Designation:D412–98a(Reapproved2002)e1
Standard Test Methods for
Vulcanized Rubber and Thermoplastic Elastomers—Tension1
This standard is issued under thefixed designation D412;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e1N OTE—Section9.2was editorially updated in January2003.
1.Scope
1.1These test methods cover procedures used to evaluate the tensile(tension)properties of vulcanized thermoset rubbers and thermoplastic elastomers.These methods are not appli-cable to ebonite and similar hard,low elongation materials. The methods appear as follows:
Test Method A—Dumbbell and Straight Section Specimens
Test Method B—Cut Ring Specimens
N OTE1—These two different methods do not produce identical results.
1.2The values stated in either SI or non-SI units shall be regarded separately as normative for this standard.The values in each system may not be exact equivalents;therefore each system must be used independently,without combining values.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility 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 Documents
2.1ASTM Standards:
D1349Practice for Rubber—Standard Temperatures for Testing2
D1566Terminology Relating to Rubber2
D3182Practice for Rubber—Materials,Equipment and Procedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized Sheets2
D3183Practice for Rubber—Preparation of Pieces for Test Purposes from Products2
D3767Practice for Rubber—Measurement of Dimensions2 D4483Practice for Determining Precision for Test Method Standards in the Rubber and Carbon Black Industries2
E4Practices for Force Verification of Testing Machines3 2.2ASTM Adjunct:
Cut Ring Specimens,Method B(D412)4
2.3ISO Standards:
ISO37Rubber,Vulcanized and Thermoplastic Determina-tion of Tensile Stress-Strain Properties5
3.Terminology
3.1Definitions:
3.1.1tensile set—the extension remaining after a specimen has been stretched and allowed to retract in a specified manner, expressed as a percentage of the original length.(D1566) 3.1.2tensile set-after-break—the tensile set measured by fitting the two broken dumbbell pieces together at the point of rupture.
3.1.3tensile strength—the maximum tensile stress applied in stretching a specimen to rupture.(D1566)
3.1.4tensile stress—a stress applied to stretch a test piece (specimen).(D1566)
3.1.5tensile stress at-given-elongation—the stress required to stretch the uniform cross section of a test specimen to a given elongation.(D1566)
3.1.6thermoplastic elastomers—a diverse family of rubber-like materials that unlike conventional vulcanized rubbers can be processed and recycled like thermoplastic materials.
3.1.7ultimate elongation—the elongation at which rupture occurs in the application of continued tensile stress.
3.1.8yield point—that point on the stress-strain curve,short of ultimate failure,where the rate of stress with respect to strain,goes through a zero value and may become negative. (D1566)
3.1.9yield strain—the level of strain at the yield point. (D1566)
1These test methods are under the jurisdiction of ASTM Committee D11on
Rubber and are the direct responsibility of Subcommittee D11.10on Physical Testing.
Current edition approved Dec.10,2002.Published January2003.Originally approved in1935.Last previous edition approved in1998as D412–98a.
2Annual Book of ASTM Standards,V ol09.01.
3Annual Book of ASTM Standards,V ol03.01.
4Detailed drawings are available from ASTM Headquarters,100Barr Harbor Drive,Conshohocken,PA19428.Order Adjunct No.ADJD0412.
5Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036.
1
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
3.1.10yield stress—the level of stress at the yield point. (D1566)
4.Summary of Test Method
4.1The determination of tensile properties starts with test pieces taken from the sample material and includes the preparation of the specimens and the testing of the specimens. Specimens may be in the shape of dumbbells,rings or straight pieces of uniform cross-sectional area.
4.2Measurements for tensile stress,tensile stress at a given elongation,tensile strength,yield point,and ultimate elonga-tion are made on specimens that have not been prestressed. Tensile stress,yield point,and tensile strength are based on the original cross-sectional area of a uniform cross-section of the specimen.
4.3Measurement of tensile set is made after a previously unstressed specimen has been extended and allowed to retract by a prescribed procedure.Measurement of“set after break”is also described.
