Effect of compaction on multi-physical properties of hemp-black liquor composites

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Effect of compaction on multi-physical properties of

hemp-black liquor composites

Marie Viel, Florence Collet, Christophe Lanos

To cite this version:

Marie Viel, Florence Collet, Christophe Lanos. Effect of compaction on multi-physical properties of

hemp-black liquor composites. Journal of Materials Research and Technology, Elsevier, 2020, 9 (2),

pp.2487-2494. �10.1016/j.jmrt.2019.12.079�. �hal-02562384�

w w w . j m r t . c o m . b r

Availableonlineatwww.sciencedirect.com

Original

Article

Effect

of

compaction

on

multi-physical

properties

of

hemp-black

liquor

composites

Marie

Viel

_,

_Florence

_Collet

_,

_Christophe

_Lanos

a_{UniversitédeRennes,LaboratoireGénieCiviletGénieMécanique,BP90422,Rennes,France} b_{UniversitédeNantes,InstitutdeRechercheenGénieCiviletMécanique,BP92208,Nantes,France}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received8September2019

Accepted24December2019

Availableonline27January2020

Keywords:

Sustainablebuildingmaterials

Hempshiv

Thermalproperties

Mechanicalproperties

Moisturebuffervalue

a

b

s

t

r

a

c

t

Thisstudyaimstodevelopfullyagro-basedinsulatingbuildingmaterials.Previousstudies

investigatedseveraltypesofaggregatesandbinderstodevelopcomposites.Thethermal

conductivityofsuchcompositeappearsmainlyimpactedbythedensity.Thispaperaimsto

investigatetheeffectofdensityonvariousmulti-physicalpropertiesofcomposites,using

thesameformulationandadjustingtheformingstep.Thus,specimensareproducedwith

thesamehempshivtoblackliquorratiobutdifferentcompactionstress.Theeffectof

com-pactiononbulkdensity,porosity,mechanicalresistance,thermalconductivityandMoisture

BufferValue(MBV)isanalyzed.Itisshownthatitispossibletoreachthermalconductivity

thatislowenoughtobeconsideredasbuildinginsulatingmaterial.Thankstothisstudy,the

requiredcompactionstresstoensuretargetedvaluesofdensity,thenthermalconductivity

andMBV,isidentified.

©2020TheAuthors.PublishedbyElsevierB.V.Thisisanopenaccessarticleunderthe

CCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

1.

Introduction

Theagriculturalwastevaluationisoneofthecurrent

chal-lengesinthefieldofgreenbuildingmaterial[1–3].Agricultural

wastecanbeusedtoproducebio-basedpanelswithlow

envi-ronmental impact(embodied energy and carbon footprint)

andhighhygrothermalefficiency[2,4–6].Aspartofthe

ISO-BIOproject[7],thedevelopedthermalinsulatingpanelsare

ecofriendlycompositesmadeofaggregatescomingfromlocal

agricultureandgreenbinders.Thegluingeffectisobtainedby

couplingthermalandmechanicaltreatment.

∗ _{Correspondingauthor.}

E-mails:marie.viel@univ-nantes.fr(M.Viel),florence.collet@univ-rennes1.fr(F.Collet),christophe.lanos@univ-rennes1.fr(C.Lanos).

In a previous study, presented in [8], various

compos-iteswereinvestigatedwithBiofibat® hempshivorcorncob

residuesasaggregates,andcorncobextract,flaxfinesextract,

blackliquor,BioChoice® ligninorPLAasbinders.Aftermixing,

thecompositesareproducedbycompactingandthen

heat-ingleadingtothegluingoftheaggregates.Thisstudyshowed

thatthedevelopedcompositeshadlowthermalconductivity

(rangingfrom0.067to0.148W/(m.K))andexcellentmoisture

bufferingability(MBV>2g/(m2_{.%RH)).More,thethermal}

con-ductivityincreasedlinearlywithdensity,whateverthekindof

aggregateandofbinder.

https://doi.org/10.1016/j.jmrt.2019.12.079

2238-7854/©2020 The Authors. Publishedby Elsevier B.V. This isan open access articleunder the CC BY-NC-ND license (http://

2488

Thedensityofcompositesismostlyimpliedbythe

com-pactionstressappliedduringtheirproduction,amongother

factors.Theinfluenceofcompactiononphysicalproperties

(density,thermalconductivityandcompressivestressin

par-ticular)ofcompositeshasbeenhighlightedbyBalciunas[9]

inthecaseofhemp-sapropel composites(sedimentrichin

organicmatter)compactedat20,40and60%oftheirinitial

volume.

