Analysis of water sorption and thermal conductivity of expanded polystyrene insulation materials

Analysisofwatersorptionandthermalconductivityofexpandedpolystyreneinsulationmaterials

´kosLakatosandFerencKalma´rA

BuildingServ.Eng.Res.Technol.

34(4)407–416

!TheCharteredInstitutionofBuildingServicesEngineers2012

DOI:10.1177/0143624412462043bse.sagepub.com

Abstract

Thisarticlepresentstheresultsofwatersorptionpropertiesinvestigationandthermalconductivitymeasurementsofexpandedpolystyrenethermalinsulationmaterialswithdifferentmassdensities.ThesorptionbehaviouroftheexpandedpolystyrenematerialswasachievedinaClimacell111typeclimaticchamber,afterdryinginaVenticell111typedesiccatorapparatus.Therelativehumidityvariedfrom25%to90%at293Kfor240min.ThethermalconductivityofeachsamplewasdeterminedusingaHolometrix2000(HLS)heatflowmeter.Inthisarticle,thesorptionisotherms,sorptionkinetics,thermalconductiv-itiesandthepredictionofchangesinfunctionofwatercontentoffourpureexpandedpolystyrene(30,100,150,200andgrey)slabswithdifferentdensities(14,17.5,23.7and27.5kg/m3)andoneexpandedpolystyrenemixedwithgraphitearegiven(greyexpandedpolystyrene).

Practicalapplication:Thethermalconductivityaswellasthemoisturecontentarekeythermaltrans-portpropertiesofbuildingmaterials.Theroleofinsulatingmaterialsinthebuildingenergyandmoisturebalanceismoresignificantwhencomparedwiththeothermaterialsofthebuildingstructures.Thelaboratorymeasurementsofthesevaluesoftheinsulatingmaterialsareveryimportanteitherforthemanufacturersorthecontractors.Theavailablebibliographicdataforthesematerialsarestronglyincom-pleteandsomewhereoutofdate.

Keywords

Polystyrene,thermalconductivity,sorptionisotherm

Introduction

IntheEuropeanUnion(EU),buildingsaccountfora20–40%ofthetotalfinalenergyconsump-tion.1Becausenooneofthememberstatesisindependentfromenergypointofview,inthebuildingsector,themaingoalsaretheincreaseofenergyefficiencyandutilizationofrenewableenergysources.Thisispartofthe20-20-20EU

DepartmentofBuildingServicesandBuildingEngineering,FacultyofEngineering,UniversityofDebrecen,Debrecen,Hungary

Correspondingauthor:

´kosLakatos,DepartmentofBuildingServicesandBuildingA

Engineering,FacultyofEngineering,UniversityofDebrecen,H-4028Debrecen,Hungary.Email:alakatos@eng.unideb.hu

408JournalofBuildingServicesEngineeringResearch&Technology34(4)

target.Tofulfilthefixedgoals,severalDirectiveswereprepared.OneoftheDirectivesisthe2002/91/ECDirectivedealingwithenergyperformanceofbuildings.2ThisDirectivein2010wasrevisedandadoptedas2010/31/EUDirective.3AccordingtothisDirectiveasof31December2020,newbuild-ingsintheEUwillhavetoconsume‘nearlyzero’energyandtheusedenergywillbe‘toaverylargeextent’fromrenewablesources.Publicauthoritiesthatownoroccupyanewbuildingshouldsetanexamplebybuilding,buyingorrentingsuch‘nearlyzeroenergybuilding’asof31December2018.Inthiscon-text,properinsulationofbuildingsenvelopeisoneoftheleadingchallengesofthebuildingindustry.TheEuropeanmarketofinsulationmaterialsischaracterizedbythedominationoftwogroupsofproducts:inorganicfibrousmaterialsandorganicfoamymaterials.4InmostEuropeancountries,becauseofwellela-boratedtechnologies,polystyrene(PS)istheleadingmaterialusedforadditionalinsulationofexistingbuildings.Becauseofrelativelyhighinvestmentcostsandspecialtechnologyneeded,mineralwoolisusedespeciallyatnewbuild-ings.Polyurethane(PU)isusedmostlyatpre-fabricatedwallpanelsandroofs.Testsrelatedtoitsageingweredoneindifferentresearchinstitutions.5Theanalysisofthermalpropertiesofcommoninsulationmaterialswasdoneandpresentedindifferentpapers.6Thepay-backtimeandtheoptimumthicknessofusedinsu-lationmaterialwasanalysedbydifferentauthors.Theenergyanalysisofoptimalwallinsulationthicknesswasdone7andacorrel-ationbetweenthermalconductivityandthethicknessofselectedinsulationmaterialsforbuildingwallshasbeenanalysed.8Therearecaseswhentheoptimizationisbasedonthelifecyclecostanalysis.Someauthorsuseddif-ferentfuelsasprimaryenergycarriertoobtaintheoptimalthickness,9otherspreparedgeneral-izedchartsforselectingtheoptimuminsulationthicknessasafunctionofdegreedaysandwallthermalresistance.10Thermalpropertiesofmostusedmaterialsareveryimportanttobe

