1、Designation:D284212Standard Test Method forWater Absorption of Rigid Cellular Plastics1This standard is issued under the fixed designation D2842;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in pa
2、rentheses 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.Scope*1.1 This test method covers the determination of the waterabsorption
3、of rigid cellular plastics by measuring the change inbuoyant force resulting from immersion under a 5.1-cm(2-in.)head of water for the specified immersion period of 96 h.1.2 This test method describes two procedures that shall beused to measure the change in buoyant force.ProcedureAshallbe used for
4、materials that either experience rapid waterabsorption or that show an increase in volume during theexposure period,or both.Materials that do not exhibit either ofthese characteristics shall be evaluated by Procedure B.1.3 For specific applications,immersion periods varyingfrom the normal 96-h test
5、requirement shall be agreed uponbetween the manufacturer and the purchaser.1.4 The values stated in SI units are to be regarded as thestandard.1.5 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 t
6、o establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE1This test method is equivalent to ISO 2896.2.Referenced Documents2.1 ASTM Standards:2E96 Test Methods for Water Vapor Transmission of Materi-alsE691 Practice for Conducti
7、ng an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 2896 Cellular Plastics,RigidDetermination of WaterAbsorption33.Terminology3.1 DefinitionsThere are no terms in this test method thatare new or other than dictionary definitions.4.Summary of Test Method4.1 The
8、buoyant force of an object less dense than water isequal to the weight of water it displaces when submerged,lessthe dry weight of the object.Water absorbed into the objectlowers the buoyant force by increasing the weight of thesample.By knowing the volume and initial dry weight of thesample,the init
9、ial buoyant force can be calculated or the initialbuoyant force can be determined by direct measurement.Thefinal buoyant force at the end of the immersion period ismeasured with an underwater weighing assembly.The differ-ence between the initial and final buoyant force is the weight ofthe water abso
10、rbed per unit of specimen volume.5.Significance and Use5.1 The purpose of this test method is to provide a means forcomparing relative water absorption tendencies between dif-ferent cellular plastics.It is intended for use in specifications,product evaluation,and quality control.It is applicable tos
11、pecific end-use design requirements only to the extent that theend-use conditions are similar to the immersion period(nor-mally 96 h)and 5.1-cm(2-in.)head requirements of the testmethod.NOTE2Studies by ASTM Subcommittee D20.22 show that somecellular plastics,particularly those with open cells or nat
12、ural interstices,continue to absorb additional significant amounts of water beyond the96-h immersion period.It was also found that water absorption of somecellular plastics is significantly higher when exposed to a greater pressurehead,as might be encountered in certain underwater installations.5.2
13、This test method provides a means for measuringabsorption as a result of direct contact exposure to free water.Results by this test method cannot be used to compare the1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22
14、 on Cellular Materials-Plastics and Elastomers.Current edition approved Oct.1,2012.Published November 2012.Originallyapproved in 1969.Last previous edition approved in 2006 as D2842-06.DOI:10.1520/D2842-12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Ser
15、vice at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036.*A Summary of Changes section appears at the end of this s
16、tandardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 resistance of cellular plastics to water vapor transmission andsubsequent condensation within the cells.To determine resis-tance to water vapor transmission,see Test Methods E96.5.3 Water absorption testing is subject to several importantvariables,which if not considered,prohibit sufficient agree-ment among testing laboratories.Development of this testmethod has taken into account