Thisstudyfocusesonthecompositesobtainedwithhemp

shivandblackliquor.

Hemp shiv are lightweight aggregates withhigh

poros-ityandinterestinghygrothermalproperties[10].Thismakes

themperfectlysuitedforthedevelopmentofbio-based

insu-latingmaterials.Theyarethemostcommonlyusedaggregates

intheliteraturefortheproductionofbuildingmaterials[2].

Blackliquorisarenewablebinderfromlocalindustry,is

betterfortheenvironment(lessCO2emissionand

preserva-tionoffossilresources)thanusingpetroleum-basedbinder

(urea-formaldehyderesin orphenolic resin). More, the use

ofblackliquorleadstoabetterhygrothermalpropertiesof

bio-basedcompositesthantheuseofpetroleum-basedbinder

(polyvinylacetate)ashighlightedinpreviousstudy[11].Black

liquorisreadilyavailablecomponentsincetentonnesofblack

liquorareproducedpertonneofpulpusingtheKraftpulping

process[12,13].Currently,blackliquorismainlyusedforthe

productionofenergy.However,efficientenergyproductionis

cumbersomeandexpensive[12,14,15].Itistherefore

impor-tanttoseektoenhancethisco-productinadifferentway.Due

toitschemicalcomposition(Kraftlignin,polysaccharides,

aro-maticsandaliphaticscomponents),blackliquorrepresentsan

interestingalternativeforthesynthesisofsustainable

chem-icals[16–18].

Forthisstudy,thecompositesareproducedwiththesame

hempshivtoblackliquorratiobutsevendifferentcompaction

stressesappliedduringformingstep(15.6,31.2,62.5,125,250,

500and1000kPa).

Thus, this study investigates the effect of compaction

conditions on density, porosity, mechanical, thermal and

hygricperformancesofcomposites.Itwillthenbepossible

todefine productioncompaction regardingtarget valuesof

multi-physicalproperties.

2.

Materials

and

method

2.1. Rawmaterials

Thecompositesare producedwithBiofibat® hemp shiv as

aggregatesandblackliquorasbinder.

TheBiofibat® hempshivwere producedin2016yearby

CAVAC(Sainte-Gemme-la-Plaine,France).Itsparticlesize

dis-tributionwasdeterminedbyimageanalysisasdescribedby

Amzianeetal[19].Thelengthofhempshivrangesfroml10

=5.5mmtol90=19.4mm,withanmediumvaluel50of11.5

mm(Fig.1).Thewidthrangesfromrangesfromw10=1.7mm

tow90=4.8mm,withanmediumvaluew50of2.9mm.The

elongationratio(length/width)rangesfrom2.2to6.5.

Bulkhempshivhaveinterestingthermalproperties(with

athermalconductivitybetween48and59mW/(m.K)[9,20,10])

due to their low bulk density. They also show excellent

Fig.1–ParticlesizedistributionofBiofibat® hempshiv.

Table1–Chemicalcompositionofkraftblackliquor accordingtothesafetydatasheet.

Components Content(%inweight)

Alkalilignin 14.1 Carboxylicacid 1.1 Aceticacid 4 Formicacid 10 Hydroxideacid 2.8 Polysaccharides 5.4 Sulfate 3.4 Sulfur 8.3 Sodium 15.9 Othercomponents 35

abilitytoregulateambientrelativehumidity(MBVabout2.31 g/(m2_.%RH)[10]).

Theblackliquorisalowcostby-productfrom thekraft

paperindustry[18].Itiscomposedofabout70%drymatter.

Itschemicalcompositionmainlyincludesligninandinorganic

componentswhichmainlycomefromthepaperindustry

pro-cess.Italsoincludesfewpolysaccharidesandsomearomatic

andaliphaticcomponents(Table1)[16,21].Fig.2isa

diagram-maticillustrationoftheblackliquorstructure.Durmazetal

andNayerietalalsoobservedthattheblackliquorprotectthe

ligno-cellulosicresourcesfromfungaldevelopment[17,22].

2.2. Composites

Foreachkindofcomposites,sixspecimens(10×10×10cm3₎

areproduced.Threeofthemareusedforthermalandhygric

characterization,thethreeothersformechanical

characteri-zationandmeasurementofskeletondensity.Thesameblack

liquortohempshivdrymassratioof15%isused.Thisvalue

ischoseninordertoensureagoodcohesion[23].

