Standard Test Method for
Rubber Property—Durometer Hardness1
This standard is issued under thefixed designation D2240;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.
1.Scope
1.1This test method covers twelve types of rubber hardness measurement devices known as durometers:Types A,B,C,D, DO,E,M,O,OO,OOO,OOO-S,and R.The procedure for determining indentation hardness of substances classified as thermoplastic elastomers,vulcanized(thermoset)rubber,elas-tomeric materials,cellular materials,gel-like materials,and some plastics is also described.
1.2This test method is not equivalent to other indentation hardness methods and instrument types,specifically those described in Test Method D1415.
1.3This test method is not applicable to the testing of coated fabrics.
1.4All materials,instruments,or equipment used for the determination of mass,force,or dimension shall have trace-ability to the National Institute for Standards and Technology, or other internationally recognized organizations parallel in nature.
1.5The values stated in SI units are to be regarded as standard.The values given in parentheses are for information only.Many of the stated dimensions in SI are direct conver-sions from the U.S.Customary System to accommodate the instrumentation,practices,and procedures that existed prior to the Metric Conversion Act of1975.
1.6This 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:2
D374Test Methods for Thickness of Solid Electrical Insu-lation
D618Practice for Conditioning Plastics for Testing
D785Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials
D1349Practice for Rubber—Standard Temperatures for Testing
D1415Test Method for Rubber Property—International Hardness
D4483Practice for Determining Precision for Test Method Standards in the Rubber and Carbon Black Industries
F1957Test Method for Composite Foam Hardness-Durometer Hardness
2.2ISO Standard:3
ISO/IEC17025:1999General Requirements for the Com-petence of Testing and Calibration Laboratories
3.Summary of Test Method
3.1This test method permits hardness measurements based on either initial indentation or indentation after a specified period of time,or both.Durometers with maximum reading indicators used to determine maximum hardness values of a material may yield lower hardness when the maximum indi-cator is used.
3.2The procedures for Type M,or micro hardness durom-eters,accommodate specimens that are,by their dimensions or configuration,ordinarily unable to have their durometer hard-ness determined by the other durometer types described.Type M durometers are intended for the testing of specimens having a thickness or cross-sectional diameter of1.25mm(0.050in.) or greater,although specimens of lesser dimensions may be successfully accommodated under the conditions specified in Section6,and have a Type M durometer hardness range between20and90.Those specimens which have a durometer hardness range other than specified shall use another suitable procedure for determining durometer hardness.
4.Significance and Use
4.1This test method is based on the penetration of a specific type of indentor when forced into the material under specified conditions.The indentation hardness is inversely related to the penetration and is dependent on the elastic modulus and viscoelastic behavior of the material.The geometry of the
1This test method is under the jurisdiction of ASTM Committee D11on Rubber and is the direct responsibility of Subcommittee D11.10on Physical Testing.
Current edition approved Aug.15,2005.Published September2005.Originally approved in19.Last previous edition approved in2004as D2240–04e1.
2For referenced ASTM standards,visit the ASTM website,www.astm.org,or contact ASTM Customer Service at service@astm.org.For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on the ASTM website.
3Available from International Organization for Standardization(ISO),1rue de Varembé,Case postale56,CH-1211,Geneva20,Switzerland.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States. --`,,```,,,,````-`-`,,`,,`,`,,`---
indentor and the applied force influence the measurements such that no simple relationship exists between the measure-ments obtained with one type of durometer and those obtained with another type of durometer or other instruments used for measuring hardness .This test method is an empirical test intended primarily for control purposes.No simple relationship exists between indentation hardness determined by this test method and any fundamental property of the material tested.For specification purposes,it is recommended that Test Method D 785be used for materials other than those described in 1.1.5.Apparatus
5.1Hardness Measuring Apparatus,or Durometer,and an Operating Stand ,Type 1,Type 2,or Type 3(see 5.1.2)consisting of the following components:5.1.1Durometer :
5.1.1.1Presser Foot ,the configuration and the total area of a durometer presser foot may produce varying results when there are significant differences between them.It is recom-mended that when comparing durometer hardness determina-tions of the same type (see 4.1),that the comparisons be between durometers of similar presser foot configurations and total area,and that the presser foot configuration and size be noted in the Hardness Measurement Report (see 10.2.4and 5.1.1.3).
5.1.1.2Presser Foot ,Types A,B,C,D,DO,E,O,OO,OOO,and OOO-S,with an orifice (to allow for the protrusion of the indentor)having a diameter as specified in Fig.1(a,b,c,d,e,f,and g),with the center a minimum of
6.0mm (0.24in.)from any edge of the foot.When the presser foot is not of a flat circular design,the area shall not be less than 500mm 2(19.7in.2).
N OTE 1—The Type OOO and the Type OOO-S,designated herein,differ in their indentor configuration,spring force,and the results obtained.See Table 1and Fig.1(e and g).
5.1.1.3Presser Foot —flat circular designs designated as Type xR ,where x is the standard durometer designation and R indicates the flat circular press foot described herein,for example,Type aR ,dR ,and the like.The presser foot,having a
centrally located orifice (to allow for the protrusion of the indentor)of a diameter as specified in Fig.1(a through g).The flat circular presser foot shall be 1860.5mm (0.7160.02in.)in diameter.These durometer types shall be used in an operating stand (see 5.1.2).
