1、Designation: D 4272 03Standard Test Method forTotal Energy Impact of Plastic Films By Dart Drop1This standard is issued under the fixed designation D 4272; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes the determination of the totalenergy impact of plastic films by measuring the kinetic energylost by a fr
3、ee-falling dart that passes through the film.1.2 The values stated in SI units are to be regarded as thestandard. The values given in brackets are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
4、 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 1The ISO reference for this test method is ISO 7765-2;however, this test method is not equivalent to Test Method D 4272. TheISO test method ca
5、lls for a direct readout of energy by using a load cellas part of the impactor head, while Test Method D 4272 calls for aconstant weight impactor, then measuring the time of travel through agiven distance to get energy values. Therefore, the two are not equivalentin this respect.2. Referenced Docume
6、nts2.1 ASTM Standards:2D 374 Test Methods for Thickness of Solid Electrical Insu-lationD 618 Practice for Conditioning Plastics for TestingD 1709 Test Methods for Impact Resistance of Plastic Filmby the Free-Falling Dart MethodD 3420 Test Method for Pendulum Impact Resistance ofPlastic FilmE 171 Spe
7、cification for Standard Atmospheres for Condi-tioning and Testing Flexible Barrier MaterialsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:3ISO 77652 Plastics Film and SheetingDetermination ofImpact Resistance by the Free Falling Dar
8、t MethodPart2: Instrumented Puncture Test3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 free-fall timethe measured time required for the dartto travel through the sensing area with no film specimen in theclamp.3.1.2 missile weightthe weight of the dart plus the totalvalue of
9、incremental weights attached, including the lockingcollar.3.1.3 test-fall timethe measured time for the dart to travelthrough the sensing area with a film specimen in the clamp.4. Summary of Test Method4.1 The velocity of a freely falling dart of specified shapethat has passed through a sheet of pla
10、stic film is determined bymeans of a photoelectric speed trap. The kinetic energycorresponding to this velocity is calculated and compared withthe kinetic energy of the same dart measured without a plasticfilm in place. The loss in kinetic energy of the dart due torupturing of the film is used as an
11、 index of impact resistance.5. Significance and Use5.1 Evaluation of the impact toughness of film is importantin predicting the performance of a material in applications suchas packaging, construction, and other uses. The test simulatesthe action encountered in applications where moderate-velocitybl
12、unt impacts occur in relatively small areas of film.5.2 The values obtained by this test method are highlydependent on the method and conditions of film fabrication aswell as the type and grade of resin.5.3 Test methods employing different missile velocities,impinging surface diameters, or effective
13、 specimen diameterswill most likely produce different results. Data obtained by thistest method cannot necessarily be compared directly with thoseobtained by other test methods.5.4 The impact resistance of a film, while partly dependenton thickness, does not have a simple correlation with samplethic
14、kness. Hence, impact values expressed in joules (ftlbf)normalized over a range of thickness will not necessarily be1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film and Sheeting.Current edition approved Novemb
15、er 1, 2003. Published January 2004. Originallyapproved in 1983. Last previous edition approved in 1999 as D 4272 - 99.2For 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 t
16、o the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
17、t Conshohocken, PA 19428-2959, United States.linear with thickness. Data from this test method are compa-rable only for specimens that vary by no more than 615 %from the nominal or average thickness of the specimens tested.5.5 The test results obtained by this test method are greatlyinfluenced by th
18、e quality of film under test. The influence ofvariability of data obtained by this procedure will, therefore,depend strongly on the sample quality, uniformity of filmthickness, the presence of die marks, contaminants, etc.5.6 Several impact test methods are used for film. It issometimes desirable to
19、 know the relationships among testresults derived by different test methods. A study was con-ducted in which four films made from two resins (polypropy-lene and linear low-density polyethylene), with two filmthicknesses for each resin, were impacted using Test MethodsD 1709 (Test Method A), Test Met