Forpreparation,thehempshivaremixedwiththeblack

liquorinamixerwithaflatpaddleduring5minutes.Themix

issplitinto threepartstoproducethreespecimens.

Speci-mensare moldedandcompacted5timesusinganInstron

5988testingmachinefittedwithaupperplunger,toensurea

goodparticlesarrangement.Theyaremaintainedunder

com-pressionandheated(for2hoursat190◦_{C),cooledtoroom}

Fig.2–Diagrammaticillustrationoftheblackliquor

structure[21].

Tostudytheeffectofcompactiononmulti-physical

prop-erties,sevencompactionlevelsareconsidered:15.6,31.2,62.5,

125,250,500and1000kPa.

2.3. Characterizationmethods

2.3.1. Densitiesandporosity

Thedensityistheratiooftheweighttothesizeofthe

speci-men(whichisapproximately10×10×10cm3_{).Theweightis}

obtainedwithananalyticalbalance(SartoriusLP8200S,

Göt-tingen,Germany).Eachdimension(length,width,height)is

theaverageoffourvaluesmeasuredwithanelectroniccaliper

(readabilityof0.1mm).Itismeasuredonthesixspecimensof

eachkindofcomposite.

Theskeletondensity s istheratio oftheweighttothe

skeletonvolumeofthespecimen.Thismeasurementis

car-riedoutusingapycnometeraccordingtothestandardASTM

D854[24].Aknownmassmsampleofdryandcrumbled

com-posites(foravolumeofabout 200ml) isintroduced into a

pycnometerofabout600ml.Then,thepycnometerisfilled

withtoluene.Itisregularlyshakentoremoveairbubbles.After

ensuringthatnoairbubblesaretrappedbetweenthe

parti-cles,thepycnometeriscompletelyfilledwithtolueneandthe

volumeoftoluenedisplacedbythecrumblesampleVsampleis

determinedfollowingtheequation(1).Threemeasurements

areperformedforeachcomposite.

s= msample Vsample = msample Vpycno−Vtoluene = m2−m1 m4 water−m3−m2_toluene (1) with:

• m1:massoftheemptypycnometerwithground-glass

stop-per;

• m2:massofthepycnometerwithground-glassstopperand

sample;

• m3:massofthepycnometercompletelyfilledwithtoluene

withground-glassstopperandsample;

• m4:massofthepycnometercompletelyfilledwithwater

withground-glassstopper;

• toluene:densityofthetolueneatthetemperatureofthe

mea-surement;

• water:densityofwateratthetemperatureofthe

measure-ment.

Thetotalporosityntofacompositeisthevolumeratioof

theporositytothetotalvolumeofthespecimen.Itisthen

relatedtoapperentandskeletondensityofcomposite

follow-ing(Equation(2)).

nt=

s−app

s (2)

with:

• s:densityoftheskeletonofthesample;

• app:densityofapparentdensityofthesample.

2.3.2. Mechanicalcharacterization

Foreachcomposite,acompressiontestisperformedonthree

specimensto determinethe averagecompressive strength.

The test is carried out on a testing machine (Zwick/Roell

2490

ProLine,Metz,France)fittedwitha20kNloadcell(Zwick/Roell

XForce,Metz,France).Theloadisappliedonthespecimen,by

themonotonousdisplacementoftheuppersteelplatewith

cross-headspeedof0.05mms−1_.

FollowingtherecommendationsoftheNFEN826standard

[25],the resultsofthe compressiontests arestudiedusing

stress-straincurvesasdescribedbyVieletal[8].

2.3.3. Thermalcharacterization

For each composite,the thermalconductivity ismeasured

three times on three pairs of specimensobtained by

cou-plingthreespecimens,withthehotwiretransientmethod[26]

usingcommercial “CTmeter”device (SMEE,Voiron,France).

Theheatingpowerandtimeare 142mWand 120seconds.

Previouslytothemeasurement,specimensarestabilizedat

(23◦_{C;drystate)andat(23}◦_C;50%RH).

Thedrystateisreachedafterthedryingofcompositesin

anovenat60◦_{Cuntiltheirmassstabilization(thevariation}

mustbelowerthan0.1%betweentwoconsecutiveweighing

forthreeconsecutive weighingwitha 24-hourstime step).

Then,thecompositesareplacedindesiccatorat23◦_C.The

measurementsareperformedoncetheweightstabilizationof

compositesisreached(samestabilizationcriterionas

previ-ously).Thestabilizationat(23◦_{C;50%RH)isperformedina}

climatechamber.

