ASTM D575 – 91 R96

Designation: D 575 – 91 (Reapproved 1996) Standard Test Methods for Rubber Properties in Compression1 This standard is issued under the fixed designation D 575; 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. 1. Scope 1.1 These test methods cover two test procedures for deter- mining the compression-deflection characteristics of rubber compounds other than those usually classified as hard rubber and sponge rubber. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This 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 2.1 ASTM Standards: D 3183 Practice for Rubber—Preparation of Pieces for Test Purposes from Products2 D 3767 Practice for Rubber—Measurement of Dimen- sions2 D 4483 Practice for Determining Precision for Test Method Standards in the Rubber and Carbon Black Industries2 E 4 Practices for Force Verification of Testing Machines3 3. Summary of Test Methods 3.1 These tests constitute one kind of compression stiffness measurement. Deflection is the change in thickness of the specimen upon application of a compressive force. The two different procedures are as follows: 3.1.1 Test Method A—Compression Test of Specified Deflection—A compression test in which the force required to cause a specified deflection is determined. 3.1.2 Test Method B—Compression Test at Specified Force—A compression test in which the specified mass or compressive force is placed on the specimen and the resulting deflection is measured and recorded. 4. Significance and Use 4.1 These test methods are useful in comparing stiffness of rubber materials in compression. They can be used by rubber technologists to aid in development of materials for compres- sive applications. 5. Apparatus 5.1 Compression Testing Machine—A compression testing machine conforming to the requirements of Practices E 4, and having a rate of head travel of 12 6 3 mm/m (0.5 6 0.1 in./min), may be used for either type of test. Any other type machine that will meet these requirements may be used. For example, a platform scale equipped with a yoke over the platform and a hand-operated screw to apply the force will serve if it will conform to the requirements prescribed for accuracy and rate of travel. Compression tests at specified forces may be performed on any machine that applies minor and major forces gently, without impact, or by placing speci- fied masses gently on the specimen. The machine shall be equipped to permit measurement of the deflection caused by the increase from minor force to major force. 5.2 Deflection Gage—The deflection shall be read on a gage of dial type graduated in hundredths of millimetres (or thou- sands of an inch). 5.3 Micrometer—The thickness of the specimen shall be measured in accordance with Test Method A of Practice D 3767. 6. Test Specimens 6.1 The test may be performed either on rubber products or on standard test specimens, as specified. NOTE 1—Comparable results are obtained only when tests are made on specimens of exactly the same size and shape, tested to the same percentage deflection, or tested under the same force. 6.2 Standard test specimens shall be 28.6 6 0.1 mm (1.129 6 0.005 in.) in diameter (650 mm2(1.000 in.2) in area) and 12.5 6 0.5 mm (0.49 6 0.02 in.) in thickness, from which all molded surface layers have been removed. 7. Preparation of Specimens 7.1 The standard test specimens may be prepared as fol- lows: A slab approximately 13 mm (0.51 in.) in thickness may be cut from a product or may be molded from the same compound used in the preparation of the product and ground on both sides to obtain smooth parallel surfaces and the standard thickness of 12.5 6 0.5 mm (0.49 6 0.02 in.). The grinding shall be carried out as prescribed in Section 5 of Practice 1 These test methods are under the jurisdiction of ASTM Committee D-11 on Rubber and are the direct responsibility of Subcommittee D11.10 on Physical Testing. Current edition approved March 15, 1991. Published May 1991. Originally issued in 1940. Last previous edition D 575 – 88. 2 Annual Book of ASTM Standards, Vol 09.01. 3 Annual Book of ASTM Standards, Vol 03.01. 1 AMERICAN SOCIETY FOR TESTING AND MATERIALS 100 Barr Harbor Dr., West Conshohocken, PA 19428 Reprinted from the Annual Book of ASTM Standards. Copyright ASTM NOTICE:¬This¬standard¬has¬either¬been¬superseded¬and¬replaced¬by¬a¬new¬version¬or discontinued.¬Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information. D 3183 and shall be done without overheating the rubber. The specimens may then be cut from the slabs by means of a suitable rotating hollow cutting tool similar to that illustrated in Fig. 1. In cutting the specimen, the die shall be suitably rotated in a drill press or similar device and lubricated with soapy water so that a smooth-cut surface having square edges is obtained. The cutting pressure shall be kept sufficiently low to avoid “cupping’’ of the cut surface. NOTE 2—The cutting tool is larger in diameter than the specimen to allow for cutting pressure. 