(a)Durometers having a presser foot configuration other than that indicated in 5.1.1.3shall not use the Type xR designation,and it is recommended that their presser foot configuration and size be stated in the Hardness Measurement Report (see 10.2.4).
5.1.1.4Presser Foot,Type M ,with a centrally located orifice (to allow for the protrusion of the indentor),having a diameter as specified in Fig.1(d),with the center a minimum of 1.60mm (0.063in.)from any edge of the flat circular presser foot.The Type M durometer shall be used in a Type 3operating stand (see 5.1.2.4).
5.1.1.5Indentor ,formed from steel rod and hardened to 500HV10and shaped in accordance with Fig.1(a,b,c,d,e,or g),polished over the contact area so that no flaws are visible under 203magnification,with an indentor extension of 2.5060.04mm (0.09860.002in.).
5.1.1.6Indentor,Type OOO-S ,formed from steel rod and hardened to 500HV10,shaped in accordance with Fig.1(f),polished over the contact area so that no flaws are visible under 203magnification,with an indentor extension of 5.0060.04mm (0.19860.002in.).
5.1.1.7Indentor,Type M ,formed from steel rod and hard-ened to 500HV10and shaped in accordance with Fig.1(d),polished over the contact area so that no flaws are visible under 503magnification,with an indentor extension of 1.2560.02mm (0.04960.001in.).
5.1.1.8Indentor Extension Indicator ,analog or digital elec-tronic,having a display that is an inverse function of the indentor extension so that:
(1)The display shall indicate from 0to 100with no less than 100equal divisions throughout the range at a rate of one hardness point for each 0.025mm (0.001in.)of indentor
movement,
FIG.1(a)Type A and C
Indentor
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(2)The display for Type OOO-S durometers shall indicate from 0to 100with no less than 100equal divisions throughout the range at a rate of one hardness point for each 0.050mm (0.002in.)of indentor movement,
(3)The display for Type M durometers shall indicate from 0to 100with no less than 100equal divisions at a rate of one hardness point for each 0.0125mm (0.0005in.)of indentor movement,and
(4)In the case of analog dial indicators having a display of 360°,the points indicating 0and 100may be at the same point on the dial and indicate 0,100,or both.
5.1.1.9Timing Device (optional),capable of being set to a desired elapsed time,signaling the operator or holding the
hardness reading when the desired elapsed time has been reached.The timer shall be automatically activated when the presser foot is in contact with the specimen being tested,for example,the initial indentor travel has ceased.Digital elec-tronic durometers may be equipped with electronic timing devices that shall not affect the indicated reading or determi-nations attained by more than one-half of the calibration tolerance stated in Table 1.
5.1.1.10Maximum Indicators (optional),maximum indicat-ing pointers are auxiliary analog indicating hands designed to remain at the maximum hardness value attained until reset
by
FIG.1(b)Type B and D Indentor
(continued)
FIG.1(c)Type O,DO,and OO Indentor
(continued)
FIG.1(d)Type M Indentor
(continued)
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the operator.Electronic maximum indicators are digital dis-plays electronically indicating and maintaining the maximum value hardness valued achieved until reset by the operator.5.1.1.11Analog maximum indicating pointers have been shown to have a nominal effect on the values attained,however,this effect is greater on durometers of lesser total mainspring loads;for example,the effect of a maximum indicating pointer on Type D durometer determinations will be less than those determinations achieved using a Type A durometer.Analog style durometers may be equipped with maximum indicating pointers.The effect of a maximum indicating pointer shall be noted at the time of calibration in the calibration report (see 10.1.5),and when reporting hardness determinations (see 10.2.4).Analog Type M,OO,OOO,and Type OOO-S durometers shall not be equipped with maximum indicating pointers.
5.1.1.12Digital electronic durometers may be equipped with electronic maximum indicators that shall not affect the indicated reading or determinations attained by more than one half of the spring calibration tolerance stated in Table 1.
5.1.1.13Calibrated Spring ,for applying force to the inden-tor,in accordance with Fig.1(a through g)and capable of applying the forces as specified in Table 1.5.1.2Operating Stand (Fig.2):
5.1.2.1Type 1,Type 2,and Type 3shall be capable of supporting the durometer presser foot surface parallel to the specimen support table (Fig.3)throughout the travel of each.The durometer presser foot to specimen support table parallel-ism shall be verified each time the test specimen support table is adjusted to accommodate specimens of varying dimensions.This may be accomplished by applying the durometer presser foot to the point of contact with the specimen support table and making adjustments by way of the durometer mounting assem-bly or as specified by the manufacturer.
5.1.2.2Operating Stand,Type 1(specimen to indentor type),shall be capable of applying the specimen to the indentor in a manner that minimizes shock.
5.1.2.3Operating Stand,Type 2(indentor to specimen type),shall be capable of controlling the rate of descent of the indentor to the specimen at a maximum of 3.20mm/s
(0.125
FIG.1(e)Type OOO Indentor
(continued)
FIG.1(f)Type OOO-S Indentor
(continued)
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in./s)and applying a force sufficient to overcome the calibrated spring force as shown in Table 1.