knowntoperformcorrectcalculationsrelatedtoheatlossthroughbuildingenvelope.ThethermaltransportinPSandPUfoaminsula-tionswithspecialemphasisontheradiativetransferiswelldescribed.11TheeffectofmolecularweightdistributiononthephysicalpropertiesofPSwasanalysedfewdecadesago,butbecauseofitsincidence,thephysicalpropertiesofPSwereanalysed,especiallytakingintoaccounttheageingwhichcanleadtovariationintimeoftheseproperties.12,13ThepropertiesofPS/graphitenanocompositeswereanalysedandtheresearchshowsthatduetotheinterfacialinteractionbetweenthegraphitenanolayersandthepolymer,thecompositesexhibithigherglasstransitiontemperatureandhigherthermalstabilitywhencomparedtoPS.14BecausetheflammabilityproblemsofPS,somestudiesrelatingtoflammabilityofPS-layeredsilicate(clay)nanocompositeswerecar-riedout.15Nevertheless,inordertodeterminecorrectlytheheatlossthroughabuildingelem-ent,theheatconductivityvariationofinsula-tionmaterialshouldbeknownindifferentenvironmentalconditions.Humiditycontenthasanimportantinfluenceonthermalconduct-ivityofPSwhichshouldbetakenintoaccountwhenbuildingsareinsulatedwiththismaterial.Hungarianstandard(MSZ-04-140-2:1991,powerengineeringdimensioningcalculusesofbuildingsandbuildingenvelopestructures)containssomediagramsrelatedtovapourabsorptionofPSbutourresearchdemonstratesthatthesediagramsshouldnotbeusedhence-forthbecausethereareimportantdifferencesbetweenstandardandmeasuredvalues.Thisstandardprovidesacomprehensivedescriptionontheconservationofthebuildingstructures,describesthehealthcareofthepeoplelivingandworkinginthebuildings,furthermoreregularizesthecalculationsandsizingmethodsofthethermalcategoriesofbuildings.

Materialandmethods

Boththesorptionandthethermalconductivitymeasurementswerecarriedoutafterdryingthe

LakatosandKalma´rsamplesinaVenticelldryinginstrument.With

thisdevice,materialscanbedriedsettingdiffer-entairtemperatures(upto523K).Itworkswithhotaircirculationusinganinbuiltventilator.16Forthesorptionmeasurements,threesampleswith8Â8Â5cm3geometrieswerepreparedfromtheoriginalpiecestoperformthemeasure-mentsonthreespecimensfromthesamemater-ial.Theresultswereobtainedbyaveragingofthreemeasurements.BeforetreatingthesamplesintheClimacellclimaticchamber,samplesweredriedtochangelessweightat343Kundernormalatmosphericpressure(105Pa)atalltimes.ThistemperaturewaschosenbecauseitisfairlyunderthemeltingpointofthePS(about373K)andduringthedehydratingpro-cessatthistemperature,thematerialdoesnotsufferlossesinitsphysicalandchemicalproper-ties.Todeterminethesorptioncurves(moisturecontentofmaterialinfunctionofrelativehumidity(RH%)ofairat293K),thesampleswerekeptintheCLCchamberunder25%,50%,63%,76%and90%RHfor240min.Thewater/moisturecontent(!(%))ofasolidmaterialcanbecalculatedfromequation(1)

!¼

mwÀmd

mð1Þ

d

wheremdandmwarethemassofthedriedandthedampedsamples,respectively.