7.2 When rubber products are subjected to these tests, the surfaces that will contact the platens of the testing machine shall be cleaned of any dust, bloom, grease, or other foreign material. Grinding is not required because tests on products are intended to be nondestructive. 8. Test Conditions 8.1 The temperature of the testing room shall be maintained at 23 6 2°C (73.4 6 3.6°F). The specimens to be tested shall be kept in this room for at least 3 h prior to the time of testing. Specimens that have compression properties affected by atmo- spheric moisture shall be conditioned in an atmosphere con- trolled to 50 6 6 % relative humidity for at least 24 h. Test Method A—Compression Test at Specified Deflection 9. Nature of Test 9.1 In this test method the compressive forces are applied and removed in three successive cycles. The first two cycles are for the purpose of conditioning the specimen, and the readings are taken during the third application of force. 10. Procedure 10.1 After measuring the thickness of the test specimen, place the specimen between the platens of the testing machine. Place sheets of sandpaper4 between the rubber surfaces and the testing machine platens. The sandpaper resists lateral slippage of the rubber at the contact surfaces and should be slightly larger than the specimen. Omit the sandpaper when the surface of the specimen is bonded to metal. 10.2 Apply the force to produce a deflection rate of 12 6 3 mm/min (0.5 6 0.1 in./min) until the specified deflection is reached, after which release the force immediately at the same rate. Repeat this loading cycle a second time. Apply the force a third time until the specified deflection is again reached. Read and record the force required. 10.3 If desired, the machine may be stopped at intervals of 5 % deflection during the third application and the force recorded for each deflection so that a stress-strain curve may be drawn. 10.4 Deflection percentage shall be based on the thickness of the specimen prior to the first force application. 10.5 Report the median of values taken from three speci- mens. Test Method B—Compression Test at Specified Force 11. Nature of Test 11.1 This test is intended for rapid testing with a constant force type of machine, although it can be performed on the other machines described in 5.1. Because speed with reason- able accuracy is desired, a single force application cycle is used. 12. Procedure 12.1 Apply a specified minor mass or force for a period long enough to adjust the deflection gage, after which apply the major force for 3 s. Read the deflection on the dial gage at the end of the 3-s period. The reading shall not include any deflection caused by the minor force. Calculate the percent deflection on the basis of the original thickness of the speci- men. 12.2 Report the median of values taken from three speci- mens. 13. Report 13.1 Report the following information: 13.1.1 Deflection expressed as a percentage of the original thickness of the specimen, 13.1.2 Force in kilopascals or pounds-force per square inch, based on original cross section, 13.1.3 Description of sample and type of test specimen, including dimensions, 13.1.4 Description of test method and apparatus, and 13.1.5 Date of test. 14. Precision and Bias 5 14.1 This precision and bias section has been prepared in accordance with Practice D 4483. Refer to Practice D 4483 for terminology and other statistical calculation details. 14.2 The 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 in this section. The precision parameters should not be used for acceptance/rejection testing of any group of materials without documentation that they are appli- cable to those particular materials and the specific testing protocols that are included in this test method. 4 400 Grit waterproof sandpaper has been found satisfactory. 5 The full details and test results of the interlaboratory test program used for this precision section are contained in RR: D11-1058, available from ASTM Headquar- ters. FIG. 1 Cutting Tool D 575 2 14.3 Two separate precision programs were conducted for this test method, one in 1983 and a second in 1989. 14.3.1 AType 1 (interlaboratory) precision was evaluated in both programs. Both repeatability and reproducibility are short term; a period of a few days separates replicate test results. A test result is the value, as specified by this test method, obtained on a single determination(s) or measurement(s) of the property or parameter in question. The third deflection cycle is used for the measurement. For the 1983 program, three different materials were used; these were tested in three laboratories on two different days. 14.4 For the 1989 program seven materials were tested in nine laboratories on two separate days. 14.4.1 The results of the precision calculations for repeat- ability and reproducibility are given in Tables 1-4, in ascending order of material average or level, for each of the materials evaluated. Table 1 and Table 2 are for the 1983 program (No. 1), and Table 3 and Table 4 are for the 1989 program (No. 2). 