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Dow Corning® Silicone Reactive Hot-Melt Adhesive Window ......Dow Corning ® silicone reactive...
Transcript of Dow Corning® Silicone Reactive Hot-Melt Adhesive Window ......Dow Corning ® silicone reactive...
Dow Corning® Silicone Reactive Hot-Melt Adhesive Window Assembly Sealants
Technical Manual
Table of ContentsIntroduction
Product Information
Quality Assurance
IndustryCertifications
SubstrateSelection
Adhesion
MaterialCompatibility
ShelfLifeandStorageConditions
Sealant Design Considerations
CureRequirements
DeterminingandMaintainingSealant JointDimensions
Glue-LineThicknessandJoint MovementCalculations
DeterminingThermally-induced DifferentialMovement
DeterminingSealantGlue-LineThickness
BiteCalculationforWindLoad
BiteCalculationforDeadLoad
SettingBlocks
TypicalYield
Application
SafeHandlingInstructions
VolatileOrganicContent(VOC)
ProductHandlingPrecautions
SafetyInstructions
RecommendedPersonal ProtectiveEquipment
QualityControl
DeterminationofCureState
SubstratePreparation
In-ShopApplication
DispensingEquipment
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GlazingTable
ManufacturingProcessConditions
DispensingTemperatures
DispensingTooHot
DispensingTooCold
GlazingProcess
GeneralConsiderationsforApplying Dow Corning®InstantGlazeWindow AssemblySealants
ShutDownConsiderations
QualityControlandApplicationIssues
BeadLocation
BeadConsistencyandUniformity
SubstrateIssues:UnevenSurfaces inWindowSash
EquipmentIssues
EnvironmentalIssues
Deglazing and Reglazing of Window Units
ShopReglazing
FieldReglazing
Finished Unit Recommendations
Comparative Performance
GreenStrength
Adhesion-in-peelStrength
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IntroductionThismanual is intended to provide technical information,selectionandapplicationguidelinesfortheDow Corning® brandofpatented,neutral-cure,reactivehot-meltadhesives.Thesehot-meltadhesiveproductsaredesignedforautomat-ed back-bedding application in the assemblyofwindowsand doors, and become part of a total manufacturingproductivity solution when used with standard hot-meltdispensingequipmentandanautomatedX–Yglazingtable.
Thismanualcannotbeconsideredacomprehensiveguide asfenestrationproductsvaryinmanyaspects,includingde-sign,customerrequirements,manufacturingenvironmentsandend-useapplications.Forthepurposeofthismanual,anyreferencetowindowscanbeconsideredinterchangeablewithdoors.
DowCorningTechnicalCustomerServiceprovidesprocess workflowsandresourcestomanageproductandtechnicalinformationinquiriesfromcustomers.Theseinquiriesmayincludebutarenotlimitedto:
• Productrecommendations• Producttroubleshooting• Applicationassistance• Environmental,health,safetyandsustainabilitydata
Inquiriesarereceivedviae-mailortelephone:
• E-mail:[email protected]• Telephone:+18002482481
Product InformationDowCorningcurrentlyoffers threemoisture-reactivehot-meltproductsasawindowassemblysealant/adhesivetomeetcustomer-specificapplicationneeds.Theseproductscanbeusedindifferentapplicationsinthewindowindustrythatrequirebondingandsealing.
• DowCorning® InstantGlaze Window Assembly Seal-ant: Thissealantisdesignedforuseasaback-beddingsealant onmost commonwindowmaterials for stan-dard and impact-resistant glazing, and is compatiblewithcommoninsulatingglasssealants.Dow Corning® InstantGlazeSealantdispensesintoacrystalclearseal-antbeadorcanbecustompigmentedforlargevolumeapplications. It provides instant green strength, a15-minuteopentime,primerlessadhesionand±50%movementcapability.
• Dow Corning® InstantGlaze II Window Assembly Sealant: This sealant is offered as a lower viscosityand lower durometer alternative to Dow Corning® InstantGlaze Sealant for use by customers where these
features are desirable.Dow Corning® InstantGlaze II Sealantdispensesintoacrystalclearsealantbeadorcanbecustompigmentedforlargevolumeapplications.Itprovidesinstantgreenstrength,a15-minuteopentime,primerlessadhesionand±50%movementcapability.
• Dow Corning® InstantGlaze III Window Assembly Adhesive: This sealant is designed for use wherebetter resistance to creep, due to higher static loadsin the window design, is desirable.Dow Corning® InstantGlaze III Adhesive dispenses into a translucent sealant bead or can be custom pigmented for large volume applications. It provides instant green strength, a 15-minute open time, primerless adhesion and±50% movementcapability.
Formore information, visit dowcorning.com/construction orwww.instantglaze.comfor(Material)SafetyDataSheets,productdata sheetsandadditional informationonall Dow Corning®siliconereactivehot-meltadhesivewindowassemblysealants.
Quality AssuranceDowCorningconductsqualityassurancetestinginitsseal- antmanufacturingfacilities thatarecertifiedinaccordancetoISO9001andResponsibleCare®RC14001requirements.
Industry CertificationsEach product is approved as a bonding, back-bedding sealant compound by theAmericanArchitecturalManu-facturersAssociation (AAMA) andmay be found on the AAMAVerifiedComponentsList.ThemostrecentversionofthislistmaybefoundontheAAMAwebsite:
www.aamanet.org/general/1/111/verified-components.
Verified components on this list are tested perAAMA 800-10, Voluntary Specifications and Test Methods for Sealants, Section 1.1, Back-Bedding Glazing Compounds.
As of the publication date of thismanual, these productsareverifiedasback-beddingglazingcompoundsforcertifiedwindowsanddoors:
• AAMA805.2-10,GroupC:Dow Corning® InstantGlaze Sealant and Dow Corning® InstantGlaze II Sealant
• AAMA805.2-10,GroupA:Dow Corning® InstantGlaze IIIAdhesive
TheAAMA805.2classification is forapumpableandgunnablecompoundused tobedglass to the surroundingsubstrateandisintendedtobondtheglasstothesubstrateandpreventairinfiltrationandwaterpenetration.The805.2 compoundscurerelativelyhardandstiffandpermitlimited movementwithoutlossofbond.Theperformancerequire-mentsforthe805.2classificationinclude:
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• Hardness:When tested in accordance toASTMC661, theShoreAhardnessshallnotexceed70durometer.
• Thin Film Integrity:Thereshallbenopresenceofvoidswithinthe805.2compoundwhentestedinaccordancetoAAMA800-10,Section2.3.
• Peel Strength:Whenlaboratorytestedforpeeladhesion (modifiedASTMC794),805.2compoundsshallexhibitpeelstrengthsofatleast12.5pli(lbfperinchofwidth).
• Failure Mode:When laboratory testedforpeeladhe- sion(modifiedASTMC794)or,alternatively,lapshear(modifiedASTMC961),GroupCshalldemonstratepredominantlycohesivefailure(>90%).GroupAislimitedtochemicallycuringsealantswhichdemonstrateadhesivefailurebutwhichhavebeenshowntoprovideacceptablefieldperformance.
• Vehicle Migration:Thereisnovehiclemigrationfroman 805.2compoundedgewhentested inaccordancewith amodifiedASTMD2203(AAMA800-10,Section2.8.1).
• Low Temperature Flexibility: 805.2 compoundsshallhavenocracksand/orlossofadhesionfromthetestpanelwhentestedinaccordancewithamodifiedASTMC734(AAMA800-10,Section2.9.1).
• Water Resistance:805.2compoundsshalldemonstrate nopresenceofvoids,cracks,separationorbreakdown whentestedinaccordancetoAAMA800-10,Section2.11.1.
Substrate SelectionDow Corning® InstantGlazeWindowAssemblyproductsaresuitableforback-beddingapplicationsutilizing,butnotlimitedto,thefollowingsubstrates:
• Aluminum◦ Anodized◦ Millfinished◦ Kynar®(polyvinylidenefluoride)finish◦ Duranar®finish
• Fiberglassandothercompositematerials• Glass• PolyvinylChloride• Wood◦ Clad◦ Primedorunprimed◦ Treated
AdhesionAll Dow Corning®windowassemblysealantsaredesignedtoexhibitexcellentadhesiontocommonsubstratesovera widetemperaturerangeanddonotrequiresurfacepriming. Substratesmaybesubjecttofurthertreatmentandcoating toenhancedurability.Allsubstratesshouldbetestedaspart of the sealant selection process. Consult a DowCorning
ApplicationEngineerwhensubstrateschangeornon-typical finishesarespecified.
TheDowCorning test laboratory located inMidland,Michiganoffersavarietyofcapabilitiestoensurethata particularsealantwillmeetacustomer’sdesignrequirementsforthewindowapplication.TheadhesionofDowCorningproductstoacustomer-specificsubstrateisevaluatedusingamodifiedversionofASTMC794Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants.
