research article permittivity and electromagnetic...

Research ArticlePermittivity and Electromagnetic InterferenceShielding Investigations of Activated Charcoal LoadedAcrylic Coating Compositions

Sharief ud Din Khan1 Manju Arora2 M A Wahab1 and Parveen Saini2

1 Department of Physics Jamia Millia Islamia New Delhi 110025 India2 CSIR-National Physical Laboratory Dr KS Krishnan Marg New Delhi 110012 India

Correspondence should be addressed to Parveen Saini pksaininplindiaorg

Received 6 March 2014 Revised 4 April 2014 Accepted 4 April 2014 Published 4 May 2014

Academic Editor Yves Grohens

Copyright copy 2014 Sharief ud Din Khan et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Acrylic resin (AR) based electromagnetic interference (EMI) shielding composites have been prepared by incorporation of up to30wt activated charcoal (AC) in AR matrix These composites have been characterized by XRD Raman spectroscopy scanningelectron microscopy dielectric and EMI shielding measurement techniques XRD patterns and Raman studies confirm theincorporation of AC particles inside AR matrix and suggest possible interactions between phases The SEM images show thatincorporation of AC particles leads to systematic change in the morphology of composites especially the formation of porousstructure The dielectric measurements show that 30wt AC loading composite display higher relative permittivity value (sim79)compared to pristine AR (sim5) Further the porous structure electrical conductivity and permittivity value contribute towards EMIshielding effectiveness value of minus36 dB (attenuation of gt999 of incident radiation) for these composites thereby demonstratingtheir suitability for making efficient EMI shielding coatings

1 Introduction

Electromagnetic (EM) interference (EMI) is an offshootof explosive growth of electronics and telecommunicationin the modern society [1ndash3] The EMI among electronicinstrumentsappliances may lead to degradation of deviceperformance and may even adversely affect human health[4 5] Due to possible hazards of EMI only the use ofEMwave receiptingemitting electronic gadgets is prohibitedinside sensitive zones for example during flight or insidehospitalrsquos ICUs [1 5 6] Therefore systematic strategies andsuitable counter measures are essential to preventsuppressEMI so as to ensure uninterrupted performance of appliances[1ndash9] The primary mechanism of shielding is based onreflection and the material used for shielding by reflectionrequires mobile charge carriers that is shield should haveconducting property [9 10] Consequently metals (in theform of filler coatings or laminates) are the most common

shielding material which uses primarily reflection mecha-nism for shielding along with minor absorption componentHowever metals suffer from problems like poor wearscratchresistance corrosion susceptibility high density difficultprocessing and high cost [1 6 9] The secondary shieldingmechanism is absorption for which shield material shouldhave electrical or magnetic dipoles [9ndash12] along-with finiteelectrical conductivity For such purpose materials withhigh dielectric constant like ZnO SiO

2 TiO

2 BaTiO

3 or

high magnetic permeability for example carbonyl ironNi Co or Fe metals 120574-Fe

2O3 Fe3O4 and so forth are

used [1 13] However these materials or their compositespossess problems like low permittivity or permeability atgigahertz frequencies weight penalties narrow-band actionand processing difficulties [1 3 13 14] Other than reflectionand absorption another mechanism of shielding is multiplereflections which refer to the reflections at various surfacesor interfaces in the shield [1] This mechanism requires

Hindawi Publishing CorporationJournal of PolymersVolume 2014 Article ID 193058 7 pageshttpdxdoiorg1011552014193058

2 Journal of Polymers

the presence of a large interfacial area and porous structureAn example of a shield with a large surface area is conductingcomposite material containing filler foamed composites andhoneycomb structures [3]

Interestingly the properties of such composites are highlydependent on nature and concentration constituent phasesCarbon based materials (carbon black (CB) graphite acti-vated carbon (AC) fullerenes carbon nanofibers (CNFs)cabon nanotubes (CNTs) and recently graphene) are attrac-tive choice as a filler due to good electricalthermal con-ductivity low density excellent corrosion resistance andreinforcing capability [1 3 7 9 10 12 15ndash21] ParticularlyAC with high electrical conductivity and large surface areais an economical alternative Similarly acrylics are extremelypopular matrix materials due to low cost solutionthermalprocessability high filler reception capacity and ability ofacrylic resins (AR) to form hard abrasion resistant andmechanically strongtough impermeable coatings [22ndash24]

