Challengesinprocessingandmarketinghightemperaturecompoundsforbipolarplates–opportunitiesinapplyingit

Dipl.‐Chem.ThorstenDerieth,ZBTGmbH

Mag.(FH)Hans‐PeterKoch,Ensinger GmbH

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Bipolarplate‐concepts for PEM‐FCs

DANA

Source:WilhelmEisenhuth GmbHSource:Gräbener Maschinetechnik GmbH

InfluencesinHT‐PEM‐FC

• T>160°C

• Phosphoricacidmedia

• Electrochemicalpotential

• Mechanicalstress

Metalplates Compoundplates

Differenceinvolume&weight

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Feedstock for composite based bipolarplates

Graphite

(conductivefiller1)

Carbonblack

(conductivefiller2)

Polymer(bindingmatrix)

Matrixselectionforcompositebipolarplates

Thermosets(LT&HT) LT‐Thermoplastics(PP)

CheapHighthermalstability<180°CGoodchemicalstability<180°CFeasibleforhotpressing

VerycheapGoodchemicalstability<80°CGoodthermalstability<80°CRecyclingpossibleExtrusionestablishedInjectionmoldingpossible

HT‐Thermoplastics(PPS)

Excellentchemicalstability>180°CExcellentthermalstability>180°CRecyclingpossibleExtrusionestablishedInjectionmoldingpossible

Source:Epoxid:chemie.fu‐berlin.de,Phenolharz:kern.de,PPS,PPundPeek:Wikipedia

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Fillerselectionforcompositebipolarplates

Source:AMGMiningAGSource: adherent‐tech.com

Source:tms.org

Source:ptonline.com

Source:celgard.com

Graphite

(conductivefiller)

Polymer

(binder)

Further

conductive

additives

Binary

compound

Multi

component

compound

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Lookinsidethecomposites

Graphite+polymer Graphite+CB+polymer

Graphite+CNT+polymer Ggraphite+CF+polymer

Graphite+CB+CNT+polymer

Whyiscompoundingsoambitious– weighttovolumeratio

96vol%

processingnotpossible

62vol%

functionalityforbipolarplates

33vol%

nofunctionalityformagnetism

Whyiscompoundingsoambitious– weighttovolumeratio

62vol%

processabilityinPPispossibly

71vol%

processabilitynearlynotpossiblyinPPS

>74 closepackingofspheres

Whyiscompoundingsoambitious– bulkdensitydisaster

Relationbetweenvolumegraphitetopolymer@80wt%:177:1

@80wt%&@100kg/h 2660lgraphitein15lPPS (121lgraphitein22lPP)

Compoundingsuccessfullyestablished

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Furtherprocessingofthesecomposites

Thermosets Thermoplastics

EstablishedtechnologyforLT‐ andHT‐BPPDifficultwithshapesandinletsLongproductiontimeRecyclingnotpossibleLimitedopportunitiesformassproductionMassmarketentrybarrierforPEM‐FC

EstablishedtechnologyforLT‐BPPHighaccuracyandreproducibilityInletsandmanifoldsinonestepMassproductiontechniqueEnablescheapandreproduciblearticlesHighinitialinvestmentforIM‐toolLimitationsinsize

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WhyisIMofthesecompositessoambitious?PP&PPS

5000kN clampforce350MPa IM‐ pressure

>80wt%fillingcontent veryhighviscosityverygoodthermalconductivity rapidlysolidification

withplastic

withcompound

320MPa

0,2sec

ChallenginginprocessingbutwellestablishedatZBTsince2002forlowtemperaturebipolarplatesbasedonPP

Source:JensDoerner ,IPEDuisburg

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WhyisIMofthesecompositessoambitious?PPvs.PPS

Differencebetweenprocessingtemperatureandsolidificationtemperatureasindicatorfora

goodprocessability

Source:reproducedfromHiekisch,Fa.TiconaPPSmeetsalltheotherrequirements

foruseinHT‐PEM‐FC

Processing temp. Solidificationtemp.

