1、Designation: D2842 06 D2842 12Standard 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.
2、 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.1. Scope*1.1 This test method covers the determination of the w
3、ater absorption 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 be used to measure the change in buoyant force. Procedu
4、re A shall beused for materials that either experience rapid water absorption or that show an increase in volume during the exposure period,or both. Materials that do not exhibit either of these characteristics shall be evaluated by Procedure B.1.3 For specific applications, immersion periods varyin
5、g from the normal 96-h test requirement shall be agreed upon betweenthe manufacturer and the purchaser.1.4 The values stated in SI units are to be regarded as the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibil
6、ityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1This test method is equivalent to ISO 2896.NOTE 1This test method is equivalent to ISO 2896.2. Referenced Documents2.1 ASTM Standards:2E96/
7、E96ME96 Test Methods for Water Vapor Transmission of MaterialsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 ISO Standard:ISO 2896 Cellular Plastics, RigidDetermination of Water Absorption33. Terminology3.1 DefinitionsThere are no terms in this t
8、est method that are new or other than dictionary definitions.3.1 DefinitionsThere are no terms in this test method that are new or other than dictionary definitions.4. Summary of Test Method4.1 The buoyant force of an object less dense than water is equal to the weight of water it displaces when sub
9、merged, less thedry weight of the object. Water absorbed into the object lowers the buoyant force by increasing the weight of the sample. Byknowing the volume and initial dry weight of the sample, the initial buoyant force can be calculated or the initial buoyant forcecan be determined by direct mea
10、surement. The final buoyant force at the end of the immersion period is measured with anunderwater weighing assembly. The difference between the initial and final buoyant force is the weight of the water absorbed perunit of specimen volume.5. Significance and Use5.1 The purpose of this test method i
11、s to provide a means for comparing relative water absorption tendencies between differentcellular plastics. It is intended for use in specifications, product evaluation, and quality control. It is applicable to specific end-usedesign requirements only to the extent that the end-use conditions are si
12、milar to the immersion period (normally 96 h) and 5.1-cm2-in. head requirements of the test method.NOTE 2Studies by ASTM Subcommittee D20.22 show that some cellular plastics, particularly those with open cells or natural interstices, continueto absorb additional significant amounts of water beyond t
13、he 96-h immersion period. It was also found that water absorption of some cellular plasticsis significantly higher when exposed to a greater pressure head, as might be encountered in certain underwater installations.*A Summary of Changes section appears at the end of this standardCopyright ASTM Inte
14、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 This test method provides a means for measuring absorption as a result of direct contact exposure to free water. Results bythis test method cannot be used to compare the resistance of cellular plastics
15、 to water vapor transmission and subsequentcondensation within the cells. To determine resistance to water vapor transmission, see Test Methods E96/E96ME96.5.3 Water absorption testing is subject to several important variables, which if not considered, prohibit sufficient agreementamong testing labo
16、ratories. Development of this test method has taken into account the most serious of the possible sources oferror.NOTE 3In some methods, an error is encountered due to a rapid absorption of water before an accurate initial weight can be obtained. This test methodaccounts for that potential error by
17、providing Procedure A for use with materials that behave in this manner. In this procedure the only submergedmeasurement required is a final weighing taken after the 96-h immersion period.NOTE 4The increase in volume that occurs with some foams when immersed is accounted for in Procedure A. This pro
18、cedure shouldshall be usedfor materials that exhibit this type of behavior. This is accounted for by basing all buoyant force calculations on the volume of the wet specimen at theconclusion of the immersion period.NOTE 5The problem of air bubbles clinging to the submerged specimen and affecting the
19、end result is minimized by specifying deaerated distilledwater.NOTE 6Surface cells opened during specimen preparation result in an error when calculating the apparent volume of the test specimen. The degreeof this error is a function of cell size. This test method accounts for this error in that all
20、 calculations are based on the true specimen volume. The truespecimen volume is determined in Procedure A as the measured volume minus the volume of surface cells opened by cutting. This correction is notrequired in Procedure B since the true specimen volume is determined by direct measurement.5.4 T
21、he volume error associated with surface cells opened during specimen preparation decreases as the cell size decreases. Thistest method provides the option to ignore this variable with cellular plastics estimated to that have an average cell diameter of 0.03cm or less. For cellular plastics having gr
22、eater than 0.03-cm average cell diameter and in all cases of dispute, measurement of cellsize shall be mandatory in determining the specimen volume.5.5 For most materials the size of the test specimens is small compared with the size of the products actually installed in thefield. If the surface-to-
23、volume ratios for the test specimens and the corresponding products are different, it is possible that the testresults may be are misleading.5.6 In most cases water retention is a secondary performance characteristic that has an influence on a primary characteristic,such as thermal performance, surf
24、ace accumulation of moisture, localized collection of electrolytes, dimensional stability, etc.5.7 Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any testspecimen preparation, conditioning, dimensions, or testing parameters covered
25、 in the materials specification, or both, shall takeprecedence over those mentioned in this test method. If there are no material specifications, then the default conditions in thisstandard shall apply.6. Apparatus6.1 BalanceA balance capable of weighing up to 2500 g with a sensitivity of 0.10.01 g.
