research article shear flow induced alignment of carbon...

Research ArticleShear Flow Induced Alignment of Carbon Nanotubes inNatural Rubber

Yan He Zhifang Cao and Lianxiang Ma

College of Mechanic and Electronic Engineering Qingdao University of Science and Technology No 99 Songling RoadQingdao Shandong 266061 China

Correspondence should be addressed to Zhifang Cao czfqustfoxmailcom

Received 5 June 2015 Revised 26 August 2015 Accepted 10 September 2015

Academic Editor Marilyn L Minus

Copyright copy 2015 Yan He et al This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A new procedure for the fabrication of natural rubber composite with aligned carbon nanotubes is provided in this study Thetwo-step approach is based on (i) the preparation of mixture latex of natural rubber multiwalled carbon nanotubes and othercomponents and (ii) the orientation of carbon nanotubes by a flow field Rubber composite sheets filled with variable volumefraction of aligned carbon nanotubes were fabricated and then confirmed by transmission electron microscopy and Ramanspectroscopy studies An obvious increase in thermal conductivity has been obtained after the alignment of carbon nanotubesThe dynamic mechanical analysis was carried out in a tear mode for the composite

1 Introduction

Carbon nanotube (CNT) is a kind of tube-like materialwhich is rather like a rolled-up graphene sheet composedof a hexagonal network of carbon atoms where the internalspace is empty A great deal of attention has been paidon this tiny but fascinating material since it was found byIijima [1] a scholar on electron microscope of Japan in1991 It is reported that it shows a tremendous potential innumerous fields [2ndash5] Rubber is a conventionalmaterial usedwidely In order to achieve optimal enhancement in thermalelectric and mechanical properties of natural rubber a lot ofimprovement approaches have been proposed among themadding CNTs with excellent properties is an effective wayPeddini et al [6] researched the morphology and rheology ofstyrene-butadiene rubber with multiwall carbon nanotubesand they found that the glass transition temperature of thecomposite increased 45∘C Wang et al [7] added CNTsto silicone rubber to improve the materialrsquos sensitivity andsensing linearity for pressure Kueseng et al [8] obtainedcomposite with high electrical conductivity by adding CNTsto NRNBR through a two-roll mill and its maximumdamping parameter had also decreased

Carbon nanotube has an extremely high thermal conduc-tivity which can reach up to 6600W(msdotK) by theoretical

calculation [9] and its experimental thermal conductivitycan be over 3000W(msdotK) [10] so it is expected to increasethe thermal conductivity of composite drastically It wasreported that the thermal conductivity of composites filledwith CNTs can be increased markedly comparing to thematrix material Hwang et al [11] focused on enhancing thethermal conductivity of poly(ether-ether-ketone) by addingCNTsThe thermal conductivity of composite they fabricatedincreased to 036Wmminus1Kminus1 Heat is transmitted by phononalong the axial direction of the carbon nanotubes showingobvious directivity [12] that is to say it is hard for heat to passthrough a carbon nanotube wall reaching another carbonnanotube If the CNTs can be oriented in the matrix it canincrease the electric and thermal conductivity of compositeeffectively preventing the accumulation of static electricity[13] Different approaches for aligning carbon nanofillershave been reported in literatures mainly based on mechan-ical stretching [14 15] or the application of an electric field[16] or magnetic field [17 18] It is a challenge to orient CNTsin matrix material especially in natural rubber due to itsthermosetting property which limits the movement of CNTeven at a high temperature By utilizing suitable solvent wegot a rubber latex filled with CNTs and then fabricated anatural rubber sheet filled with aligned carbon nanotubes ina controllable direction by a flow field Vigolo et al [19] have

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2015 Article ID 964723 8 pageshttpdxdoiorg1011552015964723

2 International Journal of Polymer Science

(a) (b) (c)

Figure 1 Apparatus used for alignment of CNTs in natural rubber

successfully aligned CNTs in aqueous solutions of sodiumdodecyl sulfate through a flow field caused by injection Tothe best of the authorsrsquo knowledge this is the first reporton the production of aligned carbon nanotube-filled rubberby a flow field although there have been a few reports onthe alignment of carbon nanotubes in polymers using othermethods

2 Materials and Methods

21 Materials MWCNTs with purity gt 95 diameters inrange of 40sim60 nm and length gt 5 120583m were procured fromNa Mi Gang Limited Company of Shenzhen China Naturalrubber was obtained from Hainan Natural Rubber IndustryGroup All other chemicals used were of analytical gradeunless otherwise stated