FormeasuringthethermalconductivityofeachPSsamples,Lambda2000heatflowmeter(HFM)wasused.ThisequipmentisdesignedtodeterminethethermalconductivityofinsulationmaterialsinaccordancewithstandardASTMC518andISO8301protocols.Asamplewith30Â30Â5cm3geometryisplacedinthetestsec-tionbetweentwoplateswhicharemaintainedatdifferenttemperatures(T1¼285KandT2¼295K,withTmean¼290K)duringthetest.Afterachievingthermalequilibriumandestab-lishingauniformtemperaturegradientthrough-outthesample,thermalconductivityisdetermined.Todeterminethethermalconduct-ivityofasample,threeindependent

409

measurementswerecarriedout.Thethermalcon-ductivityofanalysedmaterialwasthemeanvalueofthethreemeasuredresults.

ForunderstandingthemeasurementmethodofHolometrixLambdaequipment,thefollow-ingcommentsareindispensable.Themagnitudeoftheheatflow(q)dependsonseveralfactors:a.thermalconductivityofsamples(󰀂¼k);b.thethicknessofthespecimen(Áx);

c.thetemperaturedifferenceacrossthespeci-men(ÁT);and

d.areathroughwhichtheheatflows(A).TheFourierheatflowequation(equation(2))givestherelationshipbetweentheseparam-eterswhenthetestsectionreachesthermalequilibrium

q¼󰀂AÁTÁx

ð2Þ

Oneortwoheatflowtransducersmeasuretheheatflowthroughthespecimen.Thesignalofaheatflowtransducer(involts(V))ispropor-tionaltotheheatflowthroughthetransducer.IntheLambda2000HFMinstrument,theareaoftheheatflowtransducerrepresentstheareathroughwhichtheheatconductionisrealizedanditisthesameforallspecimens;therefore,theheatflowwillbe(equation(3))

q¼NV

ð3Þ

whereNisthecalibrationfactorthatrelatesthevoltagesignaloftheheatflowtransducertotheheatfluxthroughthespecimen.Forcalibrationofapparatus,afibrousglassboardstandardsamplewith󰀂¼0.05W/mKwasused.Usingequations(2)and(3),theheatconductivitycanbedetermined(equation(4))

󰀂¼k¼N

VÁxÁT

ð4Þ

410JournalofBuildingServicesEngineeringResearch&Technology34(4)

Table1.ThemoisturecontentofthedifferentPSsamplesafterdampening.

Watersorptionafter6hat293K

Density(kg/m3)ColourcodeRH(%)90766350250

14Blue

17.5Yellow

23.7Black1

27.5Black2

13.62Grey

Moisturecontent(%)1.050.940.920.10.880

0.980.860.850.840.7930

0.870.670.650.620.60

0.690.570.540.530.50

1.161.1161.091.051.010

PS:polystyrene;RH:relativehumidity.

Thetermreproducibilityindicatesthevari-ationofthetestresultsofonespecimenfromtesttotest.Factorssuchashowwellthespeci-menmakescontactwiththeplatesandthetem-peraturestabilityaffectthereproducibility.Ifthethermalresistanceofthetestspecimeniscommensurablewiththereferencestandard’sÆ5%orbetteraccuracycanbeobtained.

Resultsanddiscussion

SorptionisothermsaswellasthermalpropertiesofexpandedPS(EPS)slabswereinvestigated.Theresultsofmeasurementsaredividedintotwogroups.Atfirst,thesorptionbehaviourandwateruptakingpropertiesareintroduceddependingonthematerialdensity.Thereafter,thechangeofthethermalconductivitywithincreasingmassdensitywillbereported.TheresultsgrouparecomparedtorelevantHungarian(MSZ-04-140-2:1991)andinter-national(EN13163)standardseither.

Sorptionversusmassdensity

FoammaterialsmadeofPScontainconsider-ablequantityofairclosedintocells.Thenumberandsizeofcellsareincreasingatlowermaterialdensities.Thesebubblescanbefilledupwithwatersothatsomethermalpropertiesof

