1、Designation: D 4508 06Standard Test Method forChip Impact Strength of Plastics1This standard is issued under the fixed designation D 4508; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in paren
2、theses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The purpose of this test method is to provide an impacttest that can be performed on small specimens of plastics ofdifferent thicknesses. This test
3、method is especially suited forobserving the effects of microcracks caused by weathering, orby exposure to solvents or other hostile environments, on thesurface of plastic materials. It is not meant to be used as areplacement for any existing impact test, but can be used tomeasure impact on coupons
4、machined from finished parts thatcannot be tested by the drop-weight, Izod, or Charpy methodbecause of shape or thickness limitations.1.2 The chip-impact test is run on small, flat, unnotchedspecimens using a standard pendulum-impact device. The testplaces the impacted surface in tension and, for no
5、tch-sensitivematerials, is extremely sensitive to the presence of surfacemicrocracks. Thus, for plastics that develop surface crackswhen exposed outdoors, the chip-impact test is a severe test ofthe weathered impact strength.1.3 Round-robin testing has indicated that materials thatbreak at total ene
6、rgy values of less than 0.17 joules 1.5 in.-lbfhave within-laboratory coefficients of variation of approxi-mately 30 %. Therefore, such values are considered out of thenormal testing range for this test.1.4 The values stated in SI units are to be regarded asstandard. The values given in brackets are
7、 for information only.1.5 There is no ISO equivalent to this test method.1.6 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
8、the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 256 Test Methods for Determining the Izod PendulumImpact Resistance of PlasticsD 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1600 Terminology for Abbre
9、viated Terms Relating toPlasticsD 4066 Classification System for Nylon Injection and Ex-trusion Materials (PA)D 5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Defin
10、itionsFor definitions of plastic terms see Termi-nology D 883 and for abbreviations see Terminology D 1600.There are no terms in this test method that require new orother-than-dictionary definitions.4. Significance and Use4.1 The chip-impact test is a variation of the Izod impacttest described in Te
11、st Methods D 256.4.2 The specimen geometry has been chosen to fit threebasic criteria as follows:4.2.1 The specimen is relatively thin and is struck on thebroad surface so that the test result is sensitive to the conditionof the surface,4.2.2 The specimen is relatively small for efficient utiliza-ti
12、on of space in accelerated testing media or devices and tominimize amounts of material needed for testing, and4.2.3 The specimen can be tested using a standard Izodpendulum tester.4.3 It has been found that a 12.7-mm 0.500-in. wide stripwith a thickness in the range from 1.02 to 3.18 mm 0.040 to0.12
13、5 in. meets the above criteria. Much experimental workon 1.78-mm 0.070-in. strips has demonstrated the utility ofthe chip-impact test to track weather aging of a variety ofmaterials.4.4 The distance (L) between clamping and impact points(striker height) will affect test results. Extensive experiment
14、alwork has established that a ratio of L = 2.182 h (where L is thedistance between clamping and impact points and h is thethickness of the specimen) will provide accurate and sensitive1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subc
15、ommittee D20.10 on Mechanical Properties.Current edition approved March 15, 2006. Published March 2006. Originallyapproved in 1985. Last previous edition approved in 2005 as D 4508 - 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
16、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.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 S
17、tates.chip-impact values. Increasing this ratio (that is, raising thestriker height for a given thickness) lowers chip-impact valuesand reduces sensitivity of the test. Decreasing the above ratio(that is, lowering the striker height for a given thickness)results in a shearing of the specimen rather
18、than the desiredbending and breaking.4.5 In general, the chip-impact value during weatheringvaries according to specimen thickness, even after adjustingstriker heights for constant deflection, as given in Table 1.Report the thickness of the specimen, along with the testvalues, making comparisons onl