22 Experimental Details 10 g of natural rubber was usedfor each preparation of samples in this experiment and theother constituents were weighed as shown in Table 1 Thenatural rubber was dissolved in 200mL of methylbenzene for24 h and then a kind of rubber latex can be obtained aftera period of mechanical agitation Then a certain number ofmultiwalled carbon nanotubes (MWCNTs) were dispersed in75mL of methylbenzene by ultrasound for 30min at roomtemperature which contributed to a stable suspension Eachof the other components showed in Table 1 was also put into75mL of methylbenzene and followed by this was ultrasonicdispersing for 30min at 50∘C so that a suspension withadditives can be obtained Mix the three reagents mentionedabove together in a 3-mouth flask to get a kind of uniform andstable mixture latex during which the mechanical agitationwas needed The next step was to realize the directionalalignment ofMWCNTs for this themixture latex containingall components including natural rubber CNTs and additiveswas compelled to pass through a sieve with holes whosediameter is 1mm and depth is 12mm by pressure Theapparatus was shown in Figure 1 the cavity in picture (a) was

Table 1 The composition of composite

Constituent phra

Natural rubber 100

Sulfur (S) 3

Zinc oxide 5

Accelerator ZDC 1

Stearic acid 2

Antioxidant RD 1

Ethylxanthic acid potassium salt 1

MWCNTs VariatebaPer hundred of rubber in qualitybThe amount of the CNTs was determined by its volume fraction whichcan be calculated from the equation 119872CNTs120588CNTs = (119872CNTs120588CNTs +119872NR120588NR+119881Add) times 119862119862 isin (0 2 4 6 8 10) where119881Add is the total volumeof all the additives used in the formula and each of them can be got from itsquality and density

used for adding mixture the part in picture (b) is the corecomponent in which a row of holes was manufactured forconvenient operation the disk over the cavity connected tothe plunger was used for load-bearing to provide a constantpressure just as shown in picture (c) So the mixture latexcan be extruded through the sieve under pressure It wasreported that there existed a flow field in the fluid passingthrough a hole [20] So the MWCNTs can be oriented alongthe shear force caused by the flow field The mixture latexpassed through the sieve was collected in a mold shown inFigure 2 which was composed of three parts that can beassembled to a rectangular box A suitable opening can becontrolled by different assembling just as shown in pictures(b) and (c) In the experiment the latex was collected inthe opening in picture (b) and then changed its opening toa status in picture (c) to get a sample with CNTs orientedperpendicular to the biggest plane After that the latex with

International Journal of Polymer Science 3

(a) (b) (c)

Figure 2 Mold for mixture latex after alignment of CNTs

oriented MWCNTs was defoamed in vacuum for 30 minutesand then put under a fume cupboard for 24 hours duringwhich the methylbenzene in the sample could volatilizeand the rubber could be cross-linked So we could get asample from themold for properties testing For the propertycomparison of composite with oriented CNTs to the randomCNTs composite with random CNTs was also prepared Justlike the procedure described above the mixture latex wasprepared in the same way then it was put into amold directlyinstead of passing through a sieve with holes After that thesample was set in vacuum and then a fume cupboard in thesame way So we can also get a sample of composite withrandom CNTs

3 Results and Discussion

31 Morphology Characterization The feature of WMCNTscan be observed under transmission electron microscope(TEM) In order to check the dispersion and arrangement ofcarbon nanotubes in rubber pictures of samples were takenby transmission electron microscope (JEM-2100 JEOL) ata voltage of 200 kV For this ultramicrocut with thicknessaround 50 nm was made along the direction of shear flowby a cryoultramicrotome Pictures for samples with differentvolume fraction of WMCNTs aligned by a flow field andnot were shown in Figure 3 Among them (a) and (c) areones for composites with filler volume fraction of 2 and6 respectively whose WMCNTs were not oriented by aflow field As shown in the picturesWMCNTs were isotropicand dispersed disorderly without directionality From theview of WMCNTs length there are many short WMCNTsor points They are ones that are perpendicular or nearlyperpendicular to the surface of the image which were cutshort during the ultramicrocut section And (b) and (d) areones for composites with oriented WMCNTs of 2 vol and 6 vol respectively by a shear flow As shown in thepictures many of the MWCNTs were in the same directionto a great extent along the arrows in the pictures distributingalong one direction more than its perpendicular direction at

the same time the chopped MWCNTs significantly reducedin number It means that the MWCNTs perpendicular tothe image surface reduced and they have been arrangedsubstantially in the same direction It is noteworthy thatthere was little aggregate in rubber matrix indicating gooddispersion of carbon nanotubes