2.3.4. Hygriccharacterization

Foreach composite,the moisturebuffervalueismeasured

onthreespecimens,accordingtotheNordtestprotocol[27].

Itrelates the amount ofmoistureuptakeor release tothe

exchangeareaasafunctionofrelativehumidity(Equation(3)).

MBV= m

A.(RHhigh−RHlow)

(3) with:

• MBV:moisturebuffervalue(g/(m2_.%RH));

• m:moistureuptake/releaseduringtheperiod(g);

• A:opensurfacearea(m2_);

• RHhigh/low:high/lowrelativehumiditylevel(%).

Specimens are sealed on all their surfaces except one.

Afterstabilizationat(23◦_{C;50%RH),therelativehumidityis}

submittedtodailycyclicvariations:8/16hoursat75/33%RH

(absorption/desorption period), during 5 days in a climate

chamber(VötschVC4060,Balingen,Germany).

3.

Results

3.1. Densitiesandporosity

Table 2gives the physicalproperties of compositesversus

compactionstress.

Theapparentdensityofdevelopedcomposites,atdrystate,

rangesfrom128to247kg/m3_{.Itincreaseswiththecompaction}

pressurefollowingthe equationgiveninFig.4withahigh

correlationcoefficient.So,itispossibletoidentifythe

com-pactionpressuretoapplyforatargetdensity.Thenon-linear

curvegivenbyFig.4isduetothemechanismsofcompaction

Table2–Effectofcompactiononapparentdensitiesat (23◦_{C;50%RH)and23}◦_{C;drypoint),skeletondensity} andporosityofcomposites.

p 23◦C−50%RH 23◦C−dry s ntot (kPa) (kg/m3_{) (kg/m}3_{) (kg/m}3_{) (%)} 15.6 135.8±3.7 127.6±3.7 1345.2±46.4 90.5 31.2 144.4±3.8 135.3±3.6 1325.2±11.4 89.8 62.5 155.0±2.8 144.9±2.7 1294.2±5.4 88.8 125 171.6±1.2 160.3±1.2 1282.9±6.7 87.5 250 191.4±0.9 180.7±0.9 1211.0±7.2 85.1 500 229.4±3.3 213.7±3.1 1269.9±2.1 83.2 1000 265.9±1.3 247.0±1.6 1283.0±11.0 80.7

Fig.4–Apparentdensityofcompositesat(23◦_C;drypoint) versusthepressureapplied(p)duringthecomposites process.

that take placeduring thecomposites production:(i) grain rearrangementand(ii)elasticandplasticdeformationsof par-ticles[28].TheCooper-Eatonmodelmakesitpossibletoclearly

distinguishthesetwophenomena[29].

Furthermore,the densityofcompositesincreases by7%

fromthedrypointtothewetpointat(23◦_C;50%RH).

Thedevelopedcompositeshaveverysimilarskeleton

den-sitiesrangingfrom1211to1345kg/m3_{.Theaverageofthese}

valuesis1300kg/m3_{withavariationof±3.33%.The}

formula-tionsofthesevencompositesdevelopedinthispaperarethe

same,soitisconsistenttohavethesameskeletondensity.

Moreover,thehemp-starchcompositesdevelopedby

Bour-dotetal,haveaskeletondensityclosetothisvalue.Indeed,

theyhaveaskeletondensityof1249kg/m3_{withavariationof}

±1.02%[30].

Sincetheskeletondensityisthesameforallcomposites,

thetotalporosityofthecompositesevolveslinearlywiththeir

apparentdensity,followingtherelationshipbetweenthese3

valuesgivenEquation(2),andashighlightedinFig.5.Atthe

drypointanditrangesfrom80.7%to90.5%.

3.2. Mechanicalresistance

Thedevelopedcompositesmadewithhempshivshow

com-pactingbehavior(continuousstressincreasedversusstrain

-Fig.6).Thus,themechanicalperformanceisgivenbythe

com-pressivestrengthobtainedforthelongitudinaldeformation

Fig.5–Porosityofthedevelopedcompositesversustheir

apparentdensityat(23◦_C;drypoint).

Fig.6–Stress-straincurveofthecompositescompressedat

31.2kPaduringtheproductionprocess.

Table3–Stressat10%deformationforeachcomposites.

p(kPa) 23◦C−50%RH(kg/m3) 10%(kPa) h=3m(%) 15.6 134.7±3.0 54.6±10.8 0.50 31.2 144.9±1.2 87.7±0.1 0.28 62.5 150.6±0.4 105.7±6.2 0.24 125 169.1±1.4 194.8±12.9 0.19 250 203.2±1.1 230.1±6.5 0.22 500 221.8±3.8 613.3±7.8 0.09 1000 270.8±16.7 802.7±131.2 0.09

Table3and Fig.7showthemechanicalproperties

mea-suredoncomposites.