Herein we have synthesized porous and electrically con-ducting ACAR composites by solvent assisted dispersionof 1ndash30wt AC particles within AR matrix The synthe-sized composites have been characterized by techniquessuch as XRD Raman spectroscopy and scanning electronmicroscopy The dielectric and EMI shielding measurementswere also performedThese porous compositions containingelectrically conducting filler are expected to display goodEMI shielding performance

2 Materials and Method

Acrylic resin (AR was procured from Pidilite Industries Lim-ited India) xylene (Rankem India) and activated charcoal(AC Merck) were used as received Formation of ACARcomposites involves the preparation of separate dispersionand dissolution of AC and AR in xylene using magnetic stir-rer (REMI 5MLH) followed by their mixing and continuedstirring till the formation of viscous syrup This syrup waspoured into a Petri dish and allowed to dry at 50ndash60∘C toobtain filmsheet of composite In a typical synthesis 14 g ofAR was dissolved in 20mL of xylene and a known amountof AC powder was added into it to obtain composites withdifferent wt namely 1 3 5 10 20 and 30wt

3 Measurement and Characterization

XRD patterns were recorded using Bruker-D8 advanceddiffractometer in the 2120579 range of 10ndash70∘ and using Cu K120572line as radiation source The morphological information wasrecorded using scanning electronmicroscope (SEM Leo 440UK) MicroRaman spectrometer (Lab RAM HR 800 HoribaJY) having 6328 nm laser source was used for recordingRaman spectra of these samples in 3500ndash400 cmminus1 regionThe laser beam was focused on the sample using confocalmicroscope with LWD times50 objective Shielding effectiveness(SE) measurements were performed by placing the samples(sim07 120583m thick) between a 101 GHz frequency microwavesource and a horn type antenna-detector system

20 40 60

(b)

Inte

nsity

(au

)

(c)

(d)

(e)

(f)

2120579 (deg)

(a)

Figure 1 X-ray diffraction patterns of (a) pure AR (b) 5wt (c)10 wt (d) 20wt (e) 30 and (f) pure AC

4 Results and Discussion

41 Structure Characterization Figure 1 shows the XRD pat-terns of pure AR and AC as well as their composites Thecharacteristic signatures of AR (Figure 1(a)) are located at2120579 values of sim16∘ and sim31∘ and 44∘ whereas ACrsquos signa-tures (Figure 1(f)) appear at 25∘ and 43∘ [24] The ACARcomposites give superimposed signatures of both phases(Figures 1(b) (c) (d) and (e)) with systematic shifting ofthe peak positions and relative change in the peak intensityParticularly the shifting of 2120579 = 1595∘ peak of AR towardslower angle indicates the interaction between the phases

42 Morphological Details The SEM image of blank AR film(Figure 2(a)) displays smooth and featureless morphologyHowever the incorporation of ACwithin theACmatrix leadsto disturbance of ARrsquos morphology and appearance of rough-porous microstructure of AC particles

As the AC content increases its signature evolves suchthat the composite with 30wt loading of AC clearly showsthe porous structures and channels (bright regions) made upof electrically conducting AC phase coated and infiltratedwith nonconducting AR matrix As these composites displayporous structure and electrically conducting in nature theyare expected to display good EMI shielding efficiency due toreflection absorption andmultiple reflection phenomena [1ndash5 9 12 13 18 25 26]

43 Raman Spectroscopy Raman spectra of carbon and itsconjugated analogues give two strong bands at sim1560 (G-band) and sim1360 cmminus1 (D-band) that are dominated by sp2(graphitic structure) and sp3 (defect structures) hybridizedcarbons respectively [27 28] Figure 3 shows that for pureAC G-band appears at 1582 cmminus1 which shifts to 1598 cmminus1

Journal of Polymers 3

(a) (b)

(c) (d)

(e) (f)

Figure 2 SEM images of (a) pure acrylic resin (b) 1 wt (c) 5 wt (d) 10wt (e) 20wt and (f) 30wt of AC

on increasing activated carbon percentage in the compos-ites Similarly a shift in the disorder band (D-band) from1304 cmminus1 (for AC) to 1320 cmminus1 (for 30wt AC containingcomposite) was observed [27] Such a shift in the G and Dbands on increasing the activated carbon concentration incomposites is attributed to the increase in electron-phononinteractions which blueshifts and sharpens the G peak andbroadens D band