thematerialcansufferinadequatechanges.Thisisthemainreasonoftheimportanceofthesorptionmeasurementsofmaterials.InTable1,theresultsofthesorptionmeasure-mentscarriedoutat293Kfor6harepresented.Figure1(a)indicatestheso-calledsorptioniso-thermcurves,whichwerecreatedfromthedataofTable1.TheincreasingmoisturecontentdependingontheincreasingRHcanbeseenforeachEPSsample.Theblue(EPS30),yellow(EPS100),black1(EPS150)andblack2(EPS200)labelsarethecoloursignsofpureEPSmaterialsandbelongstothe14,17.5,23.7and27.5kg/m3densities,respectively.Furthermore,thegreylabelwith13.62kg/m3massdensitybelongstothemixedEPS–graphitesamples.InFigure1(a),therisingmoisturecon-tentdependingonthedensitycanbeseen.ComparedtoFigure1(b)(takenfromHungarianstandard,MSZ-04-140-2:1991),wherethesorptiondataoftheEPSsampleswithdifferentdensitiesareshown,itcanbeobservedthatthereareimportantdifferences.InFigure1(a),from0%to30%,agreatjumpinthemoisturecurvescanbeseenbecauseoftheinitialmonoandmultilayerabsorptionpro-cesses,buttheseriesdonotshowremarkablechangesbetween50%and80%.Over80%RH,thegrowthinthecurvesisobservable.Atthispoint,thecapillarycondensationtakes

´rLakatosandKalma411

(a)

1,2

(b)

Moisture content (%)Blue

YellowBlack1Black2Grey

2

Moisture content (%)0,61

16 kg/m25 kg/m

3

33

0,0049 kg/m

04080

04080

Relative humidity (%)Relative humidity (%)

Figure1.Thesorptionisothermcurvescreatedfromthe(a)measurementresults,forallEPSsamplesand(b)Hungarianstandard,forEPSsamples,withdifferentdensities.EPS:expandedpolystyrene.

place,incontrasttoFigure1(b),wherethewatercontentisrisingcontinuously.ThemoisturecontentvalueisdependentonthedensityofEPSslabs:thelowerthedensityisthehigheristhemoisturecontent.Suchdependencycanbefoundinotherpapers.17–20InFigure2(a)and(b),themoisturecontentsatgivenrelativehumidities(25–90%)areillustratedinthefunc-tionofmassdensities.Theobtainedvaluesareinaccordancewiththeresultspresentedinpre-viousworks,18,21–24namely,thatthewatercon-tentisincreasingifthedensityoftheEPSisdecreasing.Inthesereferences,thewaterabsorptionmeasurementswerecarriedoutbyimmersionsforseveraldays.Ourexperimentsweredoneusingtheabovepresentedclimaticchambermethod(waterabsorptionfromair).Figure2(a)belongstothemeasurementresults,whileFigure2(b)istakenfromtheHungarianstandard04140:2-1991.Themeasurementresultsshownearlylineardecreaseofthewatercontentwiththedensity.FromthegraphinFigure2(b),takenfromtheHungarianstand-ard,suchdependencecannotbeseen.Toevalu-atethemassdensitydependenceofthemoisturecontentatanoptionalRHoftheair,thelog–logplotofFigure2(a)wascreated(Figure3).Theslopeoftheeachlog(moisturecontent)–log(density)functiongivesthek-value,thedensitydependenceexponent.Thesevaluescanbe

foundinTable2,wherethepartialpressuresareindicatedinsteadoftherelativehumidities.Thesek-valuesarenegatives,representingthefallofthedensitydependence.Thedecreasingexponentsareplottedinfunctionofpartialpres-sure(Figure4).AfitofasimpleexponentialfunctionwasachievedonthedataofFigure4.Thisfittingprocedureresultedinasimpleequa-tionbetweenk(thedecreaseofthemoisturecon-tentinfunctionofdensity)andthepartialpressure(Pp,calculatedfromRH),withA1asaconstant(equation(5))

󰀂󰀃Pp

k¼ÀA1exp

3

ð5Þ

Furthermore,thesek-valuesdenotethedens-itydependenceofthemoistureabsorptioncap-ability.ForhighRH,thedependenceofthemoisturecontentfromthedensityisshowingsquareroot,forlowRH%thisdependencyisnearlylinear.

Thermalconductivityversusmassdensity

Figure5representsthecomparisonofthermalconductivitymeasurementresultscarriedoutwithHLSequipment,withthevaluesofthemanufacturerandtheupdatedHungarian

412JournalofBuildingServicesEngineeringResearch&Technology34(4)

(a)

Moisture content (%)0,9

(b)

Moisture content (%)2,22,01,81,61,41,21,00,80,60,40,2

25%50%63%76%90%

0,6

25%50%63%76%90%

18

24

30

122040

Density (kg/m3)Density (kg/m3)

Figure2.(a)ThemeasuredmoisturecontentsatthegivenRH%asafunctionofmassdensitiesand(b)themoisturecontentstakenfromtheHungarianstandardatthegivenRH%asafunctionofmassdensities.RH:relativehumidity.

