1、Designation: D4272 14D4272/D4272M 15Standard Test Method forTotal Energy Impact of Plastic Films Byby Dart Drop1This standard is issued under the fixed designation D4272;D4272/D4272M; the number immediately following the designation indicatesthe year of original adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes the determination of the total energy impact of plastic films by measuring th
3、e kinetic energy lostby a free-falling dart that passes through the film.1.2 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. The values givenin parentheses are for information only.stated in each system may not be exact equivalents; therefore,
4、 each system shall be usedindependently of the other. Combining values from the two systems may result in non-conformance with the standard1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard t
5、o establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1Film has been arbitrarily defined as sheeting having nominal thickness not greater than 0.25 m (0.010 in.).mm 0.010 in.NOTE 2This test method and ISO 77652 address the same
6、 subject matter, but differ in technical content (and results cannot be directly comparedbetween the two test methods). The ISO test method calls for a direct readout of energy by using a load cell as part of the impactor head, while TestMethod D4272 calls for a constant weight impactor, then measur
7、ing the time of travel through a given distance to get energy values.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1709 Test Methods for Impact Resistance of Plastic Film by the Free-Falling Dart MethodD3420 Test M
8、ethod for Pendulum Impact Resistance of Plastic FilmD5947 Test Methods for Physical Dimensions of Solid Plastics SpecimensD6988 Guide for Determination of Thickness of Plastic Film Test SpecimensE171 Practice for Conditioning and Testing Flexible Barrier PackagingE691 Practice for Conducting an Inte
9、rlaboratory Study to Determine the Precision of a Test Method2.2 ISO Standard:3ISO 77652 Plastics Film and SheetingDetermination of Impact Resistance by the Free Falling Dart MethodPart 2:Instrumented Puncture Test3. Terminology3.1 TerminologyFor definitions, see Terminology D883.3.2 Definitions of
10、Terms Specific to This Standard:3.2.1 free-fall timethe measured time required for the dart to travel through the sensing area with no film specimen in theclamp.3.2.2 missile mass (SI units)the total mass of the dart (kg) including any attached incremental weights and the locking collar.3.2.3 missil
11、e weight (in.-lb units)the total weight of the dart (lb) including any attached incremental weights and the lockingcollar.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.19 on Film, Sheeting, and MoldedProducts.Curre
12、nt edition approved April 1, 2014Oct. 1, 2015. Published April 2014October 2015. Originally approved in 1983. Last previous edition approved in 20092014 asD4272 - 09.D4272 - 14. DOI: 10.1520/D4272-14.10.1520/D4272_D4272M-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or cont
13、actASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This doc
14、ument is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as
15、 appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*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. Unite
16、d States13.2.3.1 DiscussionIn the energy calculation, the weight is divided by the gravitational constant, “g” to obtain the mass.3.2.4 test-fall timethe measured time for the dart to travel through the sensing area with a film specimen in the clamp.4. Summary of Test Method4.1 The velocity of a fre
17、ely falling dart of specified shape that has passed through a sheet of plastic film is determined by meansof a photoelectric speed trap. The kinetic energy corresponding to this velocity is calculated and compared with the kinetic energyof the same dart measured without a plastic film in place. The
18、loss in kinetic energy of the dart due to rupturing of the film is usedas an index of impact resistance.FIG. 1 Elements of an Instrumented Dart Drop SystemD4272/D4272M 1525. Significance and Use5.1 Evaluation of the impact toughness of film is important in predicting the performance of a material in