44 Dielectric Constant or Permittivity Measurements Thestudy of dielectric constant as a function of temperature orfrequency is one of the most convenient and sensitive meth-ods of investigating the polarization and charge localization

effects It is well known that the polarization of a material iscontrolled by the electronic ionic and dipolar polarizationElectronic polarization occurs during a very short intervalof time (of the order of 10minus15 sec) and the process of ionicpolarization occurs in the range of 10minus13-10minus12 sec while thedipole polarization requires relatively longer time [1 5 9]In case of polar polymers the dielectric constant begins todrop after a certain critical frequency The dipole moleculescannot orient themselves in the lower temperature regionHowever as the temperature increases orientation of dipolesis facilitated and this increases the dielectric constant So inthis paper room temperature dielectric constant of ACARcomposites has been measured as a function of frequencyas shown in Figure 4 to understand the effect of filler


2000 1500 1000 500

Inte

nsity

(au

)

(a)

(b)

(c)

(d)

(e)

(f)

Wavenumber (cmminus1)

Figure 3 Raman spectra of (a) pure acrylic resin (b) 1 wt (c)5 wt (d) 10wt (e) 20wt and (f) 30wt of AC

40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100

(f)

Die

lect

ric co

nsta

nt

Frequency (MHz)

(a)(b) (c)

(d)

(e)

Figure 4 Dielectricmeasurement of (a) pure acrylic resin (b) 1 wt(c) 5 wt (d) 10wt and (e) 30wt of AC

concentration on polarization behaviour The results showthat at low frequencies the electric dipoles have sufficienttime to align with the field before the field changes itsdirection consequently the dielectric constant is high [1 29]However at higher frequencies dipoles fail to follow therapidly changing electric vector consequently the dielectricconstant value decreases

Further it can be seen (Figure 4) that the increase inAC concentration leads to systematic increase in the relativedielectric constant or permittivity (1205761015840) that is from sim5 forpure AC to sim79 for 30 AC based composites This canbe attributed to the increase in the space charge buildupdue to Maxwell-Wagner interfacial polarization [1 9 18 29]occurring as a consequence of large difference in the electrical

conductivity of AC (highly conducting) and AR (insulatingmatrix) It is important to highlight that good dielectricproperties and electrical conductivity values are essentialrequirements for displaying goodEMI shielding performance[1 8 9 30 31]

45 EMI Shielding Performance TheEMI shielding effective-ness (SE) of a material is the ability to attenuate EM radiationthat can be expressed in terms of ratio of incoming (incident)and outgoing (transmitted) power [1ndash3 6ndash9 12 15 18 29ndash31] The EMI attenuation offered by a shield may depend onthe three mechanisms reflection of the wave from the frontface of shield absorption of the wave as it passes throughthe shieldrsquos thickness and multiple reflections of the waves atvarious interfaces as shown in Figure 5 Therefore SE of EMIshielding materials is determined by three losses namelyreflection loss (SE

119877) absorption loss (SE

119860) and multiple

reflection losses (SE119872) and can be expressed as [1ndash3 9 18 27]

SE119879(dB) = (SE

119877+ SE119860+ SE119872) = 10 log

10(

119875

119879

119875

119868

)

= 20 log10(

119864

119879

119864

119868

) = 20 log10(

119867

119879

119867

119868

)

(1)

where 119875119868(119864119868or119867119868) and 119875

119879(119864119879or119867119879) are the power (electric

or magnetic field intensity) of incident and transmitted EMwaves respectively As the119875

119879is always less than119875

119868 therefore

SE is a negative quantity such that a shift towards morenegative value means increase in magnitude of 119878119864

119879 It is

important to note that the 119878119864119879can be expressed as [1 6 32 33]

SE119879(dB) = minus10log

10(

120590T16120596120576

1015840120583

1015840) minus 868119905(

120590

119879120596120583

1015840

2

)

(12)

(2)

where 1205761015840(1205831015840) and 12057610158401015840(12058310158401015840) represent real and imaginary partsof complex permittivity (permeability) respectively that canbe correlated with the total conductivity (120590

119879) as

120590

119879= (120590ac + 120590dc) = 120596120576119900120576

10158401015840 (3)

where 120590ac and 120590dc are frequency (119891 = 1205962120587) dependent (ac)and independent (dc) components of 120590

