1、Designation: D1938 14Standard Test Method forTear-Propagation Resistance (Trouser Tear) of Plastic Filmand Thin Sheeting by a Single-Tear Method1This standard is issued under the fixed designation D1938; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, 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 forcenecessary to propagate a tear
3、in plastic film and thin sheeting(thickness of 1 mm (0.04 in.) or less) by a single-tear method.The method is not applicable for film or sheeting materialwhere brittle failures occur during testing.NOTE 1Film has been arbitrarily defined as sheeting having nominalthickness not greater than 0.25 mm (
4、0.010 in.).1.2 Constant-Rate-of-Grip Separation Test This testmethod employs a constant rate of separation of the gripsholding the test specimen.1.2.1 Specimen extension may be measured in this testmethod by grip separation.1.3 The values stated in SI units are to be regarded asstandard. The values
5、given in parentheses are provided forinformation only.1.4 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 safety and health practices and determine the applica-bility
6、of regulatory limitations prior to use.NOTE 2This standard is similar to ISO 6383-1, but is not consideredtechnically equivalent. The specimen size for ISO 6383-1 is larger, and themethod specifies different test speeds.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plasti
7、cs for TestingD882 Test Method for Tensile Properties of Thin PlasticSheetingD883 Terminology Relating to PlasticsD4000 Classification System for Specifying Plastic Materi-alsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6988 Guide for Determination of Thickness of Plastic Fi
8、lmTest SpecimensE4 Practices for Force Verification of Testing MachinesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 6383-1 Film and SheetingDetermination of Tear Re-sistance Part 1 Trouser Tear Method33. Terminology3.1 Definitio
9、ns: For definitions of terms used in this testmethod, refer to Terminology D883.4. Summary of Test Method4.1 The force to propagate a tear across a film or sheetingspecimen is measured using a constant-rate-of-grip separationmachine as described in Test Methods D882 and is calculatedfrom the load-ti
10、me chart.5. Significance and Use5.1 This test method is of value in rating the tear-propagation resistance of various plastic films and thin sheetingof comparable thickness. For highly extensible film or sheetingthe deformation energy of the specimen legs is significantlygreater than the tearing ene
11、rgy. The tear-propagation resistancein slightly extensible or non-extensible film or sheeting isdistinguished from the tear-propagation resistance in highlyextensible film or sheeting by the load-time or load-displacement data, (Fig. 1 and Fig. 2). The tear-propagationforce for slightly extensible o
12、r non-extensible material isdetermined from the average tear force versus the initial andpeak force for a highly extensible material.5.2 This test method shall be used for specification accep-tance testing only after it has been demonstrated that the datafor the particular material are acceptably re
13、producible.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film, Sheeting, andMolded Products.Current edition approved Dec. 1, 2014. Published December 2014. Originallyapproved in 1962. Last previous edition appr
14、oved in 2008 as D1938 08. DOI:10.1520/D1938-14.2For 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.3Available fro
15、m American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*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 States15.3 The
16、data obtained by this test method furnish informa-tion for ranking the tear-propagation resistance of plastic filmsand sheeting of similar composition. Actual use performancemay not necessarily correlate with data from this test method.Sets of data from specimens of dissimilar thickness are usuallyn
17、ot comparable.5.4 Before proceeding with this test method, referenceshould be made to the specification of the material being tested.Any test specimen preparation, conditioning, dimensions, ortesting parameters, or combination thereof, covered in therelevant ASTM material specification shall take pr
18、ecedenceover those mentioned in this test method. If there are norelevant ASTM material specifications, then the default condi-tions apply. Table 1 of Classification Systems D4000 lists theASTM materials standards that currently exist.6. Apparatus6.1 Testing MachineA testing machine of the constantr
19、ate-of crosshead-movement type and comprising essentiallythe following:6.1.1 Fixed MemberA fixed or essentially stationarymember carrying one grip.6.1.2 Movable MemberA movable member carrying asecond grip.6.1.3 GripsPreferably, a set of self-aligning grips forholding the test specimen between the f