19、 applications such aspackaging, construction, and other uses. The test simulates the action encountered in applications where moderate-velocity bluntimpacts occur in relatively small areas of film.5.2 The values obtained by this test method are highly dependent on the method and conditions of film f
20、abrication as well asthe type and grade of resin.5.3 Test methods employing different missile velocities, impinging surface diameters, or effective specimen diameters will mostlikely produce different results. Data obtained by this test method cannot necessarily be compared directly with those obtai
21、ned byother test methods.5.4 The impact resistance of a film, while partly dependent on thickness, does not have a simple correlation with samplethickness. Hence, impact values expressed in joules (ftlbf)ftlbf normalized over a range of thickness will not necessarily belinear with thickness. Data fr
22、om this test method are comparable only for specimens that vary by no more than 615 % from thenominal or average thickness of the specimens tested.5.5 The test results obtained by this test method are greatly influenced by the quality of film under test. The influence ofvariability of data obtained
23、by this procedure will, therefore, depend strongly on the sample quality, uniformity of film thickness,the presence of die marks, contaminants, etc.5.6 Several impact test methods are used for film. It is sometimes desirable to know the relationships among test results derivedby different test metho
24、ds. A study was conducted in which four films made from two resins (polypropylene and linear low-densitypolyethylene), with two film thicknesses for each resin, were impacted using Test Methods D1709 (Test Method A), Test MethodD3420 (Procedures A and B), and Test Method D4272. The test results are
25、shown in Appendix X2. Differences in results betweenTest Methods D1709 and D3420 are expected since Test Methods D1709 represents failure-initiated energy, while Test MethodD4272 is initiation plus completion energy. Some films may show consistency when the initiation energy is the same as the total
26、energy. This statement and the test data also appear in the significance and appendixes sections of Test Methods D1709 and D3420.6. Apparatus6.1 The test apparatus shall be constructed essentially as shown in Fig. 1 and include the following:6.1.1 A rigid base containing a specimen clamping device,
27、a light sensitive speed trap, and a dart well or chamber for catchingand retrieving the dart after impact.6.1.2 Arigid fixture for holding the dart at the proper height above the film surface. In some equipment designs the dart holdingfixture is an integral part of the base unit.6.1.3 The dimensions
28、 of the impact apparatus shall conform to 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 prevent movement between the specimen clamp and components of the timingsystem during impact. It shall be located on
29、a flat surface that provides adequate support to prevent downward movement of theunit during impact. It shall be leveled to insure that the impact surface of the specimen is exactly perpendicular to the trajectoryof the dart.6.2.2 Specimen ClampThe apparatus shall be equipped with a circular clamp t
30、o hold the specimen. The clamp shall bemechanically, pneumatically, or hydraulically actuated. The diameter of the clamped area shall be 127 6 2 mm (5.05.0 6 0.1in.).in. In some equipment designs the clamping surface is equipped with rubber O-rings, round gaskets or other circular devicesto prevent
31、slippage of the specimen during impact. The clamp shall hold the specimen so that the impact surface is exactlyperpendicular to the trajectory of the dart and at the correct distance from the tip of the dart. During impact, the specimen shallbe held with enough force to prevent slippage but not grea
32、t enough to distort, fracture, or otherwise damage the specimen in sucha way as to affect the impact strength of the film.6.2.3 Light-Sensitive Speed TrapA system comprised of photocells, lasers, or other non-mechanical devices connected to thetiming device to measure the time-of-flight of the dart.