119879The first and second

terms in right-hand side of (2) represent attenuations dueto reflection and absorption respectively Equations (2) and(3) reveal that for moderately conducting and nonmagneticmaterials (1205831015840 sim 1 and 12058310158401015840 sim 0) both electrical conductivityand permittivity are important for enhancement of totalshielding effectiveness In the present system good dielectricand electric properties are expected to improve EMI shieldingperformance [1 3 34ndash36]

The EMI shielding plot (Figure 6) revealed that pureAR displays poor EMI shielding response with SE

119879value

of only minus24 dB However incorporation of AC phase leadsto increase in SE value which scales with AC concentrationsuch that composite containing 30 AC displays SE valueof minus36 dB It is important to point out that addition of ACleads to improvement in electrical conductivity as well as


(primary reflection) (primary transmission)

(secondary transmissions)(secondary reflections)

Absorbance (A)

Multiple internal

reflections (MIRs)

Residual field strength

Incident signal (EiHi)

Reflected signal (ErHr)

Rereflected signal (ErrHrr)

E120575 H120575

Skindepth 120575

Transmitted signal (Et Ht)

EiHi

Transmitted signal (EstHst)

(37 of EiHi) Distance from shielrsquos face t

Figure 5 Graphical representation of EMI shielding

0 5 10 15 20 25 30

EMI s

hiel

ding

effec

tiven

ess (

dB)

Filler content (wt)

(f)

(e)

(d)

(c)(b)

(a)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Figure 6 EMI shielding effectiveness of (a) pure AR and itscomposites containing (b) 1 wt (c) 5 wt (d) 10wt (e) 20wtand (f) 30wt of AC

permittivity which collectively contributes towards improvedantiradiation performance The above attenuation value isnear the total shielding value of minus30 dB for phase segregatedcomposites based on 066 vol [37] loading of reducedgraphene oxide in thermoplastic matrix However the use ofactivated charcoal (cheap porous and electrically conductingfiller) compared to other nanofillers (costly difficult toprocess due to agglomeration and dispersion issues andcommercially unviable) to obtain comparable EMI shieldingperformance (at lesser thickness) highlights the technolog-ical importance of our work It should also be noted thatthe regions where filler is present are electrically conduct-ing (therefore reflecting) whereas the acrylic containingregions are electrically insulating (therefore nonreflecting)These two regions form a kind of electromagnetically activepseudopore and also contribute towards multiple reflectionsNevertheless the high attenuation value in our case (ieblocking ofgt999of the incident electromagnetic radiation)demonstrates the technological potential of these compositesfor making EMI shields

5 Conclusion

ACAR composites containing up to 30wt AC have beensuccessfully prepared via a facile and scalable solutionblending approach The XRD patterns show superimposedsignatures of AC and AR with systematic variation in thepeak position and relative intensity This confirms the incor-poration of AC particles inside AR matrix and interactionsbetween phases thatwere also complemented byRaman spec-troscopy results The morphological investigations revealedthat incorporated AC particles regulate the compositersquos mor-phology and promote the formation of porous structure Thedielectric measurements revealed that pure AR displays lowrelative permittivity value (sim5) that increases with incorpo-ration of AC and becomes sim79 for 30wt AC containingcomposite which also displays EMI shielding effectivenessvalue of minus36 dBThis shielding value corresponds to blockageof gt999 of the incident electromagnetic radiation andsuggests that ACAR composites are promising material formaking efficient EMI shields

Conflict of Interests

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

References

[1] P Saini and M Arora ldquoMicrowave absorption and EMIshielding behavior of nanocomposites based on intrinsicallyconducting polymers graphene and carbon nanotubesrdquo inNewPolymers for Special Applications A De Souza Gomes EdA DeSouza Gomes Ed InTech 2012

[2] H W Ott Electromagnetic Compatibility Engineering JohnWiley amp Sons Hoboken NJ USA 2009

[3] P Saini ldquoElectrical properties and electromagnetic interferenceshielding response of electrically conducting thermosettingnanocompositesrdquo in Thermoset Nanocomposites V Mittal EdWiley-VCH Verlag GmbH amp Co KGaA Weinheim Germany2013

