1、Designation: C 870 96 (Reapproved 2004)Standard Practice forConditioning of Thermal Insulating Materials1This standard is issued under the fixed designation C 870; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. 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 practice covers the conditioning of thermal insu-lating materials for tests. Since prior exposure of insulatingmaterial
3、s to high or low humidity may affect the equilibriummoisture content, a procedure is also given for preconditioningthe materials.1.2 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
4、 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationE 41 Terminology Relating to ConditioningE 171 Specification for Standard Atmospheres for Condi
5、-tioning and Testing Flexible Barrier MaterialsE 337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)2.2 ISO Standard:3ISO 544 Standard Atmospheres for Conditioning and/orTesting3. Terminology3.1 DefinitionsDefinitions of terms in the field
6、 of thermalinsulating materials are given in Terminology C 168. Thefollowing definitions are derived from Terminology E41:3.1.1 moisture contentthe moisture present in a material,as determined by definite prescribed methods, expressed as apercentage of the mass of the sample on either of the followi
7、ngbases: (1) original mass (see 3.1.1); (2) moisture-free weight(see 3.1.2).3.1.1.1 DiscussionThis is variously referred to as mois-ture content, or moisture “as is” or “as received.”3.1.1.2 DiscussionThis is also referred to as moistureregain (frequently contracted to “regain”), or moisture content
8、on the “oven-dry,” “moisture-free,” or “dry” basis.3.1.2 moisture equilibriumthe condition reached by asample when the net difference between the amount of mois-ture sorbed and the amount desorbed, as shown by a change inmass, shows no trend and becomes insignificant.3.1.2.1 DiscussionSuperficial eq
9、uilibrium with the film ofair in contact with the specimen is reached very rapidly. Stableequilibrium can be reached in a reasonable time only if the airto which the sample is exposed is in motion. Stable equilibriumwith air in motion is considered to be realized when successiveweighings do not show
10、 a progressive change in mass greaterthan the tolerances established for the various insulatingmaterials.3.1.3 moisture regainthe moisture in a material deter-mined under prescribed conditions, and expressed as a percent-age of the mass of the moisture-free specimen.3.1.3.1 DiscussionMoisture regain
11、 calculations are com-monly based on the mass of a specimen that has been dried byheating in an oven. If the air in the oven contains moisture, theoven-dried specimen will contain some moisture even when itno longer shows a significant change in mass. In order toensure that the specimen is moisture-
12、free, it must be exposed todesiccated air until it shows no further significant change in itsmass. For drying temperatures above 100C (212F), themoisture content of the oven atmosphere is negligible.3.1.3.2 DiscussionMoisture regain may be calculatedfrom moisture content using Eq 1, and moisture con
13、tent may becalculated from moisture regain using Eq 2 as follows:R 5C100 2 C3 100 (1)C 5R100 1 R3 100 (2)where:C = moisture content, % (see 3.1.1), andR = moisture regain, % (see 3.1.3).3.2 Definitions of Terms Specific to This StandardThefollowing descriptions apply only to the usage of terms in th
14、ispractice:1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.31 on Chemical andPhysical Properties.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 1977. Last previous edition
15、approved in 2000 as C 870 77 (2000).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 standards Document Summary page onthe ASTM website.3Available from American
16、National Standards Institute, 11 West 42nd Street,13th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.1 conditioned moisture equilibriumThe moisture con-dition reached by a sample or specimen during fre
17、e exposure tomoving air controlled at specified conditions. For test purposes,moisture equilibrium must be reached by absorption, startingfrom a relatively low moisture content (see 3.2.4). Moistureequilibrium for testing is considered to have been reachedwhen the rate of increase in the mass of a s
18、ample or specimendoes not exceed that specified for the material being tested. Inthe absence of a specified rate, an increase of less than 0.1 %of the sample mass after a 24-h exposure is consideredsatisfactory.3.2.2 preconditioned moisture equilibriumThe moisturecondition reached by a sample or spe
19、cimen after exposure tomoving air at the standard atmosphere for preconditioning. Thefinal condition may be established after a specified period oftime, or at a moisture equilibrium that is considered to havebeen reached when the change in mass of a specimen insuccessive weighings made at intervals
20、of not less than 2 hdoes not exceed 0.2 % of the mass of the specimen.3.2.2.1 DiscussionBecause the standard preconditioningatmosphere covers a range of relative humidities, the closeapproach to equilibrium is, in general, warranted only at the topof the range. At lower humidities exposure for sever
21、al hours isusually sufficient.3.2.3 standard conditioning atmosphereAir maintained ata relative humidity of 50 6 5 % and at a temperature of 23 62C (73 6 4F). This atmosphere may be used for testingwithout preconditioning specimens if it has been determinedthat the property being measured is not aff
22、ected by the moisturecontent of the material. Other atmospheric conditions may bespecified for specific materials; such conditions and theirtolerances will be included in pertinent standards. See Speci-fication E 171 for other suggested atmospheric conditions.3.2.4 standard preconditioning atmospher
23、eAn atmo-sphere having uncontrolled humidity and a constant tempera-ture within the range from 100 to 120C (212 to 248F), or aspecified lower temperature if these temperatures would bedestructive to the specimens.3.2.5 See Appendix X1-Appendix X3 for related nonman-datory information.4. Summary of P
24、ractice4.1 Specimens are brought to a low moisture content in thepreconditioning atmosphere, and subsequently brought to con-ditioned moisture equilibrium in the conditioning atmospherein accordance with the specified test method.5. Significance and Use5.1 The conditioning prescribed in this recomme
