1、Designation: D 2842 06Standard Test Method forWater Absorption of Rigid Cellular Plastics1This standard is issued under the fixed designation D 2842; 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers the determination of the waterab
3、sorption 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. ProcedureAshallb
4、e used for 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 nor
5、mal 96-h test 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 o
6、f this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1This test method is equivalent to ISO 2896.2. Referenced Documents2.1 ASTM Standards:2E 96/E 96M Test Methods for Water Vapor Transmission ofMaterialsE
7、691 Practice for Conducting 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. Su
8、mmary of Test Method4.1 The 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 d
9、ry weight of thesample, the initial 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 fo
10、rce is the weight ofthe water absorbed 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
11、 quality control. It is applicable tospecific 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.NOTE 2Studies by ASTM Subcommittee D20.22 show that somecellular plastics,
12、 particularly those with open cells or natural 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 encounte
13、red in certain underwater installations.5.2 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 theresistance of cellular plastics to water vapor transmission andsubsequent condensation w
14、ithin the cells. To determine resis-tance to water vapor transmission, see Test Methods E 96.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved No
15、v. 1, 2006. Published November 2006. Originallyapproved in 1969. Last previous edition approved in 2001 as D 2842 - 01.2For 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
16、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 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
17、st Conshohocken, PA 19428-2959, United States.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 the most serious of the possiblesources of er
18、ror.NOTE 3In some methods, an error is encountered due to a rapidabsorption of water before an accurate initial weight can be obtained. Thistest method accounts for that potential error by providing Procedure A foruse with materials that behave in this manner. In this procedure the onlysubmerged mea
19、surement required is a final weighing taken after the 96-himmersion period.NOTE 4The increase in volume that occurs with some foams whenimmersed is accounted for in Procedure A. This procedure should be usedfor materials that exhibit this type of behavior. This is accounted for bybasing all buoyant
20、force calculations on the volume of the wet specimenat the conclusion of the immersion period.NOTE 5The problem of air bubbles clinging to the submergedspecimen and affecting the end result is minimized by specifyingdeaerated distilled water.NOTE 6Surface cells opened during specimen preparation res
21、ult in anerror when calculating the apparent volume of the test specimen. Thedegree of this error is a function of cell size. This test method accounts forthis error in that all calculations are based on the true specimen volume.The true specimen volume is determined in Procedure A as the measuredvo
22、lume minus the volume of surface cells opened by cutting. Thiscorrection is not required in Procedure B since the true specimen volumeis determined by direct measurement.5.4 The volume error associated with surface cells openedduring specimen preparation decreases as the cell size de-creases. This t
23、est method provides the option to ignore thisvariable with cellular plastics estimated to have an average celldiameter of 0.03 cm or less. For cellular plastics having greaterthan 0.03-cm average cell diameter and in all cases of dispute,measurement of cell size shall be mandatory in determining the
24、specimen volume.5.5 For most materials the size of the test specimens is smallcompared with the size of the products actually installed in thefield. If the surface-to-volume ratios for the test specimens andthe corresponding products are different, the test results may bemisleading.5.6 In most cases
25、 water retention is a secondary perfor-mance characteristic that has an influence on a primarycharacteristic, such as thermal performance, surface accumu-lation of moisture, localized collection of electrolytes, etc.5.7 Before proceeding with this test method, reference shallbe made to the specifica
26、tion of the material being tested. Anytest specimen preparation, conditioning, dimensions, or testingparameters covered in the materials specification, or both, shalltake precedence over those mentioned in this test method. Ifthere are no material specifications, then the default conditionsapply.6.
27、Apparatus6.1 BalanceA balance capable of weighing up to 2500 gwith a sensitivity of 0.1 g. Balance must have provision forattaching wire sling below balance platform for making sub-merged weighings.6.2 Underwater Weighing Jig, constructed so that specimenfloats against jig ceiling with 15.2 by 15.2-
28、cm 6 by 6-in.specimen face in the horizontal position. The jig should trap noair when submerged. The approximate dry weight is to be 2500g. Fig. 1 shows two recommended styles of jig construction.6.3 Immersion TankAn open-top tank or aquarium ofsufficient size to accommodate at least three specimens
29、 withthe top 15.2 by 15.2-cm 6 by 6-in. faces in the horizontalposition and additional space for the weighing jig. (A 75.8-dm20-gal glass aquarium, 76.2 by 33.0 by 30.4 cm 30 by 13 by12 in. high is of sufficient size for testing up to six specimens.)6.4 Balance PlatformA mounting platform to be plac
30、edacross the top of the immersion tank to support the balance. Ahole in the platform must be provided at an appropriatelocation to accommodate wire sling from balance to jig.6.5 Conditioning OvenForced-air circulating oven ca-pable of maintaining 50 6 3C 122 6 5F for 24 h.6.6 Desiccator, containing