5.1.2.4Operating Stand,Type 3(indentor to specimen type),hydraulic dampening,pneumatic dampening,or electro-mechanical (required for the operation of Type M durometers)shall be capable of controlling the rate of descent of the indentor to the specimen at a maximum of 3.2mm/s (0.125in./s)and applying a force sufficient to overcome the calibrated spring force as shown in Table 1.Manual application,Type 1or Type 2operating stands are not acceptable for Type M durometer operation.
5.1.2.5The entire instrument should be plumb and level,and resting on a surface that will minimize vibration.Operating the instrument under adverse conditions will negatively affect the determinations attained.
5.1.2.6Specimen Support Table ,(Fig.3)integral to the operating stand,and having a solid flat surface.The specimen support platform may have orifices designed to accept various inserts or support fixtures (Fig.3)to provide for the support of irregularly configured specimens.When inserts are used to support test specimens,care must be taken to align the indentor to the center of the insert,or the point at which the indentor is to contact the specimen.Care should be exercised to assure that
the indentor does not abruptly contact the specimen support table as damage to the indentor may result.6.Test Specimen
6.1The test specimen,herein referred to as “specimen”or “test specimen”interchangeably,shall be at least 6.0mm (0.24in.)in thickness unless it is known that results equivalent to the 6.0-mm (0.24-in.)values are obtained with a thinner specimen.6.1.1A specimen may be composed of plied pieces to obtain the necessary thickness,but determinations made on such specimens may not agree with those made on solid specimens,as the surfaces of the plied specimens may not be in complete contact.The lateral dimensions of the specimen shall be sufficient to permit measurements at least 12.0mm (0.48in.)from any edge,unless it is known that identical results are obtained when measurements are made at a lesser distance from an edge.
6.1.2The surfaces of the specimen shall be flat and parallel over an area to permit the presser foot to contact the specimen over an area having a radius of at least 6.0mm (0.24in.)from the indentor point.The specimen shall be suitably supported to provide for positioning and stability.A suitable
hardness
FIG.1(g)Type E Indentor (continued)TABLE 1Durometer Spring Force Calibration A
All Values are in N
Indicated Value Type A,B,E,O Type C,D,DO Type M Type OO,OOO Type OOO-S 00.5500.3240.2030.16710 1.3 4.4450.3680.2940.34320 2.058.0.4120.3850.52030 2.813.3350.4560.4760.690 3.5517.780.50.5660.87350 4.322.2250.5440.657 1.04960 5.0526.670.50.748 1.22670 5.831.1150.6330.839 1.40280 6.5535.560.6770.93 1.579907.340.0050.721 1.02 1.755100
8.0544.450.765 1.111 1.932N/durometer unit 0.0750.44450.00440.009080.01765Spring Calibration Tolerance
60.075N
60.4445N
60.0176N
60.0182N
60.0353N
A
Refer to 5.1.1.3for the Type xR
designation.
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determination cannot be made on an uneven or rough point of contact with the indentor.
6.2Type OOO,OOO-S,and M test specimens should be at least 1.25mm (0.05in.)in thickness,unless it is known that
results equivalent to the 1.25-mm (0.05-in.)values are obtained with a thinner specimen.
6.2.1A Type M specimen that is not of a configuration described in 6.2.2may be composed of plied pieces to
obtain
FIG.2Durometer Operating
Stand
FIG.3Small Specimen Support
Table
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the necessary thickness,but determinations made on such specimens may not agree with those made on solid specimens because the surfaces of the plied specimens may not be in complete contact.The lateral dimensions of the specimen should be sufficient to permit measurements at least 2.50mm (0.10in.)from any edge unless it is known that identical results are obtained when measurements are made at lesser distance from an edge.A suitable hardness determination cannot be made on an uneven or rough point of contact with the indentor.6.2.2The Type M specimen,when configured as an o-ring,circular band,or other irregular shape shall be at least 1.25mm (0.05in.)in cross-sectional diameter,unless it is known that results equivalent to the 1.25-mm (0.05-in.)values are obtained with a thinner specimen.The specimen shall be suitably supported in a fixture (Fig.3)to provide for positioning and stability.
6.3The minimum requirement for the thickness of the specimen is dependent on the extent of penetration of the indentor into the specimen;for example,thinner specimens may be used for materials having higher hardness values.The minimum distance from the edge at which measurements may be made likewise decreases as the hardness increases.
7.Calibration
7.1Indentor Extension Adjustment Procedure :
7.1.1Place precision ground dimensional blocks (Grade B or better)on the support table and beneath the durometer presser foot and indentor.Arrange the blocks so that the durometer presser foot contacts the larger block(s)and the indentor tip just contacts the smaller block (Fig.4).It is necessary to observe the arrangement of the blocks and the presser foot/indentor under a minimum of 203magnification to assure proper alignment.
7.1.2Indentor extension and shape shall be in accordance with 5.1.1.5,5.1.1.6,or 5.1.1.7,respective to durometer type.See Fig.1(a through g).Examination of the indentor under 203magnification,503for Type M indentors,is required to examine the indentor condition.Misshapen or damaged inden-tors shall be replaced.
