1、Designation: D2838 091Standard Test Method forShrink Tension and Orientation Release Stress of PlasticFilm and Thin Sheeting1This standard is issued under the fixed designation D2838; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorially corrected Note 1 in August 2015.1. Scope*1.1 This test method covers the determination of the shrink
3、tension and related characteristics, that is, shrink force andorientation release stress, of heat-shrinkable plastic film andsheeting of less than 1.0 mm (0.04 in.) thickness. Twoprocedures are described that permit the measurement of shrinkforces at predetermined temperatures. They are as follows:1
4、.1.1 Procedure A is designed to measure the maximumforce exerted by a specimen that is totally restrained fromshrinking as it is heated rapidly to a specific temperature.1.1.2 Procedure B is designed to measure the maximumforce exerted by a specimen that is permitted to shrink apredetermined amount
5、prior to restraint while being heatedrapidly to a specific temperature.1.2 Orientation release stress can be determined from thedata obtained using Procedure A.1.3 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.4 This standard do
6、es 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 safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1Film has been arbitrarily def
7、ined as sheeting having nominalthickness not greater than 0.25 mm (0.010 in.).NOTE 2There is no known ISO equivalent to this test method.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD4000 Classification System for
8、Specifying Plastic Materi-alsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6287 Practice for Cutting Film and Sheeting Test Speci-mensD6988 Guide for Determination of Thickness of Plastic FilmTest SpecimensE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Ha
9、zard Precision Liquids3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 orientation release stress, nthe maximum shrinktension developed by a film in a specified direction throughoutits range of shrink temperatures while totally restrained fromshrinking.3.1.2 shrink force, nthe
10、force per original unit widthdeveloped by a film in a specified direction and at a specifiedtemperature in its attempt to shrink while under restraint.3.1.3 shrink tension, nthe force per original averagecross-sectional area developed by a film in a specified directionand at a specified temperature
11、in its attempt to shrink whileunder restraint.3.2 Definitions:3.2.1 For definitions of terms used in this test method, referto Terminology D883.4. Summary of Test Method4.1 A 25.4-mm (1-in.) wide strip of film or sheeting isclamped in the arms of a shrink tension holder (see Fig. 1), onearm of which
12、 contains a strain gage. The holder is immersed ina hot bath and the force exerted by the film is measured by thestrain gage. The data is collected by a data acquisition device.The tests may be carried out with or without free shrinkage ofthe material before restraint.5. Significance and Use5.1 As a
13、 result of the manufacturing process, internalstresses are locked into the film and these can be released by1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film, Sheeting, andMolded Products.Current edition approv
14、ed May 1, 2009. Published June 2009. Originallyapproved in 1969. Last previous edition approved in 2008 as D2838 - 08. DOI:10.1520/D2838-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
15、e information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1heating. For any given type of film or she
16、eting, the tempera-tures at which shrinkage will begin are related to processingtechniques employed to manufacture the film and also may berelated to a phase transition in the base resin.5.2 Shrink tension affects the appearance and performanceof a film in a shrink-packaging application. It may also
17、 be usedto determine the degree and direction of orientation. Theorientation exerts a great influence upon important physicalcharacteristics such as tensile strength, stiffness, tearresistance, and impact strength.5.3 Data from Procedure A are most useful for determiningthe degree and direction of o
18、rientation, orientation releasestress, and the maximum force that the film can exert at a giventemperature.5.4 Since, in actual applications, film is seldom, if ever,totally restrained, data from Procedure B are useful in estimat-ing the force an item to be packaged will actually receive andin predi
19、cting the appearance of packaged items.5.5 The characterization of shrink tension as a function oftemperature, and the resultant determination of orientationrelease stress and its corresponding temperature, is usuallycarried out only for a particular material of specified thicknessfor a defined fabr