26、 Balance must have a provision forattaching the wire sling below the balance platform for making submerged weighings.6.2 Underwater Weighing Jig, constructed so that specimen floats against jig ceiling with 15.2 by 15.2-cm 6 by 6-in. specimenface in the horizontal position. The jig shouldshall trap
27、no air when submerged. The approximate dry weight is to be 2500 g. Fig.1 shows two recommended styles of jig construction.6.3 Immersion TankAn open-top tank or aquarium of sufficient size to accommodate at least three specimens with the top 15.2by 15.2-cm 6 by 6-in. faces in the horizontal position
28、and additional space for the weighing jig. (A 75.8-dm 20-gal glassaquarium, 76.2 by 33.0 by 30.4 cm 30 by 13 by 12 in. high is of sufficient size for testing up to six specimens.)6.4 Balance PlatformA mounting platform to be placed across the top of the immersion tank to support the balance. A holei
29、n the platform must be provided at an appropriate location to accommodate wire sling from balance to jig.6.5 Conditioning OvenForced-air circulating oven capable of maintaining 50 6 3C 122 6 5F for 24 h.6.6 Desiccator, containing desiccant with high affinity for water vapor (anhydrous calcium chlori
30、de or equivalent) formaintaining dryness of test specimens upon removal from conditioning oven.6.7 Vernier Calipers or Dial MicrometerMeasuring device capable of measuring specimen to nearest 0.002 cm 0.001 in.Fig. 2 shows a recommended measuring device.1 This test method is under the jurisdiction o
31、f ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand Elastomers.Current edition approved Nov. 1, 2006Oct. 1, 2012. Published November 2006November 2012. Originally approved in 1969. Last previous edition approved in 20012006as D
32、2842 - 01.D2842 - 06. DOI: 10.1520/D2842-06.10.1520/D2842-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM websi
33、te.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.D2842 1226.8 Cell-Size Specimen SlicerCutting blade apparatus capable of slicing thin specimens (0.01 to 0.04 cm) for cellsize cell sizeviewing. Fig. 3 shows an acceptable alternative slic
34、ing apparatus.6.9 Cell-Size ProjectorConventional 35-mm slide projector that accepts standard 5.1 by 5.1-cm 2 by 2-in. slides. See Note7.6.10 Cell-Size Scale Slide Assembly, consisting of two pieces of slide glass hinged by tape along one edge, between which acalibrated scale (3.0 mm in length) prin
35、ted on a thin plastic sheet is placed. See Fig. 4.NOTE 7Microscopic or digital imaging techniques for measuring cell-sizes can be suitable replacements for the technique described in this standard.FIG. 1 Underwater Weighing JigsD2842 1237. Reagents and Materials7.1 Distilled WaterSufficient amount o
36、f freshly distilled water to maintain a 5.08-cm 2-in. head over specimens and jig atall times.7.2 Gas Barrier FilmLayer of low permeance (polyethylene, saran, or equivalent) plastic film covering surface of water toretard air pick up by deaerated water.8. Test Specimens8.1 Three test specimens shall
37、 be tested from each sample.8.2 Test Specimen Size:FIG. 2 Dual-Dial Micrometer Measuring DeviceD2842 1248.2.1 The recommended test specimen size shall be 15 cm 6 in. in width by 15 cm in length by 7.5 cm 3 in. in thicknessfor any material which can be cut to this size from larger stock without subst
38、antially changing its original character.8.2.2 Test specimen size shall be 15 cm 6 in. in width by 15 cm in length by the actual thicknesses for materials having lessthan 7.5 cm 3 in. overall thickness. This is intended for materials normally produced and sold with natural or laminated skinsurfaces