0,0Lg of Moisture ContentTable2.Thedensitydependenceexpo-nents(k)infunctionofpartialpressure.k

lg90lg76lg63lg50lg25

–0,1

Partialpressureat293K(mbar)5.911.814.86817.93621.24

–0,2

–0,3

1,2

1.41,3

Lg of Density

À0.84À0.81À0.8À0.75À0.56

Figure3.Thelogarithmofmeasuredmoisturecon-tentsatthegivenRH%asafunctionofthelogarithmofmassdensities.

RH:relativehumidity.

(MSZ-04-140-2:1991)andinternational(MSZEN13163)standards,furthermorewiththeresultspresentedinaBuildingPhysicsHandbook.25Oneconspicuousdifferencecanbeobserved.Thethermalconductivitiesaredecreasingwithincreasingdensity,butthevaluesfromtheHungarianstandardaregoingagainstwiththeothers(seethedashedlineonFigure5).ThethermalconductanceoftheEPSslabsisdefinedbyfourphenomena:the

conductionthroughthewallsofthecells,theconductanceandconvectionoftheairlockedinthecells,furthermoretheradiationinsidetheslabs.Themainfactorsforthechangeofthethermalconductivityvaluearetheconduc-tionofthesolidpartandtheroleoftheair.Withdecreasingdensity,thenumberandthesizeoftheairporesareincreasing.Theconvec-tionoftheairisamplified,however,theconduc-tionofthewallsarereducedbecausethedensityrateofthesolidconstituentisdecreased.IfthedensityofEPSslabsisincreasing,thesizeandnumberoftheairbubblesaredecreasing,sotheeffectoftheconductanceandconvectionofairisnearlynegligiblecomparedtothesolidconduct-ance.Wesupposethatthereisacriticalnumber

LakatosandKalma´r0,9

s0,8

tnenopx0,7

e citeData

niK0,6

ExpDec 1 of A

0,5

71421

Partial pressure (mbar)

Figure4.TheslopesofthelinesrepresentedinFigure3,asafunctionofpartialpressure.

)KMeasured (W/mK)mLambda cp/W0,049

Lambda oszt( Lambda 1991HSytLambda 13163en

ivitcu0,042

dnoc lamr0,035

ehT121824

Density (kg/m3)

Figure5.Thethermalconductivityasafunctionofmassdensity.

and/oracriticalsizeoftheporeswheretheheatconductivityversusdensityfunctionturnsback.Thisiscausedbythehigherrateofthesolidconstituentalongwiththeraisingofthecon-ductanceofthesolidcells.So,itshouldbeaminimum(greaterthanzero)valueofthether-malconductivityoftheEPSslabs.Ourresults,namelythatthedecreasingdensityincreasesthethermalconductivity,agreewiththeconclusionsofotherresearcherspublishedinpreviousworks.26–29413

Thermalconductivityversuswatercontent

Asmentionedabove,theairasafillingofthecellshasagreatinfluenceontheconductivityoftheEPSmaterials.Thermalconductivitycanrisesignificantlyifwaterinfiltratesintothecellsanddisplacesthegasmolecules.Usingthedatapre-sentedinTable1andasimpleequation(equa-tion(6))takenfromIvan,29thermalconductivities(󰀂wet)arecalculatedinfunctionofwatercontent(!).Inequation(6),󰀂0istheinitialvalueofthermalconductivity(afterdrying)andz¼2forplasticfoams.TheseroughestimationsarecollectedinTable3

󰀂󰀄!z󰀅

wet¼󰀂0Â1þ100ð6Þ

Theexpectedthermalconductivitiesaredepictedinfunctionofwatercontent,aswellasthelinearfitanalysisofthesefunctionsareshowninFigure6.Thevalueof󰀂isincreasingwithincreasingmoisturecontent(!)asequation(6)requires,andtheslopeofthefitlinesareincreasingwithdecreasingdensityasbeforeexplained.InFigure7,therelativechange‘C’ofthecalculatedthermalconductivityvaluesareshowninfunctionofpartialpressurecalcu-latedfromtheRH.TheC(percentchangeofthermalconductivity)valuesaregivenfromthecorrelationof󰀂wetto󰀂0usingequation(7)