7.1.3A combination of dimensional gage blocks shall be used to achieve a difference of 2.54+0.00/–0.0254mm (0.100+0.00/–0.001in.)between them.For Type OOO-S durometers,the gage block dimensions are 5.08+0.00/–0.0508mm (0.200+0.00/–0.002in.).For Type M durometers,the gage block
dimensions are 1.27+0.0/–0.0127mm (0.050+0.00/–0.0005in.)between them (Fig.4).
7.1.4Carefully lower the durometer presser foot until it contacts the largest dimensional block(s),the indentor tip should just contact the smaller block,verifying full indentor extension.
7.1.5Adjust the indentor extension to 2.5060.04mm (0.09860.002in.).For Type OOO-S durometers,adjust the indentor extension to 5.060.04mm (0.19860.002in.).For Type M durometers,adjust the indentor extension to 1.2560.02mm (0.04960.001in.),following the manufacturer’s recommended procedure.
7.1.5.1When performing the procedures in 7.1,care should be used so as not to cause damage to the indentor tip.Fig.4depicts a suitable arrangement for gaging indentor extension.7.1.6Parallelism of the durometer presser foot to the support surface,and hence the dimensional gage blocks,at the time of instrument calibration,may be in accordance with Test Methods D 374,Machinist’s Micrometers,or otherwise ac-complished in accordance with the procedures specified by the manufacturer.
7.2Indentor Display Adjustment :
7.2.1After adjusting the indentor extension as indicated in 7.1,use a similar arrangement of dimensional gage blocks to verify the linear relationship between indentor travel and indicated display at two points:0and 100.Following the manufacturer’s recommendations,make adjustments so that:7.2.2The indicator displays a value equal to the indentor travel measured to within:
–0.0+1.0durometer units measured at 0;60.50durometer units measured at 100;
61durometer units at all other points delineated in 7.4.7.2.3Each durometer point indicated is equal to 0.025mm (0.001in.)of indentor travel,except for:
7.2.3.1Type M Durometers,each indicated point is equal to 0.0125mm (0.0005in.)of indentor travel;
7.2.3.2Type OOO-S Durometers,each indicated point is equal to 0.050mm (0.002in.)of indentor travel.
7.2.4The indicator shall not display a value greater than 100or less than 0at the time of calibration.
7.2.5Other means of determining indentor extension or indentor travel,such as optical or laser measurement methods,are acceptable.The instrumentation used shall have traceability as described in 1.4.
7.2.6The durometer shall be supported in a suitable fashion when performing the procedures described in 7.1and 7.2.7.3Calibration Device :
7.3.1The durometer spring shall be calibrated by support-ing the durometer in a calibrating device,see Fig.5,in a vertical position and applying a measurable force to the indentor tip.The force may be measured by means of a balance as depicted in Fig.5,or an electronic force cell.The calibrating device shall be capable of measuring applied force to within 0.5%of the maximum spring force necessary to achieve 100durometer units.
7.3.2Care should be taken to ensure that the force is applied vertically to the indentor tip,as lateral force will cause errors in calibration.See 7.1.5.1and 7.1.6
.
FIG.4Detail of Indentor Extension and Display
Adjustment
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7.4Spring Calibration —The durometer spring shall be calibrated at displayed readings of 10,20,30,40,50,60,70,80,and 90.The measured force (9.83mass in kilograms)shall be within the spring calibration tolerance specified in Table 1.Table 1identifies the measured force applied to the indentor for the entire range of the instrument,although it is necessary only to verify the spring calibration at points listed herein.7.5Spring Calibration Procedure :
7.5.1Ensure that the indentor extension has been adjusted in accordance with 7.1,and the linear relationship between indentor travel and display is as specified in 7.2.
7.5.2Place the durometer in the calibration device as depicted in Fig.5.Apply the forces indicated in Table 1so that forces applied are aligned with the centerline of the indentor in a fashion that eliminates shock or vibration and adjust the durometer according to manufacturers’recommendations so that:
7.5.3At the points enumerated in 7.4,the display shall indicate a value equal to 0.025mm (0.001in.)of indentor travel.For Type OOO-S durometers,the display shall indicate a value equal to 0.05mm (0.002in.)of indentor travel.For Type M durometers,the display shall indicate a value equal to 0.0125mm (0.0005in.)of indentor travel within the spring calibration tolerances specified in 7.6.
7.6Spring calibration tolerances are 61.0durometer units for Types A,B,C,D,E,O,and DO,62.0durometer units for Types OO,OOO,and OOO-S,and .0durometer units for Type M,while not indicating below 0or above 100at the time of calibration (see Table 1).
7.7Spring Force Combinations :
7.7.1For Type A,B,E,and O durometers:Force,N =0.55+0.075HA
Where HA =hardness reading on Type A,B,E,and O durometers.
7.7.2For Type C,D,and DO durometers:Force,N =0.4445HD
Where HD =hardness reading on Type C,D,and DO durometers.
7.7.3For Type M durometers:Force,N =0.324+0.0044HM
Where HM =hardness reading on Type M durometers.
7.7.4For Type OO and OOO durometers:Force,N =0.203+0.00908HOO
Where HOO =hardness reading on Type OO durometers.7.7.5For Type OOO-S durometers:
Force,N =0.167+0.01765HOOO-S
Where HOOO-S =hardness reading on Type OOO-S durometers.