[4] L Olmedo P Hourquebie and F Jousse Handbook of OrganicConductive Molecules and Polymers vol 2 John Wiley amp SonsChichester UK 1997


[5] P Saini M Arora G Gupta B K Gupta V N Singh andV Choudhary ldquoHigh permittivity polyaniline-barium titanatenanocomposites with excellent electro-magnetic interferenceshielding responserdquo Nanoscale vol 5 pp 4330ndash4336 2013

[6] P Saini V Choudhary B P Singh R B Mathur and SK Dhawan ldquoEnhanced microwave absorption behavior ofpolyaniline-CNTpolystyrene blend in 124-180 GHz rangerdquoSynthetic Metals vol 161 no 15-16 pp 1522ndash1526 2011

[7] Y Yang M C Gupta K L Dudley and R W Lawrence ldquoCon-ductive carbon nanofiber-polymer foam structuresrdquo AdvancedMaterials vol 17 no 16 pp 1999ndash2003 2005

[8] N F Colaneri and L W Shacklette ldquoEMI shielding measure-ments of conductive polymer blendsrdquo IEEE Transactions onInstrumentation and Measurement vol 41 no 2 pp 291ndash2971992

[9] P Saini V Choudhary B P Singh R B Mathur andS K Dhawan ldquoPolyaniline-MWCNT nanocomposites formicrowave absorption and EMI shieldingrdquoMaterials Chemistryand Physics vol 113 no 2-3 pp 919ndash926 2009

[10] D D L Chung ldquoElectromagnetic interference shielding effec-tiveness of carbonmaterialsrdquoCarbon vol 39 no 2 pp 279ndash2852001

[11] SMAbbas A KDixit R Chatterjee andTCGoel ldquoComplexpermittivity and microwave absorption properties of BaTiO

3-

polyaniline compositerdquo Materials Science and Engineering Bvol 123 no 2 pp 167ndash171 2005

[12] D D L Chung ldquoMaterials for electromagnetic interferenceshieldingrdquo Journal of Materials Engineering and Performancevol 9 no 3 pp 350ndash354 2000

[13] P Saini V Choudhary N Vijayan and R K KotnalaldquoImproved electromagnetic interference shielding response ofpoly (aniline)-coated fabrics containing dielectric andmagneticnanoparticlesrdquo Journal of Physical Chemistry C vol 116 pp13403ndash13412 2012

[14] P Singh V K Babbar A Razdan S L Srivastava and R KPuri ldquoComplex permeability and permittivity and microwaveabsorption studies of Ca(CoTi)

119909Fe12minus2119909

O19hexaferrite compos-

ites in X-band microwave frequenciesrdquo Materials Science andEngineering B vol 67 no 3 pp 132ndash138 1999

[15] N Li Y Huang F Du et al ldquoElectromagnetic Interference(EMI) shielding of single-walled carbon nanotube epoxy com-positesrdquo Nano Letters vol 6 no 6 pp 1141ndash1145 2006

[16] P Saini and V Choudhary ldquoEnhanced electromagnetic inter-ference shielding effectiveness of polyaniline functionalizedcarbon nanotubes filled polystyrenerdquo Journal of NanoparticleResearch vol 15 article 1415 7 pages 2013

[17] S N Tripathi P Saini D Gupta and V Choudhary ldquoElectricaland mechanical properties of PMMAreduced graphene oxidenanocomposites prepared via in situ polymerizationrdquo Journal ofMaterial Science vol 48 pp 6223ndash6232 2013

[18] P Saini V Choudhary K N Sood and S K DhawanldquoElectromagnetic interference shielding behavior of polyani-linegraphite composites prepared by in situ emulsion pathwayrdquoJournal of Applied Polymer Science vol 113 no 5 pp 3146ndash31552009

[19] J Wu and D D L Chung ldquoIncreasing the electromagneticinterference shielding effectiveness of carbon fiber polymer-matrix composite by using activated carbon fibersrdquoCarbon vol40 no 3 pp 445ndash447 2002

[20] E Varrla S Venkataraman and R Sundara ldquoFunctionalizedgraphene-PVDF foam composites for EMI shieldingrdquo Macro-molecular Materials and Engineering vol 296 no 10 pp 894ndash898 2011

[21] Y Yang M C Gupta K L Dudley and R W LawrenceldquoNovel carbon nanotubemdashpolystyrene foam composites forelectromagnetic interference shieldingrdquoNano Letters vol 5 no11 pp 2131ndash2134 2005