14.5 The precision of this test method may be expressed in the format of the following statements that use an “appropriate value” of r, R, (r), or (R), to be used in decisions about test results. The appropriate value is that value of r or R associated with a mean level in the precision tables closest to the mean level under consideration at any given time for any given material in routine testing operations. 14.6 Repeatability—The repeatability, r, of this test method has been established as the appropriate value tabulated in the precision tables. 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. 14.7 Reproducibility—The reproducibility, R, of this test method has been established as the appropriate value tabulated in precision tables. 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. 14.8 Repeatability and reproducibility expressed as a per- centage of the mean level, (r) and (R), 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. 14.9 The user of this test method should give greater emphasis to Program 2 (1989) precision results. This 1989 program was substantially more comprehensive and the results are more typical of the current status of this test method. 14.10 Bias—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. 15. Keywords 15.1 rubber in compression TABLE 1 Program 1, 1983 Precision,A Type 1 Precision—Method A (kPa)B NOTE 1—Sr 5 repeatability standard deviation, in measurement units, r 5 repeatability, in measurement units, (r) 5 repeatability, (relative) percent, SR 5 reproducibility standard deviation, in measurement units, R 5 reproducibility, in measurement units, and (R) 5 reproducibility (relative) percent. Material (kPa) Average Level Within Laboratories Between Laboratories Sr r (r) SR R (R) No. 3 Cl-Butyl 1106 28.2 79.8 7.2 40.4 114 10.3 No. 2 EPDM 1731 92.8 263 15.2 69.3 196 11.3 No. 1 SBR 1746 41.5 117 6.7 77.3 219 12.5 Pooled (average) values 1528 60.9 172 11.3 64.3 182 11.9 AThree laboratories participating. BkPa 5 psi 3 6.89. TABLE 2 Program 1, 1983 Precision,A Type 1 Precision—Method B (% DEF) NOTE 1—Sr 5 repeatability standard deviation, in measurement units, r 5 repeatability, in measurement units, (r)5 repeatability, (relative) percent, SR 5 reproducibility standard deviation, in measurement units, R 5 reproducibility, in measurement units, and (R) 5 reproducibility (relative) percent. Material AverageLevel,% Within Laboratories Between Laboratories Sr r (r) SR R (R) No. 1 SBR 36.0 1.11 3.14 8.7 1.38 3.91 10.9 No. 2 EPDM 37.1 1.16 3.28 8.9 2.57 7.27 19.7 No. 3 Cl-Butyl 43.7 0.78 2.20 5.1 2.03 5.74 13.2 Pooled (average) values 38.9 1.03 2.91 7.5 2.05 5.80 14.9 AThree laboratories participating. TABLE 3 Program 2, 1989 Precision,A Type 1 Precision—Method A (kPa)B NOTE 1—Sr 5 repeatability standard deviation, in measurement units, r 5 repeatability, in measurement units, (r) 5 repeatability, (relative) percent, SR 5 reproducibility standard deviation, in measurement units, R 5 reproducibility, in measurement units, and (R) 5 reproducibility (relative) percent. Material Average Level, kPa Within Laboratories Between Laboratories Sr r (r) SR R (R) NR/RSS 836 20.8 58.9 7.0 74.4 211 25.2 CR 1012 14.8 41.9 4.1 72.7 206 20.3 SBR 1528 18.5 52.4 3.4 59.1 167 11.0 IIR 1564 18.8 53.2 3.4 120 340 21.7 IR 1694 40.4 114 6.8 79.2 224 13.2 EPDM 2218 45.1 128 5.8 179 507 22.8 SIR 20 2591 62.0 175 6.8 206 583 22.5 Pooled (average) values 1636 36.2 102 6.3 118.5 335 20.5 ANine laboratories participating. BkPa 5 psi 3 6.89. D 575 3 The American Society for Testing and Materials 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. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, 100 Barr Harbor Drive, West Conshohocken, PA 19428. TABLE 4 Program 2, 1989 Precision,A Type 1 Precision—Method B NOTE 1—Sr 5 repeatability standard deviation, in measurement units, r 5 repeatability, in measurement units, (r) 5 repeatability, (relative) percent, SR 5 reproducibility standard deviation, in measurement units, R 5 reproducibility, in measurement units, and (R) 5 reproducibility (relative) percent. Material Average Level, % Within Laboratories Between Laboratories Sr r (r) SR R (R) SIR 20 6.89 0.207 0.59 8.5 0.597 1.69 24.5 EPDM 8.90 0.246 0.70 7.8 0.658 1.86 20.9 IIR 9.42 0.252 0.71 7.6 1.50 4.24 45.0 IR 10.7 0.218 0.62 5.8 0.711 2.01 18.8 SBR 11.6 0.237 0.67 5.8 1.62 4.59 39.4 CR 17.3 0.433 1.23 7.1 1.35 3.83 22.2 NR/RSS 20.6 0.561 1.59 7.7 1.66 4.71 22.8 Pooled (average) values 12.4 0.334 0.94 7.6 1.27 3.60 29.1 ANine laboratories participating. 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