7.8The rubber reference block(s)provided for verifying durometer operation and state of calibration are not to be relied upon as calibration standards.The calibration procedures outlined in Section 7are the only valid calibration procedures.7.8.1The use of metal reference blocks is no longer recommended (see Note 2).
7.9Verifying the state of durometer calibration,during routine use ,may be accomplished by:
7.9.1Verifying that the zero reading is no more than 1indicated point above zero,and not below zero (on durometers so equipped),when the durometer is positioned so that no external force is placed upon the indentor.
7.9.2Verifying that the 100reading is no more than 100and no less than 99when the durometer is positioned on a flat surface of a non-metallic material so that the presser foot is in complete contact,causing the indentor to be fully retracted.7.9.2.1It is important that when performing the verification of 100,as described in 7.9.2,that extreme care be taken so as to not cause damage to the indentor.Verification of the 100value is not recommended for durometers having a spring force greater than 10N (Types C,D,and DO).
7.9.2.2When performing the verification of 100,as de-scribed in 7.9.2,the non-metallic material shall be of a hardness value greater than 100of the type (scale)of the durometer being employed.Tempered glass of a thickness greater than 6.35mm (0.25in.)has been found satisfactory for this application.
7.9.3Verifying the displayed reading at any other point using commercially available rubber reference blocks which are certified to a stated value of the type (scale)of the durometer being employed.The displayed value of the durom-eter should be within 62durometer points of the reference block’s stated value.
7.9.4Verification of the zero and 100readings of a durom-eter provide reasonable assurance that the linear relationship between the indicated display and the durometer mechanism remain valid.
7.9.5Verification of points between zero and 100provide reasonable assurance that the curvilinear relationship between the indicated display and the durometer mechanism remain valid.
7.9.6This is not a calibration procedure,it is a means by which a user may routinely verify that the durometer may be functioning correctly.(See Note 2.)
8.Laboratory Atmosphere and Test Specimen Conditioning
8.1Tests shall be conducted in the standard laboratory atmosphere,as defined in Practice D 618,Section 4.2.
8.2The instrument shall be maintained in the standard laboratory atmosphere,as defined in Practice D 618,Section 4.1,for 12h prior to performing a
test.
FIG.5Example of Durometer Calibration
Apparatus
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8.4These procedures may be modified if agreed upon between laboratories or between supplier and user and are in accordance with alternative procedures identified in Practice D618.
8.5No conclusive evaluation has been made on durometers at temperatures other than23.06 2.0°C(73.46 3.6°F). Conditioning at temperatures other than the above may show changes in calibration.Durometer use at temperatures other than the above should be decided locally(see Practice D1349).
9.Procedure
9.1Operating Stand Operation(Type3Operating Stand Required for Type M):
9.1.1Care shall be exercised to minimize the exposure of the instrument to environmental conditions that are adverse to the performance of the instrument,or adversely affect test results.
9.1.2Adjust the presser foot to support table parallelism as described in5.1.2.1.It is necessary to make this adjustment each time the support table is moved to accommodate speci-mens of varying dimensions.
9.1.3Prior to conducting a test,adjust the vertical distance from the presser foot to the contact surface of the test specimen to25.462.5mm(1.0060.100in.),unless it is known that identical results are obtained with presser foot at a greater or lesser vertical distance from the test specimen contact surface, or if otherwise stipulated by the manufacturer.
9.1.4Place the specimen on the specimen support table,in
a manner that the contact point of the indentor is in accordance with Section6,unless it is known that identical results are obtained when measurements are made with the indentor at a lesser distance from the edge of the test specimen.
9.1.5Actuate the release lever(Fig.2)of the operating stand or activate the electromechanical device,allowing the durometer to descend at a controlled rate and apply the presser foot to the specimen in accordance with5.1.2.In the case of “specimen to indentor”type operating stands,operate the lever or other mechanism to apply the specimen to the indentor in a manner that assures parallel contact of the specimen to the durometer presser foot without shock and with just sufficient force to overcome the calibrated spring force as shown in Table 1.
9.1.6An operating stand that applies the mass at a con-trolled rate of descent,without shock is mandatory for Type M durometers.Hand-held application or the use of a Type1or Type2operating stand for the Type M durometer is not an acceptable practice,see5.1.2.4.
9.1.7For any material covered in1.1,once the presser foot is in contact with the specimen,for example,when the initial indentor travel has ceased,the maximum indicated reading shall be recorded.The time interval of1s,between initial indentor travel cessation and the recording of the indicated reading,shall be considered standard.Other time intervals, when agreed upon among laboratories or between supplier and user,may be used and reported accordingly.The indicated hardness reading may change with time.
9.1.7.1If the durometer is equipped with an electronic maximum indicator or timing device(refer to5.1.1.9)the indicated reading shall be recorded within160.3s of the cessation of indentor travel and reported(refer to10.2.9for reporting protocols),unless otherwise noted.
9.1.7.2If the durometer is equipped with an analog type maximum indicator(refer to5.1.1.10),the maximum indicated reading may be recorded and shall be reported(refer to10.2.9), unless otherwise noted.
