1、Designation: C792 04 (Reapproved 2008)C792 15Standard Test Method forEffects of Heat Aging on Weight Loss, Cracking, andChalking of Elastomeric Sealants1This standard is issued under the fixed designation C792; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of 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. S
3、cope1.1 This test method covers a laboratory procedure for determining the effects of heat aging on weight loss, cracking, andchalking 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 the s
4、afety problems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.1.3 There is no known ISO equivalent to this test method.2. Referenced Docu
5、ments2.1 ASTM Standards:2C717 Terminology of Building Seals and Sealants3. Terminology3.1 DefinitionsSee Terminology C717 for definitions of the following terms used in this test method: compound, elastomeric,non-sag sealant, sealant, and self-leveling sealant.4. Summary of Test Method4.1 Three seal
6、ant specimens are spread on thin aluminum plates and, after determining net weights of sealant, are cured for 7days at 23 6 2C (74 6 3.6F) and 50 6 5 % relative humidity. Standard Conditions. Immediately following this initial cure timetwo specimens are exposed in a forced-draft oven maintained at 7
7、0 6 2C (1586 3.6F) for 21 days. At the end of this exposurethe percentage weight loss of the sealant is determined and examination is made for presence of cracks and chalking.5. Significance and Use5.1 Weight loss through volatilization of components of a sealant in a building joint may affect seala
8、nt appearance because ofshrinkage and sealant performance because of the loss of functional sealant components. Exposure to high-temperatureenvironments will accelerate the loss of volatiles.5.2 This test method measures weight loss. It can be used in combination with a knowledge of sealant density
9、to estimateshrinkage. In addition, when compared to sealant theoretical weight solids, it provides an estimate of the extent to which functionalsealant components can be volatilized when exposed to high service temperatures. Substantial losses of this type may help predictearly failures in durabilit
10、y. Also, development of cracks or chalking, or both, lessens sealant service life. However, a sealant thatdevelops no cracks or chalking, or low weight loss in this test method, does not necessarily assure good durability.6. Apparatus6.1 Forced-Draft Oven, controlled at 70 6 2C (158 6 3.6F).6.2 Bala
11、nce, sensitive to 0.01 g.1 This test method is under the jurisdiction of ASTM Committee C24 on Building Seals and Sealants and is the direct responsibility of Subcommittee C24.20 on GeneralTest Methods.Current edition approved May 1, 2008March 15, 2015. Published June 2008April 2015. Originally appr
12、oved in 1975. Last previous edition approved in 20042008 asC792 04.C792 04(2008). DOI: 10.1520/C0792-04R08.10.1520/C0792-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, re
13、fer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all c
14、hanges accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
15、 United States16.3 Rectangular Brass Frame, with inside dimensions 130 by 40 by 6.4 mm (5 by 112 by 14 in.).6.4 Aluminum Plates, three, each 152 by 80 by 0.6 to 1.6 mm (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
16、(6 in.) long.7. Procedure7.1 Unless otherwise specified by those authorizing the test, standard conditions of temperature and relative humidity for thetest shall be 23 6 2C,found in Terminology C717(73 6 3.6F) and 50 6 5 %, respectively7.2 Test of Multicomponent Sealants:7.2.1 Condition at least 400
17、 g of base compound and appropriate amount of curing agent in a closed container for at least 24h at standard conditions; then mix thoroughly for 5 min.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 an aluminum plate, with a portio
18、n of the conditioned compound, and strikeit off flat with a straightedge. Immediately lift the frame from the sealant after separating it by running a thin-bladed knife alongthe inside of the frame (Note 1). Prepare three such specimens, weigh each to the nearest 0.01 g, and cure them for 7 days ats
19、tandard conditions.7.2.4 Following the 7-day curing period, place two of the three specimens in the draft oven for 21 days, leaving the third(control) specimen at standard conditonsconditions for the same period.7.2.5 At the end of the 21-day period, remove the specimens from the oven and allow to c
20、ool for 1 h at standard conditions.Weigh them to the nearest 0.01 g and calculate the percent weight loss of the sealants as follows:Weight loss,%5W22W 3!/W22W1!#3100 (1)where:W 1 = weight of aluminum plate,W2 = weight of aluminum plate with fresh sealant, andW3 = weight of plate with sealant after
21、heat aging 21 days.7.2.6 Examine the sealants for cracking and chalking and compare with the third (control) specimen.NOTE 1In the case of a pourable grade compound, do not lift the rectangular frame until the sealant is sufficiently set that it will retain its rectangularshape.7.3 Test of Single-Co
22、mponent Sealants:7.3.1 Condition at least 400 g of compound in a closed container 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
23、sample tested:8.1.1 Identification of the sealant tested.8.1.2 Description of the type of sealant, such as single- or multicomponent, 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 with the control spe
24、cimen. Fig. 1 includes examples of cracking obtainablein this test. Number 0 represents no cracking.8.1.5 Variation, if any, from the specified test procedure.9. Precision9.1 Astatistical analysis made from the results obtained from a round-robin test in which each of three laboratories tested seven
25、sealant samples in accordance with the prescribed test for effect of heat aging on weight loss resulted in the following:9.1.1 Repeatability (that is, the difference between two determinations of weight loss on the same sample within the samelaboratory) was 0.51 % weight loss.9.1.2 Reproducibility (
26、that is, the difference between the results of two laboratories, each making two weight loss determinationson the same sample) was 0.90 %.9.2 The results obtained by the three laboratories in which each laboratory tested seven sealant samples in accordance with theprescribed test for the effect of c
27、racking and chalking were close to unanimous. The exception was the report of one laboratoryindicating no cracking or chalking of one sample, whereas the remaining two laboratories reported slight cracking and chalking.C792 15210. Keywords10.1 chalking; compound; cracking; elastomeric sealants; heat
28、 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 advised that determination of the validity of any such pa
29、tent 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 reapproved or withdrawn.Your comments are invited eit
30、her 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 you feel that your comments have not received a fair
31、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 stand
32、ard 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). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1Number 0 represents no cracking.FIG. 1 Examples of Cracking Obtainable in This TestC792 153
