1、Designation: D779 16Standard Test Method forDetermining the Water Vapor Resistance of Sheet Materialsin Contact with Liquid Water by the Dry Indicator Method1This standard is issued under the fixed designation D779; the number immediately following the designation indicates the year oforiginal adopt
2、ion or, 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.1. Scope1.1 This test method covers the determination of the timerequired for water v
3、apor to pass through a sheet membrane incontact with liquid water using the dry-indicator method.1.2 The method has been used to evaluate water resistivebarriers, flexible flashing and other materials used in buildingconstruction in order to measure their resistance to water vaportransmission.1.3 Th
4、e values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated
5、 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.2. Referenced Documents2.1 ASTM Standards:2D585 Practice for Sampling and Accepting a Single Lot ofPaper,
6、Paperboard, Fiberboard, and Related Product(Withdrawn 2010)3D685 Practice for Conditioning Paper and Paper Productsfor TestingE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE631 Terminology of Building Constructions3
7、. Terminology3.1 DefinitionsFor definitions of general terms related tobuilding construction used in this test method, refer to Termi-nology E631.4. Summary of Test Method4.1 This test method consists of bringing one side of the testspecimen in contact with water and finding the time requiredfor wat
8、er vapor to pass through the specimen, as indicated bythe development of color in an indicator powder consisting ofa mixture of water-soluble dye, sugar, and starch. The sugarserves the two-fold purpose of masking the color of theparticles of dye as long as they are dry, and of absorbing thetransude
9、d moisture and holding it in close proximity to the dye.The starch increases the stability of the mixture.4.2 Five tests are made on each side of the test specimen andreported as two separate averages. If the material being testedis intended to be exposed to water on only one side then fivetests are
10、 to be made on the side specified for water exposure.5. Significance and Use5.1 The dry indicator used in this test method is so stronglyhygroscopic it will change color in a moderate- to high-humidity atmosphere without contacting liquid water. It willalso change when in contact with liquid water.5
11、.2 This test method is of value for materials that come incontact with water on one face and where it is important toevaluate the length of time for water vapor to pass through thematerial.6. Interferences6.1 This test method is sometimes not applicable to mate-rials containing large amounts of wate
12、r-soluble components.7. Apparatus7.1 Any form of apparatus for applying the test may be usedthat fulfills the following conditions:7.1.1 One surface of the specimen is wetted uniformly at themoment the count of time is begun,7.1.2 The indicator on the opposite surface is continuouslyvisible,1This te
13、st method is under the jurisdiction of ASTM Committee E06 onPerformance of Buildings and is the direct responsibility of Subcommittee E06.55on Performance of Building Enclosures.Current edition approved Feb. 1, 2016. Published March 2016. Originallyapproved in 1944. Last previous edition approved in
14、 2003 as D779-03 which waswithdrawn February 2011 and reinstated in February 2016. DOI: 10.1520/D0779-16.2For 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 standar
15、ds Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.1.3 No moisture reaches the indicator except that whichp
16、asses through the specimen from the wetted surface, and7.1.4 No moisture that does so reach the indicator escapesfrom contact with it.7.1.5 A float arrangement is one apparatus that fulfills therequirements of 7.1 and is made of a thin-walled aluminum panapproximately 5 in. (127 mm) in diameter and
17、1 in. (25.4 mm)high, with a hole 2 in. (50.8 mm) in diameter cut in the bottom.The surface is coated with paraffin or beeswax to make it morewater repellent. The watch glass is clamped over the specimenby means of a wire-frame clamp hinged at one side andfastened under a spring at the opposite side.
18、7.1.6 Instead of using the float arrangement described in7.1.5, it is also permissible to form a boat, by folding up theedges of the specimen or by dipping the four edges of thespecimen in hot wax, and floating it on the surface of the water.If the specimen does not easily float on its own it can be
19、supported by a hollow cylinder having the upper end barelysubmerged under the surface of the water in a suitable vessel.The dry indicator powder is applied to the top surface inaccordance with Section 12 (with watch glass) or Section 13(without watch glass) just before floating the specimen on thewa
20、ter.7.2 Shaker and Desiccator Assembly (Fig. 1) for theIndicatorThe shaker is prepared from a 10-mL screw-topvial by cutting away most of the metal of the flat portion of thetop, fitting a 70-mesh (27.5-mesh/mm) wire screen inside thetop, and screwing it back in place. The desiccator is made of asma
21、ll wide-mouth bottle containing desiccant covered with alayer of glass wool. A hole is bored in the cork stopper justlarge enough to admit the shaker. The bottle remains on its sideand the vial is inserted through the hole with the screened endinside. The assembly is kept in the usual type of labora
22、torydesiccator when not in use.7.3 Watch glass, 2-in. (50-mm) diameter.7.4 Stopwatch or electric timer, reading to 1 s.8. Reagents and Materials8.1 DesiccantAnhydrous calcium chloride, activatedalumina, or silica gel.8.2 IndicatorThe water-transudation indicator is com-posed of pure, powdered cane s
23、ugar (do not use confectionerssugar, which contains starch), pure soluble starch, and methylviolet dye (Color Index 680). Pass each ingredient separatelythrough a No. 100 screen (39.4 mesh/mm), and completely dryit in a desiccator over a desiccant (see 8.1) before making themixture. When dry, weigh
24、and mix the following proportionsby weight:Sugar 45Soluble starch 5Dye 18.2.1 Mix the ingredients by screening repeatedly through aNo. 60 screen (23.6 mesh/mm) until the mixture is uniform.Keep the indicator in a desiccator when it is not being used.8.3 WaterDistilled or demineralized9. Sampling, Te
