZDA, the tensile strength and the Young's modulus are 102.1 and 1,974 MPa, about 1.65 and 1.72 times of the pure PPESK, respectively. Conductivity measurements indicate that a typical percolation transition behavior takes place for MWNT‐DHPZDA content in the range from 0.5 to 2 wt%. Additionally, introducing MWNT‐DHPZDA into PPESK is favorable to improvement of the thermal stability. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers  相似文献   

10.
The preparation and characterization of a biobased electromagnetic absorbing composites derived from natural lacquer as a renewable resource with microwave‐absorption fillers, including Ni–Zn ferrite and carbonyl iron (CI) as magnetic metals and soot and carbon nanotube (CNT) as carbon materials, were investigated in terms of the gel content, hardness, drying properties, and electromagnetic absorption properties. Interestingly, composites with ferrite and CI contained up to 320 and 550 wt %, respectively, of these compounds. This quite high loading capacity of the metal fillers in a natural‐lacquer base could have been due to the high compatibility between the filler and the natural lacquer; this indicated that the natural lacquer worked as a binder for these metals. The morphology of the biobased composite was characterized by scanning electron microscopy. The electromagnetic absorption properties of composites were characterized in the frequency range from 0.05 and 20 GHz by the reflection loss (RL) measurement method in terms of the kind of fillers and filler loading. The natural lacquer did not affect the absorption properties of the fillers. Biobased composites showed over 99% electromagnetic absorption in the frequency range 3.0–4.0 GHz for 280 wt % ferrite and 8.9–9.7 GHz for 200 wt % CI. Conversely, 10 and 20 wt % soot exhibited good performance (RL < ?20 dB) between 16.5 and 17.3 and between 8.8 and 9.2 GHz, respectively. The areas with RL values of less than ?20 dB of the CNT composites were 10.4–11.0 GHz for 5 wt % and 14.6–15.2 GHz for 10 wt %. Hence, natural lacquer can be used as a binder material for electromagnetic absorption composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44131.  相似文献   

11.
Cellulose triacetate (CTA) and multiwalled carbon nanotube (MWNT) composite films were prepared by dispersing different weight percentages of MWNTs into a CTA solution. These composite blends were characterized by UV–vis spectroscopy (UV), and their surface mophology, thermal stability, and amended crystallinity were determined by atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD), respectively. Measurements of the complex impedance of the composite samples were made in the form of films. Sheets prepared from conventional techniques were used to study microwave absorption in the microwave range of 2–12 GHz, and the effects of sample thickness on microwave absorption were investigated. The experimental results show that the electrical conductivity of composites increases with the increase in MWNT loading without a percolation threshold. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers  相似文献   

12.
Polycarbonate (PC) composites containing 1 wt % multiwalled carbon nanotubes (MWNT) were produced in a small‐scale DACA microcompounder under variation of mixing temperature and mixing speed at fixed mixing time according to a two‐factor and three‐level factorial design. The extruded strands were compression molded under comparable conditions, and their volume resistivity values indicated differences of about 14 orders of magnitude as well as big differences in the state of MWNT agglomerate dispersion (evaluated as macrodispersion index) are observed. The results indicate that mixing at high melt temperature and high speed can lead to the composites having low resistivity and high dispersion index at low mixing energy input. The influence of compression molding parameters was investigated on precompounded PC composites containing 1 and 2 wt % MWNT. Compression molding parameters such as temperature, time, and speed were varied according to a three‐level and three‐factor factorial design. By adjusting compression molding parameters, the volume resistivity of PC with 1 wt % MWNT composites can be varied over eight orders of magnitude, whereas for 2 wt % MWNT, the variation was within one decade. The electrical volume resistivity results indicate the highest influence of the compression molding temperature followed by time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