Material CompatibilityTheDowCorningtestlaboratoryconductscompatibilitytestingaccordingtoASTMC1087Standard Test Method for Determining Compatibility of Liquid-Applied Sealants with Accessories Used in Structural Glazing Systems.Inaddition tothesuitabilityofsubstratesforadhesion,componentssuchassettingblocks,weatherstripping,gasketsandother windowaccessorymaterialsmustbecompatiblewith Dow Corning®sealants.Chemicalincompatibilitiesbetween materialsmayresultindiscoloration,lossofadhesion and/orinhibitthecureofthesiliconesealant.
Basedonhistoricaltesting,somecommonmaterials,suchas siliconeweatherseals,siliconeinsulatingglasssealants,polyurethanefoamtapeandvinylextrusions,arefoundto becompatiblewithDow Corning®InstantGlazeWindow Assemblyproductswithnodiscolorationorcureinhibition.
Othermaterials,suchasethylenepropylenedienemonomer (EPDM)rubber,neoprene,Santoprene®,Kraton®andother similarorganicmaterialsaretypicallyfoundtocauseslight discolorationoflight-coloredsealants.Thesematerialsare usuallyapprovedforincidentalcontactwithglazing-typesiliconesofallcolors;butpigmentedsealantsmaybepreferableifthesealantlineisvisibleorifanypotentialdiscolorationneedstobemasked.
ContactaDowCorningApplicationEngineerforquestionsregardingcompatibilityandtesting.Standardtestsrequirefourweeksfromreceiptoftestsamples.DowCorningcanaccommodatenon-standardtestswithsufficientleadtimes,whichmaybesubject toaservicefee.Testreportsfrom DowCorningshouldnotbeinterpretedasapprovals.
Shelf Life and Storage ConditionsItisimportanttouseanyDowCorningproductwithinitsrecommendedshelflife.Theexpirationdate(EXPDATE)isclearlydisplayedonthepackaginglabel.Dow Corning®
InstantGlazeWindowAssemblyproductsshouldbestoredintheiroriginal,unopenedcontainersinacleananddryenvironment below 90°F (32°C). These products have a shelflifeof12monthsfromthedateofmanufacturewhen storedbelow90°F,andarepackagedinair-tightcontainersbecauseofitsreactivitytoatmosphericmoisture.
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Figure 1:Typicalcure-in-depthratesforDow Corning® InstantGlaze WindowAssemblyproductsatthreedifferentsetsoftemperaturesandrelativehumidities
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Sealant Design ConsiderationsProperly installed and fully cured back-bedding sealantallowthewindowunittoholduptoawiderangeofweatheconditions and pass design pressure testing.The sealanserves a primary purpose as aweatherseal to prevent ainfiltrationandwaterpenetration.Thesealant isdesignetoadhereandabsorbstressesbetweenthewindowsashantheglassasaconsequenceofmovement fromthermallinduced expansion or contraction and wind loads. Thmovementcapabilityofafully-curedsealanthelpsabsorthese stresses, rather than distribute them throughout thwindowunittoothercomponents,suchastheglass.
Theglue-linethicknessofacuredsealantmustbedesignetoaccommodatejointmovementsduetodifferencesinththermalexpansionofthedifferentmaterialsinthewindowunit.Thejointbite—theminimumwidthorcontactsurfacofthesealantonboththewindowsashandglass—musbedesignedtoaccommodatebothdeadloadsanddynamiloadssuchasfromthermalfluctuations,windorimpacInallcases,opposite-sidemechanicalsupportssuchasglazinbeadsarerequiredastheproductsinthismanualarenoconsideredstructuralsealantsasdefinedbyASTMC118Standard Specification for Structural Silicone Sealants.
Cure RequirementsAll Dow Corning®one-partwindowsealantscurebyre-actingwithmoistureintheatmosphere.Therateofcuredependsonthediffusionofatmosphericmoisturethroughtheinterfaceoftheexposedsealantwithinthesealantjoint.Therefore,one-partsealantscurefromtheoutsidesurfaceinward.Therateofmoisturediffusionisaffectedbyseveralfactorsincluding:
• Partial pressure of water vapor: This depends ontemperatureandhumidityintheimmediatesurroundings,and is thedrivingforce fordiffusion. Increasing tem-peraturewithout changing thewater content in theatmosphere(suchthat therelativehumiditydecreases)willnotacceleratecure.
• Dimensions of the sealant joint: The diffusion rateof moisture obeys Fick’s law and is proportional to the square root of time. Therefore, the length of time needed for the one-part sealant to fully cure increases significantlywithanincreasinglydeepersealantjoint.
• Joint configuration or joint design: Areas such as corner keys and windows with tight clearances maynotaffordone-partsealantswithsufficientexposuretoatmosphericmoisture,andtightclearanceswithlittleaccess to theatmospherewillslowthecureprocess.Conversely, porous substrates will interfere less withthe cure process and small amounts of absorbedmoisture(suchaswithwoodsubstrates)mayacceleratethecureprocess.
• Sealant composition: Silicones are more permeablethan organic materials. To improve mechanical strength,
s silicone sealants are formulated with inorganic fillers,r which decrease the moisture diffusion rate. Thist decrease will depend on the type and the amount ofir fillerinthesealant.d
Figure1providesunidirectionalcure-in-depthprofilesfordthreedifferentsetsofconditionsoverthefirst48hoursyafterapplicationthatmaybeexpectedfromDow Corning® eInstantGlazeWindowAssemblyproducts.Theactualcurebperformancemayvarydependingonjointdesign.eAll Dow Corning®InstantGlazeWindowAssemblyproducts provideinstantgreenstrength.Greenstrengthcanbede-dscribedastheinitialshearstrengthbeforethesealantstartseto exhibit sufficient cure that, in turn, buildsmechanicalandadhesionstrength.Thegreenstrengthofthesehot-melteproductswill reduce hold times in thewindow assemblytprocessnecessaryforsufficientcuretooccur.UnitsmadecwithDow Corning®InstantGlazeWindowAssemblyprod-t. ucts have been successfully tested for air infiltration andg waterpenetrationwithinhoursofmanufactureaccordingtotASTME283Standard Test Method for Determining Rate 4 of Air Leakage through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the
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SpecimenandASTME331Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference.
Whilesealantgreenstrengthdoesallowforimprovedman-ufacturingthroughput,careshouldstillbetakentoensurewindowunitsarenotallowedtorackduringthepackagingorshippingprocess.Ifthesealantisnotfullycured,unitsthatbecomeout-of-squarecansetintothisdistortedshapeduetotherackingforcesovercomingthegreenstrengthofthematerial.
Determining and Maintaining Sealant Joint DimensionsNote: It is the responsibility of the window manufacturer to determine the appropriate bead size that will deliver the necessary joint dimensions for each product design, joint configuration and application based on the sealant properties provided in the product data sheet. It is incum-bent on the window manufacturers to rely on their experience and to validate product design by performing the necessary unitized industry tests.Glue-line thickness is defined as the sealant thickness necessary to absorbmovement expected between thewindowsashandtheglassduetoclimatic-inducedloads.Todetermineglue-linethickness,thefirststepistoidentifythedirectionandmagnitudeofthemovement.Thesealantgenerallyundergoesthemostmovementinthedirectionofthelongestdimensionofthewindow.
Asabasisfordeterminingtheappropriateglue-linethicknesswhenusingDow Corning®InstantGlazeWindowAssembly products,itisrecommendedtostartwitha3/16-inch(5mm) nominalbeaddiameter.Theinitialbeaddiameterwillcon-tractinvolumebyapproximately6%asitcoolsdownfrom itsrecommendeddispensingtemperature.Thisbeaddiam-eter, assuming no squeeze out, results in a typical bite(contactwidth)ofapproximately1/2inch(13mm),andacompressed sealant glue-line thickness of approximately0.055 inch (1.3mm).WhileDow Corning® InstantGlaze Window Assembly products may in some applicationsexhibit sufficient stiffness between the window sash andtheinsulatingglass(IG)unit,thisbehaviorcannotbesolelyreliedupontomaintainglue-linethickness.Bumpers,suchas thoseused in aluminumapplications, and/orglazinglegs,suchasthoseseeninvinylandwoodapplications,arerequiredtomaintaintheappropriateglue-linethicknessandtominimize excessive squeeze out.DowCorning recom-mends glue-line thickness requirements be assessed byconductingmovementcapabilitytestsand/orfiniteelementanalysisforeachwindowdesign.
