1、Designation: C 793 05Standard Test Method forEffects of Laboratory Accelerated Weathering onElastomeric Joint Sealants1This standard is issued under the fixed designation C 793; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 test method covers a laboratory procedure fordetermining the effects of accelerated weathering on cured-i
3、n-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 information only.1.3 The committee with jurisdiction over this standard is notaware of any comparable
4、 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 of the user of this standard to establish appro-priate safety and health practices and determine the a
5、pplica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 717 Terminology of Building Seals and SealantsC 1442 Practice for Conducting Tests on Sealants UsingArtificial Weathering ApparatusG 151 Practice for Exposing Nonmetallic Materials in Ac-celerated Test
6、Devices that use Laboratory Light Sources3. Terminology3.1 DefinitionsSee Terminology C 717 for applicabledefinitions of the following terms: cure, elastomeric, joint,sealant, and substrate.4. Summary of Test Method4.1 Three sealant specimens are spread on aluminum platesand exposed in one of the la
7、boratory accelerated weatheringchambers specified in Section 6 and operated in accordancewith specifications in Section 8 and Practice C 1442.4.2 Following this treatment the specimens are exposed for24 h in a freezer maintained at 26 6 2C (15 6 4F).4.3 At the end of the cold exposure, the specimens
8、 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 alaboratory accelerated weathering machine with actinic radia-tion, moisture and heat appears to be
9、 a feasible means to giveindications of early degradation by the appearance of sealantcracking. However, simulated weather factors in combinationwith extension may produce more severe degradation thanweather factors only. Therefore, the effect of the weatheringtest is made more sensitive by the addi
10、tion of the bending ofthe specimen at cold temperature.6. Apparatus6.1 Exposure ApparatusThe exposure apparatus shall beone of the three types of laboratory accelerated weatheringdevices described in Practice C 1442 that use either xenon arc,fluorescent UV, or open flame carbon arc radiation. Consul
11、tPractice C 1442, 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 shall be by mutual agreement among the interestedparties.6.2 Freezer or Cold Box, having a temperat
12、ure 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.).1This test method is under the jurisdiction ofASTM Committee C24 on BuildingSeals and Sealants and is the dire
13、ct responsibility of Subcommittee C24.40 onWeathering.Current edition approved July 1, 2005. Published August 2005. Originallyapproved in 1975. Last previous edition approved in 2004 as C 793 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
14、serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.5 Steel Mandrel, 12.7 mm (12 in.) in diameter and
15、 about102 mm (4 in.) long.6.6 Thin-Bladed Knife.6.7 Straightedge, metal or plastic, about 152 mm (6 in.)long.6.8 Spatula, steel, about 152 mm (6 in.) long.7. Standard Test Conditions7.1 Unless otherwise specified by those authorizing the test,standard conditions shall be as described in TerminologyC
16、 717.8. 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 required, 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
17、 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 separating it by running a thin-bladed knife alongthe inside of the frame (Note 1). Prepare three such specimensand cure them for 21 days at stan
18、dard 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 rectangularshape.8.1.3 At the end of the curing period, leave one specimenunexposed at standard conditions to be used as an unexposedfile specimen
19、 and place the other two in the weathering deviceselected. Condition test specimens in the artificial weatheringdevice with the sealant surface facing the exposure source andpositioned at the specified distance from the source. Specimensshould be confined to an exposure area in which the irradiancei
20、s 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 procedures described in PracticeG 151, Section 5.1.4 to ensure equal radiant exposure on allspecimens or compensation for differences within the ex
21、posurechamber. If the specimens do not completely fill the racks, fillthe empty spaces with blank metal panels to maintain the testconditions within the chamber. Test conditions in each type ofdevice are in accordance with the procedures in C 1442,Section 7 on Apparatus and the following:8.1.3.1 Unl
22、ess the default cycle is selected by mutualagreement, the exposure cycle shall be the cycle described in7.2.4 and 7.4.3 of Practice C 1442 for the xenon arc and openflame carbon arc devices, respectively.8.1.3.2 The exposure duration shall be a minimum of 250 hfor the fluorescent UV/condensation and
23、 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 (459 kJ/(m2 nm) at 340 nm).NOTE 2See Annex A1 in Practice C 1442 for determining the xenonarc exposure time required to obtain the same radi
24、ant 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 unexposed 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 t
25、his 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 each 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 c
26、losedcontainer 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 following information foreach sample tested:9.1.1 Identification of the sealant tested.9.1.2 Description of the type of sealant, such as singl
27、e- ormulticomponent, nonsag or pourable, color, etc.9.1.3 Type, manufacturer and model of artificial weatheringapparatus used. Irradiance level and actual time (number ofhours) in weathering apparatus.9.1.4 Description of specimens after accelerated weather-ing, as compared to the unexposed file spe
28、cimen. Fig. 1includes examples of cracking obtainable after the weatheringtest. Number 0 represents no cracks.9.1.5 Description of specimens after bend test. Fig. 2includes examples of cracking obtainable after the bend test.Number 0 represents no cracks.9.1.6 Variations, if any, from the specified
29、test procedure.10. Precision10.1 Round robin tests to provide a precision statement ondetermination of the effects of laboratory accelerated weather-ing on elastomeric 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 tes
30、ted 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 the 24 determina-tions.11. Keywords11.1 accelerated weathering; sealant; ultraviolet; weatheringC793052NOTE 1Number 0 represents no cracks
31、.FIG. 1 Examples of Cracking Obtainable After the Weathering TestNOTE 1Number 0 represents no cracks.FIG. 2 Examples of Cracking Obtainable After the Bend TestC793053ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin thi
32、s standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be
33、 reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresp
34、onsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C793054