32 Polarized Raman Characterization Polarized Ramanspectroscopy is a powerful tool for investigating the orienta-tion of CNTs in a polymer matrix by the analysis of intensityvariation of the G-band with the variation of angle betweenthe CNT axis and polarization direction of the incident lightThe composite with random MWCNTs was isotropous sothe variation of the angle between axis of oriented CNTs andlaser source could not cause a change in the intensity of thecomposite material spectrum [16 21ndash24] However for thecomposite with oriented CNTs it would lead to a significantchange in the absorption strength of each characteristic peakThe samples with variable volume fraction of oriented CNTswere characterized through polarized Raman spectrum (byRenishaw inVia) and three samples for each formula weretested The polarized Raman spectrum of composite filledwith 6 vol of oriented MWCNTs was shown in Figure 4which was stimulated by a laser of 785 nm The peak around1310 cmminus1 is called D-band caused by defects located alongthe nanotube sidewalls [25] The peak around 1580 cmminus1named as G-band resulted by the elongation of the carbon-carbon bonds along the longitudinal axis of the nanotubes[26] And the peak around 2620 cmminus1 called G1015840-band isknown to be an overtone or a second-order harmonic ofthe D-band The direction 0∘ means that the exciting laseris parallel to the axis of oriented CNTs which has beendetermined by polarized Raman testing that the intensityof Raman scattering is maximum The minimum intensityof Raman scattering can be obtained when the direction is90∘ at which the exciting laser is orthogonal to the axis oforiented CNTs The ratio G0∘G90∘ of the intensity of peaksat 0∘ and 90∘ can be used to measure the alignment of carbonnanotubes In principle for nanotubes dispersed randomly in


(a) (b)

(c) (d)

Figure 3 (a) and (c) are TEM images of composite with random MWCNTs at the volume fraction of 2 and 6 respectively (b) and (d)are TEM images of composite containing 2 vol and 6 vol of MWCNTs oriented by a shear flow respectively

1200 1500 1800 2100 2400 2700

Raman shift (cmminus1)

Inte

nsity

(au

)

90∘

0∘

Figure 4 Polarized Raman spectra of composite with alignedMWCNTs of 6 vol

the composite it should be equal to 1 The ratio G0∘G90∘measured from sample is 1890 which indicates that thecarbon nanotubes are aligned preferentially along a certaindirection in accordance with the result by TEM

The average D peaks and G peaks intensity of Ramanspectra of oriented MWCNTsNR nanocomposite with dif-ferent CNT contents were compared in Table 2 As shown

Table 2 Raman spectra intensity and its ratio of oriented MWC-NTsNR nanocomposite at different MWCNT contents

Volume fraction () 2 4 6 8 10

Intensity (au)

D-bandD0∘ 3063 3136 3292 3428 3842D90∘ 1592 1529 1622 1878 1921

D0∘D90∘ 1924 205 2030 1825 2000

G-bandG0∘ 1369 2434 2543 2608 2857G90∘ 863 1340 1345 1569 1724

G0∘G90∘ 1586 1816 1890 1660 1657

in the table the intensity of the D peaks and G peaksdecreases with increasing the polarization angle And theratio of G0∘G90∘ is always higher than 1 as well as theratio of D0∘D90∘ The obtained G0∘G90∘ ratios are higherthan those found in the literature by electric field andmagnetic field which generally do not exceed 15 [16 27]The peaks generated by CNTs increase in intensity with theincreasing of nanotube concentrationThis phenomenonwasprobably due to a thermal effect arising from the absorptionin the polymer because most of the thermal energy wasaccumulated by nanotubes under the laser beam [28] Theratio G0∘G90∘ maximized at 6 concentration and thendeteriorated because of the aggregation of CNTs with theincreasing of filler concentration above 6 which was dis-advantage to the orientation of CNTs


IR detector

SampleSoftware for

test andanalysis

Laser pulse

Figure 5 Illustration of laser flash analysis technique

33 Thermal Conductivity of Composite Laser flash analysis(LFA) is currently themost popularmethod ofmeasuring thethermal conductivity of composite materials In this methodthe thermal conductivity could not be measured directlybut could be computed by thermal diffusivity heat capacityand density measured Thermal conductivity measurementswere determined using a Netzsch Laser Flash Analysis (LFA447) in our experiment The lower surface of a plane-parallelsample is heated by a laser pulse and temperature riseon the top surface is measured using an IR detector asillustrated in Figure 5 In addition to thermal diffusivity theheat capacity can also be calculated by the heat capacityof a master standard and its ratio of testing sample in thesame procedure The density of samples was measured byan ultramicrodensitometer ldquoST-XS-365Mrdquo So the thermalconductivity of composite can be calculated by the followingformula

120582 = 120572120588119862

119901 (1)

where 120582 is the thermal conductivity in Wmminus1sdotKminus1 120572 isthermal diffusivity in cm2s 120588 is density of samples in gcm3and 119862