Foragivencompactionpressure(between15.6and500kPa)

duringthe productionofcomposites, theexperimental

val-uesareveryclosetoeachotherbetweenthethreespecimens.

Incontrast,thecompositescompressedat1000kPaduring

theproductionprocesshaveexperimentalvalueswithalarger

measurementdeviation(coefficientofvariationofabout16%)

duetoasignificantvariationinapparentdensitiesbetween

thethreespecimens.Thecompressivestrengthrangesfrom

55to803kPa.Thecompositecompressedat1000kPaduring

theproductionprocesshasthehighestcompressivestrength

and thecomposite compressedat15.6 kPahasthe lowest.

Fig.7underlinesthatcompressivestrength evolveslinearly

withbulkdensity.

Fig.7–Stressat10%deformationofthedeveloped

compositesversustheirapparentdensity.

Table4–Effectofcompactionandhumidity(dryand 50%RH)onthermalconductivityofhemp-blackliquor compositesat23◦_C. p dry dry 50%RH 50%RH kPa (kg/m3_{) (mW/(m.K)) (kg/m}3_{) (mW/(m.K))} 15.6 127.6 62.8 134.6 71.0 ±3.7 ±1.1 ±3.4 ±1.1 31.2 135.3 65.7 143.3 73.1 ±3.6 ±1.9 ±3.9 ±1.8 62.5 144.9 65.6 153.7 72.7 ±2.7 ±1.3 ±2.7 ±1.0 125 160.3 68.9 170.1 77.8 ±1.2 ±0.9 ±1.1 ±1.0 250 180.7 71.1 190.4 78.2 ±3.1 ±1.5 ±1.0 ±3.0 500 213.7 79.8 225.4 91 ±0.9 ±2.8 ±3.4 ±1.9 1000 247.0 93.2 258.8 101.5 ±1.6 ±1.9 ±1.6 ±1.8

For3metershighwall,thestressinducedbythe compos-itesdensityleadsto_h=3mdeformationslowerthan0.50%.The mechanicalpropertiesmeettherequirementstobeusedas buildinginsulatingpanelswithoutcompactionrisk.

Balciunas et al[9] also noticedon hemp-saprobel

com-posites that the compressive strength (from broken before

measurementto2080kPa)increaseswiththeapparentdensity

ofcomposites(from157to401kg/m3_).

3.3. Thermalconductivity

Thethermalconductivityofhemp-blackliquorcomposites

rangesfrom62.8to93.2mW/(m.K)atdrypointandfrom71.0to

101.5mW/(m.K)atwetpoint(Table4).Thecompositewiththe

lowestcompactionpressure(15.6kPa)meetstherequirements

tobeclassifiedasinsulatingbuildingmaterialsregardingthe

NFP75-101standard(<65mW/(m.K))[31].

Fig.8underlinesthatthethermalconductivityincreases

linearlywithdensitywithahighcorrelationcoefficient.More,

Fig.8alsohighlightsthattheslopeistwicetheslopeobtained

foragro-resources[10].Thismaybeattributedtotheaddition

ofbinderandthecompactionwhichreducesinter-particular

2492

Fig.8–Thermalconductivityofhemp-blackliquor

compositesversustheirapparentdensity:(a)Comparison

betweenthecomposites(yellowcurve)andthe

agro-resourcesinbulk(greencurve[10])atdrypointand(b)

Comparisonofthermalconductivityvaluesbetweendry

point(yellowcurve)andwetpoint(orangecurve).

Table5–EffectofcompactiononMBVofcomposites (averagevalueandstandarddeviation).

p MBVabs MBVdes MBVav (kPa) (g/(m2_{.%RH)) (g/(m}2_{.%RH)) (g/(m}2_.%RH)) 15.6 2.50±0.03 2.77±0.02 2.63±0.02 31.2 2.60±0.09 2.86±0.09 2.73±0.09 62.5 2.82±0.11 3.06±0.11 2.94±0.11 125 2.63±0.07 2.87±0.06 2.75±0.06 500 2.31±0.01 2.49±0.01 2.40±0.01 1000 2.31±0.12 2.49±0.10 2.40±0.11

regression,it ispossibletoidentifythe requireddensity to reachatargetthermalconductivity.