20、ixed member and themovable member of the testing machine. The grips shouldminimize both slippage and uneven stress distribution.6.1.3.1 Fixed grips are rigidly attached to the fixed andmovable members of the testing machine. Fixed grips are to beused only if alignment can be verified when the test s
21、pecimenis inserted and clamped so that the long axis of the testspecimen coincides with the direction of pull through thecenter line of the grip assembly.6.1.3.2 Self-aligning grips are attached to the fixed andmovable member of the testing machine in such a manner thatthey will move freely into ali
22、gnment as soon as any load isapplied so that the long axis of the test specimen will coincidewith the direction of the applied pull through the center line ofthe grip assembly. The specimens shall be aligned with thedirection of pull so that no rotary motion that may induceslippage will occur in the
23、 grips.NOTE 3Grips lined with thin rubber have successfully been used.Grips may be of the self-tightening type. In cases where specimensfrequently fail at the edge of the grips, the radius of curvature of the edgesof the grips may be increased slightly at the point where they come incontact with the
24、 specimen.6.1.4 Drive MechanismA drive mechanism capable ofseparating the movable member (grip) from the stationarymember (grip) at a controlled velocity of 250 mm (10 in.) 65 % min.6.1.5 Load IndicatorA suitable load-indicating mecha-nism capable of showing the total tensile load carried by thetest
25、 specimen held by the grips. The testing machine shall beessentially free from inertia lag at the specified rate of testingand shall indicate the load with an accuracy of 61 %. Theaccuracy of the testing machine shall be verified in accordancewith Practices E4.6.1.6 Crosshead Extension IndicatorA su
26、itable extension-indicating mechanism capable of showing the amount ofchange in the separation of the grips (crosshead movement).6.2 ThicknessA micrometer as prescribed in Test MethodsD5947 and D6988, or an equivalent measuring device, readingto 0.0025 mm (0.0001 in.) or less. The pressure exerted b
27、y thegage on the specimen being measured shall not distort ordeform the specimen. For thin films, 0.025 mm (0.001 in.), orfilms which exhibit visual deformation during measurement, amaximum pressure of 70 kPa (10 psi) is recommended. Forthicker or stiffer films and thin sheeting, the pressure shall
28、bebetween 160 and 185 kPa (23 and 27 psi).6.3 DieA die having the dimensions shown in Fig. 3 shallbe used to cut all specimens. The cutting edge of the die shallhave a 5 negative rake, and shall be kept sharp and free fromnicks to avoid leaving ragged edges on the specimen. TheFIG. 1 Load-Time Chart
29、 for Low-Extensible FilmFIG. 2 Load-Time Chart for Highly Extensible FilmFIG. 3 Single-Tear SpecimenD1938 142sample shall rest on a smooth, slightly yielding surface thatwill not injure the die blade. Care shall be taken that the cutedges of the specimen are parallel and perpendicular to thesamples
30、longitudinal and transverse directions.7. Test Specimens7.1 The specimens shall conform to the dimensions shownin Fig. 3 and shall not vary by more than 0.5 % from thesedimensions.NOTE 4The thickness of the test specimens shall be uniform to within5 % of the thickness over the length of the unslit p
31、ortion of the specimen.7.2 Measure the thickness of the specimen below the slit(see Fig. 3) in several places and record it in millimetres to thenearest 0.0025 mm (0.0001 in.).7.3 Cut enough specimens to provide a minimum of fivetear-propagation force determinations each in the machinedirection and
32、in the transverse direction of the material beingtested.NOTE 5This is required because the properties of anisotropic speci-mens vary with direction.8. Conditioning8.1 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
33、in accordance with Procedure A ofPractice D618 unless otherwise specified by agreement or therelevant ASTM material specification. In cases ofdisagreement, the tolerances shall be 61C (61.8F) and65 % relative humidity.8.2 Test ConditionsConduct the tests at 23 6 2C (73.4 63.6F) and 50 6 10 % relativ
34、e humidity unless otherwisespecified by agreement or the relevant ASTM material speci-fication. In cases of disagreement, the tolerances shall be 61C(61.8F) and 6 5 % relative humidity.9. Procedure9.1 Secure Tongue A (see Fig. 3) in one grip and Tongue Bin the other grip of the constant-rate-of-grip