9.1.7.3If the durometer is not equipped with the devices described in5.1.1.9or5.1.1.10,the indicated reading shall be recorded within1s as is possible and reported(refer to10.2.9), unless otherwise noted.
9.1.8Makefive determinations of hardness at different positions on the specimen at least6.0mm(0.24in.)apart,0.80 mm(0.030in.)apart for Type M;and calculate the arithmetic mean,or alternatively calculate the median.The means of calculating the determinations shall be reported according to 10.2.8
9.2Manual(Hand Held)Operation of Durometer:
9.2.1Care shall be exercised to minimize the exposure of the instrument to environmental conditions that are adverse to the performance of the instrument,or adversely affect test results.
9.2.2Place the specimen on aflat,hard,horizontal surface. Hold the durometer in a vertical position with the indentor tip at a distance from any edge of the specimen as described in Section6,unless it is known that identical results are obtained when measurements are made with the indentor at a lesser distance.
9.2.3Apply the presser foot to the specimen,maintaining it in a vertical position keeping the presser foot parallel to the specimen,with afirm smooth downward action that will avoid shock,rolling of the presser foot over the specimen,or the application of lateral force.Apply sufficient pressure to assure firm contact between the presser foot and the specimen.
9.2.4For any material covered in1.1,after the presser foot is in contact with the specimen,the indicated reading shall be recorded within160.1s,or after any period of time agreed upon among laboratories or between supplier and user.If the durometer is equipped with a maximum indicator,the maxi-mum indicated reading shall be recorded within160.1s of the cessation of initial indentor travel.The indicated hardness reading may change with time.
9.2.5Makefive determinations of hardness at different positions on the specimen at least6.0mm(0.24in.)apart and calculate the arithmetic mean,or alternatively calculate the median.The means of calculating the determinations shall be reported according to10.2.8.
9.3It is acknowledged that durometer readings below20or above90are not considered reliable.It is suggested that readings in these ranges not be recorded.
9.4Manual operation(handheld)of a durometer will cause variations in the results attained.Improved repeatability may be obtained by using a mass,securely affixed to the durometer and centered on the axis of the indentor.Recommended
masses --` , , ` ` ` , , , , ` ` ` ` -` -` , , ` , , ` , ` , , ` ---are1kg for Type A,B,E,and O durometers,5kg for Type C, D,and DO durometers,and400g for Type OO,OOO,and OOO-S durometers.The introduction of an additional mass on Type M durometers is not permitted.Further improvement may be achieved by the use of a durometer operating stand that controls the rate of descent of the durometer presser foot to the test specimen and incorporates the masses described above.
10.Report
10.1Instrument Calibration Report(Durometer or Operat-ing Stand):
10.1.1Date of calibration.
10.1.2Date of last calibration.
10.1.3Calibration due date(see Note2).
10.1.4Manufacturer,type,model,and serial number of the instrument,and a notation when a maximum indicator or timing device is present.
10.1.5Values obtained(pre-and post-calibration results), including a notation of the effect of a maximum indicator,if present.The method of reporting the calibrated value shall be by attaining the arithmetic mean of the determinations.
10.1.6Ambient temperature.
10.1.7Relative humidity.
10.1.8Technician identification.
10.1.9Applicable standards to which the instrument is calibrated.
10.1.10Calibrating instrument information to include type, serial number,manufacturer,date of last calibration,calibration due date(see Note2),and a statement of traceability of standards used to NIST or other acceptable organization.See 1.4.
10.2Hardness Measurement Report:
10.2.1Date of test.
10.2.2Relative humidity.
10.2.3Ambient temperature.
10.2.4Manufacturer,type,and serial number of the durom-eter or operating stand,or both,including a notation when a maximum indicator or timing device is present,date of last calibration,and calibration due date(see Note2).
N OTE2—The calibration interval(calibration due date)for a durometer is to be determined by the user,based upon frequency of use,severity of conditions,environmental factors,and other variables.
Periodic checking of the operation and state of durometer calibration using commercially available rubber test blocks(refer to7.8),specifically designed for this purpose,is recommended.
An instrument that has been exposed to severe shock,is visibly damaged,produces test determinations more than2points different from calibrated rubber test blocks or other reference standard,or is otherwise suspected of unreliability,should be removed from service and returned to a qualified calibration facility.
A calibration interval of one year is recommended for durometer test blocks and durometer instruments that are infrequently used,more often for others.
The calibration interval for instruments and peripheral devices em-ployed in the calibration of durometers is to be determined by the calibration service provider.It is recommended that the protocols outlined in ISO/IEC17025,as required by the manufacturer,and those to which the service is provided,be followed.
10.2.5Means of testing,whether manual(hand held),Type 1operating stand(specimen to indentor),Type2operating stand(indentor to specimen type),or Type3operating stand (electromechanical or hydraulically dampened).
10.2.6Description of test specimen,including thickness, number of pieces plied if less than the thickness indicated in Section6,including the vulcanization date.
10.2.7Complete identification of material tested.
10.2.8Hardness value obtained and method of calculation, either arithmetic mean or alternatively,the median.