C¼

󰀂wetÀ󰀂0

󰀂Â100ð7Þ

0

Fittingthe(C$Pp)curvesinFigure7withmathematicalfunctions,anexponentialfunctionisderivedforthepureEPSsamples(blue,yellow,black1andblack2);furthermore,asimplelinearfit(equation(8))forthecarbo-natedEPSgivesR2¼99%match

C¼A2ÂPp

ð8Þ

ThedefinedexponentialfunctiondeterminedonthepureEPSsamples

C¼A󰀂ÀP󰀃3Âexpp

3

ð9Þ

414JournalofBuildingServicesEngineeringResearch&Technology34(4)

Table3.Thecalculatedthermalconductivitiesbasedonthemoisturecontent.Blue02550637690Yellow02550637690Grey02550637690

!(%)00.880.10.920.9361.046!(%)00.7930.840.850.8610.981!(%)01.011.051.091.1161.16

󰀂wet(W/mK)0.0440.0447740.0447840.044810.0448240.04492󰀂wet(W/mK)0.0370.0375870.0376220.0376290.0376370.037726󰀂wet(W/mK)0.0310.0316260.0316510.0316760.0316920.031719

Black102550637690Black202550637690

!(%)00.60.6180.90.670.87!(%)00.50.5250.5350.5680.6885

󰀂wet(W/mK)0.0360.03320.03450.03670.03820.036626󰀂wet(W/mK)0.0350.035350.0353680.0353750.0353980.035482

2,4

Percental change oftherma; conductivity (%)c(%)=0,02*Pp+1,

2,22,01,81,61,41,21,0

0

5

10

15

20

blue%yellow%black1%black2%grey%

0,045

Thermal conductivity (W/mK)λblue=0,00088*ω+0,044

0,040

λyellow=0,00074*ω+0,037

0,035

BlueBlack1YellowBlack2Grey

c(%)=6*10–4*exp(–Pp/3)+K

λblack1=0,00072*ω+0,036

λblack2=0,0007*ω+0,035

λgrey=0,00062*ω+0,031

0,030

0,0

Partial pressure (mbar)

0,6

1,2

Moisture content (%)

Figure6.Thecalculatedthermalconductivitiesasafunctionofmoisturecontent.

Figure7.ThedependenceofthepercentchangeofthethermalconductivityofeachEPSsamplefromthepartialpressure.

EPS:expandedpolystyrene.

LakatosandKalma´rwhereA2andA3areconstants.Equation(9)is

similartoequation(3)representingthepartialpressure(moisturecontent)dependenceofthewatersorptioncapability,sothatthethermalconductivitychange.

Conclusions

Nowadays,theproperuseofinsulationisbecom-ingmoreimportantthanever.Therearemanydifferentwaystoinsulatebuildingswithmater-ials.Thedeterminationofthepropertiesoftheinsulationmaterialsaswellasthevariationofpropertiesintimedependingonvariousexternaleffectsisverysignificant.Inthisarticle,acompre-hensivedescriptionofthesorptionandthermalbehaviourofEPSinsulatingsampleswithdiffer-entdensitiesarepresented.Thesorptionmeasure-mentsshownthatthePSsamples,havinglowdensities,canabsorbimportantquantityofwaterfromtheair.Theeffectsofabsorbedwateraredescribed;furthermore,thethermalconductivityvariationdependingondensityisshown.Somethermalconductivityvalueswerecalculatedbasedonthewatercontentandtheinfluenceofthepartialpressurewasdetermined.Themeasurableamountoftheadsorbedwatercanincreasethethermalconductivityoftheinsu-lationmaterials,sothatcanreducethethermalefficiencyofbuildingsandraisestheU-value.Furthermore,ourmeasurementsprovedthatthedensityshouldbethemainparameterfordefiningthephysicalpropertiesofthePSsamples.Acknowledgements

TheauthorsacknowledgethesupportofCellplast

PlasticLtd(H-4200,Hajduszoboszlo

,Szovatistr3/b)forensuringthePSspecimens.Thisstudyissup-portedbyandTA

TA

MOP4.2.1/B-09/1/KONV-2010-0007MOP4.2.4.A/1-11-1-2012-0001projects.Theprojectsareco-financedbytheEUandtheEuropeanSocialFund.

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