25、nded prac-tice is designed to obtain reproducible test results on thermalinsulating materials. Results of tests obtained on these materi-als under uncontrolled atmospheric conditions may not becomparable with each other. Some of the physical properties ofthermal insulating materials are influenced b
26、y relative humidityand temperature in a manner that affects the results of tests. Inorder that reliable comparisons may be made among differentmaterials and products, and between different laboratories, it isnecessary to standardize the humidity and temperature condi-tions to which insulating materi
27、als are subjected prior to andduring testing.NOTE 1In some cases (for example, dimensionally unstable materi-als), the dry mass cannot easily be established and original mass has to beused.5.2 It may be important to the user of thermal insulation toknow physical properties (influenced by humidity) a
28、t theambient conditions of use, as well as at standard conditionscustomarily specified for testing. In such instances, thosespecial ambient conditions should be stated in the pertinentmaterial specifications and test methods.6. Apparatus6.1 Conditioning Room or Chamber:6.1.1 Equipment for maintainin
29、g the standard atmospherefor testing insulating materials throughout the room or chamberwithin the tolerance given in 3.2.4, and including facilities forcirculating the air over the exposed sample or specimen or,alternatively, facilities such as a revolving rack for moving thespecimens in the prevai
30、ling atmosphere.6.1.2 Equipment for recording the temperature and relativehumidity of the air in the conditioning room or chamber.6.2 Instrumentation, for checking the recorded relative hu-midity, as directed on Test Method E 337.6.3 Preconditioning Cabinet, Room, or Chamber, equippedwith apparatus
31、for maintaining to standard preconditioningatmosphere throughout, within the tolerance given in 3.2.3.6.4 Balance, having a sensitivity of 1 part in 1000 of themass of the specimen.7. Procedure7.1 Determine the temperature and relative humidity of theair in the conditioning room or chamber (6.1) and
32、, if precon-ditioning is required, in the preconditioning chamber (6.3)inaccordance with Test Method E 337. If necessary, adjust theconditions within the specified limits before proceeding tocondition the sample or specimen.7.2 If both preconditioning and conditioning are specified inthe test method
33、 or in a material specification, proceed asdirected in 7.3, 7.4, and 7.5. If preconditioning is not required,condition the sample or specimen as directed in 7.3 and 7.5.7.3 Expose the specimens or samples in the preconditioningor conditioning atmosphere in such a manner that the movingair will have
34、access freely to all surfaces of the material. Unlessotherwise specified in the applicable test method or materialspecification, expose specimens after cutting and sizing.7.4 Place the specimen or sample in the standard precondi-tioning atmosphere. Keep the sample or specimen in thisatmosphere until
35、 it has attained moisture equilibrium forpreconditioning as defined in 3.2.1.7.5 Place the specimen or sample in the standard condition-ing atmosphere as defined in 3.2.4. Keep the sample orspecimen in this atmosphere until the material has attainedconditioned moisture equilibrium for testing as def
36、ined in3.2.2.C 870 96 (2004)28. Keywords8.1 conditioning; preconditioning; thermal insulatingmaterialsAPPENDIXES(Nonmandatory Information)X1. IMPORTANCE OF TEMPERATUREX1.1 A tolerance of 1C has been adopted in a number ofcountries. It is recommended, along with 62 % relative hu-midity, by Specificat
37、ion E 171 and ISO 544 on standardatmospheres whenever close tolerances are required. Bothtemperature and relative humidity can have significant effectson the physical properties of insulating materials. For someproperties a change of 1C may have nearly as much effect asa change of 2 % relative humid
38、ity. For organic fibers and foammaterials, the temperature effect may be greater than therelative humidity effect.X2. IMPORTANCE OF PRECONDITIONINGX2.1 The physical properties of a sample at 50 % relativehumidity depend upon whether the sample was brought to50 % from higher or lower relative humidit
39、ies. This “humidityhysteresis effect” can be 5 to 25 % of the test value for manyphysical properties. For example, a hysteresis effect of 1.5 %moisture content (or 25 % of the test value of 6 % moisturecontent) is typical. Preconditioning on the dry side with ahumidity range specified would avoid mo
40、st of the hysteresiseffect and result in the moisture content of a given samplebeing established within 0.15 %, when the sample is laterconditioned to 50 % relative humidity and 23C. Conditioningdown to 50 % gives most materials a moisture content verynearly the same as conditioning up to 60 %.X2.2
41、For the sake of obtaining close interlaboratory agree-ment, especially on physical properties, a specified precondi-tioning procedure is necessary, but not always sufficient. Whilepreconditioning practically eliminates the hysteresis effect, ithas little influence on strain relaxation effects. The l
42、atterdepends upon the entire previous moisture history of thesample, especially on the conditions of initial drying andtension, and on the duration and degree of subsequent excur-sions to high humidities (that is, above about 58 % relativehumidity). Consequently, for very close interlaboratory agree
43、-ment, a standardized procedure for handling the sample frommanufacture to resting may be required.X2.3 For production control and similar intralaboratorypurposes, the preconditioning step often may be eliminated.For some properties and materials preconditioning may not benecessary, either because o
44、f the smallness of the humidityhysteresis effect or because of lower test accuracyrequirements.X3. IMPORTANCE OF ACCURATE RELATIVE HUMIDITY CONDITIONINGX3.1 It is essential that the relative humidity be determinedwith accuracy and that it be rechecked frequently. The proce-dure of Test Method E 337
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