5.Significance and Use
5.1All materials and products covered by these test meth-ods must withstand tensile forces for adequate performance in certain applications.These test methods allow for the measure-ment of such tensile properties.However,tensile properties alone may not directly relate to the total end use performance of the product because of the wide range of potential perfor-mance requirements in actual use.
5.2Tensile properties depend both on the material and the conditions of test(extension rate,temperature,humidity,speci-men geometry,pretest conditioning,etc.);therefore materials should be compared only when tested under the same condi-tions.
5.3Temperature and rate of extension may have substantial effects on tensile properties and therefore should be controlled. These effects will vary depending on the type of material being tested.
5.4Tensile set represents residual deformation which is partly permanent and partly recoverable after s
tretching and retraction.For this reason,the periods of extension and recovery(and other conditions of test)must be controlled to obtain comparable results.
6.Apparatus
6.1Testing Machine—Tension tests shall be made on a power driven machine equipped to produce a uniform rate of grip separation of500650mm/min(2062in./min)for a distance of at least750mm(30in.)(see Note1).The testing machine shall have both a suitable dynamometer and an indicating or recording system for measuring the applied force within62%.If the capacity range cannot be changed for a test (as in the case of pendulum dynamometers)the applied force at break shall be measured within62%of the full scale value, and the smallest tensile force measured shall be accurate to within10%.If the dynamometer is of the compensating type for measuring tensile stress directly,means shall be provided to adjust for the cross-sectional area of the specimen.The response of the recorder shall be sufficiently rapid that the applied force is measured with the requisite accuracy during the extension of the specimen to rupture.If the testing machine is not equipped with a recorder,a device shall be provided that indicates,after rupture,the maximum force applied during extension.Testing machine systems shall be capable of mea-suring elongation of the test specimen in minimum increments of10%.
N OTE2—A rate of elongation of10006100mm/min(4064in./min) may be used and notation of the speed made in the report.In case of dispute,the test shall be repeated and the rate of elongation shall be at500 650mm/min(2062in./min).
6.2Test Chamber for Elevated and Low Temperatures—The test chamber shall conform with the following requirements: 6.2.1Air shall be circulated through the chamber at a velocity of1to2m/s(3.3to6.6ft/s)at the location of the grips or spindles and specimens maintained within2°C(3.6°F)of the specified temperature.
6.2.2A calibrated sensing device shall be located near the grips or spindles for measuring the actual temperature.
6.2.3The chamber shall be vented to an exhaust system or to the outside atmosphere to remove fumes liberated at high temperatures.
6.2.4Provisions shall be made for suspending specimens vertically near the grips or spindles for conditioning prior to test.The specimens shall not touch each other or the sides of the chamber except for momentary contact when agitated by the circulating air.
6.2.5Fast acting grips suitable for manipulation at high or low temperatures may be provided to permit placing dumbbells or straight specimens in the grips in the shortest time possible to minimize any change in temperature of the chamber.
6.2.6The dynamometer shall be suitable for use at the temperature of test or it shall be thermally insulated from the chamber.
6.2.7Provision shall be made for measuring the elongation of specimens in the chamber.If a scale is used to measure the extension between the bench-marks,the scale shall be located parallel and close to the grip path during specimen extension and shall be controlled from outside the chamber.
6.3Dial Micrometer—The dial micrometer shall conform to the requirements of Practice D3767(Method A).For ring specimens,see14.10of these test methods.
6.4Apparatus for Tensile Set Test—The testing machine described in6.1or an apparatus similar to that shown in Fig.1 may be used.A stop watch or other suitable timing device measuring in minute intervals for at least30min,shall be provided.A scale or other device shall be provided for measuring tensile set to within1%.
7.Selection of Test Specimens
7.1Consider the following information in making selec-tions:
7.1.1Since anisotropy or grain directionality due toflow introduced during processing and preparation may have an influence on tensile properties,dumbbell or straight specimens should be cut so the lengthwise direction of the specimen
is
editorially
parallel to the grain direction when this direction is known. Ring specimens normally give an average of with and across the grain properties.