Thethermalconductivityatwetpointisabout10%higher thanthethermalconductivityatdrypoint.Theslopeversus densityremainsthesame.

Balciunasetal[9]hadthesamefindingsonhemp-saprobel

compositesthatthethermalconductivityincreaseswiththe

apparentdensityofcomposite(=53to73mW/(m.K)for=

147to401kg/m3_).

3.4. Moisturebuffervalue(MBV)

Following Table 5, the MBV ranges from 2.40 to 2.94

g/(m2_{.%RH).Allthecompositesareexcellenthygricregulators}

accordingtotheNordtestclassification(MBV>2g/(m2_.%RH))

[27].

Fig.9–MBVofhemp-blackliquorcompositesversus

density.

ThelowestMBVisobtainedforthetwocompositeswiththe

highestdensities(compactedat500and1000kPa).Thehighest

MBVisobtainedforthecompositecompactedat62.5kPa.Fig.9

givestheMBVversustheapparentdensityofcomposites.

Inafirsttime, theMBVincreasesupto2.94g/(m2_.%RH)

foradensityof170kg/m3_{.Then,itdecreases downto2.40}

g/(m2_{.%RH)fordensityof200kg/m}3_{.Finally,theMBVremains}

constant.Suchevolutionmaybeexplained:

• Inafirsttime,bytheincreaseinspecificsurfaceareawith

densitywhichleadstohighersorptionandthushigherMBV;

• Then, bythe decrease in vapor permeability induced by

lower inter-particular porosity which reduces the vapor

penetrationinthecomposite,andthustheMBV.

Thecombinationofthesetwoparametersleadsto

iden-tify anoptimumvalue ofdensity,and thus of compaction

pressure.Inordertovalidatethesehypothesis,

complemen-taryinvestigationsregardingvaporpermeabilityandspecific

surfaceareaarerequired.

BourdotetalfindthesameMBVwithhemp-starch

com-posites.Indeed,thesecompositeshaveanaverageMBVof2.63

g/(m2_{.%RH)foranaveragedensityof136kg/m}3_{[30].However,}

MaaloufetalfindaslightlylowerMBVwithalsohemp-starch

composites.ThesecompositeshaveanaverageMBVof2.46

g/(m2_{.%RH)foranaveragedensityof170kg/m}3_[32].

ColletandalfindalowerMBVrangingfrom1.94to2.15

g/(m2_{.%RH)forthehempconcreteswhichhaveadensity}

rang-ingfrom430to460kg/m3_{[33].Thisdifferencecanbeexplained}

bytheuseoflessbinderinthecaseofthecomposites

devel-opedinthispaper.

4.

Conclusion

Thedevelopedcompositesareproducedwithhempshivand

blackliquorwithseveralcompactionpressures.

Thecompositesdensityrangesfrom128to347kg/m3_at

drystate.Thedensityiscorrelatedtothecompactionpressure

appliedduringtheproduction.Regardingthetotalporosityof

thecomposites,itisinverselyproportionaltotheirapparent

Thethermalconductivityincreaseslinearlywithdensity

between62.8and93.2mW/(m.K)atdrystate(23◦_C;0%RH)and

between71.0to101.5mW/(m.K)atwetpoint(23◦_C;50%RH).

Allthedevelopedcompositesareexcellenthygric

regula-torsastheirMBVranges from2.40to2.94g/(m2_{.%RH). The}

MBVevolves with densityand shows anoptimalvalue for

densityaround170kg/m3_.

Amongdevelopedcomposites,thecompositewiththe

low-estdensityshowshighthermalandhygricperformances.On

the one hand,its thermal conductivity meets the

require-mentstomakeitconsideredasinsulatingbuildingmaterial.

Ontheotherhand,itisanexcellenthygricregulator,withMBV

of2.77g/(m2_{.%RH)andhassufficientmechanicalproperties}

foritsuse(selfbearingmaterials).

Acknowledgments

ThisprojecthasreceivedfundingfromtheEuropeanUnion’s

Horizon2020researchand innovationprogramundergrant

agreementNo.636835–Theauthorswouldliketothankthem.

CAVAC,industrialpartneroftheISOBIOproject,is

grate-fullyacknowledgedbytheauthorsforprovidingrawmaterials.

ThanksareduetoTonyHautecoeurforhisparticipationin

thecompletionofthiswork.ThanksareduetoYannLecieux

(Mechanicaltests).ThanksarealsoduetoCélineLeutellierfor

havingreviewedtheEnglishlanguage.

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