Attentionshouldnextbegiventotheapplicationprocesstoverifythatasufficient,uniformandconsistentbeadisappliedaroundtheentireperimeteroftheglazinglegwith
noskips,thinspotsorshallowareas.Iftheapplicationequipmentisnotrobustenoughtoensureaconsistentlyappliedminimumglue-lineprofile(biteandthickness)accordingtodesigncalculations,asafetyfactorshouldbe appliedtoincreasetheoverallbeadsizesothatthedesign requirementsaremetinworst-casesituationsorlocations.
Care should also be taken in the dispensing process toensuretheglue-linethicknessdoesnotfallbelowthedesignrequirement.Excessivesealantcompressionafterbeddingthe glass and installing opposite-side glazing beads mayreduce theglue-line thickness such that severe climatic-induced movements may exceed the sealant’s movementcapability.Wood, vinyl andfiberglass sashprofiles typical-lyhaveglazingdamstoestablishandmaintainthedesignglue-line thickness. It is unacceptable for glass tomakecontactwithaluminumsashprofiles such that tapesandbumpersareoccasionallyusedtoensureandmaintaintheappropriateglue-line thickness.Regardlessof themethodtomaintainglue-linethickness,themaintakeawayshouldbethatadefinablethicknessisrequiredtoallowthesealanttoperformitsdesignedfunctions.
Glue-Line Thickness and Joint Movement CalculationsAproperlydesignedglue-linethicknesswillfacilitatethe assemblyprocessofwindowunitsandminimizestresses onthesealantjointandinterfacesresultingfrommovements duetothermalexpansionandwindloads.Glazedwindowsundergoexpansionandcontractionmovementsduetodiurnal temperaturecycles,heattraps,windloadsandproximitytoheatingandairconditioningvents.Theglue-lineshouldbedesignedtoaccommodatethesemovementsinordertominimizestressandpreventtheglassfrombreaking.
Thermally-induced movement may be estimated for any window sash profile or IG unit if its length (longest di- mension),compositionandlinearcoefficientofthermalexpansion(CTE)areknown.LinearCTEvaluesfortypicalwindowsashmaterialsintheproximityof77°F(25°C)arelistedinTable1.
Table 1: Linear coefficient of thermal expansion for typicalwindowsashmaterials
MaterialLinear Thermal Expansion Coefficients
10–6 in/in∙°F 10–6 m/m∙K
Aluminum 12.3 – 13.2 22.2 – 23.8
Fiberglass 6.5 11.7
Float Glass 5.0 – 5.1 9.0 – 9.2
PVC 28 50.4
Wood 2.1 – 3.0 3.8 – 5.4
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Themaximumthermalmovement(expansionorcontraction) foraparticularmaterialfromachangeintemperatureΔT canbecalculatedasfollows:
Movement(in)=Length(in)×CTE(in/in∙°F)×ΔT(°F)
Figure2 compares themovement, either contractionor expansion, for every10 lineal inchesof typicalwindowmaterials resulting from a 10°F (5.6°C) change in tem-peratureusingtheaveragelinearCTEdatafromTable1.
Determining Thermally-induced Differential MovementGlazedwindowsundergoexpansionandcontractionmove-mentsduetodiurnal temperaturecycles,heat trapsandproximitytoheatingandairconditioningvents.Theglue-lineshouldbedesigned toaccommodate thesemovementstominimizestressandprevent theglass frombreaking.Thermally-induceddifferentialmovementmaybeestimatedforanywindowsashprofileandIGunitifitslength(longestdimension),compositionandCTEareknown.CTEvaluesfortypicalwindowsashmaterialcompositionsintheprox- imityof77°F(25°C)arelistedinTable1.BecauseIGunitsarealmostalwayssupportedonthebottombysettingblocks, andbecauseaspect ratios are such thatwindowsare typi-cally taller than they are wide, the largest magnitude ofthermalmovementistypicallyintheverticaldirection.Thethermally-inducedmovement in the vertical directionδv maybeestimatedbythefollowingformulawhereh is the heightofthewindowunit;CTEsashandCTEglass the linear CTEof thewindowsashandglass lite, respectively;andΔTsashandΔTglassthedifferentialtemperatureofthewindowsashandglasslite,respectively,relativetowhenthewindowunitwasassembledduringthemanufacturingprocess.
δv=h ∙(CTEsash ∙ΔTsash–CTEglass∙ΔTglass)
Assumingawindowisfreetoexpandandcontractinbothhorizontaldirectionsfromitscenterline, thermally inducedmovementδwexperiencedbythesealantacrossthewidth fromthecenterlineofthewindowmaybeestimatedbythe followingformulawherewisthewidthofthewindowunit.
δw=(w/2)∙(CTEsash ∙ΔTsash–CTEglass∙ΔTglass)
Indetermining thermally-inducedmovement inawindowunit,thedesignerseekstheresultwiththehighermagnitudeforthepurposeofcalculatingtheglue-linethickness.Unlessthewidthofthewindowunitismorethantwiceitsheight,inalmostallcasesthemovementintheverticaldirectionisgoingtobethevalueofhighermagnitude.
Sample Calculations
Awindowmanufacturerisassemblingaseriesofwindowsintended foruse inanenvironmentwhere theexpectedmaximumandminimumtemperaturesare140°F(60°C)and–15°F (–26°C), respectively. The factory where the unitsaremanufacturedismaintainedat65°F(18°C).Therefore,the temperature differential is greatest during the coldcondition,(65°F–(–15°F)=80°F).BecausetheIGunithasinsulatingcapability, it isexpectedtobewarmer thanthewindowsash.Figure3shows the resultingmovement fordifferentwindowheightswhenΔTglass isvariedfrom40°Fto80°F.Thetemperatureofthewindowsash,eitherPVC(topgraph)oraluminum(bottomgraph),isassumedtobe10°F(5.6°C)cooler.
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Figure 3:Thermally-inducedmovementasafunctionofwindowheightandΔTglasswhereΔTsashisassumedtobe10°Fcooler
Sample CalculationsJointmovement:
• Fora3ft×5ftglasslitefixedatthesillandatemper- aturechangeof40°Foverthecourseofa24-hourday,theglass(CTE~5.1×10–6/°F)willexhibitamaximum jointmovementbof:5ft∙(12in/ft)∙5.1×10–6in/in∙°F∙40°F=0.012in
• Avinylsashprofile(CTE~28×10–6/°F)willexpandby 0.067infromanincreaseof40°F
• Differentialmovementbis0.067–0.012=0.055inSealantmovement:
• Foradifferentialmovementb=0.055in,aback-bedding sealantwithaninitialglue-linethicknessofa=0.05inwilldeformtothefollowingdimension:
c=(0.050)2+(0.055)2=0.074in• Thetotalmovementofthisglue-lineprofileduetoa40°F
changeintemperatureis:
Consulttheproductdatasheetforthemovementcapabilityratingofanyback-beddingsealanttodetermineiftheglue-line thickness tobeused is suitable for thedesignof thewindowunit.
FollowingASTMC719Standard Test Method for Adhesion and Cohesion of Elastomeric Joint Sealants Under Cyclic Movement (Hockman Cycle) protocol, the movementcapability forallDow Corning® InstantGlazeWindowAssemblyproductsis±50%.Usingtherelationshipbetween
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Pythagorean theorem: a2 + b2 = c2
a = original glue-line thicknessb = joint movementc = deformed glue line after joint movement
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Determining Sealant Glue-Line ThicknessTherequiredglue-linethicknessaforadifferentialmovement bcanbecalculatedusingthePythagoreanTheorem(Figure4). Likewise,theallowablemovementbforaparticularglue-line thickness acanbecalculated.Thedeformedglue-linedimensioncwillbelimitedbythemovementcapabilityofthesealantundergoingshearinthejointconfiguration.
Insulating Glass Unit
Sealant
Window Profile
a and casitrelatestomovementcapabilityM,themaximumvalueforccanbedetermined.
c=a(1+M/100%)Therefore,c=1.5aforaback-beddingsealantratedwith±50%movementcapability, and theminimumglue-linethicknessthatwillbeabletoaccommodateamaximumallowablemovementbduetoachangeintemperatureis:
a=b2/1.25Figure5showstheeffectofglue-linethicknessaonthemax- imum allowable movement b for a back-bedding sealantratedwith±50%movementcapability.
Movementdirectionshouldalsobetakenintoconsideration. Intheworstcasescenario,thermally-drivenmovementwill occurinonedirectionduetosettingblockspreventinganydownwardmovementoftheIGunit.Inasystemwherethe IGunitisnotsupportedbysettingblocks,theIGunitmay moveinbothdirections.
Somevariabilityinthewindowsashsurfaceflatnessshouldbeanticipated.Theprocessequipmentthatextrudestheseal-antbeadcanalsobeexpectedtodemonstratevariability.Hence,aminimumglue-linethicknessof0.035in(0.9mm)shouldbeobservedregardlessofthecalculations.