19、y between samples with simi-lar thickness.4.6 The standard Izod Methods A, C, D, and E require thatthe type of failure for each specimen be recorded as one of thefour coded categories defined as follows:C=complete breaka break in which the specimen separates into two ormore pieces,H=hinge breakan in
20、complete break such that one part of the specimencannot support itself above the horizontal when the other part is heldvertically (less than 90 included angle),P=partial breakan incomplete break that does not meet the definitionfor a hinge break, but has fractured at least 90 % of the distance be-tw
21、een the surface of the impact side and the opposite side.NB = non-breakan incomplete break where the fracture extends less than90 % of the distance between the impacted surface and the oppositeside. Do not report non-break data as a standard result, but use suchdata, if appropriate, to establish rel
22、ative sensitivity to aging on a timebasis.4.6.1 Impact values cannot be directly compared for anytwo materials that experience different types of failure asdefined in the method for this code.4.7 Before proceeding with this test method, make referenceto the specification of the material being tested
23、. Any testspecimen preparation, conditioning, dimensions, or testingparameters, or a combination thereof, covered in the materialspecification shall take precedence over those mentioned in thistest method. If there are no material specifications, then thedefault conditions apply.5. Apparatus5.1 The
24、apparatus shall be a cantilever beam (Izod-type)impact machine as described in the Annex and Test MethodsD 256, Method A. The following modifications must be madeto the specimen holder and impacting hammer (see Fig. 1). Thespecimen holder shall be constructed from a 12.7 by 12.7-mm0.5 by 0.5-in. ste
25、el bar, the front face of which shall berecessed 1.9 mm 0.075 in. deep and 7.94 mm 0.312 in. longfrom the top surface to accept the chip-impact specimen.Corresponding to this recessed area is an adjustable clamp tohold the specimen in place. This specimen holder is clampedinto the standard Izod vise
26、 and adjusted to proper height basedon specimen thickness. This adjustment is made by positioningthe adjustment screw in the vertical portion of the specimenholder.5.2 The chip-impact striker (see Fig. 2) has a flat face andbevelled bottom edge to facilitate clearance of specimens thatdo not complet
27、ely break-off on impact (hinge or partialbreaks). It is permissible to use the standard Izod striker withno significant change in impact strength.5.3 Calibration of the cantilever beam impact machine shallbe carried out as described in Test Methods D 256.6. Test Specimen6.1 Measure test specimens in
28、 accordance with Test MethodD 5947. The standard test specimen shall be 12.7 mm 0.5 in.wide by 19.05 mm 0.750 in. long by 1.02 to 3.175 mm 0.040to 0.125 in. in depth. The preferred depth is (1.778 mm 0.070in.). Cut or mill the specimens from molded plaques, extrudedsheets, or finished products to th
29、e proper 12.7-mm 0.5-in.width. Smooth edges are necessary to minimize edge effects.6.2 For determining the effect of aging or environmentalexposure, cut the material to be tested into a convenient size forthe exposure apparatus. Expose these sections for the requiredtime in the desired environment.
30、After exposure, cut eachsection into 12.7 by 19.05-mm 0.5 by 0.75-in. chips forimpacting testing. Test each chip by striking it on the exposedside.7. Conditioning7.1 Condition the test specimens at 23 6 2C73.4 6 3.6F and 50 6 5 % relative humidity for not lessthan 40 h prior to test, in accordance w
31、ith MethodAof PracticeD 618, unless otherwise specified.7.2 Conduct tests in the standard laboratory atmosphere of23 6 2C 73.4 6 3.6F and 50 6 5 % relative humidity,unless otherwise specified.7.3 Note that for some hygroscopic materials, such asnylons, the material specifications (for example, Speci
32、ficationD 4066) call for testing “dry as molded specimens.” Suchrequirements take precedence over routine preconditioning to50 % relative humidity and require sealing specimens in watervapor-impermeable containers as soon as molded or extruded,and not removing them until ready for testing.7.4 Post-C
33、onditioning of Specimens After Exposure to Hos-tile Environment:7.4.1 Specimens shall be conditioned in accordance withsection 7.1 or 7.3 prior to subjecting the specimens to thehostile environment, unless otherwise specified.7.4.2 The post-conditioning of specimens which have beenexposed to hostile
34、 environments requires careful consideration.The ultimate purpose of the exposure and test must beTABLE 1 Striker Height Adjustment for Constant DeflectionhALBmm in. mm in.1.016 0.040 2.21 0.091.143 0.045 2.49 0.101.270 0.050 2.77 0.111.397 0.055 3.05 0.121.524 0.060 3.33 0.131.651 0.065 3.61 0.141.