119901is heat capacity in Jkgminus1Kminus1

Samples were cut into cylinders in diameter of 127mmand thickness around 1mm and then coated with graphitespray to increase the light absorption and infrared emissionof surface Allmeasurements were taken at room temperaturewith a laser voltage power of 304V a medium pulse withwidth of 018ms and a laser transmission filter of 100All signal curves were fitted using a Cowan plus impulsecorrection model Thermal conductivity of composite withvariable volume fraction of MWCNTs aligned by a flow fieldand not generated from the LFA was illustrated in Figure 4and the standard deviationwas includedThe average thermalconductivity of a composite material depends upon therelative contributions of the individual components in eachsystem [29] As shown in Figure 4 its thermal conductivityincreases gradually with the increase of filler volume fractionfor both the composites with randomMWCNTs and alignedMWCNTs because the more MWCNTs were added in thecomposite the more integrated network was formed Andthe composite with aligned carbon nanotubes always hasa higher thermal conductivity at the same filler volumefraction due to the anisotropy of heat conduction alongcarbon nanotubes The thermal conductivity of compositewith 10 vol of MWCNTs aligned by a flow field can be

0 2 4 6 8 10015

020

025

030

035

040

045

050

Ther

mal

cond

uctiv

ity (W

(m

k))

Volume fraction ()

Random Aligned

Figure 6 Thermal conductivity of composite

up to 0475Wmminus1kminus1 which shows an enormous superioritycomparing to natural rubber filled with carbon black at thesame filler concentration whose thermal conductivity was022Wmminus1kminus1 at filling concentration of 10 vol [30] Thethermal conductivity increased by 191 comparing withthe composite with random MWCNTs at the same fillingfactor and increased by 129 comparing with the matrixmaterial without MWCNTs addedThe thermal conductivityof composite fabricated in this method is generally higherthan or comparable to that of other polymers with CNTs [31ndash33] in spite of the lower thermal conductivity of pure naturalrubber (Figure 6)

34 Mechanical Characterization Carbon nanotubes canalways improve the mechanical properties of compositegreatly due to its extremely high modulus and strength [3435] In order to investigate the effect of alignment of MWC-NTs on the composite dynamic mechanical analysis (DMA)tests (by Dynamic Mechanical Analyzer from METTLER-TOLEDO) have been carried out both on composite withaligned MWCNTs and on composite with random MWC-NTs Samples were cut into dimensions of 4mm times 4mm andtheir thickness was around 1mm but their accurate value wasobtained by a thickness gauge as an input variable for DMAFor this the axis of the orientedMWCNTswas perpendicularto the plane of 4mm times 4mm that means the shear forcewas perpendicular to axis of the oriented MWCNTs in thetesting The dynamic mechanical behavior of composite hasbeen obtained by a shear mode at 10Hz and a heating scan of3∘Cmin which was reported in Figure 7 and Table 3

In Figure 7 dynamic mechanical behavior of compositewith 10 vol of MWCNTs oriented by a flow field and notthe curves of storage modulus1198721015840 scaled by the left scale andloss factor tan 120575 scaled by the right scale are included in thefigure As shown the alignment of MWCNTs can increase


Table 3 Dynamic mechanical properties of composite with differ-ent MWCNT contents

Volumefraction()

Aligned or not Modulus1198721015840aMPa 119879119892

b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778

aMaximum storage modulus of compositebTreat the temperature at which the curve of loss factor (tan 120575) gets a peak asglass transition temperature

13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00

Aligned MWCNTsRandom MWCNTs

0

300

600

900

1200

1500

1800

M998400

(MPa

)

minus40 minus20 0 20minus60

Temperature (∘C)

Figure 7 Dynamic mechanical behavior of composite with 10 vol ofMWCNTs oriented by a flow field and not Storagemodulus1198721015840and loss factor tan 120575 are included

the maximum storage modulus of composite dramatically(from 13770MPa to 15711MPa) this is because that for thecomposite with alignedMWCNTs there are more MWCNTspreventing the shear deformation in the shear plane whichcan lead to a high modulus For this we can refer to Figure 8The modulus 1198721015840 got a maximum when the composite wasat glass transition temperature at which the macromolecularchains began to move actively and a constant shear forcecan only cause a little deformation After that the compositecame in an elastomeric state and the modulus tended to bestable with a small value We usually treat the temperatureat which the curve of loss factor tan 120575 has a peak as theglass transition temperature (119879

119892) It was found that the

alignment of MWCNTs made 119879119892of composite with 10 vol

Shear force

Shear force

Shear force

Shear force

Composite with aligned MWCNTs

Composite with random MWCNTs

Figure 8 Samples for DMA test

Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16

0minus20 minus10minus40minus50minus60 minus30

Temperature (∘C)

