Standard Test Methods for Rubber …

1 Designation: D 395 03 (Reapproved 2008) Standard Test Methods forRubber property compression set1 This Standard is issued under the fixed designation D 395; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon ( ) indicates an editorial change since the last revision or Standard has been approved for use by agencies of the Department of These test Methods cover the testing of Rubber intendedfor use in applications in which the Rubber will be subjected tocompressive stresses in air or liquid media.

2 They are applicableparticularly to the Rubber used in machinery mountings, vibra-tion dampers, and seals. Two test Methods are covered asfollows:Test MethodSectionA compression Set Under Constant Force in Air7 10B compression Set Under Constant Deflection in Air11 The choice of test method is optional, but considerationshould be given to the nature of the service for whichcorrelation of test results may be sought. Unless otherwisestated in a detailed specification, Test Method B shall be Test Method B is not suitable for vulcanizates harderthan 90 The values stated in SI units are to be regarded as Standard does not purport to address all of thesafety concerns, if any, associated with its use.

3 It is theresponsibility of the user of this Standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to Referenced standards :2D 1349 Practice for Rubber Standard Temperatures forTestingD 3182 Practice for Rubber Materials, Equipment, andProcedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized SheetsD 3183 Practice for Rubber Preparation of Product Piecesfor Test Purposes from ProductsD 3767 Practice for Rubber Measurement of DimensionsD 4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesE 145 Specification for Gravity-Convection and Forced-Ventilation Ovens3.

4 Summary of Test A test specimen is compressed to either a deflection orby a specified force and maintained under this condition for aspecified time and at a specified The residual deformation of a test specimen is measured30 min after removal from a suitable compression device inwhich the specimen had been subjected for a definite time tocompressive deformation under specified After the measurement of the residual deformation, thecompression set, as specified in the appropriate test method, iscalculated according to Eq 1 and Eq Significance and compression set tests are intended to measure the abilityof Rubber compounds to retain elastic properties after pro-longed action of compressive stresses.

5 The actual stressingservice may involve the maintenance of a definite deflection,the constant application of a known force, or the rapidlyrepeated deformation and recovery resulting from intermittentcompressive forces. Though the latter dynamic stressing, likethe others, produces compression set, its effects as a whole aresimulated more closely by compression flexing or hysteresistests. Therefore, compression set tests are considered to bemainly applicable to service conditions involving staticstresses. tests are frequently conducted at elevated Test Specimens from each sample may be tested in duplicate(Option 1) or triplicate (Option 2). The compression set of thesample in Option 1 shall be the average of the two specimensexpressed as a percentage.

6 The compression set of the samplein Option 2 shall be the median (middle most value) of thethree specimens expressed as a The Standard test specimen shall be a cylindrical diskcut from a laboratory prepared test Methods are under the jurisdiction of ASTM Committee D11 onRubber and are the direct responsibility of Subcommittee on edition approved May 1, 2008. Published June 2008. Originallyapproved in 1934. Last previous edition approved in 2003 as D 395 referenced ASTM standards , visit the ASTM website, , orcontact ASTM Customer Service at ForAnnual Book of ASTMS tandardsvolume information, refer to the Standard s Document Summary page onthe ASTM ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United The dimensions of the Standard specimens shall be:Type1A2 BThickness, mm (in.)

7 ( ) ( )Diameter, mm (in.) ( ) ( )AType 1 specimen is used in Test Methods A and 2 specimen is used in Test Method When cutting the Standard specimen, the circular diehaving the required inside dimensions specified rotated in a drill press or similar device and lubricated bymeans of a soap solution. A minimum distance of 13 mm ( ) shall be maintained between the cutting edge of the die andthe edge of the slab. The cutting pressure shall be as light aspossible to minimize cupping of the cut edges. The dies shallbe maintained carefully so that the cutting edges are sharp andfree of An optional method of preparing the Standard specimenmay be the direct molding of a circular disk having thedimensions required for the test method used and specified It should be recognized that an equal time and temperature, ifused for both the slab and molded specimen, will not produce anequivalent state of cure in the two types of specimen.

8 A higher degree ofcure will be obtained in the molded specimen. Adjustments, preferably inthe time of cure, must be taken into consideration if comparisons betweenthe specimens prepared by different Methods are to be considered It is suggested, for the purpose of uniformity and closertolerances in the molded specimen, that the dimensions of the mold bespecified and shrinkage compensated for therein. A two-plate mold with acavity mm ( in.) in thickness and ( in.) in diameter, with overflow grooves, will provideType 1 specimens for Test Method A and Test Method B. A similar moldbut having a cavity mm ( in.) in thickness mm ( in.) in diameter will provide Type 2specimens for Test Method When the Standard test specimen is to be replaced by aspecimen taken from a vulcanized Rubber part of greaterthickness than the one indicated , the sample thicknessshall be reduced first by cutting transversely with a sharp knifeand then followed by buffing to the required thickness inaccordance with PracticeD An alternative method of preparing specimens is byplying up cylindrical disks cut from a Standard sheet preparedin accordance with PracticeD 3182using the specimen sizesspecified cutting as described.

9 Or where adrill press is not available cutting the specimens with a singlestroke from a cutting The disks shall be plied, without cementing, to thethickness required. Such plies shall be smooth, flat, of uniformthickness, and shall not exceed seven in number for Type 1specimens and four in number for Type 2 Care shall be taken during handling and placing of theplied test specimen in the test fixture by keeping the circularfaces parallel and at right angles to the axis of the The results obtained on plied specimens may bedifferent from those obtained using solid specimens and theresults may be variable, particularly if air is trapped The results obtained on the specimens prepared by oneof the Methods may be compared only to those prepared by thesame For routine or product specification testing.

10 It is some-times more convenient to prepare specimens of a different sizeor shape, or both. When such specimens are used, the resultsshould be compared only with those obtained from specimensof similar size and shape and not with those obtained withstandard specimen. For such cases, the product specificationshould define the specimen as to the size and shape. If suitablespecimens cannot be prepared from the product, the testmethod and allowable limits must be agreed upon between theproducer and the Store all vulcanized test specimens or product samplesto be tested at least 24 h but not more than 60 days. When thedate of vulcanization is not known, make tests within 60 daysafter delivery by the producer of the article represented by Allow buffed specimens to rest at least 30 min beforespecimens are cut for Condition all specimens before testing for a minimum of3hat2362 C ( F).