20、hod D 3420 (Procedures Aand B), and Test Method D 4272. The test results are shown inAppendix X2. Differences in results between Test MethodsD 1709 and D 4272 are expected since Test Methods D 1709represents failure-initiated energy, while Test Method D 4272is initiation plus completion energy. Some
21、 films may showFIG. 1 Elements of an Instrumented Dart Drop SystemD4272032consistency when the initiation energy is the same as the totalenergy. This statement and the test data also appear in thesignificance and appendixes sections of Test Methods D 1709and D 3420.6. Apparatus6.1 The test apparatus
22、 shall be constructed essentially asshown in Fig. 1 and include the following:6.1.1 A rigid base containing a specimen clamping device, alight sensitive speed trap, and a dart well or chamber forcatching and retrieving the dart after impact.6.1.2 A rigid fixture for holding the dart at the proper he
23、ightabove the film surface. The dart holding fixture may beattached to or form an integral part of the base unit.6.1.3 The dimensions of the impact apparatus shall conformto those shown in Fig. 1 and those listed below.6.2 Specific Requirements for Individual Components:6.2.1 BaseThe base shall be r
24、igid enough to preventmovement between the specimen clamp and components of thetiming system during impact. It shall be located on a flatsurface that provides adequate support to prevent downwardmovement of the unit during impact. It shall be leveled toinsure that the impact surface of the specimen
25、is exactlyperpendicular to the trajectory of the dart.6.2.2 Specimen ClampThe apparatus shall be equippedwith a circular clamp to hold the specimen. The clamp may bemechanically, pneumatically, or hydraulically actuated. Thediameter of the clamped area shall be 127 6 2 mm 5.0 6 0.1in. The clamping s
26、urface may be equipped with rubberO-rings, round gaskets or other circular devices to preventslippage of the specimen during impact. The clamp shall holdthe specimen so that the impact surface is exactly perpendicu-lar to the trajectory of the dart and at the correct distance fromthe tip of the dart
27、. During impact, the specimen shall be heldwith enough force to prevent slippage but not great enough todistort, fracture, or otherwise damage the specimen in such away as to affect the impact strength of the film.6.2.3 Light-Sensitive Speed TrapA system comprised ofphotocells, lasers, or other non-
28、mechanical devices connectedto the timing device to measure the time-of-flight of the dart.The distance from the bottom surface of the specimen to theupper (starting) sensor shall be 23.5 6 1.0 cm 9.25 6 0.40in. The length of the speed trap, that is, the distance betweenthe starting and stopping sen
29、sors shall be 19.87 6 0.51 cm7.82 6 0.20 in.6.2.4 Timing DeviceAn electronic timer capable of mea-suring to the nearest 10-5s.6.2.5 Dart WellThe bottom of the dart well shall containadequate cushioning material to prevent damage to the darthead. If the impact machine utilizes an enclosed dart well,
30、itmust contain a single unobstructed vent with a minimum areaof 645 mm21in.2 to provide adequate venting.NOTE 2Some dart impact machine designs utilize enclosed dart wellsthat do not permit adequate venting to the atmosphere during impact. Datahave shown that this has a significant effect on the obs
31、erved impact value,especially with films that exhibit high elongation during testing, resultingin atypically high impact values.NOTE 3The use of smaller, multiple vents is permitted if it can bedemonstrated that the venting efficiency is comparable and has nostatistically significant effect on the v
32、alues obtained.6.2.6 Dart Holding FixtureAn electromagnetic, pneu-matic, or mechanical system to suspend the dart in positionabove the test specimen. It shall be adjustable vertically andhorizontally relative to the impact surface to insure that the dartfalls from the correct height and directly ont
33、o the center of theclamped specimen. This fixture may be an integral part of thebase. When the dart is in position to drop, the distance betweenthe lower tip of the dart and the upper surface of the specimenshall be 66 6 1 cm 26.0 6 0.4 in. A plumb bob shall be usedto precisely center the fixture ov
34、er the specimen clamp toinsure that the dart strikes the center of the specimen. Thefixture shall release the dart without imparting any vertical orhorizontal force that might affect the trajectory of the dart.6.2.7 DartThe impact dart shall have a single 38.10 60.13 mm 1.500 6 0.005 in. diameter he
