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