1、Designation: D 2221 01Standard Test Method forCreep Properties of Package Cushioning Materials1This standard is issued under the fixed designation D 2221; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number 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. Scope1.1 This test method covers the determination of creeppr
3、operties 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 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is th
4、eresponsibility 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.2. Referenced Documents2.1 ASTM Standards:2D 4332 Practice for Conditioning Containers, Packages, orPackaging Components for Test
5、ingE 105 Practice for Probability Sampling Of MaterialsE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a Lot or Process3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 creepthe deformation of a material
6、 occurring withtime and due to an externally applied constant stress. Forcushioning 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 resu
7、lt of an applied compressive loadfor any given time interval and any given unloaded 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 p
8、laced on acushion to simulate static compressive loading of cushioningmaterial in 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 na
9、ture ofcushion thickness change under static load. Creep data ob-tained by this test 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 st
10、aticload, specimen area, shape, and thickness, by varying ambientconditions of temperature, 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, c
11、apable of being weighted toachieve the desired loading along with a base to support 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 g
12、uideand the base plate for supporting the sample.6.2.1 Base Plate (Outer Box), may 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 surfaceand used as the ba
13、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
14、to that described in 6.2.1 is placed between1This test method is under the jurisdiction of ASTM Committee D10 onPackaging and is the direct responsibility of Subcommittee D10.13 on InteriorPackaging.Current edition approved Sept. 10, 2001. Published November 2001. Originallypublished as D 2221 63 T.
15、 Last previous edition D 2221 94.2For 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 to the standards Document Summary page onthe ASTM website.1Copyright ASTM Internationa
16、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the 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 s
17、teel rule capable ofmeasurement to 0.01 in. (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
18、 intervals.Measurements are taken at the vertical 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 perp
19、endicularly attached to a platen (seeFig. 2).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 const
20、ructed to achieve the minimum static loading 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
21、 0.01 in. (0.3 mm).6.4 Flat Rigid Plate, for 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 st
22、atic load.7. Test Specimens7.1 Test specimens 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
23、 by 102 mm) thick. If thecushioning material, 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 specimenthickness, interleaving betw
24、een 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 described in Section 10.Specimens with larger a
25、reas are recommended wheneverpossible and may be dictated by the apparatus used to measureNOTE 1All dimensions are for reference only and are dependent onthe materials 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
26、Static Load Box Creep ApparatusNOTE 1All dimensions are for reference only and are dependent onthe materials tested.FIG. 2 Typical Single Point Creep ApparatusD2221012creep. Fiber length, pore size, or the nature of a material mayalso be determining factors regarding specimen size.7.2 The number of
27、specimens tested as a sample may varywidely, 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
28、 better representation of thesample, 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
29、procedures for selectingspecimens are discussed in Practice E 105. Procedures fordetermining the number of specimens required for each sampleare given in Practice E 122.8. Conditioning8.1 Precondition all specimens at any desired condition fora sufficient length of time to essentially achieve equili
30、briumwith the ambient atmosphere. In the absence of more specificrequirements, the application of Practice D 4332 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 thenconditi
31、on and test at 73.4 6 3.6F (23 6 2C) and 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.
32、6F (236 2C) and 50 65 % relative humidity. 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 a
33、n apparatus yielding values accurate to0.01 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 spec
34、imen is still under 0.025 psiload; measure 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.
35、3 Preworking (Optional)For cushioning 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 twi
36、ce at a rate not to exceed 1 cps. Rest 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 th
37、e specimenand apply the desired static 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 lo
38、ad has beenapplied. Determine the thickness 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 th
39、e initial thick-ness under load, Ti.NOTE 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 isol
40、ated from shockand vibration.9.5 Creep 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 spe
41、cified interval (Td(time interval), forexample, 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
42、 the data. Tests at relatively heavy loadings(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.
43、)9.6 Recovery DeterminationAt the end 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
44、notremain on the specimen. Record as the 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 perf
45、orm creeptests as described, but at varied 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 recor
46、d otherextreme temperatures or humidities, or both as desired, butnote that instruments or equipment may not operate at the sameefficiency at extreme conditions as at standard conditions.10. Calculations10.1 Calculate the density as follows:D 5 W/A 3 To! (1)where:D = density, lb/ft3, (g/mm3),D222101
47、3W = weight of specimen, lb g (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 in
48、itial strain for the given static 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 or
49、iginal 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 any given time interval, % 5 Ti2 Td!/Ti# 3 100 (5)where:Ti= initial thickness under load, in. (mm), andTd= deflection thickness at the given time interval, in.(mm).10.6 Calculate set after time intervals as follows:Permanent set, % 5 To2 Trinterval!/To# 3 100 (6)where
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