1、Designation: C793 05 (Reapproved 2017)Standard Test Method forEffects of Laboratory Accelerated Weathering onElastomeric Joint Sealants1This standard is issued under the fixed designation C793; 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 () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test
3、 method covers a laboratory procedure fordetermining the effects of accelerated weathering on cured-in-place elastomeric joint sealants (single- and multicomponent)for use in building construction.1.2 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for
4、information only.1.3 The committee with jurisdiction over this standard is notaware of any comparable standards published by other ASTMcommittees or other organizations.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility o
5、f the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C717 Terminology of Building Seals and SealantsC1442 Practice for Conducting Tests on Sealants UsingArt
6、ificial Weathering ApparatusG151 Practice for Exposing Nonmetallic Materials inAccel-erated Test Devices that Use Laboratory Light Sources3. Terminology3.1 DefinitionsSee Terminology C717 for applicable defi-nitions of the following terms: cure, elastomeric, joint, sealant,and substrate.4. Summary o
7、f Test Method4.1 Three sealant specimens are spread on aluminum platesand exposed in one of the laboratory accelerated weatheringchambers specified in Section 6 and operated in accordancewith specifications in Section 8 and Practice C1442.4.2 Following this treatment the specimens are exposed for24
8、h in a freezer maintained at 26 6 2C (15 6 4F).4.3 At the end of the cold exposure, the specimens are bentover a mandrel within1satthespecified temperature.5. Significance and Use5.1 It is known that solar radiation contributes to thedegradation of sealants in exterior building joints. The use of al
9、aboratory accelerated weathering machine with actinicradiation, moisture and heat appears to be a feasible means togive indications of early degradation by the appearance ofsealant cracking. However, simulated weather factors in com-bination with extension may produce more severe degradationthan wea
10、ther factors only. Therefore, the effect of the weath-ering test is made more sensitive by the addition of the bendingof the specimen at cold temperature.6. Apparatus6.1 Exposure ApparatusThe exposure apparatus shall beone of the three types of laboratory accelerated weatheringdevices described in P
11、ractice C1442 that use either xenon arc,fluorescent UV, or open flame carbon arc radiation. ConsultPractice C1442, Section 7 for the differences in test parametersamong the devices. Because of differences in test conditions,test results may differ with the type of device used. The choiceof device sh
12、all be by mutual agreement among the interestedparties.6.2 Freezer or Cold Box, having a temperature controlledat 26 6 2C (15 6 4F).6.3 Rectangular Brass Frame, with inside dimensions 130by40by3mm(5by112 by18 in.).6.4 Aluminum Plates, three, each 152 by 80 by 0.3 mm (6 by3 by 0.01 in.).6.5 Steel Man
13、drel, 12.7 mm (12 in.) in diameter and about102 mm (4 in.) long.6.6 Thin-Bladed Knife.1This test method is under the jurisdiction ofASTM Committee C24 on BuildingSeals and Sealants and is the direct responsibility of Subcommittee C24.40 onWeathering.Current edition approved Feb. 1, 2017. Published M
14、arch 2017. Originallyapproved in 1975. Last previous edition approved in 2010 as C793 05(2010). DOI:10.1520/C0793-05R17.2For 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
15、 to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization establishe
16、d in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.16.7 Straightedge, metal or plastic, about 152 mm (6 in.)long.6.8 Spatula, steel, about 152 mm (6 in.) long.7.