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Bite Calculation for Wind LoadAsidefromthermalstresses,thebondshouldbeabletoac-commodatedynamicloadsduetowind,impactfromflyingobjectsornormaloperationofwindows.Thefollowingprocedurescanbeappliedtocalculatetheminimumbite(contactwidth)necessarytosimultaneouslywithstandboththeweightoftheIGunitandanywindload.
Note: The provided bite calculations are guidelines and each window manufacturer should decide if additional structural support is needed to retain the IG unit based on knowledge of the specific finished product and intended application.
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Figure 5:Allowable jointmovementasa resultofachange in temperatureasafunctionoftheglue-linethicknessofaback- beddingsealantratedwith±50%movementcapability
Figure 4:Schematicdiagramsforthedimensionsusedtocalculate movementinthejointconfiguration.
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ApplicationSafe Handling InstructionsBeforehandlingaDow Corning®InstantGlazeWindowAs-semblyproduct,reviewtheproductandsafetydatasheetsand the container label for safe use, physical and healthhazardinformation.Anyexposureofopenedcontainerstoair is discouraged because these productswill reactwith moistureintheatmosphereandbegintocureonthematerialsurface.The presence of local exhaust ventilation shouldbe discussedwith your safety department. Be aware thatairdraftsfromventilationsystemsintheproximityofthedispensingnozzlemayaffectitstemperature,whichwillinturn impactbead size consistencyand sealantwet-outonthewindowsash.
The product and safety data sheets are available fromdowcorning.com and www.instantglaze.com.Copiesmay alsobeobtainedfromyourlocalDowCorningSalesRepre-sentativeorDistributor.
RefertoIn-Shop Applicationofthedispensingequipmentforrecommendationsonthesafeoperationofthebulkmelter.
Theminimumsealantbitewnecessarytoresistagivenwindloadcanbeapproximatedusingthefollowingformula wherewandtheshorterdimensionofarectangularIGunithavethesameunitoflength(inormm),andwindloadand stresshavethesameunitofpressure.
Forexample,themaximumallowabledesignstressforDow Corning®InstantGlazeWindowAssemblyproductsis20psi(0.14MPa).Fora6ft×8ftIGunitwithanappliedwindloadof40psf,thesealantbitedimensionwillbe:
Toanticipatebeadsizevariabilityduringsealantbeadextru-sion,regardlessofthecalculationoutput,aminimumbiteof3/8in(9.5mm)shouldalwaysbeobserved.
Bite Calculation for Dead LoadTheweightoftheIGunitactsasadeadloadforthesealant bondwhenawindowisopened.ThefollowingformulacanbeusedtocalculatetheminimumbitedimensionwtoaccommodatethisdeadloadwheretheweightoftheIGunit isbasedonaglassdensityof0.090lb∙in3(2500kg∙m3)and gravitationalaccelerationis386in∙s–2(9.81m∙s–2).
Forexample, themaximumallowabledesignstress foraconstantloadforDow Corning®InstantGlazeWindowAssemblyproductsis1.0psi(0.007MPa).Fora3ft×5ftIG unit(192-inperimeter),theminimumbitedimensionforadeadloadof50lbfis0.26in(6.60mm).
Inalmostallapplications,theIGunitshouldbesupportedon the bottom by appropriately placed setting blocks perindustryacceptedpracticesfoundintheGlassAssociationofNorthAmerica(GANA)manual.WhereIGunitsaresupportedbysettingblocks,thesealantdoesnotexperienceanydeadloadandonlyexperiencesdynamicstressessuchasthermalandwindloadingconditions.
Setting BlocksSetting blocks are almost always required bywindowindustryIGmanufacturers.Alwaysensuresettingblocks incontactwith theDow Corning® InstantGlazeWindowAssembly products have been tested and approved forchemical compatibility.The primary function of settingblocks is thesupportofboth the inboardandoutboardlites of glass on the same horizontal plane.This ensures ashearingstressdoesnotoccurduetooneofthelitesbeing supportedonlybytheIGsealantsystem.ExcessiveloadingontheIGsealantsystemmayleadtofailureoftheIGsealandultimatelyIGfailure.BysupportingtheIGunitalong
thebottomwithaminimumoftwosettingblocks,verticalloadsintheIGunitaretransmittedentirelytothewindowsash for support.However, this practice results in thethermally-inducedmovementofboth thewindowsashandglasstobeintheverticaldirection.Sincemostwindowshave aspectratioswhereheightexceedswidth,thismovementisusuallythegreaterintheverticaldimension(height).
Typical YieldThe amount ofDow Corning® InstantGlazeWindowAs- semblyproduct required tomeeta targetmanufacturingnumberofwindowunitswill dependon thebead sizeofthesealantandtheperimeterlengthoftheunit.Oncebeadsizeandglue-linethicknessareestablishedbythewindowmanufacturer,Table2canbeusedasaguidetoestimatethelinealcoverageofagallonofsealantfordifferentbeadsizes.Thenumberof identicalwindowunits thatcanbemanufacturedpergallonofsealantcanthenbecalculatediftheperimeterlengthofthewindowunitisknown.
Table 2:Effectofbeadsizeonlinealcoveragepergallonofsealant
Initial Bead Size,1 inch
Linear Coverage per Gallon2
inches feet1/8 0.125 18,800 1,5003/16 0.188 8,400 6601/4 0.250 4,700 3803/8 0.375 2,100 170
1 Basedonacircularcross-section 2 Calculatedwithconsiderationtowasteduetostart-upandpurging
w= 2×MaximumallowabledesignstressShorterdimensionofIGunit×Windload
w= =0.50in2×20psi
6ft×12in/ft×40lbf /ft2×1ft2/144in2
w= PerimeterofIGunit×MaxallowabledesignstressWeightofIGunit×Gravitationalacceleration
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Volatile Organic Content (VOC)• Non-hazardousformulation• LowVOC<15g/L
(exemptfromCaliforniaVOCregulations)
Product Handling Precautions
Theproductisgenerallydispensedaround248°F(120°C).Theuseofpersonalprotectiveequipmenttopreventcon-tactofhotmaterialorhotequipmentsurfaceswithskinoreyesisrecommended.
Safety Instructions
Safetyinstructionscontainedinthismanualapplytotasksthatmay be performedwithDow Corning® InstantGlaze WindowAssemblyproducts.Itisimportantthatthesesafety instructions are followed to protect employees, operators,andequipment.
• Becomefamiliarwithandfollowallsafetyinstructionsprescribedbyyourcompany,generalaccident-preven-tionregulationsandgovernmentsafetyregulations.
• Becomefamiliarwithandfollowallsafetyinstructionsprescribedbytheequipmentmanufacturers.
• Scheduleperiodicsafetyinspectionstoensurerequired materialandequipmentpracticesarefollowed.
• Provideappropriateemergencyandfirst-aidequipment intheproductionworkspace.
Recommended Personal Protective Equipment
Productanddispensingsystemarebothhotandpressurized.
• Safetyglasseswithsideshieldsorgoggles• Cut-resistantgloveswhenhandlingscrapersordeglaz-
ingtools• Glasshandlingjacketsand/orsleeves• Heat-resistant gloves to protect against burns when
workingwithhotmaterialsandequipment• Steel-toedshoeswhenhandlingproductcontainersand
windowunits
Quality ControlCustomersshouldexaminetheexpirationdate(EXPDATE)displayed on the packaging label to verify the product iswithin itsshelf life.Theseproductshaveashelf lifeof 12monthswhenstoredinaproperlysealed,air-tightcontain-erattemperaturesbelow90°F(32°C).Theproductshouldbeinspectedfortracesofcureuponopeningthecontainerforthefirsttime;refertothesectionDetermination of Cure State.Anyattempt topumpcuredmaterialwill impact beadqualityandcouldeventuallyleadtopumpdeteriorationandmalfunction.
Determination of Cure StateDowCorningpackages itsproducts incontainers thatareproperlysealed,buteventsmayoccur,suchasmishandlingofcontainers,thatmaycompromisetheintegrityoftheseal.Acompromisedsealmayallowairingressintothecontainer.Themoistureintheairwillproducethedetrimentaleffectofcuringthesurfaceoftheproductbeforeitcanevenbedispensedbythecustomer.
Dow Corning®InstantGlazeWindowAssemblyproductsdo notchangeinappearancebefore,duringoraftertheyarefully cured.The products undergo a change from a gum-likeconsistencyintheuncuredstateatroomtemperaturetoacross-linkedrubber-likematerialwhencured.
ToensurethatDow Corning®InstantGlazeWindowAssembly productscanbepumped,apicktestwasdevelopedtodetermineifthesurfaceoftheproductinitscontaineriscured(Figure6).