39、and for other materials in which the sample stock available for testing is less than 7.5 cm in thickness.8.2.3 For materials produced and sold with natural or laminated skin surfaces having an overall thickness greater than 7.5 cm3 in., the test specimen thickness shall be the actual thickness with
40、the length and width dimensions increased to no less thanFIG. 3 Razor Blade Cell-Size Specimen SlicerFIG. 4 Cell-Size Scale Slide AssemblyD2842 125two times the thickness dimension. To accommodate these larger specimens, the test equipment specified previously must bemodified accordingly.8.3 Test sp
41、ecimens shall be machined or sawed from the sample so as to they have smooth surfaces. All machined or sawedsurfaces mayshall be further smoothed by slicing techniques or sanding with No. 0 or finer sandpaper. Resulting dust shall beblownremoved from the specimen.9. Conditioning9.1 Unless specified
42、by the contract or relevant material specification, after cutting specimens, condition them in a forced-aircirculating oven for 24 h or more at 50 6 3C 122 6 5F.9.2 Allow specimens to cool to room temperature in a desiccator and then weigh to the nearest 0.10.01 g.9.3 Return specimens to conditionin
43、g oven for 4 additional hours at 50 6 3C 122 6 5F, cool in desiccator, and weigh tothe nearest 0.1 g. Repeat 4-h conditioning intervals until specimens reach constant weight as indicated by less than 0.2-g0.1-gweight change between successive weighings.9.4 Record final dry weight of each specimen to
44、 nearest 0.10.01 g (W1).10. Procedure10.1 Procedure A:10.1.1 Place underwater weighing jig in immersion tank.10.1.2 Immerse specimens by suitable weighted rack in open-top immersion tank filled with freshly distilled water at 23 6 2C73.4 6 3.6F. Adjust the water level to maintain a 5.1-cm 2-in. head
45、 of water over the top of specimens with 15.2 by 15.2-cm6 by 6-in. faces in the horizontal position.10.1.3 Remove obvious air bubbles clinging to the specimen with a soft-bristle brush.10.1.4 Cover entire surface of water with low-permeance plastic film.10.1.5 Leave specimens immersed for 96 h while
46、 maintaining 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 balance platform 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 balance with wire sling such tha
47、t the top horizontal surface of the jig is 5.1cm 2 in. below the surface of the water. Be sure that the submerged jig is free of trapped air bubbles.10.1.8 Weigh the empty submerged jig to the nearest 0.10.01 g (W2).10.1.9 Insert the test specimen into submerged underwater weighing jig without remov
48、ing the specimen from the water. Weighto the nearest 0.1 g (W3). Do not remove any specimens from the water until all have been weighed, as removing the specimensreduces the 5.1-cm 2-in. head.10.1.10 Remove specimens from water and immediately measure the specimen dimensions (length, width, and thic
49、kness) to thenearest 0.002 cm 0.001 in. For convenience, remove the surface water from the specimen with a towel before measuring.10.1.11 In accordance with the provisions of 4.4, the following procedure (10.1.12-10.1.15) can be omitted for cellular plasticsestimated to that have an average cell diameter of 0.03 cm or less. An average cell diameter of 0.03 cm is equivalent to a 0.018-cmaverage chord length, t, as measured in 10.1.15. In this case V1 = V2 in the calculation.10.1.12 Prepare the cell