Volume fraction ofCNTs ()ta

n120575

tan120575

Figure 9 tan 120575 of composite with various MWCNTs concentrationbefore and after alignment

of MWCNTs decrease from minus425∘C to minus430∘C Thisindicates that the random MWCNTs would provide morephysical crossing points which lead to a stronger networkpreventing the movement of molecular chains The resultingdynamic mechanical behavior for each sample was shownin Table 3 and we can see the same variation trend for acertain volume fraction of composite The curves of tan 120575for composite with various CNTs concentration were shownin Figure 9 where ldquoArdquo is for composite with aligned CNTsand ldquoRrdquo is for composite with random CNTs It was foundthat the addition of 2 vol of MWCNTs and more into theNR matrix caused a considerable downward shift which wasenlarging with the filler concentration It means that CNTswill contribute to the mechanical stiffness and strength ofnatural rubber which has been observed by other authors[36 37] And the alignment could always decrease the lossfactor perpendicular to the axis of the alignment


4 Conclusion

This work presents a new methodology to fabricate a naturalrubber composite with aligned MWCNTs Two steps wereneeded in the procedure first prepare a mixture latex ofnatural rubber MWCNTs and other components Thenorient the carbon nanotubes by a flow fieldThis was achievedby compelling the latex to pass through a sieve with holesby pressure The alignment of MWCNTs in the matrixhas been confirmed by both transmission electron micro-scope and Raman spectroscopy The thermal conductivityof composite with aligned MWCNTs has been increasedgreatly due to the priority of heat transfer along the axisof carbon nanotubes It can expand the application areas ofnatural rubberwidely combinedwith its excellentmechanicalproperties Through the dynamic mechanical analysis wefound that the alignment of MWCNTs can increase thestoragemodulus of composite at glassy state dramatically dueto more MWCNTs in the shear plane preventing the sheardeformation which can lead to a high shear modulus Andthe alignment of MWCNTs made 119879

119892of composite decrease

which indicates that the random MWCNTs would providemore physical crossing points which lead to a more strongnetwork preventing the movement of molecular chains

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The experimental research and the instrumentations usedwere partially financed by NSFC (Natural Science Foun-dation of China) project name Study on Thermal Con-ductivity Mechanism and Structure-Activity Relationship ofCarbon NanotubesRubber Composite Material Project no51276091 It was also funded by Shandong Science andTechnology Agency by the project Study on Industrializationand Application of New Carbon Materials whose Projectno is 2014ZZCX01503The authors acknowledge the supportfrom the Center of Analysis and Measurement in BeijingUniversity of Chemical Technology for the polarizationRaman tests

References

[1] S Iijima ldquoHelicalmicrotubules of graphitic carbonrdquoNature vol354 no 6348 pp 56ndash58 1991

[2] T W Ebbesen H J Lezec H Hiura J W Bennett H FGhaemi and T Thio ldquoElectrical conductivity of individualcarbon nanotubesrdquo Nature vol 382 no 6586 pp 54ndash56 1996

[3] J Zuo W Yao and K Wu ldquoSeebeck effect and mechanicalproperties of carbon nanotube-carbon fibercement nanocom-positesrdquo Fullerenes Nanotubes and Carbon Nanostructures vol23 no 5 pp 383ndash391 2015

[4] H Zanin H J Ceragioli A C Peterlevitz V Baranauskas FR Marciano and A O Lobo ldquoField emission properties ofthe graphenated carbon nanotube electroderdquo Applied SurfaceScience vol 324 pp 174ndash178 2015

[5] A E Aliev C Guthy M Zhang et al ldquoThermal transport inMWCNT sheets and yarnsrdquo Carbon vol 45 no 15 pp 2880ndash2888 2007

[6] S K Peddini C P Bosnyak NM Henderson C J Ellison andD R Paul ldquoNanocomposites from styrene-butadiene rubber(SBR) and multiwall carbon nanotubes (MWCNT) part 1morphology and rheologyrdquo Polymer vol 55 no 1 pp 258ndash2702014

[7] P Wang S Geng and T Ding ldquoEffects of carboxyl radicalon electrical resistance of multi-walled carbon nanotube filledsilicone rubber composite under pressurerdquo Composites Scienceand Technology vol 70 no 10 pp 1571ndash1573 2010

[8] P Kueseng P Sae-Oui C Sirisinha K I Jacob and N Rat-tanasom ldquoAnisotropic studies of multi-wall carbon nanotube(MWCNT)-filled natural rubber (NR) and nitrile rubber (NBR)blendsrdquo Polymer Testing vol 32 no 7 pp 1229ndash1236 2013

[9] S Berber Y-K Kwon and D Tomanek ldquoUnusually highthermal conductivity of carbon nanotubesrdquo Physical ReviewLetters vol 84 no 20 pp 4613ndash4616 2000

[10] P Kim L Shi A Majumdar and P L McEuen ldquoThermaltransport measurements of individual multiwalled nanotubesrdquoPhysical Review Letters vol 87 no 21 Article ID 215502 2001