20、ication process. For product developmentpurposes, quality control and determination of conformity tospecification limits, the measurement of shrink tension at onlyone or two specified temperatures is normally sufficient.5.6 Before proceeding with this test method, reference shallbe made to the speci
21、fication of the material being tested. Anytest specimen preparation, conditioning, dimensions, or testingparameters, or combination thereof, covered in the relevantASTM material specification shall take precedence over thosementioned in this test method. If there are no relevant ASTMmaterial specifi
22、cations, then the default conditions apply. Table1 of Classification Systems D4000 lists the ASTM materialspecifications that currently exist6. Apparatus6.1 Shrink Tension Holder3A suggested design is por-trayed in Fig. 1 and Fig. 2.6.2 Strain Gage Conditioner, four-arm bridge, preferable.3The sole
23、source of supply of the ShrinkTension Holder known to the committeeat this time is Standard Scientific Supply Company, 105 West Butternut Road,Hellertown, PA180555, ph: 610-8387500. If you are aware of alternative suppliers,please provide this information to ASTM International Headquarters. Your com
24、-ments will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.FIG. 1 Design for Shrink Tension HolderD2838 09126.3 Data Acquisition DeviceElectronic, digital or chartrecorder pen having a response of no more than 30 ms from 10to 90 % of full-scale
25、 deflection, chart width of at least 100 mmis preferable.6.4 Specimen CutterFor the apparatus and techniques forcutting film and sheeting used in this test method, refer toPractice D6287.6.5 Constant-Temperature Liquid Bath, capable of control-ling accurately to 60.5C and covering the range of inter
26、est,usually from 50 to 175C.6.6 Thermometer, covering the range of interest and con-forming to the requirement of Specification E2251.6.7 Liquid Bath, which will not plasticize or react withspecimens. Polyethylene glycol, glycerin, and water have beenfound to have wide applicability. Silicone oils a
27、re useful forsamples requiring temperatures above 175C.6.8 ThicknessSpecimen thickness shall be determined us-ing a micrometer or other suitable thickness gauge in accor-dance with Test Methods D5947 or D6988, as appropriate forthe specimen thickness.7. Test Specimens7.1 The test specimens shall con
28、sist of strips of uniformwidth and thickness. The width of the specimens shall be 25.46 0.2 mm (1.0 6 0.01 in.).7.2 Length of Test Specimens:7.2.1 Specimens for ProcedureAshall be at least 127 mm (5in.) in length.7.2.2 Length of specimens for Procedure B is dependentupon the amount of shrink desired
29、 prior to restraint.At least 50mm shall be allowed for clamping. The remaining lengthrequired can be calculated by solving for L in the followingequation:L 5 d/100 2 s! 3100 (1)where:L = specimen length required between clamps, mm or in.,d = distance between clamps, mm or in., ands = percent shrink
30、desired prior to restraint.Measure a distance equivalent to L, leaving at least 25.4 mm(1 in.) at either end of the strip for clamping and mark thebeginning and termination of the distance with a line perpen-dicular to the edge and across the width of the strip.7.3 Measure the thickness of the speci
31、men to the nearest0.0025 mm (0.0001 in.) at a minimum of four positions, but atleast at each 25.4 mm (1 in.) along the length of the specimenthat will be between the clamps. Record the thicknesses.Calculate and record their average.7.4 For each measurement of shrink tension at a giventemperature, te
32、st at least four specimens from each direction,machine and transverse, of the test sample.8. Preparation of Apparatus8.1 Set up constant-temperature bath and equilibrate at thetemperature chosen for the test. Shrink tension will normallybe observed near the softening temperature of polymericmaterial
33、.8.2 Balance and set the data acquisition device at zero inaccordance with the manufacturers instructions.9. Calibration9.1 Zero shrink holder with no load on shrink arm.9.2 Place a weight (normally 4.45 N, 454 gf, 1 lbf) equal tothe chosen full-scale value for the measurements to be made onthe shri
34、nk arm. Adjust the data acquisition device to full scalein accordance with the manufacturers instructions.FIG. 2 Circuit Diagram for Shrink, Tension HolderD2838 09139.3 Check linearity by placing weights of less mass on thearm. If the response is non-linear, have the equipment repairedto make respon