Usingascrewdriverorsimilartool,stabthesurfaceofthehot-meltproductandattemptto‘pick’up(remove)aportionofthematerial.ThetopphotographinFigure6showswhat willhappeniftheproductisuncured:thescrewdriverhead isabletopickupasmallamountofmaterialasthescrew-driverispulledquicklyawayfromthesurface.Thebottomphotographshowswhatwillhappeniftheproductiscuredattheexposedsurface:thesmallamountofmaterialthatispickedupbythetoolwillresistseparatingfromthebulkin
Good – Acceptable: Uncured product is gummy, separates easily and remains on the tool when pulled away from the surface.
Reject – Unacceptable: Cured product displays rubbery features, stretches and resists separation when pulled away from the surface.
Figure 6:DeterminationofthecurestateofDow Corning® InstantGlazeWindowAssemblyproductsusingapicktest
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thecontainer.Anyoccurrenceofcureinthecontainerwillnotallowtheproducttobeproperlypumpedanddispensed.AvideoofthepicktestmaybefoundontheYouTubewebsiteat:www.youtube.com/watch?v=R95sUPaB_Hc.
Substrate PreparationDow Corning®InstantGlazeWindowAssemblyproductsdo notrequireprimers topromoteadhesiontocommonfene-strationsubstrates.Specialsurfacepreparationprocedures,suchassolventwiping,areusuallynotrequiredwhenap-plied toclean,drysubstrates.ThewindowmanufacturingprocessshouldthereforebesetupinamannerwhereinthewindowsashandIGarekeptcleanandfreeofdustandde-brispriortothesealantbeingapplied.Itisrecommendedtocleanthesubstratewhenindoubt.
When a cleaning solvent is used, the proper choice ofsolvent is an important part of the surface preparationrequirementsforsubstratesthataretobebonded.Cleaningsolventsdiffer ineffectiveness in removingcontaminants.Beawarethat theuseofaggressivesolvents likemethylethylketonecanadverselyaffectfinishessuchaspolyesterpowder-coatedaluminum.Mildercleaningsolventssuchas isopropyl alcohol (IPA) and high-quality (greater than98%purity)white/mineral spirits canbeusedwithoutdamagingthesubstratesurface.
BeforebeddinganIGunit,theglassedgeoftheouterpane mustalsobepreparedforbonding.Thisentailsensuringthe glassedgeiscleananddry.TheIGunitshouldbefreeofany cuttingoils,grease,dirtandotherformsofcontaminationwhichmightotherwisepreventproperadhesionandad- verselyimpactthelong-termdurabilityofthebond.
Dow Corning recommends checking with the substrate supplier and IGmanufacturer for the compatibility of cleaning solvents. Always follow manufacturer/supplier safehandlingrecommendationsaswellaslocal,stateandnationalregulations.
In-Shop ApplicationDispensing EquipmentDow Corning®InstantGlazeWindowAssemblyproductsaredesigned for dispensing from automated, high-volume bulkmelters (or hot-melt pumping systems) for 5-gallon/20-liter or55-gallon/200-litercontainers inconjunctionwithauto-matedroboticorhand-assistequipment.DowCorningcanprovideengineeringassistance in thedesignofadeliverysystem.Equipmentsuppliersofbulkmelterstypicallypro- videdesign,installation,operationandmaintenancetraining.
Hot-meltpumpscanberuneitherunderconstant floworconstantpressure.Dispensingproductunderconstantpressureusually leads tomoreconsistentflow.However,thiscanleadtoslightvariationsinflowwhenchangingcontainersduetobatch-to-batchviscosityvariations.To
maintainconstantvolumetricflow,thebestsolutionistorunthehot-meltpumpatconstantpressureandtoinstalla metering(gear)pumpjustbeforethenozzle.Thevolumetric outputdependsontemperatureandcanbeadjustedwiththe helpoftheequipmentsupplierandDowCorningtechnicalservicepersonnelduringthestart-upphase.
Thehose isan importantcomponentofapumpandgundeliverysystem.Theplanninganddesignoftheproductionareawherethesealantwillbeappliedshouldbefirsttakeninto consideration before selecting the appropriate hoselength and diameter.Hoses should be designed to be asshort inlengthandassmall indiameteraspossible,andmustnothavesomuchofapressuredropsoas tostarvethedeliveryofmaterialatanypointduringthedispensingphase.Hoses thatare too longand too large indiametercanmakemaneuveringthegunordispensingheaddifficult.Longerhoses requirehigherpressures tomaintain targetflowrates,andincreaseradiantheatloss.
Airflowaroundthedispensingnozzlewillbemuchcoolerthanthehot-meltmaterialexitingthehose.Variationsinambienttemperaturemayaffectbeadconsistencyunlessheatednozzlesareusedorthenozzlehasenoughbulktomaintainareasonablyconsistenttemperature.
Glazing TableAn automated X–Y glazing table is the most efficient method for applying glazing sealants to maintain beadconsistency,reducelaborandminimizewaste.ConsultyourDowCorningSalesRepresentativeforcontactinformationformanufacturers ofmelter and table equipment.Auto-matedglazingtablesapplysealantinthemostconsistentmanner,butproblemscanoccur.Routineoperationalauditsand preventivemaintenance schedules can help ensureconsistentsealantdelivery.
Toassistwith sealant applicationfilling issues, it isgoodpracticetohaveacompatiblesiliconesealantavailableincartridgeformthatcanbedispensedusingacaulkgunfor remedial glazing, or supplement sealant to thinly applied,shalloworskippedareasoftheglazedunitpriortobedding the glass.Dow Corning® 1199 SiliconeGlazing SealantClear,Dow Corning® 9-1350SiliconeGlazingSealant orDow Corning® 791SiliconeWeatherproofingSealant canbeusedinsuchsituations.
Manufacturing Process ConditionsDow Corning® InstantGlazeWindowAssembly productsdependonmoistureintheatmospheretocompletelycurethe sealant bead even though theyprovide instant greenstrength. The atmosphere in themanufacturing and anystagingareasshouldhaveaminimumrelativehumidityof30%andpreferably50–60%.Thecure rateof theseprod- uctswillbeaffectedastemperatureandrelativehumidityvaryduetonormalseasonalfluctuations.
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The temperaturearound theglazingprocess shouldbewithin65°F(18°C)and90°F(32°C).Coldertemperatureswillreducecurespeedandadhesiondevelopment.Hottertemperatureswillinitiallyreducegreenstrengthandmaypromotesqueezeout;however,curespeedmayincrease.
Thesurfacetemperaturesoftheglassandwindowsashmust notfallsubstantiallybelowtherecommendedmanufactur- ingprocess temperature.Lower temperaturesmay lead to condensationorwetsubstratesurfaceswhichmayinfluence beadqualityorinhibitcure.
Themanufacturingenvironmentshouldbedustfree.
Dispensing TemperaturesThedispensingtemperatureiscriticalfortheproperappli-cation ofDow Corning® InstantGlazeWindowAssemblyproducts.Figure7showstheeffectoftemperatureonthehot-meltviscosityoftheseproducts,whichshouldnotbeexposedtosustainedtemperaturesabove285°F(140°C).
Table3listsrecommendedtemperaturerangesfordifferentzonesinthebulkmelterandisbetween248°F(120°C)and266°F(130°C).At248°F,theviscositiesofDow Corning® InstantGlaze II Sealant and Dow Corning® InstantGlaze III Adhesivearesimilarandapproximately75%lowerthanthat ofDow Corning®InstantGlazeSealant.Thesmallervolume zonesclosertothenozzlemaybesetathighertemperaturestoincreaseflowatthenozzlebutshouldnotexceed285°F(140°C).Thenozzletemperaturemayneedtobesethigherthan zone temperatures but should not exceed 285°F(140°C)dependingonairdrafts andheat losses from theuninsulatedmetalnozzle.Thisisgenerallyacceptablesince theresidencetimeofthehotmeltflowingthroughthenozzle isrelativelyshort.Maintainnozzletemperaturesatthelow-estpossibletemperaturewhichproducesconsistenthot-melt
Temperature, °F
Shear rate, s–1
Shear rate, s–1
Temperature, °C
0
0
0210
10
10
100
220
100
100
110
230
120
240
130
250 260 270
1000
1000
100,000
200,000
300,000
50,000
50,000
400,000
100,000
100,000
500,000
150,000
150,000
600,000
200,000
200,000
T = 120°C (248°F)
T = 130°C (266°F)
Visc
osity
, cP
Visc
osity
, cP
Visc
osity
, cP
Dow Corning® InstantGlaze Sealant Dow Corning® InstantGlaze SealantDow Corning® InstantGlaze II Sealant Dow Corning® InstantGlaze II SealantDow Corning® InstantGlaze III Adhesive Dow Corning® InstantGlaze III Adhesive
Table 3:Recommendedzonetemperaturesforhot-meltunloader
ZoneTemperature
°F °CPlaten 248 – 266 120 – 130Hose 248 – 266 120 – 130
Gun body/valve 248 – 266 120 – 130Metering pump 248 – 266 120 – 130
Nozzle1 248 – 285 120 – 1401 Mayexceed266°F(130°C)dependingondrafts,ambienttemperatureandheatlossthroughthenozzle.
flowandbeaddimensions.Takeadvantageofanyequipmentoperational safety feature thatwill protect thehot-meltproductfromoverheating.Thiswillalsoextendtheservicelifeofo-ringsandsealsusedinthedispensingequipment.
