1、Designation: C 1249 06aStandard Guide forSecondary Seal for Sealed Insulating Glass Units forStructural Sealant Glazing Applications1This standard is issued under the fixed designation C 1249; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers design and fabrication considerationsfor the edge seal of conventionally seal
3、ed insulating glassunits, herein referred to as IG units. The IG units described areused in structural silicone sealant glazing systems, hereinreferred to as SSG systems. SSG systems typically are eithertwo or four sided, glazed with a structural sealant. Otherconditions such as one, three, five, si
4、x sided may be used.1.2 This guides does not cover the IG units of other thanconventional edge seal design (Fig. 1); however, the informa-tion contained herein may be of benefit to the designers of suchIG units.1.3 In an SSG system, IG units are retained to a metalframing system by a structural seal
5、 (Fig. 2). The size and shapeof that seal, as well as numerous other SSG system designconsiderations, are not addressed in this guide.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to add
6、ress all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 The committee with jurisdiction for this standard is
7、 notaware of any comparable standard guides published by otherorganizations.2. Referenced Documents2.1 ASTM Standards:2C 639 Test Method for Rheological (Flow) Properties ofElastomeric SealantsC 679 Test Method for Tack-Free Time of ElastomericSealantsC 717 Terminology of Building Seals and Sealants
8、C 794 Test Method for Adhesion-in-Peel of ElastomericJoint SealantsC 1087 Test Method for Determining Compatibility ofLiquid-Applied Sealants with Accessories Used in Struc-tural Glazing SystemsC 1135 Test Method for Determining Tensile AdhesionProperties of Structural SealantsC 1184 Specification f
9、or Structural Silicone SealantsE 631 Terminology of Building ConstructionsE 773 Test Method for Accelerated Weathering of SealedInsulating Glass UnitsE 774 Specification for the Classification of the Durabilityof Sealed Insulating Glass Units3E 2188 Test Method for Insulating Glass Unit PerformanceE
10、 2189 Test Method for Testing Resistance to Fogging inInsulating Glass UnitsE 2190 Specification for Insulating Glass Unit Performanceand Evaluation2.2 Other Standards:Igma 73-8-2B Test Methods for Chemical Effects ofGlazing Compounds on Elastomeric Edge Seals43. Terminology3.1 Definitions:1This gui
11、de is under the jurisdiction ofASTM Committee C24 on Building Sealsand Sealants and is the direct responsibility of Subcommittee C24.10 on Specifi-cations, Guides and Practices.Current edition approved Sept. 1, 2006. Published September 2006. Originallyapproved in 1993. Last previous edition approve
12、d in 2006 as C 124906.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from IGMA, 111 E.
13、 Wacker Dr., Ste. 600, Chicago, IL 60601.FIG. 1 Sealed IG Edge Seal: Basic Components1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 Refer to Terminology C 717 for definitions of thefollowing terms used in this guide: adhesive
14、failure, bead,cohesive failure, compatibility, cure, elongation, gasket, glaz-ing, joint, lite, modulus, non-sag sealant, seal, sealant, sealantbacking, setting block, shelf-life, silicone sealant, spacer,structural sealant, substrate, tooling, and working life. Refer toTerminology E 631 for the def
15、inition of sealed insulating glassas used in this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 desiccanta hygroscopic material that adsorbs wateror may adsorb solvent vapors, or both (see Fig. 1).3.2.1.1 DiscussionThe desiccant maintains a low relativehumidity in sealed insulating
16、glass.3.2.2 primary sealAjoint seal of which the sealant resistsmoisture vapor permeation into the desiccated space of sealedinsulating glass (see Fig. 1).3.2.2.1 DiscussionIt also resists inert gas permeation (forexample, argon) from the IG unit sealed space if the intent is touse an inert gas.3.2.