35、 separation-testingmachine, using an initial grip separation of 50 mm (2 in.).Align the specimen so that its major axis coincides with animaginary line joining the centers of the grips.9.2 Using a grip-separation speed of 250 mm (10 in.)/min,start the instrument, and record the load versus extension
36、.9.3 Continue the test until the tear has propagated throughthe entire unslit 25-mm (1-in.) portion.9.4 If the tear deviates from the center line to such an extentas to reach one of the edges of the specimen, note the deviationin the report.9.5 Test not less than five specimens in each of the princi
37、palfilm or sheeting directions.10. Calculation10.1 For thin films and sheeting that have load-time chartscharacterized by Fig. 1, calculate the average tear propagationforce by averaging the load over a 25.4 mm (1 in.) interval,disregarding the initial and final portions of the curve.10.2 For thin f
38、ilms and sheeting that have load-time datacharacterized by Fig. 2, obtain and report the initial force tocontinue the propagation of the slit, the maximum force, andthe extension at maximum force. Report both the initial load,the maximum load, and extension at maximum load.10.3 For each series of te
39、sts, report the mean of all valuesobtained to three significant figures and as the mean value ofthe particular property.10.4 Calculate the estimated standard deviation and reportload to three significant figures and extension to two significantfigures.11. Report11.1 Report the following information:
40、11.1.1 Complete identification of the material tested, includ-ing type, source, manufacturers code number, form, principaldimensions, previous history, orientation of samples withrespect to principal directions of the material, etc.,11.1.2 Average thickness of test specimens,11.1.3 Number of samples
41、 tested,11.1.4 Date of test, and11.1.5 Mean of the five average tear-propagationdeterminations, usually in newtons (or pounds-force), for thematerials described in 10.1; and the mean of the five initialtear-propagation forces, the mean of the five maximum tear-propagation forces, in newtons (or poun
42、ds-force), and theextension to maximum force, in mm (in.) for materials de-scribed in 10.2. In each case, report the standard deviation ofthe data. In the cases where the specimens tear to one side, notethis together with the values obtained.12. Precision and Bias12.1 Precision:12.1.1 Table 1 and Ta
43、ble 2 are based on a round robin4conducted between 1986 and 1990 in accordance with PracticeE691 87, involving seven materials tested by seven labora-tories. For each material, all the samples were prepared at one4Supporting data on precision are available from ASTM Headquarters. RequestRR:D20-1177.
44、TABLE 1 Tear Propagation Resistance (Trouser Tear) MachineDirection (Values Expressed in Units of Grams-Force)Material Average SrASRBrCRDPolystyrene 5.04 1.54 3.47 4.32 9.72Polyester 32.75 7.08 7.08 19.81 19.81Polypropylene 70.77 20.52 38.05 57.45 106.6HDPE No. 2 127.3 48.04 56.49 134.59 158.2LDPELD
45、104228.3 33.98 33.98 95.14 95.14LLDPE 337.1 30.95 42.74 86.66 119.7HDPE No. 1 482.9 49.04 106.0 137.3 296.9ASr= within-laboratory standard deviation for the material stated. It is obtained bypooling the standard deviations of the test results from each laboratory, as follows:Sr= (S1)2+(S2)2. + (Sn)2
46、)/n1/2BSR= between-laboratories standard deviation for the material stated. It is apooling of the amounts by which the average of the test results for each laboratorydeviate from the overall average for that material.Cr = within-laboratory repeatability limit = 2.8 Sr.DR = between-laboratories repro
47、ducibility limit = 2.8 SR.D1938 143source, and randomized sections of film were sent to each ofthe laboratories which prepared the test specimens and testedthem. Each test result was the average of five determinations.Each laboratory obtained two test results for each material.(WarningThe explanatio
48、n of r and R (12.1.2 12.1.2.3) areonly intended to present a meaningful way of considering theapproximate precision of this test method. The data in Table 1and Table 2 should not be applied to acceptance or rejection ofmaterials, as these data apply only to the materials tested in theround robin and
49、 are unlikely to be rigorously representative ofother lots, formulations, conditions, materials, or laboratories.Users of this test method should apply the principles outlinedin Practice E691 to generate data specific to their materials andlaboratories (or between specific laboratories). The principlesof 12.1.2 12.1.2.3 would then be valid for such data. )12.1.2 Concept of r and R in Table 1 and Table 2If SrandSRhave been calculated from a large enough body of data andfor test results that were averages from testing five specimensfor
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