[11] Y Hwang M Kim and J Kim ldquoImprovement of the mechan-ical properties and thermal conductivity of poly(ether-ether-ketone) with the addition of graphene oxide-carbon nanotubehybrid fillersrdquo CompositesmdashPart A Applied Science and Manu-facturing vol 55 pp 195ndash202 2013

[12] D G Cahill W K Ford K E Goodson et al ldquoNanoscalethermal transportrdquo Journal of Applied Physics vol 93 no 2 pp793ndash818 2003

[13] H Huang C Liu Y Wu and S Fan ldquoAligned carbon nanotubecomposite films for thermal managementrdquoAdvancedMaterialsvol 17 no 13 pp 1652ndash1656 2005

[14] Q Wang J Dai W Li Z Wei and J Jiang ldquoThe effects of CNTalignment on electrical conductivity andmechanical propertiesof SWNTepoxy nanocompositesrdquo Composites Science andTechnology vol 68 no 7-8 pp 1644ndash1648 2008

[15] M Zhang S Fang A A Zakhidov et al ldquoStrong transparentmultifunctional carbon nanotube sheetsrdquo Science vol 309 no5738 pp 1215ndash1218 2005

[16] F Lionetto E Calo F Di Benedetto D Pisignano and AMaffezzoli ldquoA methodology to orient carbon nanotubes in athermosetting matrixrdquo Composites Science and Technology vol96 pp 47ndash55 2014

[17] S Kumar H Kaur H Kaur I Kaur K Dharamvir and L MBharadwaj ldquoMagnetic field-guided orientation of carbon nan-otubes through their conjugation withmagnetic nanoparticlesrdquoJournal of Materials Science vol 47 no 3 pp 1489ndash1496 2012

[18] S Wu R B Ladani J Zhang et al ldquoEpoxy nanocompositescontaining magnetite-carbon nanofibers aligned using a weakmagnetic fieldrdquo Polymer vol 68 pp 25ndash34 2015

[19] B Vigolo A Penicaud C Coulon et al ldquoMacroscopic fibersand ribbons of oriented carbon nanotubesrdquo Science vol 290no 5495 pp 1331ndash1334 2000

[20] Z Zhang S Tang and Y Wang ldquoMomentum and flow fieldanalysis of tiny-hole Jet-flow in high-pressure homogenizationprocessingrdquo Packaging and Food Machinery vol 23 pp 5ndash72005

[21] Z Chen Y Yang Z Wu et al ldquoElectric-field-enhanced assem-bly of single-walled carbon nanotubes on a solid surfacerdquoJournal of Physical Chemistry B vol 109 no 12 pp 5473ndash54772005


[22] J Hone M C Llaguno N M Nemes et al ldquoElectrical andthermal transport properties ofmagnetically aligned single wallcarbon nanotube filmsrdquoApplied Physics Letters vol 77 no 5 pp666ndash668 2000

[23] D W Kang and S H Ryu ldquoOrientation of carbon nanotubesin polypropylene meltrdquo Polymer International vol 62 no 2 pp152ndash157 2013

[24] C Zamora-Ledezma C Blanc N Puech et al ldquoConductivityanisotropy of assembled and oriented carbon nanotubesrdquo Phys-ical Review E vol 84 no 6 Article ID 062701 5 pages 2011

[25] J H Lehman M Terrones E Mansfield K E Hurst and VMeunier ldquoEvaluating the characteristics of multiwall carbonnanotubesrdquo Carbon vol 49 no 8 pp 2581ndash2602 2011

[26] N Romyen S Thongyai and P Praserthdam ldquoAlignment ofcarbon nanotubes in polyimide under electric and magneticfieldsrdquo Journal of Applied Polymer Science vol 123 no 6 pp3470ndash3475 2012

[27] M Abdalla D Dean M Theodore J Fielding E Nyairoand G Price ldquoMagnetically processed carbon nanotubeepoxynanocomposites morphology thermal and mechanical prop-ertiesrdquo Polymer vol 51 no 7 pp 1614ndash1620 2010

[28] M Lamy de la Chapelle C Stephan T P Nguyen et alldquoRaman characterization of single-walled carbon nanotubesand PMMAndashnanotubes compositesrdquo Synthetic Metals vol 103no 1ndash3 pp 2510ndash2512 1999

[29] F F T De Araujo and H M Rosenberg ldquoThe thermal conduc-tivity of epoxy-resinmetal-powder composite materials from17 to 300Krdquo Journal of Physics D Applied Physics vol 9 no 4article 017 pp 665ndash675 1976

[30] J-P Song Y He and L-X Ma ldquoPercolation behavior inthermal conductivity of carbon black filled rubberrdquo Journal ofEngineering Thermophysics vol 32 no 4 pp 641ndash644 2011

[31] Y Hwang M Kim and J Kim ldquoImprovement of the mechan-ical properties and thermal conductivity of poly(ether-ether-ketone) with the addition of graphene oxide-carbon nanotubehybrid fillersrdquo Composites Part A vol 55 pp 195ndash202 2013