17、3 secondary seala joint seal of which the sealantstructurally unites the two glass lites and spacer of sealedinsulating glass (see Fig. 1).3.2.4 spacera fabricated shape that creates an appropriatedistance between two lites of glass in sealed insulating glass(see Fig. 1).3.2.4.1 DiscussionAs a compo
18、nent of the edge seal sys-tem, the spacer also resists vapor migration into sealed insu-lating glass and provides a container for a desiccant.3.2.5 structural seala joint seal of which the sealantstructurally adheres an IG unit to a metal framing system (seeFig. 2).3.2.5.1 DiscussionThe structural s
19、eal transfers appliedloads to the framing system as well as accommodates differ-ential movements between the IG unit and the framing system.3.3 Symbols:Symbols:3.3.1 A = area, m2(in.2).3.3.2 Cs= sealant contact width, shear, mm (in.).3.3.3 Ct= sealant contact width, tension, mm (in.).3.3.4 D = desig
20、n factor, dimensionless.3.3.5 Fs= allowable shear stress, Pa (psi).3.3.6 Ft= allowable tensile stress, Pa (psi).3.3.7 Fy= yield stress, Pa (psi).3.3.8 H = height, m (ft).3.3.9 L = perimeter length, m (ft).3.3.10 M = mass per unit area, N/m2(lb/ft2).3.3.11 P = applied load, Pa (lbf/ft2).3.3.12 W = wi
21、dth, m (ft).4. Significance and Use4.1 It should be realized that the design of an IG unit edgeseal for use in SSG systems is a collaborative effort of at leastthe IG unit fabricator, sealant manufacturer, and design pro-fessional, among others.4.2 This guide provides information on silicone sealant
22、s thatare used for the secondary seal of IG units that are glazed intoSSG systems.4.3 Information is also provided on the other major compo-nents of the IG unit edge seal, compatibility of components,durability, and quality assurance (QA).5. Insulating Glass Unit5.1 Insulating Glass Unit ComponentsT
23、he edge seal of anSSG system IG unit consists of the two lites of glass, spacer,desiccant, primary sealant, and secondary sealant (Fig. 1) (1).5This type of IG unit is referred to commonly as a dual-seal unitin that it has separate primary and secondary seals. A single-seal IG unit is inappropriate
24、at this time for SSG systems andshould not be used. The following sections describe thecomponents of a dual-seal IG unit briefly.5.2 Glass and Architectural Coatings:5.2.1 GlassAll types of glass have been used in thefabrication of IG units, including monolithic, laminated, tem-pered, heat-strengthe
25、ned, tinted, heat-absorbing, light reduc-ing, patterned, and wired. Almost all glass is produced by thefloat manufacturing process, in which the glass ribbon thatemerges from the furnace is floated on a bath of molten tin,allowing gravity to produce essentially flat parallel surfaces.5.2.2 Architect
26、ural CoatingsThese coatings, which areapplied to the surface of the glass prior to IG unit fabrication,5The boldface numbers in parentheses refer to the list of references at the end ofthis guide.FIG. 2 Typical A-Side SSG System Mullion: Horizontal Section (Vertical Joint)C 1249 06a2are generally gr
27、ouped into one of two categories: low-emissivity or reflective. They are both metallic or metallicoxide materials and in some cases are in multi-layers, depos-ited onto or into a glass surface. The coatings are depositedprimarily by two methods: magnetic sputtering onto the glasssurface and pyroliti
28、c deposition into the glass surface. Low-emissivity coatings are visually transparent and reflect long-wave infrared radiation, thereby improving the thermal trans-mittance of the glass. In general, they also decrease but to alesser extent than reflective coatings, visible light transmission,and tra
29、nsmitted solar radiant energy. Depending on lightingconditions, reflective coatings are generally considerably lesstransparent than low-emissivity coatings. These coatings pro-vide a reduction in transmitted solar radiant energy, conductiveheat energy, and visible light into the building interior. C
30、eramicenamel, silicone, and pressure-sensitive vinyl and polyesterfilm are applied to the surface of glass to make spandrel glass.5.3 SpacerSpacers are fabricated primarily from roll-formed hollow metal shapes and are available in numerousprofiles, depending on the application. Metals typically used
31、are aluminum, both mill finish and anodized, galvanized steel,and stainless steel, with aluminum used predominately. Thespacer establishes the size of the sealed space, providessurfaces for installation of the primary sealant, is hollow fordesiccant installation, and forms the third surface of the c
32、avitycreated at the edge of the glass lites for installation of thesecondary sealant.5.4 DesiccantThese substances are hydrophilic crystal-line materials that are installed into the hollow of the spacer,usually on at least two sides of the IG unit. Commonly useddesiccants are molecular sieves or a b
33、lend of silica gel withmolecular sieves. Their purpose is to adsorb residual water andsolvent vapor in the sealed space immediately after fabricationof the IG units. They also maintain a low relative humidity inthe sealed space for the life of the IG unit by absorbinginfiltrating moisture vapor.5.5
