1、Designation: D 746 07Standard Test Method forBrittleness Temperature of Plastics and Elastomers byImpact1This standard is issued under the fixed designation D 746; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the tem-perature at which plastics and elastomers exhibit brittle failureunder
3、 specified impact conditions. Two routine inspection andacceptance procedures are also provided.NOTE 1When testing rubbers for impact brittleness use Test MethodsD 2137.1.2 The values stated in SI units are to be regarded as thestandard.1.3 Due to the potential safety and environmental hazardsassoci
4、ated with mercury-filled thermometers, the use of alter-native temperature measuring devices (such as thermocouplesand 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
5、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 2This test method and ISO 974 (E) are technically equivalentwhen using the Type B fixture and the Type III specimen, however, theminimum number of specimens that are requi
6、red to be tested is signifi-cantly different when using this test method. The ISO method requires thata minimum of 100 specimens be tested.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 832 Practice for Rubber Conditioning For Low Tempera-ture Testin
7、gD 883 Terminology Relating to PlasticsD 2137 Test Methods for Rubber PropertyBrittlenessPoint of Flexible Polymers and Coated FabricsE1 Specification for ASTM Liquid-in-Glass ThermometersE77 Test Method for Inspection and Verification of Ther-mometersE 608/E 608M Specification for Mineral-Insulated
8、, Metal-Sheathed Base Metal ThermocouplesE 1137/E 1137M Specification for Industrial Platinum Re-sistance Thermometers2.2 ISO Standard:ISO 974 (E) PlasticsDetermination of the BrittlenessTemperature by Impact32.3 ASTM Adjuncts:Detailed Drawing of a Typical Clamp43. Terminology3.1 GeneralThe definiti
9、ons of plastics used in this testmethod are in accordance with Test Method D 883 unlessotherwise specified.3.2 brittleness temperaturethat temperature, estimatedstatistically, at which 50 % of the specimens would probablyfail.4. Summary of Test Method4.1 To determine the brittleness temperature, spe
10、cimens aresecured to a specimen holder with a torque wrench. Thespecimen holder is immersed in a bath containing a heat-transfer medium that is cooled. The specimens are struck at aspecified linear speed and then examined. The brittlenesstemperature is defined as the temperature at which 50 % of the
11、specimens fail.5. Significance and Use5.1 This test method establishes the temperature at which50 % of the specimens tested fail when subjected to theconditions specified herein. The test provides for the evaluationof long-time effects such as crystallization, or those effects thatare introduced by
12、low-temperature incompatibility of plasticiz-ers in the material under test. Plastics and elastomers are usedin many applications requiring low-temperature flexing with or1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.
13、30 on Thermal Proper-ties.30.07).Current edition approved March 1, 2007. Published March 2007. Originallyapproved in 1943. Last previous edition approved in 2004 as D 746 - 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. Fo
14、r 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 fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, NewYork,NY 10036.4A detailed drawing of a typ
15、ical clamp may be obtained from ASTM Headquar-ters. Order Adjunct : ADJD0746.1*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 States.without impact. Use data obtained by this
16、method to predict thebehavior of plastic and elastomeric materials at low tempera-tures only in applications in which the conditions of deforma-tion are similar to those specified in this test method. This testmethod has been found useful for specification purposes, butdoes not necessarily measure t
17、he lowest temperature at whichthe material is suitable for use.6. Apparatus6.1 Type A:6.1.1 Specimen Clamp and Striking MemberDesign thespecimen clamp to hold the specimen or specimens as acantilever beam. Each individual specimen shall be firmly andsecurely held in a separate clamp. The striking ed
18、ge shall moverelative to the specimens at a linear speed of 2000 6 200 mm/sat impact and during at least the following 6.4 mm of travel. Inorder to maintain this speed on some instruments, it isnecessary to reduce the number of specimens tested at onetime. The distance between the center line of the
19、 striking edgeand the clamp shall be 7.87 6 0.25 mm at impact. The strikingedge shall have a radius of 1.6 6 0.1 mm. The striking arm andspecimen clamp shall have a clearance of 6.35 6 0.25 mm atand immediately following impact. These dimensional require-ments are illustrated in Fig. 1. Fig. 2 shows
20、 a typical clamp.4Use free-fitting clamping screws, 10-32 National Fine Thread.6.2 Type B:6.2.1 Specimen Clamp and Striking MemberDesign thespecimen clamp to hold the specimen or specimens as acantilever beam. Each individual specimen shall be firmly andsecurely held in a separate clamp. The strikin
21、g edge shall moverelative to the specimens at a linear speed of 2000 6 200 mm/sat impact and during at least the following 5.0 mm of travel. Inorder to maintain this speed on some instruments, it isnecessary to reduce the number of specimens tested at onetime. The radius of the lower jaw of the clam
22、p shall be4.0 6 0.1 mm. The striking edge shall have a radius of1.6 6 0.1 mm. The striking edge and specimen clamp shallhave a clearance of 3.6 6 0.1 mm at and immediately follow-ing impact. The clearance between the outside of the strikingedge and the clamp shall be 2.0 6 0.1 mm at impact. Thesedim
23、ensional requirements of the striking edge and clampingdevice are illustrated in Fig. 3. Fig. 4 shows a typical clamp.Details of the specimen clamp are given in Fig. 5.6.3 Torque Wrench, 0 to 8.5 N m.NOTE 3Because of the difference in geometry of the specimenclamps, test results obtained when using
