ASTM_D_256_-_10_2018.pdf

Designation:D25610(Reapproved 2018)Standard Test Methods forDetermining the Izod Pendulum Impact Resistance ofPlastics1This standard is issued under the fixed designation D256;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 These test methods cover the determination of theresistance of plastics to“standardized”(see Note 1)pendulum-type hammers,mounted in“standardized”machines,in break-ing standard specimens with one pendulum swing(see Note 2).The standard tests for these test methods require specimensmade with a milled notch(see Note 3).In Test Methods A,C,and D,the notch produces a stress concentration that increasesthe probability of a brittle,rather than a ductile,fracture.InTest Method E,the impact resistance is obtained by reversingthe notched specimen 180 in the clamping vise.The results ofall test methods are reported in terms of energy absorbed perunit of specimen width or per unit of cross-sectional area underthe notch.(See Note 4.)NOTE1The machines with their pendulum-type hammers have been“standardized”in that they must comply with certain requirements,including a fixed height of hammer fall that results in a substantially fixedvelocity of the hammer at the moment of impact.However,hammers ofdifferent initial energies(produced by varying their effective weights)arerecommended for use with specimens of different impact resistance.Moreover,manufacturers of the equipment are permitted to use differentlengths and constructions of pendulums with possible differences inpendulum rigidities resulting.(See Section 5.)Be aware that otherdifferences in machine design may exist.The specimens are“standard-ized”in that they are required to have one fixed length,one fixed depth,and one particular design of milled notch.The width of the specimens ispermitted to vary between limits.NOTE2Results generated using pendulums that utilize a load cell torecord the impact force and thus impact energy,may not be equivalent toresults that are generated using manually or digitally encoded testers thatmeasure the energy remaining in the pendulum after impact.NOTE3The notch in the Izod specimen serves to concentrate thestress,minimize plastic deformation,and direct the fracture to the part ofthe specimen behind the notch.Scatter in energy-to-break is thus reduced.However,because of differences in the elastic and viscoelastic propertiesof plastics,response to a given notch varies among materials.A measureof a plastics“notch sensitivity”may be obtained with Test Method D bycomparing the energies to break specimens having different radii at thebase of the notch.NOTE4Caution must be exercised in interpreting the results of thesestandard test methods.The following testing parameters may affect testresults significantly:Method of fabrication,including but not limited to processingtechnology,molding conditions,mold design,and thermaltreatments;Method of notching;Speed of notching tool;Design of notching apparatus;Quality of the notch;Time between notching and test;Test specimen thickness,Test specimen width under notch,andEnvironmental conditioning.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 user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE5These test methods resemble ISO 180:1993 in regard to titleonly.The contents are significantly different.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD3641 Practice for Injection Molding Test Specimens ofThermoplastic Molding and Extrusion MaterialsD4066 Classification System for Nylon Injection and Extru-sion Materials(PA)1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.10 on MechanicalProperties.Current edition approved Nov.1,2018.Published November 2018.Originallyapproved in 1926.Last previous edition approved in 2010 as D256-101.DOI:10.1520/D0256-10R18.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serv