34、Primary SealantThis sealant provides a high level ofmoisture vapor migration resistance and controls and mini-mizes gas and solvent migration into the IG unit sealed space.The sealant also acts as a barrier to the permeation of inertgases (for example, argon) when these gases are used in thesealed s
35、pace of the IG unit. The sealant is designed to fill thespace between the sides of the spacer and the faces of the twoglass lites and to develop adequate adhesion to the surfaces ofboth materials. The primary sealant must also have sufficientmovement capability to not fail due to limited differentia
36、lmovement that may occur between the spacer and the glasslites. Polyisobutylene-based materials have been found to bevery suitable for this purpose. The primary sealant contributeslittle to the structural function of transferring lateral loads andholding the IG unit edge assembly together. These fun
37、ctionsare fulfilled by the secondary sealant.5.6 Secondary Sealant:5.6.1 This sealant transfers negative lateral loads, occurringon the exterior lite of glass, to the interior lite of glass, whichthen transfers the load to the structural sealant that adheres theIG unit to the metal framing system. I
38、t also functions as theadhesive that unites the two glass lites and spacer together asa unit and prevents excessive movement from occurring in theprimary seal (2). The secondary sealant must maintain ad-equate adhesion to the glass lites and spacer and also maintainother performance properties, such
39、 as strength and flexibilityafter prolonged environmental exposure. Failure of the second-ary seal to do so could result in excessive movement in theprimary seal and fogging of the IG unit or adhesive or cohesivefailure of the secondary seal and catastrophic failure of the IGunit.5.6.2 Four generic
40、classes of sealants are used presently fora conventional IG unit edge seal system (non-structural seal-ant). These sealants are polysulfides, polyurethanes, hot-meltbutyls, and silicones. For SSG systems, only IG units with adual-seal (polyisobutylene primary seal and silicone secondaryseal) have th
41、e required durability for the application and are theonly sealants permitted for SSG systems.5.7 Enclosed GasThe IG unit sealed space encloses a gassuch as air, argon, krypton, or sulfur hexafloride. Air isnormally used if conventional thermal resistance properties arerequired. Argon and krypton are
42、 used to increase the IG unitthermal resistance. Sulfur hexafloride is used in applications inwhich increased resistance to sound transmission is necessary.When using gases other than air, the IG unit edge seal systemmust be capable of retaining a substantial percent of the gas forthe life of the IG
43、 unit; otherwise, thermal or sound transmissionperformance will decrease to an unacceptable level.5.8 Breather and Capillary Tubes:5.8.1 Breather TubeAbreather tube is a small tube or holethat is factory-placed through the spacer of the IG unit toaccommodate an increase in sealed air space pressure
44、when anIG unit is shipped to a higher elevation than where fabricated.The breather tube allows the sealed air space pressure toequalize to the atmospheric pressure at the installation site. Thebreather tube is sealed prior to the IG unit installation. Specialsealed space gases (see 5.7) cannot be us
45、ed in IG units thathave breather tubes.5.8.2 Capillary TubeA capillary tube is a very thin boretube of specific length and inside diameter that is factory-placed through the spacer of the IG unit. A capillary tubefulfills the same function as a breather tube and, in addition, isleft open during tran
46、sportation to permit the sealed space of theIG unit to continue to pressure equalize with fluctuatingambient air pressure. Capillary tubes should be sealed with ahigh performance sealant specified by the IG fabricator at thefinal destination immediately before installation. Special sealedspace gases
47、 (see 5.7) cannot be used in IG units that havecapillary tubes.SECONDARY SEALANT DESIGN CONSIDERATIONS6. Structural Properties6.1 General:6.1.1 The design of an IG unit edge seal parallels themethodology used for the design of the SSG system structuraljoint that adheres an IG unit to a framing syste
48、m. SSG systemstructural sealants must meet the requirements of SpecificationC 1184. Presently, there is no comparable specification forsealants used for the secondary sealant of IG units; however,C 1249 06a3sealants should meet the requirements of Specification C 1184(as a minimum) in the absence of
49、 another applicable specifi-cation.6.1.2 The following sections provide the design profes-sional with information on the design of the IG unit edge sealsecondary sealant regarding the following: allowable tensilestrength; modulus properties; appropriate design factors; anddesign of the secondary sealant for the effects of shear stress,tensile stress, and combined stresses.6.2 Sealant Yield StressThe minimum sealant yield stress(Fu) (or tensile adhesion value) is determined by Test MethodC 1135 by pulling to failure small laboratory specimens ofsealant having a cro
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