The hot-melt viscosity ofDow Corning® InstantGlaze WindowAssemblyproductswillalsodependonshearrate, whichisproportionaltothevolumetricflowratecomingoutofthenozzle.Figure8showshowthehot-meltviscosity changeswithshearrateat120°C(248°F)and130°C(266°F). ForthesealantbeadsizeslistedinTable2,theshearratecanbeexpectedtovarybetween10and200s–1inthehose andbetween100and1,000s–1inthenozzle.
Figure 7: Effect of dispensing temperature on the hot-melt viscosityofDow Corning®InstantGlazeWindowAssemblyproducts (1,000cP=1,000mPa∙s=1Pa∙s)
Figure 8:Effectof shear rateon thehot-meltviscosityof Dow Corning® InstantGlaze Window Assembly products at120°C(top)and130°C(bottom).1,000cP=1,000mPa∙s=1Pa∙s
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Dispensing Too HotCaution: Maintaining the material at temperatures over 266°F (130°C) over extended periods of time may have the following detrimental effects:
• Reduced tackiness• Beaddraggingaroundthecorners• Bubbles in sealant• Reducedpotlife• Excessivefluidity
Dispensing Too ColdOperatingattoolowatemperaturewillincreasetheviscosity, leadingtopredictableproblems:
• Difficultypumping• Unevenflowfromnozzle• Build-upofmaterialon thesideof thenozzlecausing
offsetdispensing• Stringinessbehindthenozzle
Draftsoratmosphereslowerthantypicalroomtemperatures [65°F (18°C)] may contribute to adverse dispensingperformanceatthenozzletip.
After a Dow Corning® InstantGlaze Window Assemblyproducthasbeendispensedat248°F(120°C),itwilltakeapproximatelyfiveminutesforthebeadtocooldowntoambienttemperatures.Figure9showstypicalchangesinbeadtemperatureasafunctionoftimeelapsedafterwettingouttypicalwindowsashsubstrates.Thetemperatureprofiledepends on the thermal conductivity of the substrate(s);for example,wood andPVC (and silicones) have similarthermalconductivities(~0.2W∙m–1∙K–1)comparedtowin-dowglass(~1W∙m–1∙K–1)andaluminum(~200W∙m–1∙K–1).
Glazing Process• Opentimeisdefinedasthemaximumelapsedtimeafter
dispensingthesealantforcompletingallmanufacturingstepsoneachunit.Dow Corning®InstantGlazeWindowAssemblyproductshaveupto15minutesopentimeatroom temperature.Thisprovidesprocessingflexibilityandrobustmanufacturingoptions.The15-minuteopentimeallowstheglasstoberealignedorreworkedduringinstallation,andallowsinstallationofsettingblocksandspacers,aswellasopposite-sideglazingbeadsandothercomponents,withoutadverselyaffectingthepropertiesofthesealant.
• Oncesealantisappliedtothewindowsash,theglass,settingblocksandspacersshouldbeinstalledandposi-tionedwithin15minutes.Ifthesealantisleftforlongerthan15minuteswithouttheglassbeinginstalled,thesealantshouldberemovedfromthewindowsashandafreshbeadshouldbeapplied.
• Ensuretheglassisbeddeddirectlyonthesealantandnotboundindirectcontactwiththewindowsash.
• Installsettingblocksandspacerstocontrolthepositionoftheglassinthewindowsash.Toallowforplacementof setting blocks, glassmay be shifted slightly if nec-essarybyapplyingaslow,steadyforcewithathin,hardplastic spatula. If glass shifting, repositioning or anyreworkingisrequired,itshouldbedonewithinthefirstfiveminutesafterdispensingthesealant.
• Applyopposite-sideglazingbeadsprior to leaning the windowaway from the sealant. If productionwill not allowforthis,storethewindowuniteitherflatorwith theweightoftheglassleaningonthesealant.
General Considerations for Applying Dow Corning® InstantGlaze Window Assembly SealantsFollow themanufacturer recommendations formaterialdispensingandpumpoperation.
Initial Start-Up Tips• Disconnectthehoseattheglazingtableandpositioninto
an emptydrum to capturepurgematerial and ensureallcontaminants(suchasassemblylubricantsandtestfluids) are cleared from the pumps and hoses prior toproceedingwithproduction.
Elapsed time, min
Elapsed time, min
40
40
0
0
1
1
2
2
3
3
4
4
5
5
100
100
30
30
10
10
50
50
160
160
70
70
90
90
220
220
110
110
Hot
-mel
t bea
d
tem
pera
ture
, °F
Hot
-mel
t bea
d
tem
pera
ture
, °F
Hot
-mel
t bea
d
tem
pera
ture
, °C
Hot
-mel
t bea
d
tem
pera
ture
, °C
PVC
PVC and glass
Wood
Wood and glass
Aluminum
Aluminum and glass
Figure 9: Typical changes in bead temperature as a functionoftimeelapsedafterwettingouttypicalwindowsashsubstrates(top)andwhensqueezedbetweensubstrateandglass(bottom)
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• Reconnectthehoseandbeginpurgingmaterialthrough the nozzle.Collectmaterial into a suitablewaste con-taineruntilallvisiblecontamination,suchasoilsand/orairbubbles,areno longerpresentandmaterial isextrudingsmoothlyfromthenozzle.
• Run test beads of material to ensure uniform beadapplicationonthesubstrate.
Container Changeover
• Testanewlyopenedcontainerforcure.RefertothesectionDetermination of Cure State.
• Ensurethefollowerplateniswipedfreeofdirt,dustoroilspriortopumpingmaterial.
• GreasethegasketonthefollowerplatenwithMolykote® 111 Compound (or other silicone-compatible, high-temperaturegreases).
• Afteropeningandtestingforcure,place thecontainer undertheheatedplaten.
• Opentheventvalveontheplatentoallowtrappedairtopurgefromthecontainerastheplatenisbeingloweredintothecontainer.
• Starttheheatcycleandwaitfortheplatentoreachthe targetdispensingtemperature.RefertothesectionDis- pensing Temperaturesformoreinformation.
• Apply down-force pressure (make sure the directionswitchforplatenisinthedownposition)andpurgeanyremainingairthroughtheventvalve.Itisrecommendedthatanypurgedmaterialbecollectedinasuitablewastecontainerforproperdisposal.
• Shuttheventoncehot-meltmaterialisflowingthrough theventvalvewithnoairbubbles.
• Startthepumptobegindispensingthematerialthrough thenozzle.Collectmaterialinasuitablewastecontaineruntilmaterialisrunningsmoothly.
• Run test beadsofmaterial to ensureuniformbead ap-plicationonthesubstrate.
Time at Temperature Considerations• Inasealedsystem,Dow Corning®InstantGlazeWindow
Assemblyproductsarestableforupto24hoursat248°F (120°C).Iftheglazingprocessisnottobeusedforanextendedperiod,uptoandincluding24hours,thepumpsandheatingzonescanbeshutdownorthetemperaturesloweredwithoutdetrimentaleffectsonthesealant.
• Forshutdownintervalsinexcessof24hours,poweringdown theequipment is required.Provided theproductremainssealedwithinitscontainerandequipment,the pumpcanberestartednormallywithoutaffectingmaterial. Approximateheat-uptimeis30to60minutesdepending onequipmenttypeandmanufacturerrecommendations.
• Exposureofopenedcontainerstoairshouldbeminimized because Dow Corning®InstantGlazeWindowAssemblyproductswillreactwithmoistureintheatmosphere.
Shut Down Considerations• Nozzle tips left exposed to air after shutting down
production will cure any hot-melt product left overwithinthenozzle.Attheendofaproductionrun,applyMolykote®111Compoundtothenozzletip.Immersionof thenozzle tip inanyviscositygradeof siliconeoilwillalsowork.Uponstart-up,smallamountsofcuredmaterial from within the nozzle tip can usually bedispensedduringthepurgecycle.
• Forshutdownintervalsinexcessof24hours,powering downtheequipmentisrequired.Thiswillsaveenergy, extend the service life of the o-rings and seals in thedispensing equipment and avoid exceeding productpotlife.Removethenozzlewhilewarmanduseapipe plugtocaptheapplicationheadandthehose.
• Providedtheproductremainssealedwithinitscontainer and equipment, the pump can be restarted normallywithoutanyadverseeffects.