13.
The carbon nanotube possesses outstanding physical properties. Theoretically, adding carbon nanotubes into a polymer matrix can remarkably improve the mechanical properties of the polymer matrix. In the present work, a series of composites was prepared by incorporating multiwalled carbon nanotubes (MWNTs) into an epoxy resin. The influences of MWNT content and curing temperature on the flexural properties of the epoxy resin were investigated. The results showed that a very low MWNT content should be used to ensure homogeneous dispersion of MWNTs in the epoxy matrix. A higher MWNT content may lead to deteriorated mechanical properties of the composites because of the aggregation of MWNTs. A decline in the flexural properties of the neat epoxy resin with increasing curing temperature was found. However, under the same curing conditions, improvement in flexural properties was observed for the composite with the low MWNT content and a mild curing temperature. The improvement was far beyond the predictions of the traditional short‐fiber composite theory. In fact, this improvement should be attributed to the retarding effect of MWNTs on the curing reaction of epoxy matrix. Therefore, the improvement in the flexural properties was only a pseudoreinforcement effect, not a nano‐reinforcement effect of the MWNTs on the epoxy resin. Perhaps, it is better for MWNTs to be used as functional fillers, such as electrical or thermal conductive fillers, than as reinforcements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3664–3672, 2006  相似文献   

14.
The effect of the polymeric crosslink density on the thermal conductivity of an epoxy nanocomposite was investigated by adding two different diamine‐functionalized multiwalled carbon nanotubes (diamine‐MWNTs) to the epoxy resin as co‐curing agents and conducting fillers. Tetramethylenediamine (TMDA)‐MWNTs resulted in an epoxy nanocomposite with a higher crosslink density than octamethylenediamine (OMDA)‐MWNTs. Interestingly, epoxy/TMDA‐MWNT nanocomposites under 1.5 wt % nanotube concentration, showed a higher thermal conductivity than an epoxy/OMDA‐MWNT nanocomposite with the same concentration of nanotubes. In contrast, for higher diamine‐MWNT concentrations (over 2.0 wt %), the thermal conductivity of the epoxy/OMDA‐MWNT nanocomposite was higher than that with TMDA‐MWNTs. We observed that for low MWNT concentrations, where a percolating network was not formed, a high crosslink density enhanced the thermal conductivity via phonon transport. However, for high MWNT concentrations, a high crosslink density hinders the formation of a percolating network and lowers the thermal conductivity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44253.  相似文献   

15.
We compared the thermomechanical properties, morphologies, gas permeabilities, and electrical conductivities of ultrahigh‐molecular‐weight polyethylene (UHMWPE) nanocomposite films containing two types of functionalized multiwalled carbon nanotubes (functionalized MWNTs). Both 2‐hydroxyethyl triphenyl phosphonium‐MWNT (Ph3P‐MWNT) and 1,1,1,3,3,3‐hexafluoro‐2‐phenyl‐2‐propanol‐MWNT (CF3‐MWNT) were used as reinforcing fillers in the fabrication of UHMWPE hybrid films. UHMWPE nanocomposites with various functionalized MWNT contents were solution‐cast to produce the films. The thermomechanical properties and morphologies of the UHMWPE hybrid films were then characterized using differential scanning calorimetry, thermogravimetric analysis, electron microscopy, and mechanical tensile analysis. Transmission electron microscopy studies showed that some of the MWNT particles were dispersed homogeneously within the polymer matrix (on the nanoscale), whereas others were agglomerated. We also found that the addition of only a small amount of functionalized MWNTs was sufficient to improve the thermomechanical properties and the gas barrier of the UHMWPE hybrid films. Even, those hybrid films with low functionalized MWNT contents (i.e., <1 wt%) were found to exhibit much better thermomechanical properties than the pure UHMWPE films. On the other hand, the values of the electrical conductivity remained constant, regardless of the amount of functionalized MWNTs. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers  相似文献   

16.
Yuezhen Bin 《Polymer》2006,47(4):1308-1317
The composites poly(vinyl alcohol) (PVA) and vapor growth carbon fiber (VGCFs) and multi wall carbon nanotubes (MWNTs) were prepared by gelation/crystallization from the mixture of dimethyl sulfoxide (DMSO) and water (H2O). The composite films were elongated to 5-10-fold uniaxially. The mechanical properties of PVA composites were improved significantly by introduction of VGCFs and MWNTs and also by the orientation of fillers. Compared to VGCFs, MWNTs was more effective to improve the electric conductivity of the composites because of its network structure. The change in the electrical conductivity for the PVA/MWNT composites containing 5 wt% MWNT was independent of the draw ratio up to eight-fold indicating no disruption of the network formation. A certain high level of filler content was proved to be necessary for the promotion of both mechanical and electrical properties in oriented composite.  相似文献   