17、Standard Test Conditions7.1 Unless otherwise specified by those authorizing the test,standard conditions shall be as described in Terminology C717.8. Procedure8.1 Test of Multicomponent Sealants:8.1.1 Condition at least 200 g of base compound andappropriate amount of curing agent and pigment, if req
18、uired, ina closed container for at least 24 h at standard conditions; thenmix thoroughly for 5 min.8.1.2 Fill the brass frame, after centering it on the aluminumplate, with a portion of the mixed compound and strike if offflat with a straightedge. Immediately lift the frame from thesealant after sep
19、arating it by running a thin-bladed knife alongthe inside of the frame (Note 1). Prepare three such specimensand cure them for 21 days at standard conditions.NOTE 1In the case of pourable grade compound, do not lift the brassframe until the sealant is sufficiently set so that it will retain its rect
20、angularshape.8.1.3 At the end of the curing period, leave one specimenunexposed at standard conditions to be used as an unexposedfile specimen and place the other two in the weathering deviceselected. Condition test specimens in the artificial weatheringdevice with the sealant surface facing the exp
21、osure source andpositioned at the specified distance from the source. Specimensshould be confined to an exposure area in which the irradianceis at least 90 % of the irradiance at the center of the exposurearea. Unless it is known that irradiance uniformity meets thisrequirement, use one of the proce
22、dures described in PracticeG151, Section 5.1.4 to ensure equal radiant exposure on allspecimens or compensation for differences within the exposurechamber. If the specimens do not completely fill the racks, fillthe empty spaces with blank metal panels to maintain the testconditions within the chambe
23、r. Test conditions in each type ofdevice are in accordance with the procedures in C1442, Section7 on Apparatus and the following:8.1.3.1 Unless the default cycle is selected by mutualagreement, the exposure cycle shall be the cycle described in7.2.4 and 7.4.3 of Practice C1442 for the xenon arc and
24、openflame carbon arc devices, respectively.8.1.3.2 The exposure duration shall be a minimum of 250 hfor the fluorescent UV/condensation and open flame carbon arctests. The exposure duration for the xenon arc test shall be aminimum of 250 h exposure at an irradiance level of 0.51W/(m2 nm) at 340 nm (
25、459 kJ/(m2 nm) at 340 nm).NOTE 2See Annex A1 in Practice C1442 for determining the xenonarc exposure time required to obtain the same radiant exposure at otherirradiance levels.8.1.4 At the end of exposure, remove the specimens fromthe machine and note changes in appearance as compared withthe unexp
26、osed file specimen.8.1.5 Place all three specimens and the mandrel in thefreezer, controlled at 26 6 2C (15 6 4F) for 24 h. At theend of this period, while in the freezer at this temperature, bendeach specimen, with sealant side outward, across its width,180 around the mandrel within 1 s. Examine ea
27、ch specimenfor cracks developed over the bend area.8.2 Test of Single-Component Sealants:8.2.1 Condition at least 200 g of compound in a closedcontainer for at least 24 h at standard conditions.8.2.2 Follow the same procedure as specified in 8.1.2 8.1.4.9. Report9.1 The report shall include the foll
28、owing information foreach sample tested:9.1.1 Identification of the sealant tested.9.1.2 Description of the type of sealant, such as single- ormulticomponent, nonsag or pourable, color, etc.9.1.3 Type, manufacturer and model of artificial weatheringapparatus used. Irradiance level and actual time (n
29、umber ofhours) in weathering apparatus.9.1.4 Description of specimens after acceleratedweathering, as compared to the unexposed file specimen. Fig.1 includes examples of cracking obtainable after the weather-ing test. Number 0 represents no cracks.9.1.5 Description of specimens after bend test. Fig.
30、 2includes examples of cracking obtainable after the bend test.Number 0 represents no cracks.9.1.6 Variations, if any, from the specified test procedure.10. Precision10.1 Round robin tests to provide a precision statement ondetermination of the effects of laboratory accelerated weather-ing on elasto
31、meric joint sealants based on the tests in this testmethod are pending.10.2 In a round-robin test in which each of three laborato-ries tested eight sealant samples to determine the effect of bendtest at 26C (15F) after ultraviolet exposure, as prescribedin the test, the laboratories agreed on 22 of
32、the 24 determina-tions.11. Keywords11.1 accelerated weathering; sealant; ultraviolet; weatheringC793 05 (2017)2NOTE 1Number 0 represents no cracks.FIG. 1 Examples of Cracking Obtainable After the Weathering TestNOTE 1Number 0 represents no cracks.FIG. 2 Examples of Cracking Obtainable After the Bend
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