35、mispherical stainlesssteel head. It shall have a mass of 227 6 5 g 0.50 6 0.01 lband a shaft of sufficient length and diameter to accommodateany additional weights used to increase the mass of the dart.The shaft shall be attached to the center of the flat surface ofthe dart head with its longitudina
36、l axis perpendicular to thesurface. The impact surface of the dart head shall be free ofnicks, scratches, or other irregularities.NOTE 4A stem diameter of 9.52 mm 0.37 in. has been found to besatisfactory to resist bending.6.2.8 Dart WeightsWeights to increase the mass of thedart in 227 6 5 g 0.50 6
37、 0.01 lb increments to a total of 11356 25 g 2.50 6 0.05 lb. The diameter of the weights shall be31.8 mm 1.25 in. or less and they shall attach securely to thedart stem. Weights shall be of rigid, metallic construction, thatis, not filled with lead shot or other loose material. In adjustingthe mass
38、of the dart, incremental weights may be addedindividually or as a single weight equivalent to the appropriatemass. If single weights are used, their masses shall vary in 227g 0.5 lb increments.6.3 Other Required Equipment:6.3.1 MicrometerFor measuring specimen thickness withan accuracy of 60.0025 mm
39、 60.0001 in. (See Test MethodD 374).6.3.2 Plumb BobFor adjusting the dart holding fixture sothat the dart strikes the specimen in the center of the specimenclamp.7. Test Specimens7.1 The minimum size for a single determination is at least165.0 by 152.5 mm 6.5 by 6 in. However, for convenience inhand
40、ling, 165.0 by 200 mm 6.5 by 8 in. is preferred, or a roll165.0 mm wide can be fed.7.2 The specimens shall be representative of the film understudy and shall be taken from the sample sheet in a mannerrepresentative of sound sampling practice.7.3 The sample shall be free of pinholes, wrinkles, folds,
41、 orother obvious imperfections, unless such imperfections are thevariables under study.7.4 A minimum of five test specimens is required to obtaina reliable test result for a film sample.D42720337.5 The film shall be identified with material, roll or lotnumber, extruder (if known), type (blown or cas
42、t), date ofmanufacture, treatment, sample source, and date of receipt.7.6 Measure and record the thickness of the film specimensin the area of impact to the nearest 0.0025 mm 0.0001 in.Reject samples that vary by more than 15 % from the nominalor average thickness.8. Preparation of Apparatus8.1 Turn
43、 on the counter and the power supply for thelight-sensing unit and allow to warm up in sufficient time toreach equilibrium. (See manufacturers instructions.)8.2 Without prior knowledge of the impact resistance of thefilm tested or specific instructions, use a 908 g 2 lb dartweight at 66 cm 26 in. he
44、ight.8.3 Position the dart vertically in the holder and clamp thedart with the dart-holding device. Allow a few seconds for anyvibration to subside and release the dart. Record the free-falltime.8.4 Repeat 8.3 four more times. Average the five measuredtimes and record as t1.8.4.1 The time reading of
45、 each of the five free-falls shall bewithin 630 s of the average. If it is not, check the timingsystem, the position of the sensing element, etc. until thisrepeatability is obtained with five free-falls.8.4.2 The dart shall not vibrate or rotate in the holder andshall fall straight.8.4.3 To ensure c
46、onsistency in drop of the dart and positionof impact of the dart on the film, the dart tip next to the holdercan be scribed so that it can be lined up in the same positioneach time.9. Conditioning9.1 ConditioningUnless otherwise specified, conditionthe test specimens at 23 6 2C 73.4 6 3.6F and 50 6
47、5%relative humidity for not less than 40 h prior to test inaccordance with Procedure A of Practice D 618. In cases ofdisagreement, the tolerances shall be 61C 61.8F and 62%relative humidity.9.2 Test ConditionsConduct tests in the standard labora-tory atmosphere of 23 6 2C 73.4 6 3.6F and 50 6 5%rela
48、tive humidity (Specification E 171). In cases of disagree-ment, the tolerances shall be 61C 61.8F and 62%relative humidity.10. Test Procedure10.1 Place the specimen over the bottom part of the clamp,making sure that it is uniformly flat, that it is free of wrinklesand folds, and that it covers the g
49、asket, O-ring, or othermounting surface at all points.10.2 Clamp the specimen in place.10.3 Position the dart vertically in the holder and clamp thedart with the dart-holding device.10.4 Wait a few seconds for any vibrations to subside.10.5 Release the dart. The dart shall fall straight.10.6 Record the test-fall time, t2.10.7 Examine the film to determine the type of failure: forexample, hole, tear, shatter, etc. Some ductile materials maycause deflection of the dart, thus causing erroneous results.Suc
