Properties of Solutions of Natrosol HEC文档格式.docx

Properties of Solutions of Natrosol HEC文档格式.docx

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EffectofBlending

TwoviscositytypesofNatrosolcanbeblendedtoobtainanintermediateviscosity.Becauseviscosityisanexponentialfunctionofconcentrationanddegreeofpolymerization,theviscosityresultingfromblendingisnotanarithmeticmean.Ablendingchart（VC-440）,whichisavailablefromAqualon,canbeusedtodeterminetheresultofblendingvariousamountsoftwoviscositytypesofNatrosol.Or,itcanbeusedtodeterminetheamountofNatrosolrequiredtoachieveadesiredviscositywhenblendingtwotypesofknownviscosity.

Asanexample（Figure7）,itisdesiredtoobtainasolutionofNatrosolhavingaviscosityof150cpsat5%concentration,andtheavailablematerialsconsistofNatrosol250J（200cpsat5%concentration）andNatrosol250L（100cpsat5%concentration）.Alineisdrawnconnectingthesetwoviscositiesonleftandright,respectively.（Thisisshownbythesolidlineonthechart.）Thepointatwhichthislineintersectsthedesiredviscosityline（dottedline）,150cps,isthendetermined,andthepercentageitrepresentsisreadfromthebottomofthechart.Inthisexample,42%ofNatrosol250Land58%ofNatrosol250Jtypeswillgiveaviscosityof150cps.

Figure7

BlendingChartforNatrosol

EffectofShearRate

AsolutionofNatrosolinwaterwillappeartohaveawiderangeofviscositieswhendifferentconditionsofphysicalforceareimposedonthesolution.

Theseconditionsofphysicalforcemaybereferredtoashigh,intermediate,orlowstress.Forexample,rollingorspreadingaliquidasifitwereanointmentorlotionwouldbehighstress.Ontheotherhand,aftertheliquidhasbeenapplied,gravityandsurfacetensioncontrolflow.Theseforcesareconditionsoflowstress.Intermediatestresscanbetypifiedbypouringaliquidoutofabottle.Thus,ifasolutionofhigh-viscosityNatrosolHECappearstobeaviscoussyrupasitispouredfromabottle,itwillbehaveasarunnyliquidwhenappliedasalotion,andyetwhenhighstressisremoved,itwillinstantlyreverttoitsoriginalhighviscosity.Thistypeofflowbehaviorisreferredtoaspseudo-plastic,ornon-Newtonian.Thisbehaviordiffersfromthetime-dependentviscositychangethatisusuallycalledthixotropy.AdifferentmolecularweightorviscositygradeofNatrosolwillbehaveinasimilarfashion,buttoadifferentdegree.Thelowerthemolecularweight,thelesschangeinviscositywilloccurasstressconditionsarevaried.Thesedifferencesinviscosity-stresspropertiesareshowninFigure8.

Figure8

EffectofShearRateonViscosityofSolutionsofNatrosol

EffectofMixedSolvents

NatrosolHECwillalsoimpartvariedthickeningpropertiestosolventsystemsotherthanplainwater.BehaviorofNatrosolinthesemixedsolventsystemsissimilartoitsbehaviorinwater.However,theviscosityofthesolventmustbetakenintoaccount.Forexample,ifsucrose-wateristhesolvent,andifthissolventis50timesthickerthanwater,theresultingsolutionofNatrosolinthemixedsolventwillbe50timesthickerthanitwillbeinwater.Thisbehavior,showninFigure9,ispredictableformanysolvent-watermixtures.

Figure9

EffectofMixedSolventsonViscosityofSolutionsofNatrosol

EffectofTemperature

TheviscosityofsolutionsofNatrosolchangeswithtemperature,increasingwhencooled,decreasingwhenwarmed.Figure10presentsaconvenientnomographfromwhich,knowingtheviscosityofasolutionofNatrosolatonetemperature,onecanconvenientlyestimateitsviscosityatadifferenttemperature.

Exampleusingnomograph（Figure10）:

Theviscosityofthesolutionis100cpsat25°

C.Theunknownistheviscositywhenthetemperatureisraised20°

C.Byplacingastraightedgeat20intherightcolumnandat100inthecentercolumn,onecanreadtheanswerintheleftcolumn,52cps.

Figure10

NomographforEstimatingtheViscosityofSolutionsofNatrosolHECatVaryingTemperatures

EffectofpH

SolutionsofNatrosolundergolittleviscositychangeoverthepHrangeof2to12.However,solutionspossessthegreatestviscositystabilityinthepHrangeof6.5to8.0.BelowpH3,solutionsmayshowsomedropinviscosityresultingfromacidhydrolysis.Thisiscommontoallwater-solublepolysaccharidepolymers,andisacceleratedbyhightemperatureandhighacidity.Underhighlyalkalineconditions,someoxidativedegradationmayoccur,acceleratedbyheatandlight,thatwilllowertheviscosity.SeeFigure11.

