1、Designation: D570 98 (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 numb
2、er 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 20
3、10.1. 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
4、 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 brackets are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with
5、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.NOTE 1ISO 62 is technically equivalent to this test method.2. Referenced Documents2.1 ISO Standard:ISO 62 Plasti
6、csDetermination 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 mechanica
7、lproperties, 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 i
8、smade 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 depende
9、nt 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 d
10、imen-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 laminatedf
11、orms, 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 lim
12、ited 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, capabl
13、e of maintaining uniform temperatures of50 6 3C 122 6 5.4F and of 105 to 110C 221 to 230F.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 18 in.1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand
14、 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 I
15、nstitute (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 0-521-2984
16、6-6, (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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Bo
17、x C700, West Conshohocken, PA 19428-2959, United States.in thickness. Permissible variations in thickness are 60.18 mm60.007 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. Tol
18、erance for the60-mm dimension is 62mmand60.05 mm for the 1-mmthickness. This test method and ISO 62 are technically equiva-lent when the test specimen described in 5.2 is used.5.3 The test specimen for sheets shall be in the form of a bar76.2 mm 3 in. long by 25.4 mm 1 in. wide by the thicknessof th
19、e material. When comparison of absorption values withmolded plastics is desired, specimens 3.2-mm 18-in. thickshould be used. Permissible variations in thickness shall be0.20 mm 60.008 in. except for materials which have greaterstandard commercial tolerances.5.4 The test specimen for rods shall be 2
20、5.4-mm 1-in. longfor rods 25.4 mm in diameter or under and 12.7-mm 12-in.long for larger-diameter rods. The diameter of the specimenshall be the diameter of the finished rod.5.5 The test specimen for tubes less than 76 mm 3 in. ininside diameter shall be the full section of the tube and25.4-mm 1-in.
21、 long. For tubes 76 mm 3 in. or more in insidediameter, a rectangular specimen shall be cut 76 mm in lengthin the circumferential direction of the tube and 25.4 mm inwidth lengthwise of the tube.5.6 The test specimens for sheets, rods, and tubes shall bemachined, sawed, or sheared from the sample so
22、 as to havesmooth edges free from cracks. The cut edges shall be madesmooth by finishing with No. 0 or finer sandpaper or emerycloth. Sawing, machining, and sandpapering operations shallbe slow enough so that the material is not heated appreciably.NOTE 2If there is any oil on the surface of the spec
23、imen whenreceived or as a result of machining operations, wash the specimen witha cloth wet with gasoline to remove oil, wipe with a dry cloth, and allowto stand in air for2htopermit evaporation of the gasoline. If gasolineattacks the plastic, use some suitable solvent or detergent that willevaporat
24、e within the 2-h period.5.7 The dimensions listed in the following table for thevarious specimens shall be measured to the nearest 0.025 mm0.001 in. Dimensions not listed shall be measured within 0.8mm 6132 in.Type ofSpecimenDimensions to Be Measured to theNearest 0.025 mm 0.001 in.Molded disk thick
25、nessSheet thicknessRod length and diameterTube inside and outside diameter, and wall thickness6. Conditioning6.1 Three specimens shall be conditioned as follows:6.1.1 Specimens of materials whose water-absorption valuewould be appreciably affected by temperatures in the neigh-borhood of 110C 230F, s
26、hall be dried in an oven for 24 hat 50 6 3C 122 6 5.4F, cooled in a desiccator, and imme-diately weighed to the nearest 0.001 g.NOTE 3If a static charge interferes with the weighing, lightly rub thesurface of the specimens with a grounded conductor.6.1.2 Specimens of materials, such as phenolic lami
27、natedplastics and other products whose water-absorption value hasbeen shown not to be appreciably affected by temperatures upto 110C 230F, shall be dried in an oven for1hat105to110C 221 to 230F.6.1.3 When data for comparison with absorption values forother plastics are desired, the specimens shall b
28、e dried in anoven for 24 h at 50 6 3C 122 6 5.4F, cooled in a desic-cator, and immediately weighed to the nearest 0.001 g.7. Procedure7.1 Twenty-Four Hour ImmersionThe conditioned speci-mens shall be placed in a container of distilled water main-tained at a temperature of 23 6 1C 73.4 6 1.8F, and sh
29、allrest on edge and be entirely immersed. At the end of 24, +12 ,0 h, the specimens shall be removed from the water one at atime, all surface water wiped off with a dry cloth, and weighedto the nearest 0.001 g immediately. If the specimen is116 in. orless in thickness, it shall be put in a weighing
30、bottle immedi-ately after wiping and weighed in the bottle.7.2 Two-Hour ImmersionFor all thicknesses of materialshaving a relatively high rate of absorption, and for thinspecimens of other materials which may show a significantweight increase in 2 h, the specimens shall be tested asdescribed in 7.1
31、except that the time of immersion shall bereduced to 120 6 4 min.7.3 Repeated ImmersionA specimen may be weighed tothe nearest 0.001 g after 2-h immersion, replaced in the water,and weighed again after 24 h.NOTE 4In using this test method the amount of water absorbed in 24h may be less than it would