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OpportunitiestorealizeHTbipolarplatesviaIM

Insteadofonecavitytoolwithmanyredirectionsatwocavitytoolwithcentergate equalflowlines

Firsttestingserieshavebeenproducedsuccessful– meanwhileastandardprocessatZBT

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Finallyitworksverysuccessful

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Plastic‐Material‐ConceptsForHT‐PEMs

Phenolicresin+ alreadyinuseforHTPEMFC

experiencewiththismaterialandthereforeconfidence

+ wellsuitedforthehotcompressionmoldingprocess

welltrustedproceduretoproducesmalleramountsofplates

‐ unsuitableforinjectionmolding

materialnotrecyclable,timeconsumingandcostlyprocedure,

‐ long‐termimpairmentcausedbyphosphoricacid(>180°C)

poorperformanceandfailuresinthelongrunattemperatures>180°C

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Plastic‐Material‐ConceptsForHT‐PEMs

Polyphenylenesulfide(PPS)+ materialishotcompressionmoldable

bridgetechnologyforPPSplates,onlylowinvestmentrequired

‐ longercycletimeatcompressionmolding

nocostsavingopportunity,butthepossibilitytogainexperience

‐ notyetinusecommercially

customersareevaluatingPPS,firstfeedbackisverypositive,investintooling

+ verypositivefeedbackastoresistivityagainstH3PO4

betterperformance,longtermstability

+ processablebymeansofinjectionmoldingorextrusion

shortercycletime,largerandthinnerplatesbymeansofvariothermtooling ,recyclable

+ operatingtemperaturesupto200°C

leadstohigherperformanceofthefuelcell

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StatusInMarketingOfHighlyFilledPPSCompounds

TECACOMPHTE‐CompoundsinthemarketTestswithPPSbasedcompoundshavebeencarriedoutorarecarriedoutcurrentlyfrommostoftheimportantbipolarplateproducersinEurope,USandJapan

Duetotheadvantages(comparedwithphenolicresins)offeredbythePPScompounds,customersindicateinterestafterhavingdonefirsttrialswiththismaterial

Differentfuelcellconcepts‐ askingfordifferentbipolar‐plate‐materials‐ areonthemarketcurrentlyanditisnotcertainwhichwillbethemostpreferredone.

ThatleadstoalowerwillingnesstoinvestinmoresuitabletechnologyThehotcompressiontechnologyHotcompressionmoldingofPPSbasedcompoundsisstateoftheart.Itisbasicallyeasytoswitchfromphenolicresintothethermoplasticcompoundwiththesamemachinery.

HotcompressionmoldingofPPScompoundsprovidethechancetogainfirstexperiencewiththismaterialbutwithouttheneedtoinvestinexpensivemachinery

DuetolongercycletimesofPPSduringthehotcompressionmoldingprocess(comparedwithphenolicresins)thistechnologyisnotsuitabletobringdownthecostsofbipolarplatesmadeofPPScompounds.

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StatusInMarketingOfHighlyFilledPPSCompounds

TheinjectionmoldingprocessToextracttheadvantagesofthismaterialintermsofcostsaving,meanstohavetoswitchtotheinjectionmoldingtechnology

Toinvestinvariothermtechnology(toobtainlargerandthinnerplates)willpayoffatsomethinglike100.000piecesayear

ToprocessthehighlyfilledTECACOMPHTE‐Compoundsmeanstoworkattheborderlineinrespectoftemperaturecontrolandtheinjectionpressure.Duetothisfactoneneedtohaveastronginjectionmoldingmachine.

300

5000kNclampforce

350MPaIM‐pressure

PE/PP

TECACOMPPPSHTE

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HotCompressionMoldingComparedToInjectionMolding

HotCompressionMolding

Cycletime:

Phenolicresin:+/‐3min– 5min

PPSCompound:+/‐ 10min– 20min

InjectionMolding

Cycletime:

Standardprocess(thickerandsmallerplates):

+/‐ 10seconds

Variothermprocess(biggerand/orthinnerplates)

+/‐ 2min

massproduction

costsavings

technology

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StatusInMarketingOfHighlyFilledPPSCompounds

EisenhuthGmbHinOsterodewillsoonstartaprogramtoproduceinjectionmoldedbipolarplates.ItisverylikelythattheireffortsaresuccessfulasZBTinDuisburgalreadymanagedtoproducesuchaproductbymeansofinjectionmolding.

EnsingerCompounds hasPPScompoundsavailablethatfitstothehot‐compression‐technologytogetstartedandtogainexperience

hasgotinjectionmoldablePPScompoundsforserialproduction ProducesdifferentgradesofPPcompoundsfortheuseinLTPEMfuelcells,redoxflowbatteriesandalkalineelectrolyses

Formoreinformation:Compounds:www.ensinger‐online.com/en/compounds/products/high‐content‐graphite‐compounds/Processing:www.zbt‐duisburg.de/en/portfolio/fuel‐cell‐components/injection‐moulded‐bpp/