1、Designation: D2221 01 (Reapproved 2010)Standard Test Method forCreep Properties of Package Cushioning Materials1This standard is issued under the fixed designation D2221; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、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.1. Scope1.1 This test method covers the determina
3、tion of creepproperties of package cushioning materials. It is applicable tomaterials available in bulk, sheet, or molded form used for thecushioning of articles during storage, handling, and shipment.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parent
4、heses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.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
5、 safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4332 Practice for Conditioning Containers, Packages, orPackaging Components for TestingE105 Practice for Probability Sampling Of MaterialsE122 Practice for
6、 Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or Process3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 creepthe deformation of a material occurring withtime and due to an externally applied constant stress. Forcushioni
7、ng materials specifically, it may be defined as thechange in thickness of a cushion under static compressive loadover a period of time.3.1.2 permanent setthe permanent change in thickness ofan unloaded cushion as a result of an applied compressive loadfor any given time interval and any given unload
8、ed recoverytime period.4. Summary of Test Method4.1 The test apparatus consists of a suitable testing devicehaving a base plate and a guided movable platen which can beloaded with weights. The loaded movable platen is placed on acushion to simulate static compressive loading of cushioningmaterial in
9、 actual packaging. By measuring the change inthickness of the loaded cushion with time, creep properties ofthe cushioning material can be obtained.5. Significance and Use5.1 This test method determines the extent and nature ofcushion thickness change under static load. Creep data ob-tained by this t
10、est method are applicable to the cushion underthe conditions of the particular test and are not necessarily thesame as obtained in a complete pack in actual packagingenvironments. Data may be affected by magnitude of staticload, specimen area, shape, and thickness, by varying ambientconditions of te
11、mperature, humidity, by friction in the movableplaten guide system, and by actual cushion thickness. Vibrationin the vicinity of the test fixtures may also influence dataresults.6. Apparatus6.1 Movable, Guided Platen, capable of being weighted toachieve the desired loading along with a base to suppo
12、rt thesample throughout the duration of the test. Two such assem-blies are shown in Fig. 1 and Fig. 2.6.2 Static Load Box Fixture (Fig. 1), consisting of a mov-able guided platen and an outer box that shall act as the guideand the base plate for supporting the sample.6.2.1 Base Plate (Outer Box), ma
13、y be constructed of34 in.(19.0 mm) minimum white pine and fabricated to reduceswelling which may occur at high humidity.Aflat rigid plate ofappropriate dimensions is placed on the inside bottom surface1This test method is under the jurisdiction of ASTM Committee D10 onPackaging and is the direct res
14、ponsibility of Subcommittee D10.13 on InteriorPackaging.Current edition approved Jan. 1, 2010. Published January 2010. Originallyapproved in 1963. Last previous edition approved in 1999 as D2221 99(2004).DOI: 10.1520/D222199R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or
15、contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.and used as the ba
16、se plate. The plate can be made of a materialsuch as aluminum, steel, rigid plastic sheeting or glass.6.2.2 Movable Guided Platen (Inner Box), may be loadedwith weights (for example, lead shot or molded lead weights),and fabricated in the same manner as described in 6.2.1. A flatrigid plate similar
17、to that described in 6.2.1 is placed betweenthe top of the test specimen and the movable platen and servesas a reference for measuring the height of the specimen.6.2.3 Two means of measurement, two position and fourposition, may be utilized.Amicrometer or steel rule capable ofmeasurement to 0.01 in.