35、se linear.9.4 Re-check the zero of the shrink holder with no load onthe shrink arm.10. Conditioning10.1 ConditioningCondition the test specimens at 23 62C (73.4 6 3.6F) and 50 6 10 % relative humidity for notless than 40 h prior to test in accordance with Procedure A ofPractice D618, unless otherwis
36、e specified by agreement or therelevant ASTM material specification. In cases ofdisagreement, the tolerances shall be 61C (61.8F) and65 % relative humidity.11. Procedure ATotally Restrained11.1 Clamp the first specimen in the holder under theminimum positive loading force achievable. Under no circum
37、-stances shall it exceed the maximum force observed afterimmersion of the specimen. The holder must be at ambienttemperature.11.2 Initiate data collection before immersing holder intobath. Immerse the shrink holder and specimen into the bath,taking special care to lower it in such a manner that thes
38、pecimen remains in a horizontal position. Immerse smoothlyand quickly without bumping or jerking the holder. Keep thespecimen in the bath long enough to reach a peak or plateauand 2 to 3 s thereafter.NOTE 3Slight variations from the horizontal will generally produce anegligible error. The error, how
39、ever, will increase in significance as theshrink force approaches zero. A jig may be used to aid in maintaining theproper alignment of the holder while immersing the specimen.11.3 Stop data collection and immerse the holder in a beakerof cold water until it returns to ambient temperature. Thenremove
40、 the specimen.11.4 Repeat 11.1 11.3 for each specimen in the set.11.5 Repeat 11.1 11.4 for temperature increments of nomore than 10C through the shrink temperature range of thefilm or sheeting under test. This is usually the softeningtemperature range of the material.12. Procedure BPredetermined Shr
41、ink BeforeRestraint12.1 Clamp the specimen in the holder so that the linesmarked in 7.2.2 coincide with the inside edges of the clamps.12.2 Follow the instructions given in 11.1 11.5.13. Calculation13.1 Record the maximum force (peak or plateau whicheveris greater) to the nearest 0.045 N (0.01 lbf o
42、r 4.5 gf).13.2 Shrink ForceDivide the maximum force by thespecimen width to obtain shrink force. Express shrink force ineither newtons per metre or pounds-force per inch.13.3 Shrink TensionDivide the maximum force in new-tons (or pounds force) by the product of the average thicknessin millimetres (i
43、nches) and the specimen width in millimetres(inches) to obtain the shrink tension in pascals.14. Orientation Release Stress14.1 Prepare graphs of shrink tension as a function oftemperature for each film direction of interest, using dataobtained by Procedure A.14.2 The maximum shrink tension develope
44、d for eachdirection of interest, as determined by the graphs prepared in14.1, is the orientation release stress.15. Report15.1 Report the following information:15.1.1 Complete sample identification,15.1.2 Procedure used,15.1.3 Percent shrink prior to restraint,15.1.4 Test temperature,15.1.5 Film dir
45、ection (longitudinal, transverse),15.1.6 Number of specimens tested,15.1.7 Average thickness of each specimen,15.1.8 Shrink force of each specimen,15.1.9 Shrink tension of each specimen,15.1.10 Average results, standard deviation, and confidencelimits where applicable, and15.1.11 Orientation release
46、 stress, film direction, and tem-perature where it occurs, plus plots used to obtain it.16. Precision and Bias16.1 RepeatabilityThe standard deviation of measure-ments of shrink force within a laboratory is usually a functionof the magnitude of the measurement between the limits of 9.8N/m (0.056 lbf
47、/in.) and 175 N/m (1.0 lbf/in.). The standarddeviation will increase with the magnitude of the measurement.The percent coefficient of variation (/X 100) will generallynot exceed 10 %.16.2 ReproducibilityThe standard deviation of averages ofshrink force obtained by different laboratories is relativel
48、yconstant for measurements between the limits of 9.8 N/m(0.056 lbf/in.) and 175 N/m (1.0 lbf/in.) and generally will notexceed 5.8 N/m (0.034 lbf/in.).16.3 BiasThe bias of this test method cannot be assessedsince applicable accepted reference materials are not available.17. Keywords17.1 film; orient
49、ation release stress; shrink force; shrinktension; thin sheetingD2838 0914SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D2838 - 08)that may impact the use of this standard. (May 1, 2009)(1) Added Note 1 to define film.(2) Revised 6.8 to clarify wording regarding thicknessmeasurement.Committee D20 has identified the location of selected changes to this standard since the last issue (D2838 - 07)that may impact the use of this standard. (November 1, 2008)(1) Revised
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