1、Designation: C 792 04Standard Test Method forEffects of Heat Aging on Weight Loss, Cracking, andChalking of Elastomeric Sealants1This standard is issued under the fixed designation C 792; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method co
3、vers a laboratory procedure fordetermining the effects of heat aging on weight loss, cracking,and chalking of cured-in-place elastomeric joint sealants(single- and multicomponent) for use in building construction.1.2 This standard does not purport to address all of thesafety problems, if any, associ
4、ated 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.1.3 There is no known ISO equivalent to this test method.2. Referenced Documents2.1 ASTM Standards:2C
5、717 Terminology of Building Seals and Sealants3. Terminology3.1 DefinitionsSee Terminology C 717 for definitions ofthe following terms used in this test method: compound,elastomeric, non-sag sealant, sealant, and self-leveling sealant.4. Summary of Test Method4.1 Three sealant specimens are spread o
6、n thin aluminumplates and, after determining net weights of sealant, are curedfor 7 days at 23 6 2C (74 6 3.6F) and 50 6 5 % relativehumidity. Immediately following this initial cure time twospecimens are exposed in a forced-draft oven maintained at 706 2C (1586 3.6F) for 21 days. At the end of this
7、 exposurethe percentage weight loss of the sealant is determined andexamination is made for presence of cracks and chalking.5. Significance and Use5.1 Weight loss through volatilization of components of asealant in a building joint may affect sealant appearancebecause of shrinkage and sealant perfor
8、mance because of theloss of functional sealant components. Exposure to high-temperature environments will accelerate the loss of volatiles.5.2 This test method measures weight loss. It can be used incombination with a knowledge of sealant density to estimateshrinkage. In addition, when compared to s
9、ealant theoreticalweight solids, it provides an estimate of the extent to whichfunctional sealant components can be volatilized when exposedto high service temperatures. Substantial losses of this typemay help predict early failures in durability.Also, developmentof cracks or chalking, or both, less
10、ens sealant service life.However, a sealant that develops no cracks or chalking, or lowweight loss in this test method, does not necessarily assuregood durability.6. Apparatus6.1 Forced-Draft Oven, controlled at 70 6 2C (158 63.6F).6.2 Balance, sensitive to 0.01 g.6.3 Rectangular Brass Frame, with i
11、nside dimensions 130by 40 by 6.4 mm (5 by 112 by14 in.).6.4 Aluminum Plates, three, each 152 by 80 by 0.6 to 1.6mm (24 to 16 gage).6.5 Straightedge, metal or plastic, about 152 mm (6 in.)long.6.6 Thin Knife Blade.6.7 Spatula, steel, about 152 mm (6 in.) long.7. Procedure7.1 Unless otherwise specifie
12、d by those authorizing the test,standard conditions of temperature and relative humidity forthe test shall be 23 6 2C, (73 6 3.6F) and 50 6 5%,respectively.7.2 Test of Multicomponent Sealants:1This test method is under the jurisdiction of ASTM Committee C-24 onBuilding Seals and Sealants and is the
13、direct responsibility of Subcommittee C24.20on General Test Methods.Current edition approved Dec. 1, 2004. Published January 2005. Originallyapproved in 1975. Last previous edition approved in 1998 as C 792 93 (1998).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AST
14、M Customer Service at 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.7.2.1 Condition at least 400
15、g of base compound andappropriate amount of curing agent in a closed container for atleast 24 h at standard conditions; then mix thoroughly for 5min.7.2.2 Weigh the three aluminum plates to the nearest 0.01 g.7.2.3 Fill the rectangular frame, after centering it on analuminum plate, with a portion of
16、 the conditioned compound,and strike it off flat with a straightedge. Immediately lift theframe from the sealant after separating it by running athin-bladed knife along the inside of the frame (Note 1).Prepare three such specimens, weigh each to the nearest 0.01 g,and cure them for 7 days at standar
17、d conditions.7.2.4 Following the 7-day curing period, place two of thethree specimens in the draft oven for 21 days, leaving the third(control) specimen at standard conditons for the same period.7.2.5 At the end of the 21-day period, remove the specimensfrom the oven and allow to cool for1hatstandar
18、d conditions.Weigh them to the nearest 0.01 g and calculate the percentweight loss of the sealants as follows:Weight loss, % 5 W22 W3!/W22 W1!# 3 100 (1)where:W1= weight of aluminum plate,W2= weight of aluminum plate with fresh sealant, andW3= weight of plate with sealant after heat aging 21 days.7.
19、2.6 Examine the sealants for cracking and chalking andcompare with the third (control) specimen.NOTE 1In the case of a pourable grade compound, do not lift therectangular frame until the sealant is sufficiently set that it will retain itsrectangular shape.7.3 Test of Single-Component Sealants:7.3.1
20、Condition at least 400 g of compound in a closedcontainer for at least 24 h at standard conditions.7.3.2 Follow the same procedure as specified in 7.2.1-7.2.6,eliminating the mixing necessary for multicomponent sealants.8. Report8.1 Report the following information for each sampletested:8.1.1 Identi
21、fication of the sealant tested.8.1.2 Description of the type of sealant, such as single- ormulticomponent, nonsag or self-leveling, color, etc.8.1.3 Percent weight losses of the heat-treated specimens.8.1.4 Presence of cracking and chalking as compared withthe control specimen. Fig. 1 includes examp
22、les of crackingobtainable in this test. Number 0 represents no cracking.8.1.5 Variation, if any, from the specified test procedure.9. Precision9.1 A statistical analysis made from the results obtainedfrom a round-robin test in which each of three laboratoriestested seven sealant samples in accordanc
23、e with the prescribedtest for effect of heat aging on weight loss resulted in thefollowing:9.1.1 Repeatability (that is, the difference between twodeterminations of weight loss on the same sample within thesame laboratory) was 0.51 % weight loss.9.1.2 Reproducibility (that is, the difference between
24、 theresults of two laboratories, each making two weight lossdeterminations on the same sample) was 0.90 %.9.2 The results obtained by the three laboratories in whicheach laboratory tested seven sealant samples in accordanceNOTE 1Number 0 represents no cracking.FIG. 1 Examples of Cracking Obtainable
25、in This TestC792042with the prescribed test for the effect of cracking and chalkingwere close to unanimous. The exception was the report of onelaboratory indicating no cracking or chalking of one sample,whereas the remaining two laboratories reported slight crack-ing and chalking.10. Keywords10.1 ch
26、alking; compound; cracking; elastomeric sealants;heat aging; non-sag sealants; self-leveling sealant; weight lossASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advi
27、sed 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 reviewed every five years andif not revised, either
28、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 theresponsible technical committee, which you may attend. If
29、 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).C792043