Figure11

EffectofpHonViscosityofSolutionsofNatrosol

ViscosityStability

NatrosolHECdoesnotdegradewhenproperlystoredinclosedcontainers.NinelotsofNatrosol,viscositygradesM,H,H4,andHH,weremonitoredoveraperiodofayearforviscositystability.Averageviscosityretentionwas93%.

IfNatrosoliskeptininventoryforextendedperiods,Aqualonrecommendscheckingtheviscosityatleastonceperyear.

Preservatives

NatrosolHEC,particularlytheBgrades,ismoreresistanttobiologicalattackthanaresomeotherwater-solublegumsandpolymericmaterials.Thisbetterresistanceisanimportantfactorinitsuseinlatexpaints.

SincesolutionsofNatrosolarenotimmunetobiologicalattack,itisrecommendedthatapreservativebeaddedwhenthesolutionsaretobestored.Asaconvenience,somepreservativesthathavebeenfoundeffectiveinlaboratorytestsarelistedinTableV,alongwiththenamesoftheirmanufacturers,inthecaseofproprietaryproducts.

Itissuggestedthatadvicebeobtainedfromtheproducersofthepreservativesastothekindandamountofpreservativetobeusedinspecificcompositionsforvariousendproducts.

Foruseincosmeticsandpharmaceuticals,particularcareshouldbeexercised,bothintheselectionofanacceptablepreservativeandinthemaximumquantityused.ThesameistruewhereNatrosolisusedinadhesivesorcoatingsemployedonthefood-contactsurfacesofmetalorpaperarticlesintendedforuseinthepackagingoffood.

TableV—PreservativesEffectiveforSolutionsofNatrosol

ManufacturersofTrademarkedProducts

Dowicil75

Merbac35

VancideTH

ProxelCRL

Sodiumbenzoate

Sorbicacid

Methyl-propylparabencombinations

TheDowChemicalCo.

Merck/CalgonCorp.

R.T.VanderbiltCo.,Inc.

ICIAmericasInc.

—

Asanalternativetoaddingpreservatives,someconsiderationmightbegiventoheatsterilization.Manymicroorganismsaredestroyedbyheatingsolutionsto80°

Cfor30minutes,orto100°

Cfor1minute,andsuchheatcyclesarenotsevereenoughtomateriallyaffectthepropertiesofthesolutionsofNatrosol.Thissuggestionshouldbefollowedonlywhenthesolutionistobestoredundersterileconditions,otherwisethesolutionwillbecomerecontaminatedwithmicroorganisms.Enzymes,however,canpersevereevenwhenmicroorganismsarekilled,dependingonthetimeandtemperatureofsuchheatcycles.

UseofDefoamers

SolutionsofNatrosolHECaremildlysurface-active.Theyarelowerinsurfacetensionthanwater,asshowninTableIII.Ifanydifficultyisencounteredwithairentrainmentinsolutions,adefoamershouldbeutilized.Water-dispersibledefoamerssuchasAdvantage®

357defoamer,FoamasterNDW,Colloid581-B,andDowAntifoamAFareeffective,andcanbeaddedtothewaterpriortosolutionpreparation.

ToleranceforInorganicSalts

Becauseofitssolubilityandnonioniccharacter,Natrosolcanbedissolvedinmanysaltsolutionsthatwillnotdissolveotherwater-solublepolymers.DatainTableVIshowthatNatrosolissolubleinmost10%saltsolutionsandmanyofthe50%（saturated）saltsolutions.

ThisstudyindicatedthatsolubilitywasnotaffectedbytheviscositytypeofNatrosolused.Inobtainingthesedata,1mlofasolutionofNatrosolwasaddedto15gofeachofthesaltsolutions.TheratioofNatrosoltosaltsolidsrangedfrom1:

150to1:

750.

TableVI—CompatibilityofSolutionsofNatrosolwithInorganicSaltSolutions

Salt

Natrosol250（a）HEC

10%SaltSolution

50%Salt（Saturated）

Aluminumnitrate

Aluminumsulfate

Ammoniumchloride

Ammoniumnitrate

Ammoniumsulfate

Bariumnitrate

Borax

Calciumchloride

Calciumnitrate

Calciumsulfate

Chromicnitrate

Chromicsulfate

Diammoniumphosphate

Disodiumphosphate

Ferricchloride

Ferricsulfate

Magnesiumchloride

Magnesiumsulfate

Potassiumferricyanide

Potassiumferro