TABLE2Type1Precision—Type M Durometer Method Material Within Laboratories Between Laboratories MEAN Sr A r B(r)C SR D R E(R)F 131.8 1.26 3.5811.24 3.7610.6333.41 240.8 1.14 3.237.90 2.477.0017.13 354.00.975 2.76 5.11 2.38 6.7312.46 462.80.782 2.21 3.52 2.24 6.3410.10 570.90.709 2.01 2.830.974 2.76 3. 680.6 1.686 4.77 5.92 1.61 4.56 5.65 787.7 1.15 3.25 3.71 2.637.458.50 832.40.947 2.688.26 3.10.2931.73 941.80.797 2.26 5.40 2.23 6.3115.11 1053.30.669 1. 3.55 2.29 6.4912.17 1163.20.485 1.37 2.17 2.19 6.209.80 1269.60.737 2.09 3.000.99 2.80 4.02 1378.30.784 2.22 2.84 1.04 2.94 3.75 1487.6 1.121 3.17 3.62 2.657.498.55 1534.10.85 2.407.05 1.84 5.2015.25 12.30.635 1.80 4.25 1.20 3.398.01 1754.60.56 1.59 2.90 2.15 6.0911.15 1862.9 1.12 3.17 5.04 1.47 4.16 6.61 1970.30.6 1.95 2.770.944 2.67 3.80 2081.70.483 1.37 1.67 1.10 3.10 3.80 2187.90.879 2.49 2.83 2.07 5.86 6.67 AVERAGE61.4
POOLED
VALUES
0.924 2.62 4.26 2.146 6.079.
A Sr=repeatability standard deviation,measurement units.
B r=repeatability=2.833Sr,measurement units.
C(r)=repeatability,relative,(that is,in percent).
D SR=reproducibility standard deviation,measurement units.
E R=reproducibility=2.833SR,measurement units.
F(R)=reproducibility,relative,(that is,in percent).
TABLE3Type1Precision—Type A Durometer Method Material
Average
Level
Within Laboratories Between Laboratories
Sr A r B(r)C SR D R E(R)F 151.40.6 1.83 3.56 1.56 4.418.59 265.30.878 2.48 3.81 2.21 6.069.27 368.00.433 1.23 1.80 2.28 6.459.49 Pooled61.60.677 1.92 3.11 2.018 5.729.28
A Sr=repeatability standard deviation,measurement units.
B r=repeatability=2.833Sr,measurement units.
C(r)=repeatability,relative,(that is,in percent).
D SR=reproducibility standard deviation,measurement units.
E R=reproducibility=2.833SR,measurement units.
F(R)=reproducibility,relative,(that is,in percent).
TABLE4Type1Precision—Type D Durometer Method Material
Average
Level
Within Laboratories Between Laboratories
Sr A r B(r)C SR D R E(R)F 142.60.3160.4 2.10 2.827.9818.7 254.50.791 2.24 4.11 3.5410.018.4 382.3 1.01 2.86 3.47 3.5410.012.2 Pooled59.80.762 2.16 3.61 3.329.4015.7
A Sr=repeatability standard deviation,measurement units.
B r=repeatability=2.833Sr,measurement units.
C(r)=repeatability,relative,(that is,in percent).
D SR=reproducibility standard deviation,measurement units.
E R=reproducibility=2.833SR,measurement units.
F(R)=reproducibility,relative,(that is,in
percent). --`,,```,,,,````-`-`,,`,,`,`,,`---
10.2.9Indentation hardness time interval at which determi-nation was made.Readings may be reported in the form:M/60/1where M is the type of durometer,60the reading,and 1the time in seconds that the presser foot is in contact with the specimen or from an electronic timing device.
11.Precision and Bias
11.1These precision and bias statements have been pre-pared in accordance with Practice D 4483.Refer to this Practice for terminology and other testing and statistical concepts.
11.2The Type 1precision for the Type M method was determined from an interlaboratory program with 21materials of varying hardness,with six participating laboratories.Tests were conducted on two separate days in each laboratory for the Type M testing program.All materials were supplied from a single source,being those commonly supplied as reference materials with the instruments from the manufacturer.
11.3The precision results in this precision and bias section give an estimate of the precision of this test method with the materials (rubbers)used in the particular interlaboratory pro-gram as described above.The precision parameters should not be used for acceptance or rejection testing,or both,of any group of materials without documentation that they are appli-cable to those particular materials and the specific testing protocols that include this test method.
11.4The Type 1precision for both Type A and D methods was determined from an interlaboratory program with 3materials of varying hardness,with six participating laborato-ries.Tests were conducted on two separate days in each laboratory for both A and D testing programs.All materials were supplied from a single source.
11.5A test result for hardness,for Types A,D,and M,was the median of five individual hardness readings on each day in each laboratory.
11.6Table 2shows the precision results for Type M method,4Table 3shows the precision results for Type A method,5and Table 4gives the precision results for Type D method.5
11.7Precision —The precision of this test method may be expressed in the format of the following statements which use as appropriate value r ,R ,(r),or (R),that is,that value to be used in decisions about test results (obtained with the test method).The appropriate value is that value of r or R associated with a mean level in Table 1closest to the mean level under consideration (at any given time,for any given material)in routine testing operations.
N OTE 3—A Type 1precision statement for Types E,OOO,OOO-S,and R have not yet been made available.