32、 have been had the immersion not beeninterrupted.7.4 Long-Term ImmersionTo determine the total waterabsorbed when substantially saturated, the conditioned speci-mens shall be tested as described in 7.1 except that at the endof 24 h they shall be removed from the water, wiped free ofsurface moisture
33、with a dry cloth, weighed to the nearest 0.001g immediately, and then replaced in the water. The weighingsshall be repeated at the end of the first week and every twoweeks thereafter until the increase in weight per two-weekperiod, as shown by three consecutive weighings, averages lessthan 1 % of th
34、e total increase in weight or 5 mg, whichever isgreater; the specimen shall then be considered substantiallysaturated. The difference between the substantially saturatedweight and the dry weight shall be considered as the waterabsorbed when substantially saturated.7.5 Two-Hour Boiling Water Immersio
35、nThe conditionedspecimens shall be placed in a container of boiling distilledwater, and shall be supported on edge and be entirely im-mersed. At the end of 120 6 4 min, the specimens shall beremoved from the water and cooled in distilled water main-tained at room temperature. After 15 6 1 min, the s
36、pecimensshall be removed from the water, one at a time, all surfaceTABLE 1 Time to Saturation for Various Thickness of Nylon-6Thickness, mm Typical Time to 95 % Saturation, h1 1002 4003.2 1 00010 10 00025 62 000D570 98 (2010)12water removed with a dry cloth, and the specimens weighed tothe nearest 0
37、.001 g immediately. If the specimen is116 in. orless in thickness, it shall be weighed in a weighing bottle.7.6 One-Half-Hour Boiling Water ImmersionFor allthicknesses of materials having a relatively high rate ofabsorption and for thin specimens of other materials whichmay show a significant weight
38、 increase in12 h, the specimensshall be tested as described in 7.5, except that the time ofimmersion shall be reduced to 30 6 1 min.7.7 Immersion at 50CThe conditioned specimens shallbe tested as described in 7.5, except that the time andtemperature of immersion shall be 48 6 1 h and 50 6 1C122.0 6
39、1.8F, respectively, and cooling in water beforeweighing shall be omitted.7.8 When data for comparison with absorption values forother plastics are desired, the 24-h immersion proceduredescribed in 7.1 and the equilibrium value determined in 7.4shall be used.8. Reconditioning8.1 When materials are kn
40、own or suspected to contain anyappreciable amount of water-soluble ingredients, the speci-mens, after immersion, shall be weighed, and then recondi-tioned for the same time and temperature as used in the originaldrying period. They shall then be cooled in a desiccator andimmediately reweighed. If th
41、e reconditioned weight is lowerthan the conditioned weight, the difference shall be consideredas water-soluble matter lost during the immersion test. For suchmaterials, the water-absorption value shall be taken as the sumof the increase in weight on immersion and of the weight of thewater-soluble ma
42、tter.9. Calculation and Report9.1 The report shall include the values for each specimenand the average for the three specimens as follows:9.1.1 Dimensions of the specimens before test, measured inaccordance with 5.6, and reported to the nearest 0.025 mm0.001 in.,9.1.2 Conditioning time and temperatu
43、re,9.1.3 Immersion procedure used,9.1.4 Time of immersion (long-term immersion procedureonly),9.1.5 Percentage increase in weight during immersion, cal-culated to the nearest 0.01 % as follows:Increase in weight, % 5wet weight 2 conditioned weightconditioned weight31009.1.6 Percentage of soluble mat
44、ter lost during immersion, ifdetermined, calculated to the nearest 0.01 % as follows (seeNote 5):Soluble matter lost, % 5conditioned weight 2 reconditioned weightconditioned weight3 100NOTE 5When the weight on reconditioning the specimen after im-mersion in water exceeds the conditioned weight prior
45、 to immersion,report “none” under 9.1.6.9.1.7 For long-term immersion procedure only, prepare agraph of the increase in weight as a function of the square rootof each immersion time. The initial slope of this graph isproportional to the diffusion constant of water in the plastic.The plateau region w
46、ith little or no change in weight as afunction of the square root of immersion time represents thesaturation water content of the plastic.NOTE 6Deviation from the initial slope and plateau model indicatesthat simple diffusion may be a poor model for determining water content.In such cases, additiona
47、l studies are suggested to determine a better modelfor water absorption.9.1.8 The percentage of water absorbed, which is the sum ofthe values in 9.1.5 and 9.1.6, and9.1.9 Any observations as to warping, cracking, or changein appearance of the specimens.10. Precision and Bias410.1 PrecisionAn interla
48、boratory test program was car-ried out using the procedure outlined in 7.1, involving threelaboratories and three materials.Analysis of this data yields thefollowing coefficients of variation (average of three replicates).WithinLaboratoriesBetweenLaboratoriesAverage absorption above1 % (2 materials)
49、2.33 % 4.89 %Average absorption below0.2 % (1 material)9.01 % 16.63 %NOTE 7A round robin is currently under way to more completelydetermine repeatability and reproducibility of this test method.10.2 BiasNo justifiable statement on the bias of this testmethod can be made, since the true value of the propertycannot be established by an accepted referee method.11. Keywords11.1 absorption; immersion; plastics; water4Supporting data have been filed at ASTM International Headquarters an