[22] P K Vallittu ldquoFlexural properties of acrylic resin polymersreinforced with unidirectional and woven glass fibersrdquo TheJournal of Prosthetic Dentistry vol 81 no 3 pp 318ndash326 1999

[23] H-S Park I-M Yang J-P Wu et al ldquoSynthesis of silicone-acrylic resins and their applications to superweatherable coat-ingsrdquo Journal of Applied Polymer Science vol 81 no 7 pp 1614ndash1623 2001

[24] S D Khan M Arora C Puri M A Wahab and P SainildquoSynthesis and characterization of acrylic resinactivated car-bon compositesrdquo Indian Journal of Pure andApplied Physics vol52 no 4 pp 251ndash254 2014

[25] L Olmedo P Hourquebie and F Jousse ldquoMicrowave propertiesof conductive polymersrdquo Synthetic Metals vol 69 no 1-3 pp205ndash208 1995

[26] C K Das and A Mandal ldquoMicrowave absorbing properties ofDBSA-doped polyanilineBaTiO

3-Ni05Zn05Fe2O4rdquo Journal of

Materials Science Research vol 1 no 1 pp 45ndash53 2012[27] P Saini and V Choudhary ldquoElectrostatic charge dissipation and

electro-magnetic interference shielding response of polyanilinebased conducting fabricsrdquo Indian Journal of Pure and AppliedPhysics vol 51 pp 112ndash117 2013

[28] R Kumar S R Dhakate P Saini and R B Mathur ldquoImprovedelectromagnetic interference shielding effectiveness of lightweight carbon foam by ferrocene accumulationrdquoRSCAdvancesvol 3 no 13 pp 4145ndash4151 2013

[29] P Saini andM Arora ldquoFormationmechanism electronic prop-erties andmicrowave shielding by nano-structured polyanilinesprepared by template free route using surfactant dopantsrdquoJournal of Materials Chemistry A vol 1 no 31 pp 8926ndash89342013

[30] J Joo and A J Epstein ldquoElectromagnetic radiation shielding byintrinsically conducting polymersrdquo Applied Physics Letters vol65 no 18 pp 2278ndash2280 1994

[31] LW Shacklette N F Colaneri V G Kulkarni and BWesslingldquoEMI Shielding of intrinsically conductive polymersrdquo Journal ofVinyl and Additive Technology vol 14 no 2 pp 118ndash122 1992

[32] P Saini V Choudhary and S K Dhawan ldquoElectrical propertiesand EMI shielding behavior of highly thermally stable polyani-linecolloidal graphite compositesrdquo Polymers for AdvancedTechnologies vol 20 no 4 pp 355ndash361 2009

[33] P Saini and V Choudhary ldquoStructural details electrical prop-erties and electromagnetic interference shielding response ofprocessable copolymers of anilinerdquo Journal of Materials Sciencevol 48 no 2 pp 797ndash804 2013

[34] Y K Hong C Y Lee C K Jeong D E Lee K Kim and JJoo ldquoMethod and apparatus to measure electromagnetic inter-ference shielding efficiency and its shielding characteristics inbroadband frequency rangesrdquo Review of Scientific Instrumentsvol 74 no 2 pp 1098ndash1102 2003

[35] H-B Zhang Q YanW-G Zheng Z He and Z-Z Yu ldquoToughgraphene-polymer microcellular foams for electromagneticinterference shieldingrdquo ACS Applied Materials and Interfacesvol 3 no 3 pp 918ndash924 2011


[36] Y Yang M C Gupta K L Dudley and R W LawrenceldquoA comparative study of EMI shielding properties of carbonnanofiber and multi-walled carbon nanotube filled polymercompositesrdquo Journal of Nanoscience and Nanotechnology vol 5no 6 pp 927ndash931 2005

[37] D-X Yan H Pang L Xu et al ldquoElectromagnetic interferenceshielding of segregated polymer composite with an ultralowloading of in situ thermally reduced graphene oxiderdquoNanotech-nology vol 25 no 14 Article ID 145705 2014

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



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CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


the presence of a large interfacial area and porous structureAn example of a shield with a large surface area is conductingcomposite material containing filler foamed composites andhoneycomb structures [3]