Quality Control and Application IssuesBead Location• Thesealantbeadshouldbe locatedon theglazing leg,
parallelwiththeglazingleg,andwithinthedimensionsoftheglassunit.
• Beadlocationsnotparalleltotheglazinglegoroutside of the dimensions of the glass unit may not contact theglassatsomelocationsoftheglassperimeter.
• Otherissuesthatcouldcausebeadlocationerrorsmay includetheoperatornotplacingthewindowsashsquare-lyonthetableorthetablenotʻseeingʼorsensingthewindowsashproperly.
Bead Consistency and UniformityBead consistency and uniform bead dimensions areimportant for good sealantwet-out and consistent bite.Theconsistencyof thebeadmustbecheckedoneverywindowsash. Ifbead inconsistenciesoccur,determiningandcorrectingtherootcausewillbenecessary.Asidefromthenozzleopening,flowrate–pumppressure,andtablespeedwilldefinebeadsize.Ifthebeadsizeisinconsistent,thismayindicateachangeinpumppressure,temperaturevariationsespeciallyat thenozzle tip, improperlysizedhoses,oraproblemwiththepump.
Below are some examples of bead inconsistencies andsuggestedremedies.
Skip–AnareawheretheX–Yglazingtabledoesnotapply anyback-beddingsealant:
• Apply Dow Corning® 1199 Silicone Glazing SealantClear(orothersealants,suchasDow Corning® 9-1350 SiliconeGlazingSealantorDow Corning®791Silicone WeatherproofingSealant)totheskiplocation.
14
Thinning –An area along the sealant linewhere the beaddimensionisunusuallythinandnon-uniform:
• Apply Dow Corning® 1199 Silicone Glazing SealantClear(orothersealants,suchasDow Corning® 9-1350 SiliconeGlazingSealantorDow Corning®791Silicone WeatherproofingSealant).
• Check that the dispensing pump is powered on andmaintaining pressure. If thinning occurs at the end ofthecycle,thiscouldbeanindicationthateitherthe system has too much pressure drop for the flow rate required or the melt rate of the bulk melter is notsufficientfortheapplicationrate.
Tooling–Anareaalongthesealantwherethenozzlewastoo low(orthewindowsashtoohigh)andthenozzledraggedonthesealant:
• Scrapeoffthesealantandapplynewsealant.• Adjustthenozzletotheappropriateheight.
Waviness or unevenness–Aninconsistentbead thatcanoccurwhenthenozzleistoohighabovethewindowsash:
• If the waviness results in a bead of varying heightcausingwet-out to be inconsistent, scrape off the bead and reapply. If the bead is just uneven, but the bead height is consistent, the sealant application is acceptable if the window manufacturer deems the waviness to bevisuallyacceptable.
• Adjustthenozzletotheappropriateheight.
Substrate Issues: Uneven Surfaces in Window SashUnevensurfaces,suchasimpropercleaningofweldedcornersorawarpedwindowsash,cancauseeithertoolingorwavysealantandcancontributetoaunitthatmaybeimproperlysealed.It isvital toconsistentlyprovideaflat,evenwindow sash onwhich to apply theDow Corning® InstantGlazeWindowAssemblyproduct.
Equipment IssuesIssuesmay occur evenwhen following recommendedoperational andmaintenance practices. Some of theseissuesmayadverselyaffectthequalityofthesealantbeadbeingappliedonthewindowunit.
Application Head or Nozzle• Thenozzleontheapplicationheadisoftenuninsulated.
Nozzle temperaturesareoften sethigher thanhosetemperatures,butshouldnotexceed285°F(140°C) tomaintainconsistenthot-meltflowandbeaddimensions. Thisisgenerallyacceptablebecausetheresidencetimeofthehot-meltflowingthroughthenozzleisshort.
• Anozzle tip leftexposed toairduringproductiondowntimeswillcureanyhot-meltproductleftoverwithinthe nozzle.At theendofaproductionrun,applyMolykote®
111 Compound to the nozzle tip. Immersion of thenozzle tip in any viscosity grade of silicone oil willalsowork.Removenozzlewhilewarmanduseapipeplug to cap the application head when productiondowntimesexceed24hours.Nozzles containing curedmaterial can often be purged outwith freshmaterial. Occasionally, the nozzlemayneed to be removed and cleaned or replaced if the material curehasprogressed toodeep.Dow Corning® 3522 Cleaning Solvent, which is based on odorless mineralspirits,maybeusedtodissolvecuredsilicones.
Hose
Pluganyopen-endedhosewhenproductiondowntimesex-ceed24hoursormaterialmaystarttocureandaffectflowinsubsequentproductionruns.Dow Corning® InstantGlaze WindowAssemblyproductsdonotbuildupontheinteriorhosewall, andpropercareof theoutsideof thehose in- cluding preventing excessive tight radius bending shouldleadtoalonghoselifeaslongasthesealantisnotallowedtocureontheinside.
Melt Platen Sealing RingsAvoidbuildupofproductresidueonthemeltplatensurfaceand around the sealing rings. Any residue should beconsideredcuredandwillreducetheseal’seffectiveness.Avoidtheuseofsharptoolsandremoveanyresiduebeforestart-uporwhenanewcontainer is loaded.Followallrecommendationsforlubricatingthesealingrings.Insomeinstances,thesealingringmayneedtobereplaced.
LeakageWhenairorsealantleakageoccurs,immediatelyreplacethe correspondingsealoro-ring.
Compressed Air
Compressedairisusedforpneumaticoperationsincludingtheaerationanddeaerationofthecontainer.Compressed aircomingintocontactwiththemoisture-reactiveproduct mustbecleananddry.
Environmental IssuesAirdraftsfromventilationsystemsintheproximityoftheapplicationheadmayaffectitstemperature,whichwillinturnimpactbeadsizeconsistencyandsealantwet-outonthewindowsash.Reduceandeliminateairflowonnozzleswherepossible.
Temperature and humidity conditions in themanufacturing areashouldbecontrolledyearroundifpossible.Likeother one-partRTVsealants,DowCorning®InstantGlazeWindow Assemblyproductsrequiremoistureintheairtocure.
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Deglazing and Reglazing of Window UnitsNote: It is recommended that the operator wear appropriate Personal Protection Equipment while deglazing any window and handling glass.
Deglazingcanbeusedtoremedymanufacturingissuesassociatedwiththeback-beddingsealantand/orasaquality assurance method of inspection used to confirm goodadhesionandproperfilloftheglazingjoint.
WindowunitsmanufacturedwithDow Corning® InstantGlaze WindowAssemblyproductsastheback-beddingsealantcan bedeglazedusingstandarddeglazingtools.
Toremedyamanufacturingissue,thewindowshouldbe deglazedwithin thefirst30minutesof assemblyby re-movingopposite-sideglazingbeadsandapplyingsteadypressureonacorneruntilthesealantbreaks.Next,carefullyapplypressurearoundtheperimeterof theunituntil theglassisfree.
Forcuretimesexceedingonehour,itmaybenecessaryto cuttheglassoutoftheunitusinganappropriatetoolsuchasthatshowninFigure10.First,removetheopposite-side glazingbeadsifthesearepresent.Deglazethewindowby sprayingtheperimeteroftheunitwithamildsolvent,such asisopropylalcohol(IPA),tosoftenthesealantandprovide lubricationduringcutting.Insertthecuttingtoolbetweenthe glazinglegonthewindowsashandtheglass.Workingthe bladebetweenthesetwosurfacesisthemostcriticalstep;itispossibletobreaktheglassifexcessivepressureisapplied.Oncethebladeiswellpositionedbetweentheglassandtheglazingleg,moveitslowlyaroundthewindowcuttingthesealant line and finally removing the IG unit.MultiplepassesaroundtheunitandadditionalapplicationsofIPA mayberequiredtocompletelycuttheunitfree.
Anoperatorshouldstand inanergonomicpositionas to beabletoinsertthebladeandmoveitaroundthewindowwithoutreachingwellbeyondtheirrangeofmotion.
Deglazingcanbeusedasatestforqualityassurance.During productionofwindowunits,itisagoodideatoperiodically
monitor sealant performanceand application.Quality assur-ancetestsaregoodpracticeandcanalert themanufacturer toapotential quality issue prior tomanufacturing a large quantityof units. It is the prerogativeofthewindowmanufacturertodeterminethefrequencyofanytest including deglazing basedonqualityassuranceprinciples.
