ASTM_D_570_-_98_2010e1.pdf

Designation:D57098(Reapproved 2010)1Standard Test Method forWater Absorption of Plastics1This standard is issued under the fixed designation D570;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 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 Department of Defense.1NOTERemoved ASTM D647 as a referenced document editorially in June 2010.1.Scope1.1 This test method covers the determination of the relativerate of absorption of water by plastics when immersed.Thistest method is intended to apply to the testing of all types ofplastics,including cast,hot-molded,and cold-molded resinousproducts,and both homogeneous and laminated plastics in rodand tube form and in sheets 0.13 mm(0.005 in.)or greater inthickness.1.2 The values given in SI units are to be regarded asstandard.The values stated in parentheses are for informationonly.1.3 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE1This standard is equivalent to ISO 62.2.Referenced Documents2.1 ISO Standard:ISO 62 PlasticsDetermination of Water Absorption23.Significance and Use3.1 This test method for rate of water absorption has twochief functions:first,as a guide to the proportion of waterabsorbed by a material and consequently,in those cases wherethe relationships between moisture and electrical or mechanicalproperties,dimensions,or appearance have been determined,as a guide to the effects of exposure to water or humidconditions on such properties;and second,as a control test onthe uniformity of a product.This second function is particu-larly applicable to sheet,rod,and tube arms when the test ismade on the finished product.3.2 Comparison of water absorption values of various plas-tics can be made on the basis of values obtained in accordancewith 7.1 and 7.4.3.3 Ideal diffusion of liquids3into polymers is a function ofthe square root of immersion time.Time to saturation isstrongly dependent on specimen thickness.For example,Table1 shows the time to approximate time saturation for variousthickness of nylon-6.3.4 The moisture content of a plastic is very intimatelyrelated to such properties as electrical insulation resistance,dielectric losses,mechanical strength,appearance,and dimen-sions.The effect upon these properties of change in moisturecontent due to water absorption depends largely on the type ofexposure(by immersion in water or by exposure to highhumidity),shape of the part,and inherent properties of theplastic.With nonhomogeneous materials,such as laminatedforms,the rate of water absorption may be widely differentthrough each edge and surface.Even for otherwise homoge-neous materials,it may be slightly greater through cut edgesthan through molded surfaces.Consequently,attempts tocorrelate water absorption with the surface area must generallybe limited to closely related materials and to similarly shapedspecimens:For materials of widely varying density,relationbetween water-absorption values on a volume as well as aweight basis may need to be considered.4.Apparatus4.1 BalanceAn analytical balance capable of reading0.0001 g.4.2 Oven,capable of maintaining uniform temperatures of50 6 3C(122 6 5.4F)and of 105 to 110C(221 to 230F).1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.50 on Durability of Plastics.Current edition approved April 1,2010.Published June 2010.Originallyapproved in 1940.Last previous edition approved in 2005 as D570-98(2005).DOI:10.1520/D0570-98R10E01.2Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.3Additional information regarding diffusion of liquids in polymers can be foundin the following references:(1)Diffusion,Mass Transfer in Fluid Systems,E.L.Cussler,Cambridge University Press,1985,ISBN 0-521-29846-6,(2)Diffusion inPolymers,J.Crank and G.S.Park,Academic Press,1968,and(3)“Permeation,Diffusion,and Sorption of Gases and Vapors,”R.M.Felder and G.S.Huvard,inMethods of Experimental Physics,Vol 16C,1980,Academic Press.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Test Specimen5.1 The test specimen for molded plastics shall be in theform of a disk 50.8 mm(2 in.)in diameter and 3.2 mm(18in.)in thickness.Permissible variations in thickness are 60.18 mm(60.007 in.)for hot-molded and 60.30 mm(60.012 in.)forcold-molded or cast materials.5.2 ISO Standard SpecimenThe test specimen for homo-geneous plastics shall be 60 by 60 by 1 mm.Tolerance for the6