33、 The distance from the bottom surface of the specimen to the upper (starting)sensor shall be 23.5 6 1.0 cm (9.259.25 6 0.40 in.).in. The length of the speed trap, that is, the distance between the startingand stopping sensors shall be 19.87 6 0.51 cm (7.827.82 6 0.20 in.).in.6.2.4 Timing DeviceAn el
34、ectronic timer capable of measuring to the nearest 10-5 s.6.2.5 Dart WellThe bottom of the dart well shall contain adequate cushioning material to prevent damage to the dart head.If the impact machine utilizes an enclosed dart well, it must contain a single unobstructed vent with a minimum area of 6
35、45 mm2(1in.1in.2) to provide adequate venting.NOTE 3Some dart impact machine designs utilize enclosed dart wells that do not permit adequate venting to the atmosphere during impact. Data haveshown that this has a significant effect on the observed impact value, especially with films that exhibit hig
36、h elongation during testing, resulting inatypically high impact values.NOTE 4The use of smaller, multiple vents is permitted if it can be demonstrated that the venting efficiency is comparable and has no statisticallysignificant effect on the values obtained.D4272/D4272M 1536.2.6 Dart Holding Fixtur
37、eAn electromagnetic, pneumatic, or mechanical system to suspend the dart in position above thetest specimen. It shall be adjustable vertically and horizontally relative to the impact surface to insure that the dart falls from thecorrect height and directly onto the center of the clamped specimen. In
38、 some equipment designs, this fixture is an integral part ofthe base. When the dart is in position to drop, the distance between the lower tip of the dart and the upper surface of the specimenshall be 66 6 1 cm (26.026.0 6 0.4 in.).in. A plumb bob shall be used to precisely center the fixture over t
39、he specimen clampto insure that the dart strikes the center of the specimen. The fixture 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 6 0.13 mm (1.5001.500 6 0.005 in.)in. dia
40、meter hemisphericalstainless steel head. It shall have a mass of 227 6 5 g (0.500.50 6 0.01 lb)lb and a shaft of sufficient length and diameter toaccommodate any additional weights used to increase the mass of the dart. The shaft shall be attached to the center of the flatsurface of the dart head wi
41、th its longitudinal axis perpendicular to the surface. The impact surface of the dart head shall be freeof nicks, scratches, or other irregularities.NOTE 5A stem diameter of 9.52 mm (0.37 in.)0.37 in. has been found to be satisfactory to resist bending.NOTE 6Data have shown a sensitivity of impact r
42、esults related to the condition and finish of the dart head used. The differences have been especiallysignificant when testing films exhibiting high impact, or high elongation characteristics, or both. This issue, together with related concerns, is currentlyunder study in Subcommittee D20.19.6.2.8 D
43、art WeightsWeights to increase the mass of the dart in 227 6 5 g (0.500.50 6 0.01 lb)lb increments to a total of 11356 25 g (2.502.50 6 0.05 lb).lb. The diameter of the weights shall be 31.8 mm (1.25 in.)1.25 in. or less and they shall attachsecurely to the dart stem. Weights shall be of rigid, meta
44、llic construction, that is, not filled with lead shot or other loose material.In adjusting the mass of the dart, incremental weights are added individually or as a single weight equivalent to the appropriatemass. If single weights are used, their masses shall vary in 227 g (0.5 lb)0.5 lb increments.
45、6.3 Other Required Equipment:6.3.1 Micrometer (or other suitable thickness gauge)For measuring specimen thickness in accordance with Test MethodsD5947 or Guide D6988, as appropriate for the specimen thickness6.3.2 Plumb BobFor adjusting the dart holding fixture so that the dart strikes the specimen
46、in the center of the specimen clamp.7. Test Specimens7.1 The minimum size for a single determination is at least 165.0 by 152.5 mm (6.56.5 by 6 in.).in. However, for conveniencein handling, 165.0 by 200 mm (6.56.5 by 8 in.)in. is preferred, or a roll 165.0 mm wide can be fed.7.2 The specimens shall
47、be representative of the film under study 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, or other obvious imperfections, unless such imperfections are thevariables under study.7.4 A minimum of f
48、ive test specimens is required to obtain a reliable test result for a film sample.7.5 The film shall be identified with material, roll or lot number, extruder (if known), type (blown or cast), date of manufacture,treatment, sample source, and date of receipt.7.6 Measure and record the thickness of t
49、he film specimens in accordance with either Test Methods D5947 or Guide D6988,as appropriate for the specimen thickness. . Reject samples 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 the light-sensing unit and allow to warm up in sufficient time to reachequilibrium. (See manufacturers instructions.)8.2 Without prior knowledge of the impact resistance of the film tested or specific instructions, use a 908 g (2 lb)2
