1、Designation: D746 13Standard Test Method forBrittleness Temperature of Plastics and Elastomers byImpact1This standard is issued under the fixed designation D746; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 Department of Defense.1. Scope*1.1 This test method covers the determination of
3、the tem-perature at which plastics and elastomers (as defined byTerminology D883) exhibit brittle failure under specifiedimpact conditions. Two routine inspection and acceptanceprocedures are also provided.NOTE 1When testing rubbers for impact brittleness use Test MethodD2137. When testing plastic s
4、heeting for impact brittleness, use TestMethod D1790.1.2 The values stated in SI units are to be regarded as thestandard.1.3 Due to the potential safety and environmental hazardsassociated with mercury-filled thermometers, the use of alter-native temperature measuring devices (such as thermocouplesa
5、nd RTDs) is encouraged.1.4 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
6、 to use.NOTE 2This test method and ISO 974 address the same subjectmatter, but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD832 Practice for Rubber Conditioning For Low Tempera-ture TestingD883 Terminology Relating to Plas
7、ticsD1790 Test Method for Brittleness Temperature of PlasticSheeting by ImpactD2137 Test Methods for Rubber PropertyBrittleness Pointof Flexible Polymers and Coated FabricsE1 Specification for ASTM Liquid-in-Glass ThermometersE77 Test Method for Inspection and Verification of Ther-mometersE608/E608M
8、 Specification for Mineral-Insulated, Metal-Sheathed Base Metal ThermocouplesE1137/E1137M Specification for Industrial Platinum Resis-tance Thermometers2.2 ISO Standard:ISO 974 PlasticsDetermination of the Brittleness Tem-perature by Impact32.3 ASTM Adjuncts:Detailed Drawing of a Typical Clamp43. Te
9、rminology3.1 GeneralThe definitions of plastics used in this testmethod are in accordance with Test Method D883 unlessotherwise specified.3.2 brittleness temperaturethat temperature, estimatedstatistically, at which 50 % of the specimens would probablyfail.3.3 failed specimenthe division of a specim
10、en into two ormore completely separated pieces or as any crack in thespecimen which is visible to the unaided eye.4. Summary of Test Method4.1 To determine the brittleness temperature, specimens aresecured to a specimen holder using a torque wrench. Thespecimen holder is immersed in a bath containin
11、g a heat-transfer medium, which has been cooled. The specimens arestruck at a specified linear speed and then examined forfailures. The brittleness temperature is defined as the tempera-ture at which 50 % of the specimens would probably fail.1This test method is under the jurisdiction ofASTM Committ
12、ee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Proper-ties.30.07).Current edition approved June 1, 2013. Published June 2013. Originallyapproved in 1943. Last previous edition approved in 2007 as D746 - 07. DOI:10.1520/D0746-13.2For referenced ASTM standards, vi
13、sit 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.3ISO Standards Handbook 21, Vol 1. ISO Standards are available fromAmericanNational Standards I
14、nstitute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY10036.4A detailed drawing of a typical clamp may be obtained from ASTM Headquar-ters. Order Adjunct : ADJD0746.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
15、st Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 This test method establishes the temperature at which50 % of the specimens tested would probably fail whensubjected to the conditions specified herein. The test providesfor the evaluation of long-time effects such as crystalliz
16、ation,or those effects that are introduced by low-temperature incom-patibility of plasticizers in the material under test. Plastics andelastomers are used in many applications requiring low-temperature flexing with or without impact. Use data obtainedby this method to predict the behavior of plastic
17、 and elasto-meric materials at low temperatures only in applications inwhich the conditions of deformation are similar to thosespecified in this test method. This test method has been founduseful for specification purposes, but does not necessarilymeasure the lowest temperature at which the material
18、 issuitable for use.6. Apparatus6.1 Specimen Clamp and Striking Edge:6.1.1 Type A:6.1.1.1 Design the specimen clamp to hold the specimen orspecimens as a cantilever beam. Each individual specimenshall be firmly and securely held in a separate clamp. Thestriking edge shall be hardened steel, have a r