11.7.1Repeatability —The repeatability,r ,of these test methods has been established as the appropriate value tabu-lated in Tables 2-4.Two single test results,obtained under normal test method procedures,that differ by more than this tabulated r (for any given level)must be considered as derived from different or non-identical sample populations.
11.7.2Reproducibility —The reproducibility,R ,of these test methods has been established as the appropriate value tabu-lated in Tables 2-4.Two single test results obtained in two different laboratories,under normal test method procedures,that differ by more than the tabulated R (for any given level)must be considered to have come from different or non-identical sample populations.
11.7.3Repeatability and reproducibility are expressed as a percentage of the mean level,(r)and (R),and have equivalent application statements as above for r and R .For the (r)and (R)statements,the difference in the two single test results is expressed as a percentage of the arithmetic mean of the two test results.
11.8Bias —In test method terminology,bias is the differ-ence between an average test value and the reference (or true)test property value.Reference values do not exist for this test method since the value (of the test property)is exclusively defined by this test method.Bias,therefore cannot be deter-mined.12.Keywords
12.1durometer;durometer hardness;hardness;indentation hardness;micro durometer hardness
4
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D11-1091.5
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:
D11-1029.
--`,,```,,,,````-`-`,,`,,`,`,,`---
(Nonmandatory Information)
X1.DUROMETER SELECTION GUIDE X1.1The durometer selection guide is designed to assist in
the selection of the proper durometer type for various applica-
tions.
X1.2It is generally recognized that durometer hardness
determination below20and above90are unreliable.It is
recommended that the next lower or higher type(scale)be used
in these situations.
X1.3It is also recommended that,whenever possible,an
operating stand be employed in performing durometer hardness
tests.
X2.RELATED TEST METHODS2
C367Test Methods for Strength Properties of Prefabricated Architectural Acoustical Tile or Lay-In Ceiling Panels
C473Test Methods for Physical Testing of Gypsum Panel Products
C581Practice for Determining Chemical Resistance of Thermosetting Resins Used in Glass-Fiber-Reinforced Struc-tures Intended for Liquid Service
C661Test Method for Indentation Hardness of Elastomeric-Type Sealants by Means of a Durometer
C836Specification for High Solids Content,Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course
D461Test Methods for Felt
D531Test Method for Rubber Property—Pusey and Jones Indentation
D619Test Methods for Vulcanized Fibre Used for Electri-cal Insulation
D1037Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials
D1054Test Method for Rubber Property—Resilience Us-ing a Goodyear-Healey Rebound Pendulum
D1414Test Methods for Rubber O-Rings
D1474Test Methods for Indentation Hardness of Organic Coatings
D2134Test Method for Determining the Hardness of Or-ganic Coatings with a Sward-Type Hardness Rocker
D2287Specification for Nonrigid Vinyl Chloride Polymer and Copolymer Molding and Extrusion Compounds
D2583Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor
TABLE X1.1Durometer Selection:Typical Uses
Type (Scale)Typical Examples of Materials Tested
Durometer Hardness
(Typical Uses)
A Soft vulcanized rubber,natural rubber,nitriles,thermoplastic
elastomers,flexible polyacrylics and thermosets,wax,felt,and
leathers
20–90A
B Moderately hard rubber,thermoplastic elastomers,paper products,
andfibrous materials Above90A Below20D
C Medium-hard rubber,thermoplastic elastomers,medium-hard
plastics,and thermoplastics Above90B Below20D
D Hard rubber,thermoplastic elastomers,harder plastics,and rigid
thermoplastics
Above90A
DO Moderately hard rubber,thermoplastic elastomers,and very dense textile windings Above90C Below20D
M Thin,irregularly shaped rubber,thermoplastic elastomer,and plastic
specimens
20–85A
O Soft rubber,thermoplastic elastomers,very soft plastics and
thermoplastics,medium-density textile windings
Below20DO
OO Extremely soft rubber,thermoplastic elastomers,sponge,extremely
soft plastics and thermoplastics,foams,low-density textile windings,
human and animal tissue
Below20O
CF Composite foam materials,such as amusement ride safety cushions,vehicle seats,dashboards,headrests,armrests,and door panels
See Test Method F
1957--` , , ` ` ` , , , , ` ` ` ` -` -` , , ` , , ` , ` , , ` ---
D 2632Test Method for Rubber Property—Resilience by Vertical Rebound
D 42Test Method for Elastomer Compatibility of Lubri-cating Greases and Fluids
D 5672Test Method for Flexible Cellular Materials Mea-surement of Indentation Force Deflection Using a 25-mm (1-in.)Deflection Technique
D 6546Test Methods for and Suggested Limits for Deter-mining Compatibility of Elastomer Seals for Industrial Hy-draulic Fluid Applications
F 1151Test Method for Determining Variations in Hardness of Film Ribbon Pancakes
N OTE X2.1—The hardness testing of other nonmetallic materials may be under the jurisdiction of one or more ASTM committees;the respective committee should be contacted for specific information.
ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.Users of this standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,are entirely their own responsibility.
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This standard is copyrighted by ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Individual reprints (single or multiple copies)of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585(phone),610-832-9555(fax),or service@astm.org (e-mail);or through the ASTM website
(www.astm.org).
D 2240–05
13
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