Interestingly the properties of such composites are highlydependent on nature and concentration constituent phasesCarbon based materials (carbon black (CB) graphite acti-vated carbon (AC) fullerenes carbon nanofibers (CNFs)cabon nanotubes (CNTs) and recently graphene) are attrac-tive choice as a filler due to good electricalthermal con-ductivity low density excellent corrosion resistance andreinforcing capability [1 3 7 9 10 12 15ndash21] ParticularlyAC with high electrical conductivity and large surface areais an economical alternative Similarly acrylics are extremelypopular matrix materials due to low cost solutionthermalprocessability high filler reception capacity and ability ofacrylic resins (AR) to form hard abrasion resistant andmechanically strongtough impermeable coatings [22ndash24]

Herein we have synthesized porous and electrically con-ducting ACAR composites by solvent assisted dispersionof 1ndash30wt AC particles within AR matrix The synthe-sized composites have been characterized by techniquessuch as XRD Raman spectroscopy and scanning electronmicroscopy The dielectric and EMI shielding measurementswere also performedThese porous compositions containingelectrically conducting filler are expected to display goodEMI shielding performance

2 Materials and Method

Acrylic resin (AR was procured from Pidilite Industries Lim-ited India) xylene (Rankem India) and activated charcoal(AC Merck) were used as received Formation of ACARcomposites involves the preparation of separate dispersionand dissolution of AC and AR in xylene using magnetic stir-rer (REMI 5MLH) followed by their mixing and continuedstirring till the formation of viscous syrup This syrup waspoured into a Petri dish and allowed to dry at 50ndash60∘C toobtain filmsheet of composite In a typical synthesis 14 g ofAR was dissolved in 20mL of xylene and a known amountof AC powder was added into it to obtain composites withdifferent wt namely 1 3 5 10 20 and 30wt

3 Measurement and Characterization

XRD patterns were recorded using Bruker-D8 advanceddiffractometer in the 2120579 range of 10ndash70∘ and using Cu K120572line as radiation source The morphological information wasrecorded using scanning electronmicroscope (SEM Leo 440UK) MicroRaman spectrometer (Lab RAM HR 800 HoribaJY) having 6328 nm laser source was used for recordingRaman spectra of these samples in 3500ndash400 cmminus1 regionThe laser beam was focused on the sample using confocalmicroscope with LWD times50 objective Shielding effectiveness(SE) measurements were performed by placing the samples(sim07 120583m thick) between a 101 GHz frequency microwavesource and a horn type antenna-detector system

20 40 60

(b)

Inte

nsity

(au

)

(c)

(d)

(e)

(f)

2120579 (deg)

(a)

Figure 1 X-ray diffraction patterns of (a) pure AR (b) 5wt (c)10 wt (d) 20wt (e) 30 and (f) pure AC

4 Results and Discussion

41 Structure Characterization Figure 1 shows the XRD pat-terns of pure AR and AC as well as their composites Thecharacteristic signatures of AR (Figure 1(a)) are located at2120579 values of sim16∘ and sim31∘ and 44∘ whereas ACrsquos signa-tures (Figure 1(f)) appear at 25∘ and 43∘ [24] The ACARcomposites give superimposed signatures of both phases(Figures 1(b) (c) (d) and (e)) with systematic shifting ofthe peak positions and relative change in the peak intensityParticularly the shifting of 2120579 = 1595∘ peak of AR towardslower angle indicates the interaction between the phases

42 Morphological Details The SEM image of blank AR film(Figure 2(a)) displays smooth and featureless morphologyHowever the incorporation of ACwithin theACmatrix leadsto disturbance of ARrsquos morphology and appearance of rough-porous microstructure of AC particles

As the AC content increases its signature evolves suchthat the composite with 30wt loading of AC clearly showsthe porous structures and channels (bright regions) made upof electrically conducting AC phase coated and infiltratedwith nonconducting AR matrix As these composites displayporous structure and electrically conducting in nature theyare expected to display good EMI shielding efficiency due toreflection absorption andmultiple reflection phenomena [1ndash5 9 12 13 18 25 26]

43 Raman Spectroscopy Raman spectra of carbon and itsconjugated analogues give two strong bands at sim1560 (G-band) and sim1360 cmminus1 (D-band) that are dominated by sp2(graphitic structure) and sp3 (defect structures) hybridizedcarbons respectively [27 28] Figure 3 shows that for pureAC G-band appears at 1582 cmminus1 which shifts to 1598 cmminus1