19、adius of 1.6 6 0.1mm and shall move relative to the specimens at a linear speedof 2000 6 200 mm/s at impact and during at least the follow-ing 6.4 mm of travel. In order to maintain this speed on someinstruments, it is necessary to reduce the number of specimenstested at one time. The distance betwe
20、en the center line of thestriking edge and the clamp shall be 7.87 6 0.25 mm at impact.The striking edge and specimen clamp shall have a clearance of6.35 6 0.25 mm at and immediately following impact. Thesedimensional requirements are illustrated in Fig. 1. Fig. 2 showsa typical clamp.4Use free-fitt
21、ing clamping screws, 10-32National Fine Thread.6.1.2 Type B:6.1.2.1 Design the specimen clamp to hold the specimen orspecimens as a cantilever beam. Each individual specimenshall be firmly and securely held in a separate clamp. Thestriking edge shall be hardened steel, have a radius of 1.6 6 0.1mm,
22、and shall move relative to the specimens at a linear speedof 2000 6 200 mm/s at impact and during at least the follow-ing 5.0 mm of travel. In order to maintain this speed on someinstruments, it is necessary to reduce the number of specimenstested at one time. The radius of the lower jaw of the clam
23、pshall be 4.0 6 0.1 mm. The striking edge and specimen clampshall have a clearance of 3.6 6 0.1 mm at and immediatelyfollowing impact. The clearance between the outside of thestriking edge and the clamp shall be 2.0 6 0.1 mm at impact.These dimensional requirements of the striking edge andclamping d
24、evice are illustrated in Fig. 3. Fig. 4 shows a typicalclamp. Details of the specimen clamp are given in Fig. 5.6.2 Torque Wrench, 0 to 8.5 N m.NOTE 3Because of the difference in geometry of the specimenclamps, test results obtained when using the Type A specimen clamp andstriking member may not cor
25、relate with those results obtained when usingthe Type B apparatus.6.3 Temperature-Measurement SystemThe temperature ofthe heat-transfer medium shall be determined with a tempera-ture measuring device (for example, thermocouple, resistancethermometer, or liquid-in-glass thermometer) having a suitable
26、range for the temperatures at which the determinations are tobe made. The temperature-measuring device and the relatedreadout equipment shall be accurate to at least 60.5C. Thetemperature-measuring device shall be located as close to thespecimens as possible. Thermocouples shall conform to therequir
27、ements of Specification E608/E608M. Resistance tem-perature devices shall comply with the requirements of Speci-fication E1137/E1137M. Liquid-in-glass thermometers, aredescribed in Specification E1. Use the thermometer appropriatefor the temperature range and accuracy required, and calibrateit for t
28、he appropriate immersion depth in accordance with TestMethod E77.6.4 Heat-Transfer Medium Use any liquid heat transfermedium that remains fluid at the test temperature and does notappreciably affect the material being tested. Measurement ofselected physical properties prior to and after 15-min expos
29、ureat the highest temperature used will provide an indication ofthe inertness of a plastic to the heat transfer medium.6.4.1 Where a flammable or toxic solvent is used as thecooling medium, follow customary precautions when handlingsuch materials. Methanol is the recommended heat transfermedium for
30、rubber.NOTE 4The following materials have been found suitable for use atthe indicated temperatures. When silicone oil is used, moisture from theair will condense on the surface of the oil, causing slush to form. If slushcollects on the temperature-measuring device as ice, it will affecttemperature m
31、easurement. When this occurs, remove the ice from thetemperature-measuring device.Material Temperature, C5-mm2/s viscosity silicone oil 602-mm2/s viscosity silicone oil 76Methyl alcohol 906.5 Temperature ControlSuitable means (automatic ormanual) shall be provided for controlling the temperature oft
32、he heat-transfer medium to within 60.5C of the desiredvalue. Powdered solid carbon dioxide (dry ice) and liquidnitrogen are recommended for lowering the temperature, andan electric immersion heater for raising the temperature.FIG. 1 Dimensional Requirements Between Specimen Clamp andStriking Edge (T
33、ype A)D746 1326.6 Tank, insulated.6.7 Stirrer, to provide thorough circulation of the heattransfer medium.NOTE 5Suitable apparatus is commercially available from severalsuppliers. The striking member may be motor-driven, solenoid-operated,gravity-actuated, or spring-loaded. Equip the motor-driven te
34、ster with asafety interlock to prevent striker arm motion when the cover is open.7. Test Specimen7.1 Type I (for Type A Apparatus):7.1.1 GeometryThis type of specimen shall be6.35 6 0.51 mm wide by 31.75 6 6.35 mm long as illustratedin Fig. 6.7.1.2 PreparationSpecimens shall be 1.91 6 0.13 mmthick.
