1、Designation: D746 14Standard 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 U.S. Department of Defense.1. Scope*1.1 This test method covers the determinatio
3、n of 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 plas
4、tic sheeting 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 thermocou
5、plesand 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
6、prior 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
7、 PlasticsD1790 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/
8、E608M 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 Clamp4
9、3. Terminology3.1 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 s
10、pecimen 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 cont
11、aining 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 Co
12、mmittee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Proper-ties.30.07).Current edition approved Dec. 1, 2014. Published December 2014. Originallyapproved in 1943. Last previous edition approved in 2013 as D746 13. DOI:10.1520/D0746-14.2For referenced ASTM standa
13、rds, 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.3ISO Standards Handbook 21, Vol 1. ISO Standards are available fromAmericanNational Stan
14、dards Institute (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 C
15、700, West 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 cry
16、stallization,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
17、plastic 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 m
18、aterial 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 steel, have a rad
19、ius of 1.6 6 0.1 mm andshall move relative to the specimens at a linear speed of2000 6 200 mm/s at impact and during at least the following6.4 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 between t
20、he 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-fitting
21、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 steel, have a radius of 1.6 6 0.1 mm, andshall mov
22、e relative to the specimens at a linear speed of2000 6 200 mm/s at impact and during at least the following5.0 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 clampshall be 4.0 6
23、 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 device are illus
24、trated 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 correlate with tho
25、se 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 suitablerange for the t
26、emperatures 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 therequirements of Speci
27、fication 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 the appropriate
28、immersion depth in accordance with TestMethod E77.6.4 Heat-Transfer MediumUse 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 exposureat the highes
29、t 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 rubber.NOTE 4The
30、 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 measurement. When
31、 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 ofthe heat-transfer
32、 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 (Type A)D746 1426.
33、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 tester with asafet
34、y 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. Specimens shall
35、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. 6. When usingth
36、is type of specimen, clamp it so that the entire tab is insidethe jaws for a minimum distance of 3.18 mm.7.2.2 PreparationSpecimens 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 flat sheet, or prep
37、ared 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 sharp tool, or c
38、ut 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 an automatic cut
39、tingmachine, 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 are to be die pu
40、nched,sharp dies must be used in the preparation of specimens for thisFIG. 2 Typical Clamp (Type 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
41、 143test 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 withjewelers hard Arkansas honing stones. The condition of thedie is judged by investigating the rupture point on
42、 any series ofbroken specimens. When broken specimens are removed fromthe clamps of the testing machine it is advantageous to pilethese specimens and note if there is any tendency to break at orNOTE 1Dimensions are in millimetres.FIG. 5 Details of One Form of Clamp Meeting the Requirements of 6.1.2F
43、IG. 6 Specimen GeometryD746 144near 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 ConditioningCondition the test specimens at2
44、3 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 such as crystalliza
45、tion,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 to accept lots on t
46、hebasis 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, as stated in the r
47、elevant 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 at this temperatur
48、e. 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, select the start temp
49、erature 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 the bath.9.2.3 Mou