(a) (b)

(c) (d)

(e) (f)






2000 1500 1000 500

Inte

nsity

(au

)

(a)

(b)

(c)

(d)

(e)

(f)



40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100

(f)

Die

lect

ric co

nsta

nt

Frequency (MHz)

(a)(b) (c)

(d)

(e)









SE119879(dB) = (SE

119877+ SE119860+ SE119872) = 10 log

10(

119875

119879

119875

119868

)

= 20 log10(

119864

119879

119864

119868

) = 20 log10(

119867

119879

119867

119868

)

(1)

where 119875119868(119864119868or119867119868) and 119875




119868 therefore


119879 It is



10(

120590T16120596120576

1015840120583

1015840) minus 868119905(

120590

119879120596120583

1015840

2

)

(12)

(2)


119879) as

120590

119879= (120590ac + 120590dc) = 120596120576119900120576

10158401015840 (3)





119879value





Absorbance (A)

Multiple internal

reflections (MIRs)





E120575 H120575

Skindepth 120575


EiHi




0 5 10 15 20 25 30

EMI s

hiel

ding

effec

tiven

ess (

dB)

Filler content (wt)

(f)

(e)

(d)

(c)(b)

(a)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40



5 Conclusion




References













3-





119909Fe12minus2119909




































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)

(e) (f)






2000 1500 1000 500

Inte

nsity

(au

)

(a)

(b)

(c)

(d)

(e)

(f)



40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100

(f)

Die

lect

ric co

nsta

nt

Frequency (MHz)

(a)(b) (c)

(d)

(e)









SE119879(dB) = (SE

119877+ SE119860+ SE119872) = 10 log

10(

119875

119879

119875

119868

)

= 20 log10(

119864

119879

119864

119868

) = 20 log10(

119867

119879

119867

119868

)

(1)

where 119875119868(119864119868or119867119868) and 119875




119868 therefore


119879 It is



10(

120590T16120596120576

1015840120583

1015840) minus 868119905(

120590

119879120596120583

1015840

2

)

(12)

(2)


119879) as

120590

119879= (120590ac + 120590dc) = 120596120576119900120576

10158401015840 (3)





119879value





Absorbance (A)

Multiple internal

reflections (MIRs)





E120575 H120575

Skindepth 120575


EiHi




0 5 10 15 20 25 30

EMI s

hiel

ding

effec

tiven

ess (

dB)

Filler content (wt)

(f)

(e)

(d)

(c)(b)

(a)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40



5 Conclusion




References













3-





119909Fe12minus2119909




































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




2000 1500 1000 500

Inte

nsity

(au

)

(a)

(b)

(c)

(d)

(e)

(f)



40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100

(f)

Die

lect

ric co

nsta

nt

Frequency (MHz)

(a)(b) (c)

(d)

(e)









SE119879(dB) = (SE

119877+ SE119860+ SE119872) = 10 log

10(

119875

119879

119875

119868

)

= 20 log10(

119864

119879

119864

119868

) = 20 log10(

119867

119879

119867

119868

)

(1)

where 119875119868(119864119868or119867119868) and 119875




119868 therefore


119879 It is



10(

120590T16120596120576

1015840120583

1015840) minus 868119905(

120590

119879120596120583

1015840

2

)

(12)

(2)


119879) as

120590

119879= (120590ac + 120590dc) = 120596120576119900120576

10158401015840 (3)





119879value





Absorbance (A)

Multiple internal

reflections (MIRs)





E120575 H120575

Skindepth 120575


EiHi




0 5 10 15 20 25 30

EMI s

hiel

ding

effec

tiven

ess (

dB)

Filler content (wt)

(f)

(e)

(d)

(c)(b)

(a)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40



5 Conclusion




References













3-





119909Fe12minus2119909




































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Absorbance (A)

Multiple internal

reflections (MIRs)





E120575 H120575

Skindepth 120575


EiHi




0 5 10 15 20 25 30

EMI s

hiel

ding

effec

tiven

ess (

dB)

Filler content (wt)

(f)

(e)

(d)

(c)(b)

(a)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40



5 Conclusion




References













3-





119909Fe12minus2119909




































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











3-





119909Fe12minus2119909




































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



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