18、 (0.3 mm) shall be utilized.6.2.3.1 Two PositionA vertical line, scribed at the centerof both (movable and base) flat, rigid plate edges (Fig. 1)serves as location references for specimen thickness measure-ments (distance between the plates) at various time intervals.Measurements are taken at the ve
19、rtical scribed lines at both thefront and back of the box.6.2.3.2 Four PositionMeasurements are taken at the fourbox corners for specimen thickness measurements (see6.2.3.1).6.3 The single point fixture shall consist of a supportstructure guiding a rod perpendicularly attached to a platen (seeFig. 2
20、).6.3.1 The support structure shall be constructed in such amanner as to keep the rod and platen perpendicular to the basewithout binding. The rod shall be attached to the platen so asto limit lateral motion. (The weight of both platen and rod shallbe constructed to achieve the minimum static loadin
21、g fororiginal thickness measurement in 9.2.) Weights may be addedto the platen top surface to achieve the desired static loading.6.3.2 Measurements shall be taken from the top of the rodwith a dial micrometer or other similar device capable ofmeasurement to 0.01 in. (0.3 mm).6.4 Flat Rigid Plate, fo
22、r measuring specimen thickness (see9.2) should be constructed to yield a 0.025 psi (0.17 kPa) staticload. Plates referenced in 6.2.1 and 6.2.2 used with the staticload box may be utilized if constructed to the proper weightrequired to achieve the desired static load.7. Test Specimens7.1 Test specime
23、ns shall be right square prisms or rightcylinders with the lateral dimensions at least the same as theoriginal thickness, and with minimum dimensions of not lessthan 2 by 2 by 1 in. (51 by 51 by 25 mm) thick. The preferredsize is 6 by 6 by 4 in. (152 by 152 by 102 mm) thick. If thecushioning materia
24、l, as supplied, is less than 1 in. (25.4 mm)thick, the required thickness may be obtained by using two ormore layers of the material. For thin gage materials requiringthe stacking of several layers to achieve the desired specimenNOTE 1All dimensions are for reference only and are dependent onthe mat
25、erials tested.Inside Dimensions of Outer Box165 (+2,0) 3 165 (+2,0) 3 254 (63) mmmm 2 162 165 203 254in. 0.08 6.37 6.50 8 10FIG. 1 Typical Static Load Box Creep ApparatusNOTE 1All dimensions are for reference only and are dependent onthe materials tested.FIG. 2 Typical Single Point Creep ApparatusD2
26、221 01 (2010)2thickness, interleaving between layers with light weight, non-compressible, flat, rigid plates can help stabilize the stackedspecimen. However, the cumulative thicknesses and weights ofthese plates must be accounted for in all thickness measure-ments before calculating any values descr
27、ibed in Section 10.Specimens with larger areas are recommended wheneverpossible and may be dictated by the apparatus used to measurecreep. Fiber length, pore size, or the nature of a material mayalso be determining factors regarding specimen size.7.2 The number of specimens tested as a sample may va
28、rywidely, depending on the intended use of the data. It isrecommended that at least four specimens be used for theinitial sample of a material. Then, depending on the accuracyand degree of certainty required, this sample size may beincreased or decreased. To ensure better representation of thesample
29、, individual specimens should be selected by systematicrandomization. This can be done by assigning a consecutivenumber to each of the specimens of the sample, and thenselecting the specimens which have numbers that correspond toa series drawn by lottery. Sampling procedures for selectingspecimens a
30、re discussed in Practice E105. Procedures fordetermining the number of specimens required for each sampleare given in Practice E122.8. Conditioning8.1 Precondition all specimens at any desired condition fora sufficient length of time to essentially achieve equilibriumwith the ambient atmosphere. In
31、the absence of more specificrequirements, the application of Practice D4332 is recom-mended or one of the following procedures may be followed:8.2 Precondition all specimens at 35 6 2 % relative humid-ity at 73.4 6 3.6F (23 6 2C) maximum for 24 h and thencondition and test at 73.4 6 3.6F (23 6 2C) a
32、nd 50 6 2%relative humidity. The length of conditioning shall be aminimum of 16 h, or until the differences between twosuccessive weights of the specimen determined at 1 h intervalsis less than 1 % of the average specimen weight.8.3 Conduct the test at 73.4 6 3.6F (236 2C) and 50 65 % relative humid
33、ity. If creep is determined at other tempera-tures, humidities, or both (in accordance with 9.7), conductonly the procedures described in 9.4 to 9.6 at the optionalconditions.9. Procedure9.1 Dimensions and WeightDetermine measurements forarea calculations with an apparatus yielding values accurate t