[32] J Hong J Lee C K Hong and S E Shim ldquoEffect of dispersionstate of carbon nanotube on the thermal conductivity of poly(dimethyl siloxane) compositesrdquo Current Applied Physics vol10 no 1 pp 359ndash363 2010

[33] I N Mazov I A Ilinykh V L Kuznetsov et al ldquoThermalconductivity of polypropylene-based compositeswithmultiwallcarbon nanotubes with different diameter and morphologyrdquoJournal of Alloys and Compounds vol 586 no 1 pp S440ndashS4422014

[34] H Mei H Wang N Zhang H Ding Y Wang and Q BaildquoCarbon nanotubes introduced in different phases of CPyCSiC composites effect on microstructure and properties of thematerialsrdquo Composites Science and Technology vol 115 pp 28ndash33 2015

[35] T Ogasawara S-Y Moon Y Inoue and Y ShimamuraldquoMechanical properties of aligned multi-walled carbon nan-otubeepoxy composites processed using a hot-melt prepregmethodrdquo Composites Science and Technology vol 71 no 16 pp1826ndash1833 2011

[36] S Rooj A Das K W Stockelhuber et al ldquorsquoExpanded organ-oclayrsquo assisted dispersion and simultaneous structural alter-ations of multiwall carbon nanotube (MWCNT) clusters innatural rubberrdquo Composites Science and Technology vol 107 pp36ndash43 2015

[37] L Tzounis SDebnath S Rooj et al ldquoHigh performance naturalrubber composites with a hierarchical reinforcement structure

of carbon nanotube modified natural fibersrdquo Materials andDesign vol 58 pp 1ndash11 2014

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(a) (b) (c)

Figure 1 Apparatus used for alignment of CNTs in natural rubber

successfully aligned CNTs in aqueous solutions of sodiumdodecyl sulfate through a flow field caused by injection Tothe best of the authorsrsquo knowledge this is the first reporton the production of aligned carbon nanotube-filled rubberby a flow field although there have been a few reports onthe alignment of carbon nanotubes in polymers using othermethods

2 Materials and Methods

21 Materials MWCNTs with purity gt 95 diameters inrange of 40sim60 nm and length gt 5 120583m were procured fromNa Mi Gang Limited Company of Shenzhen China Naturalrubber was obtained from Hainan Natural Rubber IndustryGroup All other chemicals used were of analytical gradeunless otherwise stated

22 Experimental Details 10 g of natural rubber was usedfor each preparation of samples in this experiment and theother constituents were weighed as shown in Table 1 Thenatural rubber was dissolved in 200mL of methylbenzene for24 h and then a kind of rubber latex can be obtained aftera period of mechanical agitation Then a certain number ofmultiwalled carbon nanotubes (MWCNTs) were dispersed in75mL of methylbenzene by ultrasound for 30min at roomtemperature which contributed to a stable suspension Eachof the other components showed in Table 1 was also put into75mL of methylbenzene and followed by this was ultrasonicdispersing for 30min at 50∘C so that a suspension withadditives can be obtained Mix the three reagents mentionedabove together in a 3-mouth flask to get a kind of uniform andstable mixture latex during which the mechanical agitationwas needed The next step was to realize the directionalalignment ofMWCNTs for this themixture latex containingall components including natural rubber CNTs and additiveswas compelled to pass through a sieve with holes whosediameter is 1mm and depth is 12mm by pressure Theapparatus was shown in Figure 1 the cavity in picture (a) was

Table 1 The composition of composite

Constituent phra

Natural rubber 100

Sulfur (S) 3

Zinc oxide 5

Accelerator ZDC 1

Stearic acid 2

Antioxidant RD 1

Ethylxanthic acid potassium salt 1

MWCNTs VariatebaPer hundred of rubber in qualitybThe amount of the CNTs was determined by its volume fraction whichcan be calculated from the equation 119872CNTs120588CNTs = (119872CNTs120588CNTs +119872NR120588NR+119881Add) times 119862119862 isin (0 2 4 6 8 10) where119881Add is the total volumeof all the additives used in the formula and each of them can be got from itsquality and density

used for adding mixture the part in picture (b) is the corecomponent in which a row of holes was manufactured forconvenient operation the disk over the cavity connected tothe plunger was used for load-bearing to provide a constantpressure just as shown in picture (c) So the mixture latexcan be extruded through the sieve under pressure It wasreported that there existed a flow field in the fluid passingthrough a hole [20] So the MWCNTs can be oriented alongthe shear force caused by the flow field The mixture latexpassed through the sieve was collected in a mold shown inFigure 2 which was composed of three parts that can beassembled to a rectangular box A suitable opening can becontrolled by different assembling just as shown in pictures(b) and (c) In the experiment the latex was collected inthe opening in picture (b) and then changed its opening toa status in picture (c) to get a sample with CNTs orientedperpendicular to the biggest plane After that the latex with