Whenusedasaqualityassuranceprocedure,unitsshouldsitfortheprescribedcuretimebeforedeglazingtocheckfor beadquality.Thesealantshouldbeinspectedforwet-outto boththeliteandthewindowsash.Forbestinspectionresults, the surface of the lite and/orwindow sash should not bedamaged.Theinspectionshouldincludethefollowing:
• Uniformityofwidthofsealantbite• Wetoutofsealantontheliteandwindowsash• Uniformityofcure• Appearanceofsealant,includinguniformityofcolor
for pigmented versions and presence of bubbles orforeignmatter
Shop ReglazingWindowunitsoriginallyglazedwithsiliconesealantsshould bereglazedwithsiliconesealants.Glazingtapeswillnot adheretoaglazinglegthathashadasilicone-basedmaterial previouslyappliedtoit.
Oncetheglassisremovedfromthewindowsash,scrapeawayexcessbeadsof sealantusingaputtyknifeoraspatulawithafinelygroundsharpblade.Awideflat-headscrewdriverisfrequentlyused.Itisunnecessarytocleantheglazinglegwithanychemicalortoremovethesealantfilm.Reapply Dow Corning® InstantGlaze WindowAssembly producttotheglazinglegandfollowregularglazinginstal-lationprocedures.
Field ReglazingDow Corning®InstantGlazeWindowAssemblyproductsare100%silicone:othercold-appliedsiliconesealantsarecompatibleandwilladheretoit.Oncetheglassisremovedfromthewindowunit,scrapeawayexcessbeadsofsealant.Itisunnecessarytocleantheglazinglegwithanychemicalortoremoveanyleftoverfilmfromthesealantbead.
Apply a fresh sealant bead to each glazing leg usingeither Dow Corning®1199SiliconeGlazingSealantorDow Corning® 791 Silicone Weatherproofing Sealant.Immediately install the new IG unit (before a sealantskin forms) and reinstall opposite-side glazingbeads andother components as needed according to the windowmanufacturer’sprocedures.
Finished Unit RecommendationsAvoidprolongedexposure tocitrus-containingcleaners,solventsandsolvent-basedcleanersastheymaydamagethecuredsealant.
Figure 10:Deglazingtool
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Green StrengthGreenstrengthcanbedescribedastheinitialshearstrength beforeasealantexhibitssignificantcureastobuildmech-anicalandadhesionstrength.TheDowCorningCorporateTestMethod(CTM)02431isusedtomeasuretheamountofshearforcerequiredtoseparateasingle-lap-jointlaminateunderambientconditions.A0.10-inglue-linethicknessisusedbetweena1×1in2overlapofmill-finishedaluminumsubstrates, which are pulled apart along its long axis at 2 in∙min–1afterpredefinedcure intervalsat24±2°Cand 50±5%RH.Theresults forDow Corning® InstantGlaze WindowAssemblyproductsareshowninFigure11.
Adhesion-in-Peel StrengthTheabilityofacuredsealanttomaintainanadhesivebond toaparticular substratewhile subjected toa180°peel is evaluatedusingamodifiedversionofASTMC794Stand-ard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants.Dow Corning® InstantGlazeWindowAssemblyproducts exhibitpeel strengthsof at least30pli after a 7-daywaterimmersiontoavarietyofcommonsubstrates.RefertothesectiononSubstrate Selection.Themodeoffailureiscohesive.
• Dow Corning® InstantGlazeSealant>45pli• Dow Corning® InstantGlazeIISealant>41pli• Dow Corning® InstantGlazeIIIAdhesive>30pli
Elapsed time after assembly
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Dow Corning® InstantGlaze SealantDow Corning® InstantGlaze II SealantDow Corning® InstantGlaze III Adhesive
Figure 11:GreenstrengthbuildupofDow Corning® InstantGlaze WindowAssemblyproductsconfiguredwitha0.10-inglue-linethicknessinasingle1×1in2overlaplap-shearjointat24±2°Cand50±5%RH
1 CTM 0243 is based onASTM C961 Standard Test Method for Lap Shear Strength of Sealants and ASTM D1002 Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal).
What are the handling precautions for DowCorning® InstantGlaze Window Assembly products?
Beforehandling, readproductandsafetydata sheetsandthecontainerlabelforsafeuse.Exposureofopenedcontainerstoairisdiscouragedbecausetheseproductswillreactwithmoistureintheatmosphere.Theproductisdispensedunderpressureat approximately248°F(120°C), and use of personal protective equipment topreventcontactwithskinoreyesisrecommended.
Is any local exhaust ventilation required?
Dow Corning® InstantGlazeWindowAssemblyprod- uctshavea lowvolatileorganiccontentof less than15 g/L.The need for local exhaust ventilation shouldbe discussed with your safety department personnel.An exhaust hood can be integrated into the design ofthe bulk melter to remove vapors directly from thecontainer.Refer to theproduct and safetydata sheetsforfurtherinformation.
DowCorning has an extensive Product StewardshiporganizationandateamofProductSafetyandRegula- toryCompliance (PS&RC) specialists to support cust-omersforproductsafetyneeds.Forfurtherinformation,please see ourwebsite, dowcorning.com, or consultyourlocalDowCorningSalesApplicationEngineer.
What purge material can be used to clean existing material from dispensing equipment before using DowCorning® InstantGlaze Window Assembly products?Dow Corning recommends retrofitted hot-melt pump-ingequipmentbedisassembled,cleanedandrebuilt if ithasbeenusedwithothertypesofhot-meltmaterials(e.g. acrylics, butyls, urethanes). Dispensing hosesshouldbereplaced.Dow Corning®3522CleaningSol- vent,basedonodorlessmineralspirits,maybeusedas apurgematerial and shouldbe appliedat room tem-perature.Ifyouneedtopurgelines,contactyourlocalDowCorningrepresentative.
How shall I conduct incoming product inspection?Non-pigmentedDow Corning® InstantGlaze Sealant andInstantGlazeIISealantareclear,butDow Corning® InstantGlaze IIIAdhesive appears translucent in its bulkform.Atypicalbeadofanynon-pigmentedsil-icone hot-melt productwill appear optically clear fordesirableaesthetics.
Thematerial,beforepumping,shouldbepliablebutnotstretchy.Astretchyresponseisanindicationofacuredsurfaceduemost likely to theproductcontainersealbeingcompromised.RefertothesectionDetermination of Cure Stateformoreinformation.
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Sealant Profile Calculation InputsLargest window height: ___________________________
Largest window width: ___________________________
IstheIGunitsupportedatthebottombysettingblocks?YesNo
IftheIGunitisnotsupportedbysettingblocks,maximumweightofIG:____________________________________
Iftheunitiswiderthanitistall,istheIGunitfreetomoveinbothhorizontaldirections?YesNo
Shoptemperatureduringfabrication:_________________
Expectedmaximumwindload:______________________
Sashmaterial: AluminumWoodVinylFiberglass Other: _________________________________________
ExpectedactualLOWtemperatureofsash,atsealantbond,duringservice:___________________________________
Expected actual HIGH temperature of sash, at sealantbond,duringservice:______________________________
Expected actual LOW temperature of glass, at sealantbond,duringservice:______________________________
Dow Corning®SealantchoiceORmovementcapabilityofselected sealant: _________________________________
How do I clean DowCorning® InstantGlaze materials off my equipment and tools?
Isopropylalcoholcanbeappliedtoareaswhere thesealant needs to be removed. This will soften thecuredmaterialandallowit tobescrubbedawaywithan abrasive pad.TheDow Corning® 3522CleaningSolvent,whichisbasedonodorlessmineralspirits,mayalsobeusedtoremovecuredsilicones.
What bead size is recommended?
Manufacturers designing and testing fenestration sys-temsshoulddeterminebeadsize thatwillprovide therequired sealantbiteandglue-line thickness.Refer tothesectionSealant Design Considerationsformoreinformation.
What can be done if the table skips or there is a gap in the sealant bead?Dow Corning®1199SiliconeGlazingSealantClearcanbeusedtopatchgapsinthesealant.Othersiliconesinuse inyourfacilitymayalsobeused(e.g.,Dow Corning® 9-1350SiliconeGlazingSealantorDow Corning® 791 SiliconeWeatherproofingSealant).RefertothesectionBead Consistency and Uniformityformoreinformation.
Are DowCorning® InstantGlaze Window Assembly products compatible with clean glass?Dow Corning® InstantGlazeWindowAssembly prod-uctsareapprovedforusewithPPGSunclean™ Glass according to PPG. Non-pigmentedDow Corning® InstantGlazeproductsdonotcontainsiliconeoils thatcan migrate to the glass, and exhibit ʻnegligible silleffectʼ and ʻnegligible picture framingʼwhen used inback-beddingapplications.
When should setting blocks be used?
DowCorning recommends that settingblocks are al-ways used based on Insulating GlassManufacturersAlliance (IGMA) and GANA guidelines. In addition to setting blocks, side placement shims may be re- quiredtoholdtheIGunitinplaceintheeventthatthewindow unit is tilted on its side during production orshipment.Consult the IGmanufacturer for additionalsupportrequirements.
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