25、st Specimens, and Test Units9.1 For acceptance purposes, sample the lot of material inaccordance with Practice D585.9.2 When sampling for other purposes, Practice E122 maybe used for an alternative.9.3 From each test unit obtained in accordance with 9.1 or9.2, cut ten test specimens, free from folds
26、, wrinkles, or otherblemishes not commonly inherent in the material.Aconvenientsize is approximately 2.5 by 2.5 in. (63 by 63 mm).9.4 Use a suitable code designation such as Side I and SideII, or when there is an obvious difference between the sides,such as Side I, coated, and Side II, uncoated. The
27、 sidedesignated is that which is to be in contact with the water.10. Preparation of Apparatus10.1 The water on which the specimens are floated shouldbe 73.4 6 0.9F (23 6 0.5C).11. Conditioning11.1 Condition and test the specimens in a standard atmo-sphere in accordance with Practice D685.12. Procedu
28、re A12.1 Place a test specimen on a level, smooth surface thatwill not affect the moisture content of the specimen, andsprinkle the indicator on the specimen by gently tapping theinverted shaker until a thin, even layer is formed, avoidingeither a very sparse covering or one in which the powder ispi
29、led up. In the former case, the color change produced by toofew dye particles may be insufficient to attract attention, unlessthey are exposed for a longer time than the proper end point.When the powder is placed on too thickly, the upper layer mayobscure changes in the indicator in contact with the
30、 paper.Also, the greater total quantity of powder may require moretime to change, since it would necessitate more moisture toaffect all the dye. Handle the test specimen with care once thepowder is applied, for jarring or excessive tipping may causerearrangement of the particles of powder, which the
31、n tend toform in clusters, thus destroying the intimate contact anduniform thin layer that is desirable. As soon as the applicationof the layer of the indicator powder is completed, cover it withthe watch glass and keep it covered during the test. Seal theperimeter of the watch glass with paraffin w
32、ax, beeswax orsimilar material so that moisture cannot escape.12.2 Place the specimen on the water, making contact withthe water at a slight angle to avoid trapping air bubbles thatFIG. 1 Longitudinal Section Showing Constructionof Desiccator and ShakerD779 162might cause uneven wetting of the speci
33、men. When testingmaterials having uneven surfaces, wet the bottom surface,using a soft brush, immediately before placing the specimen onthe water. Examine each specimen after the test, and if there isevidence of uneven wetting, discard the test result.12.3 Measure the time interval from the instant
34、of contact ofthe test specimen with water until the rate of change in thecolor of the indicator is at a maximum. This time interval isconveniently determined as the mean of the values correspond-ing to the development of pronounced color in one fourth andin three fourths of the area covered by the i
35、ndicator. Formaterials on which the color develops uniformly over thewhole area, it may be necessary to tabulate the values of thetime interval against the intensity of the color to determine themaximum rate of change. Artificial light, when used forviewing the test specimen, should be reasonably br
36、illiant butcompletely shaded from the eyes. The light should be appliedto one side of the specimen (thus avoiding reflection from thecover glass) and the eye should view from the side next to theilluminant, to avoid interference of shadows cast by theindicator particles with the judgment of the colo
37、r. The lightsource should generate as little heat as possible or be kept at adistance from the test specimen so as not to affect the resultsdue to an increase in specimen temperature. Record the testtime in minutes and seconds.12.4 Run five tests on each side of the material.13. Procedure B13.1 Same
38、 as Procedure A except without using the watchglass to cover the indicating powder.14. Report14.1 Report the following information:14.1.1 Report the average value of the time of transudationfrom each side of the specimen to the nearest second for endpoints up to 5 min, otherwise in minutes rounded t
39、o the nexthighest value for partial minutes.14.1.2 Report whether procedure A or B was used.15. Precision and Bias15.1 PrecisionThis is a significant revision of the standardto adapt it for use with building materials. Expected results forbuilding materials are in the order of several minutes andhig
40、her. Once the standard is approved, an interlaboratory studywill be conducted to determine precision, repeatability, andreproducibility for higher timeframes than previously mea-sured. Results will be available on or before September 30,2018.15.1.1 Repeatability:15.1.1.1 Repeatability within a singl
41、e laboratory appears tovary as a function of the water resistance level of the material.Other aspects of material composition and uniformity can alsoimpact test repeatability.15.1.1.2 Tests in one laboratory on three different grades ofpaper having vapor resistance values less than 60 s resulted int
42、he estimates of repeatability shown in Table 1.15.2 BiasNo information can be presented on the bias ofthe procedure in this test method, because the water vaporresistance, as determined by the dry indicator method, isdefined only in terms of the test method.16. Keywords16.1 desiccant; dry indicator;
43、 water vapor resistanceAPPENDIX(Nonmandatory Information)X1. ACCELERATED TESTINGX1.1 Investigations of the use of high temperatures (up tothe boiling point of water) in the dry-indicator test have shownthat, in general, there is good correlation between transudationtime and temperature. For products
44、 that show such relation, theuse of hot water is of value in shortening the test period, and insome instances in making the end point more distinct.4,54Codwise, P. W., “Resistance of Sized Paper Paper Trade Journal, Vol 116, No. 9, pp. 3033; TS 9093, March 4, 1943.5Mullen, E. G., “Use of the Dry Ind
45、icator Method for Testing the WaterResistance of Asphalted Papers,” Paper Trade Journal, Vol 119, No. 2, pp. 4142;TS 1112, July 13, 1944.TABLE 1 Repeatability LimitSample Result RangeStandardDeviation95 % RepeatabilityLimitssssA 5 to 10 1.1 3.1B 10to20 0.8 2.3C 20to40 1.9 5.4K 5 to 10 0.45 1.2L 10to
46、20 0.85 2.4M 20to40 1.05 2.9D779 163ASTM 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 patent rights, and the ris
47、kof 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 either for revision of thi
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