(a) (b) (c)








(a) (b)

(c) (d)


1200 1500 1800 2100 2400 2700


Inte

nsity

(au

)

90∘

0∘






Intensity (au)

D-bandD0∘ 3063 3136 3292 3428 3842D90∘ 1592 1529 1622 1878 1921

D0∘D90∘ 1924 205 2030 1825 2000

G-bandG0∘ 1369 2434 2543 2608 2857G90∘ 863 1340 1345 1569 1724

G0∘G90∘ 1586 1816 1890 1660 1657



IR detector

SampleSoftware for

test andanalysis

Laser pulse



120582 = 120572120588119862

119901 (1)




0 2 4 6 8 10015

020

025

030

035

040

045

050

Ther

mal

cond

uctiv

ity (W

(m

k))

Volume fraction ()

Random Aligned







Volumefraction()


b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778


13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00


0

300

600

900

1200

1500

1800

M998400

(MPa

)


Temperature (∘C)





Shear force

Shear force

Shear force

Shear force




Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16


Temperature (∘C)


n120575

tan120575




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)








(a) (b)

(c) (d)


1200 1500 1800 2100 2400 2700


Inte

nsity

(au

)

90∘

0∘






Intensity (au)

D-bandD0∘ 3063 3136 3292 3428 3842D90∘ 1592 1529 1622 1878 1921

D0∘D90∘ 1924 205 2030 1825 2000

G-bandG0∘ 1369 2434 2543 2608 2857G90∘ 863 1340 1345 1569 1724

G0∘G90∘ 1586 1816 1890 1660 1657



IR detector

SampleSoftware for

test andanalysis

Laser pulse



120582 = 120572120588119862

119901 (1)




0 2 4 6 8 10015

020

025

030

035

040

045

050

Ther

mal

cond

uctiv

ity (W

(m

k))

Volume fraction ()

Random Aligned







Volumefraction()


b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778


13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00


0

300

600

900

1200

1500

1800

M998400

(MPa

)


Temperature (∘C)





Shear force

Shear force

Shear force

Shear force




Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16


Temperature (∘C)


n120575

tan120575




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)


1200 1500 1800 2100 2400 2700


Inte

nsity

(au

)

90∘

0∘






Intensity (au)

D-bandD0∘ 3063 3136 3292 3428 3842D90∘ 1592 1529 1622 1878 1921

D0∘D90∘ 1924 205 2030 1825 2000

G-bandG0∘ 1369 2434 2543 2608 2857G90∘ 863 1340 1345 1569 1724

G0∘G90∘ 1586 1816 1890 1660 1657



IR detector

SampleSoftware for

test andanalysis

Laser pulse



120582 = 120572120588119862

119901 (1)




0 2 4 6 8 10015

020

025

030

035

040

045

050

Ther

mal

cond

uctiv

ity (W

(m

k))

Volume fraction ()

Random Aligned







Volumefraction()


b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778


13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00


0

300

600

900

1200

1500

1800

M998400

(MPa

)


Temperature (∘C)





Shear force

Shear force

Shear force

Shear force




Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16


Temperature (∘C)


n120575

tan120575




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




IR detector

SampleSoftware for

test andanalysis

Laser pulse



120582 = 120572120588119862

119901 (1)




0 2 4 6 8 10015

020

025

030

035

040

045

050

Ther

mal

cond

uctiv

ity (W

(m

k))

Volume fraction ()

Random Aligned







Volumefraction()


b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778


13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00


0

300

600

900

1200

1500

1800

M998400

(MPa

)


Temperature (∘C)





Shear force

Shear force

Shear force

Shear force




Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16


Temperature (∘C)


n120575

tan120575




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Volumefraction()


b∘C tan 120575max

0 mdash 5309 minus431 1566

2 N 5998 minus417 1476Y 7011 minus421 1453

4 N 7271 minus416 1447Y 8956 minus422 1378

6 N 8316 minus405 1160Y 9460 minus416 1113

8 N 9792 minus412 1085Y 11943 minus418 1021

10 N 13770 minus425 0991Y 15711 minus430 0778


13770MPa15711MPa

minus425∘C

minus430∘C

12

08

04

00


0

300

600

900

1200

1500

1800

M998400

(MPa

)


Temperature (∘C)





Shear force

Shear force

Shear force

Shear force




Random Aligned

0R-2A-2R-4A-4R-6

A-6R-8A-8R-10A-10

00

02

04

06

08

10

12

14

16

2 4 6 8 100

08

10

12

14

16


Temperature (∘C)


n120575

tan120575




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




4 Conclusion






Acknowledgments


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article shear flow induced alignment of carbon...

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