1、Designation: D4272 14Standard Test Method forTotal Energy Impact of Plastic Films By Dart Drop1This standard is issued under the fixed designation D4272; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、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 describes the determination of the totalenergy impact of plastic films by measuring the kinetic energylost by a free-
3、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 the
4、user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1Film has been arbitrarily defined as sheeting having nominalthickness not greater than 0.25 m (0.010 in.).NOTE 2This test method and ISO 77652 add
5、ress the same subjectmatter, but differ in technical content (and results cannot be directlycompared between 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 D4272 calls for a constant weight impactor,
6、thenmeasuring 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 Filmby the Free-Falling Dart MethodD34
7、20 Test Method for Pendulum Impact Resistance ofPlastic FilmD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6988 Guide for Determination of Thickness of Plastic FilmTest SpecimensE171 Practice for Conditioning and Testing Flexible BarrierPackagingE691 Practice for Conducting an
8、 Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:3ISO 77652 Plastics Film and SheetingDetermination ofImpact Resistance by the Free Falling Dart MethodPart2: Instrumented Puncture Test3. Terminology3.1 TerminologyFor definitions, see Terminology D883.3.2 Definitions
9、of Terms Specific to This Standard: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 mass (SI units)the total mass of the dart (kg)including any attached incremental weights and the lockingcollar.3.2.3 missil
10、e weight (in.-lb units)the total weight of thedart (lb) including any attached incremental weights and thelocking collar.3.2.3.1 DiscussionIn the energy calculation, the weight isdivided by the gravitational constant, “g” to obtain the mass.3.2.4 test-fall timethe measured time for the dart to trave
11、lthrough 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 this velocity is ca
12、lculated 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 is importantin pred
13、icting 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.1This test method is under the jurisdiction of ASTM Committee D20
14、 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film, Sheeting, andMolded Products.Current edition approved April 1, 2014. Published April 2014. Originallyapproved in 1983. Last previous edition approved in 2009 as D4272 - 09. DOI:10.1520/D4272-14.2For referenced ASTM standard
15、s, 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.,4th Floor, Ne
16、w 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 States15.2 The values obtained by this test method are highlydependent on the method and co
17、nditions 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 thistest method cannot necessarily be compared directly
18、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 samplethickness. Hence, impact values expressed in joules (ftlbf)normalized over a range of thickness will not necessarily belinear with thickness
19、. 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.FIG. 1 Elements of an Instrumented Dart Drop SystemD4272 1425.5 The test results obtained by this test method are greatlyinfluenced by the qual
20、ity 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 know
21、the relationships among testresults derived by different test methods. A study was con-ducted in which four films made from two resins (polypropyl-ene and linear low-density polyethylene), with two film thick-nesses for each resin, were impacted using Test MethodsD1709 (Test Method A), Test Method D
22、3420 (Procedures Aand B), and Test Method D4272. The test results are shown inAppendix X2. Differences in results between Test MethodsD1709 and D3420 are expected since Test Methods D1709represents failure-initiated energy, while Test Method D4272 isinitiation plus completion energy. Some films may
23、showconsistency 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 D1709and D3420.6. Apparatus6.1 The test apparatus shall be constructed essentially asshown in Fig. 1 and include the foll
24、owing:6.1.1 Arigid 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 fix
25、ture is 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 rigid enough to preventmovement between the specimen clamp and component
26、s 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 is exactlyperpendicular to the trajectory of the dart.6.2.2 Specimen Cl
27、ampThe apparatus shall be equippedwith a circular clamp to hold the specimen. The clamp shall bemechanically, pneumatically, or hydraulically actuated. Thediameter of the clamped area shall be 127 6 2 mm (5.0 6 0.1in.). In some equipment designs the clamping surface isequipped with rubber O-rings, r
28、ound gaskets 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 wit
29、h enough 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 devic
30、e 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 sensors shall be 19.87 6 0.51 cm(7.82 6 0.20 in
31、.).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, itmust contain a single unobstructed vent
32、 with a minimum areaof 645 mm2(1in.2) to provide adequate venting.NOTE 3Some 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 film
33、s that exhibit high elongation during testing, resultingin atypically high impact values.NOTE 4The 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 Fixtu
34、reAn electromagnetic,pneumatic, or mechanical system to suspend the dart inposition above the test specimen. It shall be adjustable verti-cally and horizontally relative to the impact surface to insurethat the dart falls from the correct height and directly onto thecenter of the clamped specimen. In
35、 some equipment designs,this fixture is an integral part of the base. When the dart is inposition to drop, the distance between the lower tip of the dartand the upper surface of the specimen shall be 66 6 1 cm (26.06 0.4 in.). A plumb bob shall be used to precisely center thefixture over the specime
36、n clamp to insure that the dart strikesthe center of the specimen. The fixture shall release the dartwithout imparting any vertical or horizontal force that mightaffect 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 hemispherical
37、stainlesssteel 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 per
38、pendicular to thesurface. The impact surface of the dart head shall be free ofnicks, scratches, or other irregularities.NOTE 5A 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 l
39、b) 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 of
40、 the dart, 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:D4272 1436.3.1 Micrometer (or other suitable thickness gauge)Formeasuring speci
41、men thickness in accordance with Test Meth-ods D5947 or Guide D6988, as appropriate for the specimenthickness.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
42、 is at least165.0 by 152.5 mm (6.5 by 6 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 sou
43、nd sampling practice.7.3 The sample shall 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 wi
44、th material, roll or lotnumber, extruder (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 accordance with either Test Methods D5947 or GuideD6988, as appropriate for the specimen thickness
45、. Rejectsamples that vary by more than 15 % from the nominal oraverage 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
46、 of the impact 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
47、 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 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 obtaine
48、d 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 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
49、.9. Conditioning9.1 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 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.9.2 Test ConditionsConduct the tests at 23 6 2C (73.4 63.6F) and 50 6 10 % relative humidity unless otherwisespecified by agreement or the relevant ASTM material speci-fication. I