7.1.2Unless otherwise noted,thermoplastic rubber or ther-moplastic elastomer specimens,or both,are to be cut from injection molded sheets or plaques with a thickness of3.06 0.3mm.Specimens of other thickness will not necessarily give comparable results.Specimens are to be tested in directions both parallel and perpendicular to the direction offlow in the mold.Sheet or plaque dimensions must be suffi
cient to do this.
7.1.3Ring specimens enable elongations to be measured by grip separation,but the elongation across the radial width of the ring specimens is not uniform.To minimize this effect the width of the ring specimens must be small compared to the diameter.
7.1.4Straight specimens tend to break in the grips if normal extension-to-break testing is conducted and should be used only when it is not feasible to prepare another type of specimen.For obtaining non-rupture stress-strain or material modulus properties,straight specimens are quite useful.
7.1.5The size of specimen type used will be determined by the material,test equipment and the sample or piece available for test.A longer specimen may be used for rubbers having low ultimate elongation to improve precision of elongation mea-surement.
8.Calibration of the Testing Machine
8.1Calibrate the testing machine in accordance with Proce-dure A of Practice E4.If the dynamometer is of the strain-gage type,calibrate the tester at one or more forces in addition to
the
requirements in Sections7and18of Practice E4.Testers having pendulum dynamometers may be calibrated as follows: 8.1.1Place one end of a dumbbell specimen in the upper grip of the testing machine.
8.1.2Remove the lower grip from the machine and attach it, by means of the gripping mechanism to the dumbbell specimen in the upper grip.
8.1.3Attach a hook to the lower end of the lower specimen grip mechanism.
8.1.4Suspend a known mass from the hook of the lower specimen grip mechanism in such a way as to permit the mass assembly to temporarily rest on the lower testing machine grip framework or holder(see Note2).
8.1.5Start the grip separation motor or mechanism,as in normal testing,and allow it to run until the mass is freely suspended by the specimen in the upper grip.
8.1.6If the dial or scale does not indicate the force applied (or its equivalent in stress for a compensating type tester) within specified tolerance,thoroughly inspect the testing ma-chine for malfun
ction(for example,excess friction in bearings and other moving parts).Ensure that the mass of the lower grip mechanism and the hook are included as part of the known mass.
8.1.7After machine friction or other malfunction has been removed,recalibrate the testing machine at a minimum of three points using known masses to produce forces of approximately 10,20and50%of capacity.If pawls or rachets are used during routine testing,use them for calibration.Check for friction in the head by calibrating with the pawls up.
N OTE3—It is advisable to provide a means for preventing the known mass from falling to thefloor in case the dumbbell should break.
8.2A rapid approximate calibration of the testing machine may be obtained by using a spring calibration device.
9.Test Temperature
9.1Unless otherwise specified,the standard temperature for testing shall be2362°C(73.463.6°F).Specimens shall be conditioned for at least3h when the test temperature is23°C (73.4°F).If the material is affected by moisture,maintain the relative humidity at5065%and condi
tion the specimens for at least24h prior to testing.When testing at any other temperature is required use one of the temperatures listed in Practice D1349.
9.2For testing at temperatures above23°C(73.4°F)preheat specimens for1062min for Method A and for662min for Method B(see Note3).Place each specimen in the test chamber at intervals ahead of testing so that all specimens of a series will be in the chamber the same length of time.The preheat time at elevated temperatures must be limited to avoid additional vulcanization or thermal aging.(Warning—In ad-dition to other precautions,suitable heat or cold resistant gloves should be worn for arm and hand protection when testing at other than23°C(73.4°F).A mask for the face is very desirable for high temperature testing to prevent the inhalation of toxic fumes when the door of the chamber is open.)
9.3For testing at temperatures below23°C(73.4°F)condi-tion the specimens at least10min prior to testing.