31、desiccant with high affinity forwater vapor (anhydrous calcium chloride or equivalent) formaintaining dryness of test specimens upon removal fromconditioning oven.6.7 Vernier Calipers or Dial MicrometerMeasuring de-vice capable of measuring specimen to nearest 0.002 cm 0.001in. Fig. 2 shows a recomm
32、ended measuring device.6.8 Cell-Size Specimen SlicerCutting blade apparatus ca-pable of slicing thin specimens (0.01 to 0.04 cm) for cellsizeviewing. Fig. 3 shows an acceptable alternative slicing appa-ratus.6.9 Cell-Size ProjectorConventional 35-mm slide projec-tor that accepts standard 5.1 by 5.1-
33、cm 2 by 2-in. slides.6.10 Cell-Size Scale Slide Assembly, consisting of twopieces of slide glass hinged by tape along one edge, betweenwhich a calibrated scale (3.0 mm in length) printed on a thinplastic sheet is placed. See Fig. 4.7. Reagents and Materials7.1 Distilled WaterSufficient amount of fre
34、shly distilledwater to maintain a 5.08-cm 2-in. head over specimens andjig at all times.7.2 Gas Barrier FilmLayer of low permeance (polyeth-ylene, saran, or equivalent) plastic film covering surface ofwater to retard air pick up by deaerated water.8. Test Specimens8.1 Three test specimens shall be t
35、ested from each sample.8.2 Test Specimen Size:8.2.1 The recommended test specimen size shall be 15 cm6 in. in width by 15 cm in length by 7.5 cm 3 in. inthickness for any material which can be cut to this size fromlarger stock without substantially changing its original charac-ter.8.2.2 Test specime
36、n size shall be 15 cm 6 in. in width by15 cm in length by the actual thicknesses for materials havingless than 7.5 cm 3 in. overall thickness. This is intended formaterials normally produced and sold with natural or laminatedskin surfaces and for other materials in which the sample stockavailable fo
37、r testing is less than 7.5 cm in thickness.8.2.3 For materials produced and sold with natural orlaminated skin surfaces having an overall thickness greaterthan 7.5 cm 3 in., the test specimen thickness shall be theD2842062actual thickness with the length and width dimensions in-creased to no less th
38、an two times the thickness dimension. Toaccommodate these larger specimens, the test equipment speci-fied previously must be modified accordingly.8.3 Test specimens shall be machined or sawed from thesample so as to have smooth surfaces. All machined or sawedsurfaces may be further smoothed by slici
39、ng techniques orFIG. 1 Underwater Weighing JigsD2842063sanding with No. 0 or finer sandpaper. Resulting dust shall beblown from the specimen.9. Conditioning9.1 Unless specified by the contract or relevant materialspecification, after cutting specimens, condition them in aforced-air circulating oven
40、for 24 h or more at 50 6 3C 1226 5F.9.2 Allow specimens to cool to room temperature in adesiccator and then weigh to the nearest 0.1 g.9.3 Return specimens to conditioning oven for 4 additionalhours at 50 6 3C 122 6 5F, cool in desiccator, and weighto the nearest 0.1 g. Repeat 4-h conditioning inter
41、vals untilspecimens reach constant weight as indicated by less than 0.2-gweight change between successive weighings.FIG. 2 Dual-Dial Micrometer Measuring DeviceD28420649.4 Record final dry weight of each specimen to nearest 0.1g(W1).10. Procedure10.1 Procedure A:10.1.1 Place underwater weighing jig
42、in immersion tank.10.1.2 Immerse specimens by suitable weighted rack inopen-top immersion tank filled with freshly distilled water at23 6 2C 73.4 6 3.6F. Adjust the water level to maintain a5.1-cm 2-in. head of water over the top of specimens with15.2 by 15.2-cm 6 by 6-in. faces in the horizontal po
43、sition.FIG. 3 Razor Blade Cell-Size Specimen SlicerFIG. 4 Cell-Size Scale Slide AssemblyD284206510.1.3 Remove obvious air bubbles clinging to the speci-men with a soft-bristle brush.10.1.4 Cover entire surface of water with low-permeanceplastic film.10.1.5 Leave specimens immersed for 96 h while mai
44、ntain-ing 5.1-cm 2-in. head of water at 23 6 2C 73.4 6 3.6F.10.1.6 At the end of 96-h immersion time, assemble balanceplatform and balance on the top of the tank, remove the plasticfilm from water, and zero balance.10.1.7 Attach the underwater weighing jig to the balancewith wire sling such that the
45、 top horizontal surface of the jig is5.1 cm 2 in. below the surface of the water. Be sure that thesubmerged jig is free of trapped air bubbles.10.1.8 Weigh the empty submerged jig to the nearest 0.1 g(W2).10.1.9 Insert the test specimen into submerged underwaterweighing jig without removing the spec
46、imen from the water.Weigh to the nearest 0.1 g (W3). Do not remove any specimensfrom the water until all have been weighed, as removing thespecimens reduces the 5.1-cm 2-in. head.10.1.10 Remove specimens from water and immediatelymeasure the specimen dimensions (length, width, and thick-ness) to the
47、 nearest 0.002 cm 0.001 in. For convenience,remove the surface water from the specimen with a towelbefore measuring.10.1.11 In accordance with the provisions of 4.4, the fol-lowing procedure (10.1.12-10.1.15) can be omitted for cellularplastics estimated to have an average cell diameter of 0.03 cmor
48、 less. An average cell diameter of 0.03 cm is equivalent to0.018-cm average chord length, t, as measured in 10.1.15.Inthis case V1= V2in the calculation.10.1.12 Prepare the cell size viewing specimen by cutting athin slice (0.01 to 0.04 cm) from one of the cut surfaces of thespecimen (Note 8). Slice
49、 thickness should be as thin aspractical so that shadowgraph will not be occluded by over-lapping cell walls. Optimum slice thickness will vary with theaverage cell size of the foam with larger cell foams requiringthicker slices.NOTE 7One cell-size measurement will provide a representativeaverage cell size for cellular plastics having symmetric cells of relativelyuniform size. However, cellular plastics known to be significantly aniso-tropic will require measurement of cell size in three normal directions f
