1、Designation: D 4272 08Standard 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 asstandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
4、he user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1This test method and ISO 77652 address the same subjectmatter, but differ in technical content (and results cannot be directlycompared between
5、the two test methods). The ISO test method calls for adirect readout of energy by using a load cell as part of the impactor head,while Test Method D 4272 calls for a constant weight impactor, thenmeasuring the time of travel through a given distance to get energy values.2. Referenced Documents2.1 AS
6、TM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1709 Test Methods for Impact Resistance of Plastic Filmby the Free-Falling Dart MethodD 3420 Test Method for Pendulum Impact Resistance ofPlastic FilmD 5947 Test Methods for Physical Dimensions
7、of SolidPlastics SpecimensD 6988 Guide for Determination of Thickness of PlasticFilm Test SpecimensE 171 Specification for Atmospheres for Conditioning andTesting Flexible Barrier MaterialsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standa
8、rd:3ISO 77652 Plastics Film and SheetingDetermination ofImpact Resistance by the Free Falling Dart MethodPart2: Instrumented Puncture Test3. Terminology3.1 TerminologyFor definitions, see Terminology D 883.3.2 Definitions of Terms Specific to This Standard: Termi-nology for Terms Specific to This St
9、andard:3.2.1 free-fall timethe measured time required for the dartto travel through the sensing area with no film specimen in theclamp.3.2.2 missile weightthe weight of the dart plus the totalvalue of incremental weights attached, including the lockingcollar.3.2.3 test-fall timethe measured time for
10、 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 plastic film is determined bymeans of a photoelectric speed trap. The kinetic energycorresponding to t
11、his 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 index of impact resistance.5. Significance and Use5.1 Evaluation of the impact toughness of film i
12、s importantin predicting the performance of a material in applications suchas packaging, construction, and other uses. The test simulatesthe action encountered in applications where moderate-velocityblunt impacts occur in relatively small areas of film.5.2 The values obtained by this test method are
13、 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 specimen diameterswill most likely produce different results. Data obtained by this1This test meth
14、od 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 March 1, 2008. Published April 2008. Originallyapproved in 1983. Last previous edition approved in 2003 as D4272 - 03.2For referenced AS
15、TM 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 from American National Standards Institute (ANSI), 25 W. 43rd St.,4t
16、h Floor, New York, NY 10036, http:/www.ansi.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.test method cannot necessarily be compared directly with thoseobtained
17、by other test methods.5.4 The impact resistance of a film, while partly dependenton thickness, does not have a simple correlation with samplethickness. Hence, impact values expressed in joules (ftlbf)normalized over a range of thickness will not necessarily belinear with thickness. Data from this te
18、st 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 the quality of film under test. The influence ofvariability of data obtained by this pr
19、ocedure will, therefore,depend strongly on the sample quality, uniformity of filmthickness, the presence of die marks, contaminants, etc.FIG. 1 Elements of an Instrumented Dart Drop SystemD42720825.6 Several impact test methods are used for film. It issometimes desirable to know the relationships am
20、ong 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 Method D 3420 (Procedures Aan
21、d 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 films may showconsistency
22、 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 shall be constructed essentially asshown in Fig. 1 and include the following:6.1.1 A
23、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 heightabove the film surface. In some equipment designs the dartholding fixture is an in
24、tegral 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 rigid enough to preventmovement between the specimen clamp and components of thetimin
25、g 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 is exactlyperpendicular to the trajectory of the dart.6.2.2 Specimen ClampThe appara
26、tus shall be equippedwith a circular clamp to hold the specimen. The clamp shall beeither mechanically, pneumatically, or hydraulically actuated.The diameter of the clamped area shall be 127 6 2 mm (5.0 60.1 in.). In some equipment designs the clamping surface isequipped with rubber O-rings, round g
27、askets or other circulardevices to prevent slippage of the specimen during impact. Theclamp shall hold the specimen so that the impact surface isexactly perpendicular to the trajectory of the dart and at thecorrect distance from the tip of the dart. During impact, thespecimen shall be held with enou
28、gh force to prevent slippagebut not great enough to distort, fracture, or otherwise damagethe specimen in such a way as to affect the impact strength ofthe film.6.2.3 Light-Sensitive Speed TrapA system comprised ofphotocells, lasers, or other non-mechanical devices connectedto the timing device to m
29、easure 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 sensors shall be 19.87 6 0.51 cm(7.82 6 0.20 in.).6.2
30、.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, itmust contain a single unobstructed vent with
31、a minimum areaof 645 mm2(1in.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 observed impact value,especially with films that
32、 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 values obtained.6.2.6 Dart Holding FixtureAn e
33、lectromagnetic, 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 onto the center of theclamped specimen. In some
34、equipment designs, this fixture isan integral part of the base. When the dart is in position to drop,the distance between the lower tip of the dart and the uppersurface of the specimen shall be 66 6 1 cm (26.0 6 0.4 in.).A plumb bob shall be used to precisely center the fixture overthe specimen clam
35、p to insure that the dart strikes the center ofthe specimen. The fixture shall release the dart withoutimparting any vertical or horizontal force that might affect thetrajectory 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 hemispherical stainl
36、esssteel head. It shall have a mass of 227 6 5 g (0.50 6 0.01 lb)and 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 longitudinal axis perpendic
37、ular 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 0.01 lb) inc
38、rements 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 of the d
39、art, incremental weights are added individu-ally or as a single weight equivalent to the appropriate mass. Ifsingle weights are used, their masses shall vary in 227 g (0.5lb) increments.6.3 Other Required Equipment:6.3.1 MicrometerFor measuring specimen thickness withan accuracy of 60.0025 mm (60.00
40、01 in.). Refer to TestMethods D 5947, Method C or Guide D 6988.6.3.2 Plumb BobFor adjusting the dart holding fixture sothat the dart strikes the specimen in the center of the specimenclamp.D42720837. Test Specimens7.1 The minimum size for a single determination is at least165.0 by 152.5 mm (6.5 by 6
41、 in.). However, for convenience inhandling, 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 sha
42、ll be free of pinholes, wrinkles, folds, 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.7.5 The film shall be identified with material, roll or lotnumber, extrude
43、r (if known), type (blown or cast), 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.) inaccordance with either Test Methods D 5947, Method C orGuide D 6988. Reject sa
44、mples that vary by more than 15 %from the nominal or average thickness.8. Preparation of Apparatus8.1 Turn 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 im
45、pact resistance of thefilm tested or specific instructions, use a 908 g (2 lb) dartweight at 66 cm (26 in.) height.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-fall
46、time.8.4 Repeat 8.3 four more times. Average the five measuredtimes and record as t1.8.4.1 The time reading of 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 fiv
47、e free-falls.8.4.2 The dart shall not vibrate or rotate in the holder andshall fall straight.8.4.3 To ensure consistency 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. Condit
48、ioning9.1 ConditioningUnless otherwise specified, conditionthe test specimens at 23 6 2C (73.4 6 3.6F) and 50 6 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 humid
49、ity.9.2 Test ConditionsConduct tests in the standard labora-tory atmosphere of 23 6 2C (73.4 6 3.6F) and 50 6 5%relative 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 gasket, O-ring, or othermounting surface at all points.10.2 Clamp the specimen in place.10.3 Position the dart vertically in the holder an