TEST METHOD A—DUMBBELL AND STRAIGHT
SPECIMENS
10.Apparatus
10.1Die—The shape and dimensions of the die for prepar-ing dumbbell specimens shall conform with those shown in Fig.  2.The inside faces in the reduced section shall be perpendicular to the plane formed by the cutting edges and polished for a distance of at least5mm(0.2in.)from the cutting edge.The die shall at all times be sharp and free of nicks(see9.2).
N OTE4—The condition of the die may be determined by investigating the rupture point on any series of broken(ruptured)specimens.Remove such specimens from the grips of the testing machine,stack the joined-together specimens on top of each other,and note if there is any tendency for tensile breaks to occur at the same position on each of the specimens. Rupture consistently at the same place indicates that the die may be dull, nicked,or bent at that location.
10.2Bench Marker—The two marks placed on the speci-men and used to measure elongation or strain are called“bench marks”(see Note4).The bench marker shall consist of a base plate containing two raised parallel projections.The surfaces of the raised projections(parallel to the plane of the base plate) are ground smooth in the same plane.The raised projection marking surfaces shall be between0.05and0.08mm(0.002 and0.003in.)wide and at least15mm(0.6in.)long.The angles between the parallel marking surfaces and the sides of the projections shall be at least75°.The distance between the centers of the two parallel projections or marking surfaces shall be within1%of the require
d or target bench mark distance.A handle attached to the back or top of the bench marker base plate is normally a part of the bench marker.
N OTE5—If a contact extensometer is used to measure elongation, bench marks are not necessary.
10.3Ink Applicator—Aflat unyielding surface(hardwood, metal,or plastic)shall be used to apply either ink or powder to the bench marker.The ink or powder shall adhere to the specimen,have no deteriorating effect on the specimen and be of contrasting color to that of the specimen.
10.4Grips—The testing machine shall have two grips,one of which shall be connected to the dynamometer.
10.4.1Grips for testing dumbbell specimens shall tighten automatically and exert a uniform pressure across the gripping surfaces,increasing as the tension increases in order to prevent slippage and to favor failure of the specimen in the straight reduced section.Constant pressure pneumatic type grips also are satisfactory.At the end of each grip a positioning device is recommended for inserting specimens to the same depth in the grip and for alignment with the direction of pull.
10.4.2Grips for testing straight specimens shall be constant pressure pneumatic,wedged,or toggle type designed to trans-mit the applied gripping force over the entire width of the gripped specimen.
11.Specimens
11.1Dumbbell Specimens—Whenever possible,the test specimens shall be injection molded or cut from aflat sheet not less than1.3mm(0.05in.)nor more than3.3mm(0.13
in.)
thick and of a size which will permit cutting a specimen by one of the standard methods (see Practice D 3182).Sheets may be prepared directly by processing or from finished articles by cutting and buffing.If obtained from a manufactured article,the specimen shall be free of surface roughness,fabric layers,etc.in accordance with the procedure described in Practice D 3183.All specimens shall be cut so that the lengthwise portion of the specimens is parallel to the grain unless otherwise specified.In the case of sheets prepared in accor-dance with Practice D 3182,the specimen shall be 2.060.2mm (0.0860.008in.)thick died out in the direction of the grain.Use Die C,Fig.2(unless otherwise noted)to cut
the specimens from the sheet with a single impact stroke (hand or machine)to ensure smooth cut surfaces.
11.1.1Marking Dumbbell Specimens —Dumbbell speci-mens shall be marked with the bench marker described in 10.2,with no tension on the specimens at the time of marking.Marks shall be placed on the reduced section,equidistant from its center and perpendicular to the longitudinal axis.The between bench mark distance shall be as follows:for Die C or Die D of Fig.2,25.0060.25mm (1.0060.01in.);for any other Die of Fig.2,50.0060.5mm (2.0060.02in.).
11.1.2Measuring Thickness of Dumbbell Specimens —Three measurements shall be made for the thickness,one at the center and one at each end of the reduced section.The median of the three measurements shall be used as the thickness in calculating the cross sectional area.Specimens with a differ-ence between the maximum and the minimum
thickness
FIG.2Standard Dies for Cutting Dumbbell
Specimens
D 412–98a (2002)e 1
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