35、Specimens shall be die-punched, cut by hand using arazor blade or other sharp tool, or cut by an automatic machinefrom flat sheet, or prepared by injection molding.7.2 Type II (for Type A Apparatus):7.2.1 Geometry (Modified T-50 Specimen)This type ofspecimen shall be T-shaped, as illustrated in Fig.
36、 6. When usingthis type of specimen, clamp it so that the entire tab is insidethe jaws for a minimum distance of 3.18 mm.7.2.2 Preparation Specimens shall be 1.91 6 0.13 mmthick. Specimens shall be die-punched, cut by hand using arazor blade or other sharp tool, or cut by an automatic machinefrom fl
37、at sheet, or prepared by injection molding.7.3 Type III (for Type B Apparatus):7.3.1 GeometryThis type of specimen shall be20.0 6 0.25 mm long by 2.5 6 0.05 mm wide and 1.6 6 0.1mm thick as illustrated in Fig. 6.7.3.2 PreparationSpecimens shall be die-punched, cut byhand using a razor blade or other
38、 sharp tool, or cut by anautomatic machine from flat sheet, or prepared by injectionmolding.7.4 Test results will vary according to molding conditionsand methods of specimen preparation. It is essential thatpreparation methods produce uniform specimens. The pre-ferred method of preparation is to use
39、 an automatic cuttingmachine, however specimens that are punched using an arborpress or hydraulically operated press are also acceptable. Nomatter which preparation method is employed, the specimenedges shall be free of all flash. Specimens that are damaged inany way shall be discarded. If specimens
40、 are to be die punched,sharp dies must be used in the preparation of specimens for thistest if reliable results are to be achieved. Careful maintenanceof die cutting edges is of extreme importance and is obtainedby daily lightly honing and touching up the cutting edges withFIG. 2 Typical Clamp (Type
41、 A)NOTE 1Dimensions are in millimetres.FIG. 3 Dimensional Details of Striking Edge and ClampingDevice, Type B (Positioning of Unnotched Test Specimen)FIG. 4 Assembled Clamp with Test Specimens, Type BD746 133jewelers hard Arkansas honing stones. The condition of thedie is judged by investigating the
42、 rupture point on any series ofbroken specimens. When broken specimens are removed fromthe clamps of the testing machine it is advantageous to pileNOTE 1Dimensions are in millimetres.FIG. 5 Details of One Form of Clamp Meeting the Requirements of 6.1.2FIG. 6 Specimen GeometryD746 134these specimens
43、and note if there is any tendency to break at ornear the same portion of each specimen. Rupture pointsconsistently at the same place are the indication that the die isdull, nicked, or bent at that particular position, or that someother defect is present.8. Conditioning8.1 Conditioning Condition the
44、test specimens at23 6 2C and 50 6 10 % relative humidity for not less than 40h prior to the test in accordance with Procedure A of PracticeD618 for those tests where conditioning is required. In cases ofdisagreement, the tolerances shall be 61C and 65 % relativehumidity.8.2 Where long-time effects s
45、uch as crystallization,incompatibility, and so forth, of materials are to be studied,condition the test specimens in accordance with Practice D832.9. Procedure9.1 Routine Inspection and Acceptance:9.1.1 For routine inspection of materials received from anapproved supplier, it shall be satisfactory t
46、o accept lots on thebasis of testing a minimum of ten specimens at a specifiedtemperature as stated in the relevant material specifications.Not more than five shall fail.9.1.2 It shall be satisfactory to accept elastomeric composi-tion on a basis of testing five specimens at a specifiedtemperature,
47、as stated in the relevant material specifications.None shall fail.9.2 Determination of Brittleness Temperature:9.2.1 In establishing the brittleness temperature of amaterial, it is recommended that the test be started at atemperature at which 50 % failure is expected. Test a minimumof ten specimens
48、at this temperature. If all of the specimensfail, increase the temperature of the bath by 10C and repeatthe test using new specimens. If none of the specimens fail,decrease the bath temperature by 10C and repeat the test usingnew specimens. If the approximate brittleness temperature isnot known, sel
49、ect the start temperature arbitrarily.9.2.2 Prior to beginning a test, prepare the bath and bringthe apparatus to the desired starting temperature. If the bath iscooled using dry ice, place a suitable amount of powdered dryice in the insulated tank and slowly add the heat-transfermedium until the tank is filled to a level 30 to 50 mm from thetop. If the apparatus is equipped with a liquid nitrogen or CO2cooling system and automatic temperature control, followinstructions provided by the manufacturer of the instrument forpreparing and operating th
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1