17.
The aim of this article was to elucidate the basic relationships between processing conditions and the mechanical and electrical properties of multiwalled carbon nanotube reinforced polymer composites. In conventional chopped fiber reinforced polymer composites, uniform distributions of fibers throughout the matrix are critical to producing materials with superior physical properties. Previous methods have dispersed carbon nanotubes by aggressive chemical modification of the nanotubes or by the use of a surfactant prior to dispersion. 1 , 2 Here, ultrasonic energy was used to uniformly disperse multiwalled nanotubes (MWNTs) in solutions and to incorporate them into composites without chemical pretreatment. Polystyrene (PS) solutions containing MWNTs were cast and spun to yield thin film MWNT composites. The rheology of PS/MWNT suspensions was modeled using the Carreau equation. MWNTs were found to align at the shear rates generated by the spin casting process. The tensile modulus and strain to failure of samples compared well to classical micromechanical models, increasing with MWNT loading. The composite films showed lower strains at the yield stress than neat PS films. The presence of MWNTs at 2.5 vol % fraction approximately doubles the tensile modulus, and transforms the film from insulating to conductive (surface resistivity, ρ, approaching 103 Ω/□). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2660–2669, 2002  相似文献   

18.
The electrical conductivity of oxidized multiwalled carbon nanotubes (MWNT)/epoxy composites is investigated with respect to the chemical treatment of the MWNT. The oxidation is carried out by refluxing the as-received MWNT in concentrated HNO3 and H2O2/NH4OH solutions, respectively, under several different treatment conditions. The oxidized MWNT are negatively charged and functionalized with carboxylic groups by both solutions. The MWNT oxidized under severe conditions are well purified, but their crystalline structures are partially damaged. It is recognized that the damage to the MWNT has considerable influence on the electrical properties of the MWNT composites, causing the electrical conductivity to be lowered at a low content of MWNT and the percolation threshold to be raised. The MWNT oxidized by the mixture of H2O2 and NH4OH solution provides epoxy composites with a higher conductivity than those produced with the MWNT oxidized by nitric acid over the whole range of MWNT, independently of the oxidation conditions.  相似文献   

19.
In this article, copper (Cu) crystallites were successfully prepared via low temperature molten salt method, and the possible formation mechanisms were proposed. The conductive fillers of multiwalled carbon nanotubes (MWCNTs) and as‐prepared Cu particles were designed and introduced into acrylonitrile‐butadiene‐styrene (ABS) blend to prepare different conductive composites. The dispersion states of conductive fillers and the morphologies of the composites were characterized using a field emission scanning electron microscope. The electrical resistivity of different composites was measured. The results showed that Cu and MWCNTs exhibited a synergistic effect in decreasing the electrical resistivity of the Cu/MWCNTs/ABS composites, because Cu that could locate between MWCNTs chain segments provides a better charge transport in the conductive pathways. Compared with pure ABS, the tensile strength, elastic modulus and thermal stability of the Cu/MWCNTs/ABS composites were significantly improved with the incorporation of Cu and MWCNTs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41738.  相似文献   

20.
This work evaluates the influence of two types of carbonaceous fillers, carbon black (CB) and carbon nanotubes (CNTs), on the electrical, electromagnetic, and rheological properties of composites based on poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) prepared by the melt mixing. Electrical conductivity, electromagnetic shielding efficiency (EMI SE) in the X‐band frequency range (8–12.4 GHz), and melt flow index (MFI) results showed that ABS/CNT composites exhibit higher electrical conductivity and EMI SE, but lower MFI when compared to ABS/CB composites. The electrical conductivity of the binary composites showed an increase of around 16 orders of magnitude, when compared to neat ABS, for both fillers. Binary composites with 5 and 15 wt % of filler showed an EMI SE of, respectively, ?44 and ?83 dB for ABS/CNT, and ?9 and ?34 dB for ABS/CB. MFI for binary composites with 5 wt % were 15.45 and 0.55 g/10 min for CB and CNT, respectively. Hybrid composites ABS/CNT.CB with 3 wt % total filler and fraction 50:50 and 75:25 showed good correlation between EMI SE and MFI. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46546.  相似文献   

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