ASTM_D_3629_-_99.pdf

Designation:D 3629 99Standard Test Method forRubber PropertyCut Growth Resistance1This standard is issued under the fixed designation D 3629;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a procedure for measuring thecut growth resistance of precut vulcanizate specimens,undercontrolled conditions of environment,temperature,frequency,and severity.1.2 The values stated in SI units are to be regarded as thestandard.1.3 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 3185 Test Methods for RubberEvaluation of SBR(Styrene-Butadiene Rubber)Including Mixtures With Oil2D 3767 Practice for RubberMeasurement of Dimensions2D 4483 Practice for Determining Precision for Test MethodStandards in the Rubber and Carbon Black Industries23.Summary of Test Method3.1 T-shaped,grooved specimens are pierced,mountedcircumferentially along the periphery of rotating disks and bentor flexed as they strike against freely rotating deflector bars ata controlled frequency.The growth of the cut is measured andexpressed as the number of kilocycles required for a 5-or10-fold increase in cut length.4.Significance and Use4.1 Fatigue life tests on rubber show notoriously highvariance.Therefore,they are not well-suited for specificationsor regulatory statutes.This test method,however,has beenshown to be useful for development studies of polymer,compounding variables,and test temperature on cut growthresistance,and it has also been shown in numerous instances torelate qualitatively to tire cut growth.5.Apparatus5.1 Flex Tester The tester is shown in Fig.1 and Fig.2.The entire mechanism is enclosed in a temperature controlledtest chamber capable of maintaining temperatures between 25and 125C(77 and 257F).Slotted disks,with spring-loaded1This test method is under the jurisdiction ofASTM Committee D-11 on Rubberand is the direct responsibility of Subcommittee D11.15 on Degradation Tests.Current edition approved Nov.10,1999.Published December 1999.Originallypublished as D 3629 78.Last previous edition D 362994.2Annual Book of ASTM Standards,Vol 09.01.FIG.1 TEXUST Flex Tester(The TEXUS Flex Tester is atrademark of Texas-U.S.Chemical Company)FIG.2 Rotating Disks1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.specimen-mounting locations,are connected to a variable-speed drive that is controllable between 10.5 and 89.0 rad/s(100 and 800 rpm).Test severity can be varied further byadjusting the flexing angle,which is accomplished by varyingthe gap width between the revolving disks and the twodeflector bars using the micrometer screws attached to thedeflector bars.NOTE1There are two flexes for each revolution of the disk.There-fore,the total number of flexes or cycles will be twice the machinerevolutions as registered on the counter.5.2 MoldA mold is required,preferably of a multiple-cavity design and having adequate overflow cavities(Fig.3).5.3 Thickness GageThe gage used for measuring thethickness of the specimens shall be in accordance with thespecifications in Practice D 3767.5.4 Piercing InstrumentA precision piercing instrument,shown in Fig.4 and Fig.5,is used to initiate a 2.0-mm(0.08-in.)cut in the exact center of the groove of the specimen.The instrument consists of a holder that keeps the specimenprecisely in the desired position for piercing and a spring-mounted plunger with a sharp 2.0-mm wide flat blade at theend.6.Preparation of Specimen6.1 Sheet the compound to 5.8 6 0.3 mm(0.23 6 0.01 in.),and mark the direction of the mill grain.Cut a rectangular piece45 6 0.3 mm(1.75 6 0.01 in.)long by 25.4 6 0.3 mm(0.560.01 in.)wide from the sheeted stock with the mill grainparallel to the width.Then cut 1.3 6 0.3 mm(0.5 6 0.01 in.)off from the length and load a“T”shaped preform into themold and cure.The grain orientation of the final specimenshould be parallel to the molded groove.NOTE2Using typical passenger tire tread formulations,a samplemass of 8 to 9 g is obtained.Recipe 1A of Methods D 3185 can be usedfor a typical tire tread compound.Care should be taken in the preparationof preforms,since excess compound prevents proper mold closure andresults in cured specimens exceeding the dimensions shown in Fig.3.6.2 Specimens shall have smooth surfaces and be free ofsurface irregularities and defects in the groove and adjacentarea.Measure the thickness in the area adjacent to the grooves.The thickness shall be 4.75 6 0.1 mm(0.188 6 0.005 in.).6.3 Deflash without rounding edges