1、Designation: D2838 18Standard 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.1. Scope*1.1 This test method covers the determination of the shrinktension and related characteristics, that is, shri
3、nk 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:1.1.1 Procedure A is designed to measure the maximu
4、mforce 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 prior to restraint while being heatedrapidly to a
5、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 does not purport to address all of thesafety concern
6、s, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE 1Film has been arbitrarily defined as sheeting having nominalthi
7、ckness not greater than 0.25 m (0.010 in.).NOTE 2There is no known ISO equivalent to this test method.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Internatio
8、nal Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD4000 Classification System for Specifying P
9、lastic 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-Hazard Precisi
10、on 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 force per or
11、iginal 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 in its attem
12、pt 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 contains a
13、strain gage. The holder is immersed in1This 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 approved April 1, 2018. Published April 2018. Originallyapproved in 1969. La
14、st previous edition approved in 2009 as D2838 - 091, whichwas withdrawn January 2018 and reinstated in April 2018. DOI: 10.1520/D7399-18 DOI: 10.1520/D2838-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
15、ASTMStandards volume 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 StatesThis international stand
16、ard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1a hot
17、bath and the force exerted by the film is measured by thestrain gage. The data is collected by a data acquisition device.The user has the option of carrying out testing with or withoutfree shrinkage of the material before restraint.5. Significance and Use5.1 As a result of the manufacturing process,
18、 internalstresses are locked into the film and these can be released byheating.NOTE 3For any given type of film or sheeting, the temperatures atwhich shrinkage will begin are related to processing techniques employedto manufacture the film and also may be related to a phase transition in thebase res
19、in.5.2 Shrink tension affects the appearance and performanceof a film in a shrink-packaging application. It is also used todetermine the degree and direction of orientation. The orien-tation exerts a great influence upon important physical charac-teristics such as tensile strength, stiffness, tear r
20、esistance, andimpact strength.5.3 Data from Procedure A are most useful for determiningthe degree and direction of orientation, 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
21、, data from Procedure B are useful in estimat-ing the force an item to be packaged will actually receive andin predicting 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 corr
22、esponding temperature, is usuallycarried out only for a particular material of specified thicknessfor a defined fabrication process. For product developmentpurposes, quality control and determination of conformity bemade to the specification of the material being tested. Any testspecimen preparation
23、, 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 specifications, then the default conditions apply. Table1 of Classificatio
24、n Systems D4000 lists the ASTM materialspecifications that currently exist.6. Apparatus6.1 Shrink Tension HolderAsuggested design is portrayedin Fig. 1 and Fig. 2.6.2 Strain Gage Conditioner, four-arm bridge, preferable.FIG. 1 Design for Shrink Tension HolderD2838 1826.3 Data Acquisition DeviceElect
25、ronic, digital or chartrecorder pen having a response of no more than 30 ms from 10to 90 % of full-scale 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 Const
26、ant-Temperature Liquid Bath, capable of control-ling accurately to 60.5C and covering the range of interest,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 withspecim
27、ens. Polyethylene glycol, glycerin, and water have beenfound to have wide applicability. Silicone oils are 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 D5
28、947 or D6988, as appropriate forthe specimen thickness.7. Test Specimens7.1 The test specimens shall consist 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
29、(5in.) in length.7.2.2 Length of specimens for Procedure B is dependentupon the amount of shrink desired 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
30、length required between clamps, mm or in.,d = distance between clamps, mm or in., ands = percent shrink 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
31、line perpen-dicular to the edge and across the width of the strip.7.3 Measure the thickness of the specimen 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
32、.Calculate and record their average.7.4 For each measurement of shrink tension at a giventemperature, test 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 f
33、or the test. Shrink tension will normallybe observed near the softening temperature of polymericmaterial.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 (normal
34、ly 4.45 N, 454 gf, 1 lbf) equal tothe chosen full-scale value for the measurements to be made onthe shrink arm. Adjust the data acquisition device to full scalein accordance with the manufacturers instructions.FIG. 2 Circuit Diagram for Shrink, Tension HolderD2838 1839.3 Check linearity by placing w
35、eights of less mass on thearm. If the response is non-linear, have the equipment repairedto make response linear.9.4 Re-check the zero of the shrink holder with no load onthe shrink arm.10. Conditioning10.1 ConditioningCondition the test specimens in accor-dance with Procedure A of Practice D618 unl
36、ess otherwisespecified by contract or the relevant ASTM material specifica-tion. Conditioning time is specified as a minimum. 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 them
37、inimum positive loading force achievable. Under no circum-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,t
38、aking special care to lower it in such a manner that thespecimen 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 4Slight variations from the horizontal
39、 will generally produce anegligible error. The error, however, will increase in significance as theshrink force approaches zero. A jig is useful 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 wa
40、ter until it returns to ambient temperature. Thenremove 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
41、 range of the material.12. Procedure BPredetermined Shrink 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
42、whicheveris greater) to the nearest 0.045 N (0.01 lbf or 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) b
43、y the product of the average thicknessin millimetres (inches) 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
44、by Procedure A.14.2 The maximum shrink tension developed 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 pri
45、or to restraint,15.1.4 Test temperature,15.1.5 Film direction (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 confidence
46、limits where applicable, and15.1.11 Orientation release stress, film direction, and tem-perature where it occurs, plus plots used to obtain it.16. Precision and Bias16.1 PrecisionThe repeatability standard deviation hasbeen determined to be between the limits of 9.8 N/m (0.056lbf/in.) and 175 N/m (1
47、.0 lbf/in.). The standard deviation willincrease with the magnitude of the measurement. The percentcoefficient of variation ( /X 100) will generally not exceed10 %. Attempts to develop a full precision and bias statementfor this test method have not been successful. For this reason,data on precision
48、 and bias cannot be given. Because this testmethod does not contain a round-robin-based numerical preci-sion and bias statement, it shall not be used as a referee testmethod in case of dispute. It is recommended that anyonewishing to participate in the development of precision and biasdata contact t
49、he Chairman, Subcommittee D20.19, ASTMInternational, 100 Barr Harbor Drive, West Conshohocken, PA19428.”17. Keywords17.1 film; orientation release stress; shrink force; shrinktension; thin sheetingD2838 184SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D2838 - 09)that may impact the use of this standard. (April 1, 2018)(1) Took information from 5.1 and added new Note 3. Subse-quent notes renumbered.(2) Revised Section 10, Conditioning.(3) Revised section on Precision and
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