35、778 0.070 3.89 0.151.905 0.075 4.17 0.162.032 0.080 4.45 0.182.159 0.085 4.72 0.192.286 0.090 5.00 0.202.413 0.095 5.28 0.212.540 0.100 5.56 0.222.667 0.105 5.84 0.232.794 0.110 6.10 0.242.921 0.115 6.38 0.253.048 0.120 6.66 0.263.175 0.125 6.93 0.27D 4508 062considered. The post-conditioning requir
36、ements for the speci-men shall be agreed upon by seller and purchaser for thepurpose of referee testing. One cannot expect comparableresults unless all details of sampling, specimen preparation,specimen conditioning, and exposures as well as testingconditions are identical in all laboratories trying
37、 to make acomparison or settle a disagreement. Specimens subjected tohigh temperatures, accelerated weathering, outdoor weather-ing, radiation, or other exposure not involving submersion inliquid shall be allowed to return to the standard laboratoryatmosphere before testing. If the original unexpose
38、d specimensused as references were tested at a temperature other than theDimensions, mm in.:A = 4.7625 0.1875B = 7.9375 0.3125C = 12.700 0.500D = 10.795 0.425E = 4.7625 0.1875F = 7.9375 0.3125G = 50.8 2.0H = 25.4 1.0I = 12.7 0.5FIG. 1 Specimen HolderFIG. 2 StrikerD 4508 063standard laboratory temper
39、ature then the specimens subjectedto the hostile environment must be allowed to reach thermalequilibrium at the test temperature before testing.NOTE 1It is possible that for hygroscopic materials such as nylonsthat have data based on “dry as molded” conditioning, returning theexposed specimens to th
40、e same conditions as the original specimen mayintroduce new (negative) effects on the test specimen, for example, bydrying in oven (heat/crystallinity) or over chemical desiccant. For thesematerials, condition the exposed sample and a “control” sample at thestandard laboratory atmosphere prior to te
41、sting.7.4.3 Specimens that have been immersed in a hostile liquidenvironment require special handling. To avoid evaporation ofthe liquid from the specimen while exposing to the standardlaboratory atmosphere, all specimens must remain in the liquiduntil testing. The liquid temperature and specimen mu
42、st bothbe at standard laboratory temperature. If the original unex-posed specimens used as references were tested at a tempera-ture other than the standard laboratory temperature the liquidand specimens subjected to the hostile environment must thenbe allowed to reach thermal equilibrium at the test
43、 temperatureprior to testing.8. Procedure8.1 For evaluation purposes within a laboratory, make fourindividual determinations on each sample to be tested. Forcomparing data between laboratories, make ten individualdeterminations of each sample to be tested. Each group shallconsist of specimens of one
44、 nominal thickness only. In the caseof specimens cut from sheets that are suspected of beinganisotropic, prepare and test specimens from each principaldirection (lengthwise and crosswise to the direction of anisot-ropy).8.2 Estimate the breaking energy for the specimen andselect a pendulum of suitab
45、le energy. Use the lightest standardpendulum that is expected to break each specimen in the groupwith a loss of not more than 85 % of its energy (Note 1). Checkthe machine with the proper pendulum in place for conformitywith the requirements of Test Method D 256 before starting thetest.NOTE 2Ideally
46、 an impact test would be conducted at a constant testvelocity. In a pendulum-type test the velocity decreases as the fractureprogresses. For specimens that have an impact energy approaching thecapacity of the pendulum, there is insufficient energy to complete thebreak and toss. By avoiding the highe
47、r 15 % scale energy readings, thevelocity of the pendulum will not be reduced below 1.34 m/s 4.4 ft/s. Onthe other hand, the use of too heavy a pendulum would reduce thesensitivity of the reading.8.3 If the machine is equipped with a mechanical pointerand dial, perform the operations below before te
48、sting thespecimens on the machine. If the machine is equipped with adigital indicating system, follow the manufacturers instruc-tions to correct for windage and friction. If excessive friction isindicated, the machine shall be adjusted before starting a test.8.3.1 With the energy-indicating pointer
49、in its normal start-ing position, but without a specimen in the vise, release thependulum from its normal starting position and note theposition the pointer attains after the swing as one reading ofFactor A.8.3.2 Without resetting the pointer, raise the pendulum andrelease again. This will cause the pointer to move up the scalean additional amount. Repeat until a swing causes no addi-tional movement of the pointer and note the final reading ason
