ASTM_D_4508_-_10.pdf

Designation:D450810Standard Test Method forChip Impact Strength of Plastics1This standard is issued under the fixed designation D4508;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()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 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 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 notch-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 energy values of less than 0.17 joules(1.5 in.-lbf)have 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 parentheses are for informationonly.1.5 There is no known 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 the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D256 Test Methods for Determining the Izod PendulumImpact Resistance of PlasticsD618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD4066 Classification System for Nylon Injection and Extru-sion Materials(PA)D5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 DefinitionsFor definitions of plastic terms see Termi-nology D883 and for abbreviations see Terminology D1600.There re 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 Test Methods D256.4.2 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-tion 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.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved April 1,2010.Published June 2010.Originallyapproved in 1985.Last previous edition approved in 2006 as D4508-06.DOI:10.1520/D4508-10.2For 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 to the standards Document Summary page onthe ASTM website.*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 States1 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 to0.125 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 experimentalwork 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 sensitivechip-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