34、o0.01 in. (0.3 mm); for weight, 0.01 lb (4.54 g).9.2 Load top surface of conditioned specimen (To), asfurnished or cut, to 0.025 psi (0.17 kPa). Loading shall beapplied evenly and gently with a flat, rigid plate (see 6.4).Aftera 30 s interval, and while the specimen is still under 0.025 psiload; mea
35、sure the thickness to the nearest 0.01 in. (0.3 mm) atthe specimen top surface geometric center (see 6.2.3). As analternative procedure, average the thickness measurementstaken at the four corners of the specimen. Record this value asthe original thickness To.9.3 Preworking (Optional)For cushioning
36、applicationswhere a high degree of compressibility and recovery of thecushion is required, a preworking of the creep test specimenprior to loading is recommended. A suggested preworkingprocedure may consist of compressing the specimen to 65 % ofits thickness twice at a rate not to exceed 1 cps. Rest
37、 thespecimen for a minimum period of 16 h. Following the restperiod, record as the preworked thickness, Tp, the thickness ofthe specimen, as determined in 9.2.9.4 Loading of SpecimenUsing either of the fixturesdescribed in Section 6, center the rigid plate on the specimenand apply the desired static
38、 load (weight of the rigid plate plusthat of the movable platen plus the lead shot or moldedweights) evenly and gently to the entire upper surface of eachspecimen. Start to measure or determine the thickness of thespecimen while under load, 60 6 5 s after the load has beenapplied. Determine the thic
39、kness by averaging the verticalperpendicular distance between the plates using either the twoor four position measuring method (see 6.2.3) for the guidedplaten fixture, or by measuring the height of the rod in thesingle point fixture. Record this thickness as the initial thick-ness under load, Ti.NO
40、TE 1Since creep tests are especially sensitive to shock andvibration, select the test apparatus location for a minimum of disturbance.When the test locations are not free from vibration or shock, design thetest equipment and mounting so that the specimen is isolated from shockand vibration.9.5 Creep
41、 DeterminationMeasure the distance betweenthe rigid plates of the loaded specimen at any desired timeinterval (such as at 6 min, 1 h, 24 h, 72 h, 96 h, etc.), after theapplication of the load. Record this thickness as the deflectedthickness under load at the specified interval (Td(time interval), fo
42、rexample, Td(96h).(More frequent readings throughout the du-ration of the test will provide more complete information onthe nature of cushioning creep.) Total test duration will bebased on the test materials, the static load being applied, andthe intended use of the data. Tests at relatively heavy l
43、oadings(as related to the materials under test) may run for considerablyshorter time than those run at more reasonable and anticipatedloadings. (Intervals for measurements may depend on the loadbeing used, the intended use of the data obtained, and testduration.)9.6 Recovery DeterminationAt the end
44、of the creep load-ing test time, remove the test load from the specimen. At threeintervals, 30 s, 30 min, and 24 h after removal of the test load,make thickness determinations of the specimen as specified in9.2. Between these determinations, the test load shall notremain on the specimen. Record as t
45、he thickness after recoveryperiod Tr(time interval), for example Tr(30 s), Tr(30 min),orTr(24h).9.7 Creep Determinations at Other Temperatures and Hu-midities (Optional)In order to establish data that will simu-late actual conditions, it may be necessary to perform creeptests as described, but at va
46、ried temperatures or humidities, orboth, which can be expected in service. In the absence of morespecific requirements, the following procedure is suggested:9.7.1 Test at 65 to + 160F (54 to 71C) and from 35 to95 % relative humidity at 73.4F (23C). Use and record otherextreme temperatures or humidit
47、ies, or both as desired, butnote that instruments or equipment may not operate at the sameefficiency at extreme conditions as at standard conditions.D2221 01 (2010)310. Calculations10.1 Calculate the density as follows:D 5 W/A 3 To! (1)where:D = density, lb/ft3, (g/mm3),W = weight of specimen, lb g
48、(mass),A = area of specimen, in.2(mm2), andTo= original thickness of specimen, in. (mm).10.2 Calculate the static stress for the given loading asfollows:Static stress, 5 F/A (2)where:F = load applied, lb g (mass), andA = area of specimen, in.2(mm2).10.3 Calculate the initial strain for the given sta
49、tic stress asfollows:initial strain, % 5 To2 Ti!/To# 3 100 (3)where:Ti= initial thickness under load, in. (mm), andTo= original thickness, in. (mm).NOTE 2Where preworking is utilized, substitute Tp, preworked thick-ness, for To.10.4 Calculate interval strain based on original thickness asfollows:Interval strain, % 5 To2 Td!/To# 3 100 (4)where:To= original thickness, in. (mm), andTd= deflection thickness, at the given time interval in.(mm).10.4.1 See Note 2.10.5 Calculate creep based on initial thickness under testload as follows:Creep, at a