24、the Type A specimen clamp andstriking member may not correlate with those results obtained when usingthe Type B apparatus.6.4 Temperature-Measurement SystemThe temperature ofthe heat-transfer medium shall be determined with a tempera-ture measuring device (for example, thermocouple, resistancethermo
25、meter, or liquid-in-glass thermometer) having a suitablerange 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 thespecime
26、ns as possible. Thermocouples shall conform to therequirements of Specification E 608/E 608M. Resistance tem-perature devices shall comply with the requirements of Speci-fication E 1137/E 1137M. Liquid-in-glass thermometers, aredescribed in Specification E1. Use the thermometer appropri-ate for the
27、temperature range and accuracy required, andcalibrate it for the appropriate immersion depth in accordancewith Test Method E77.6.5 Heat-Transfer Medium Use any liquid heat transfermedium that remains fluid at the test temperature and does notappreciably affect the material being tested. Measurement
28、ofselected physical properties prior to and after 15-min exposureat the highest temperature used will provide an indication ofthe inertness of a plastic to the heat transfer medium.6.5.1 Where a flammable or toxic solvent is used as thecooling medium, follow customary precautions when handlingsuch m
29、aterials. Methanol is the recommended heat transfermedium for 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 te
30、mperature-measuring device as ice, it will affecttemperature measurement. 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 906.6 Temperature ControlSuitable means (automatic o
31、rmanual) shall be provided for controlling the temperature ofthe 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.6.7 Tank, in
32、sulated.6.8 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 asafety interloc
33、k to prevent striker arm motion when the cover is open.FIG. 1 Dimensional Requirements Between Specimen Clamp andStriking Edge (Type A)D7460727. Test Specimen7.1 Type I (for Fixture Type A):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.
34、6.7.1.2 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 prepared by injection molding.7.2 Type II (for Fixture Type A):7.2.1 Geometry (Modified T-50 Specimen)This
35、type ofspecimen shall be T-shaped, as illustrated in Fig. 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 o
36、r other sharp tool, or cut by an automatic machinefrom flat sheet, or prepared by injection molding.7.3 Type III (for Fixture Type B):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
37、be die-punched, cut byhand using a razor blade or other 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 sp
38、ecimens. The pre-ferred method of preparation is to use 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
39、 are damaged inany way shall be discarded. If specimens 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 touch
40、ing up the cutting edges withjewelers hard Arkansas honing stones. The condition of thedie is judged by investigating the rupture point on any series ofbroken specimens. When broken specimens are removed fromthe clamps of the testing machine it is advantageous to pilethese specimens and note if ther
41、e 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 isFIG. 2 Typical Clamp (Type A)NOTEDimensions are in millimetres.FIG. 3 Dimensional Details of Striking Edge and ClampingDevice, Type B (Positioning of
42、 Unnotched Test Specimen)FIG. 4 Assembled Clamp with Test Specimens, Type BD746073NOTEDimensions are in millimetres.FIG. 5 Details of One Form of Clamp Meeting the Requirements of 6.2FIG. 6 Specimen GeometryD746074dull, nicked, or bent at that particular position, or that someother defect is present
43、.8. Conditioning8.1 Conditioning Condition the test specimens at23 6 2C and 50 6 5 % relative humidity for not less than 40h prior to the test in accordance with Procedure A of PracticeD 618 for those tests where conditioning is required. In casesof disagreement, the tolerances shall be 61C and 62%r
44、elative humidity.8.2 Where long-time effects such as crystallization, incom-patibility, and so forth, of materials are to be studied, conditionthe test specimens in accordance with Practice D 832.9. Procedure9.1 In establishing the brittleness temperature of a material,it is recommended that the tes
45、t be started at a temperature atwhich 50 % failure is expected. Test a minimum of tenspecimens at this temperature. If all of the specimens fail,increase the temperature of the bath by 10C and repeat the testusing new specimens. If none of the specimens fail, decreasethe bath temperature by 10C and
46、repeat the test using newspecimens. If the approximate brittleness temperature is notknown, select the start temperature arbitrarily.9.2 Prior to beginning a test, prepare the bath and bring theapparatus to the desired starting temperature. If the bath iscooled using dry ice, place a suitable amount
47、 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
48、 the instrument forpreparing and operating the bath.9.3 Mount the test specimens firmly in the clamping device.Secure the specimens with a torque wrench. To avoid excessivedeformation of the specimens, use a torque suitable for thematerial being tested.NOTE 6It is recommended that a clamping torque
49、of 0.56 6 0.01Nm(56 0.1 lb in.) be used to mount the samples. If slippage of thespecimens in the clamp occurs, increase the torque the minimum amountnecessary to eliminate the slippage.9.4 Mount the clamping device in the testing apparatus andlower the clamping device into the heat-transfer medium. If dryice is being used as a coolant, maintain constant temperature bythe judicious addition of small quantities of dry ice. If theapparatus is equipped with a liquid nitrogen or CO2coolingsystem and automatic temperature control, follow the manu-fact
