ASTM_D_3194_-_04_2009.pdf

Designation:D319404(Reapproved 2009)Standard Test Method forRubber From Natural SourcesPlasticity Retention Index(PRI)1This standard is issued under the fixed designation D3194;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 reapproval.1.Scope1.1 This test method gives an indication of the oxidationresistance of raw natural rubber at a specified temperature.Thisresistance is indicated by the Plasticity Retention Index(PRI),a ratio expressed as a percentage of the aged plasticity to theoriginal plasticity determined by means of a parallel plateplastometer.A low PRI value indicates a poor resistance tooxidation.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:2D1485 Practice for Rubber from Natural SourcesSampling and Sample PreparationD3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing(Withdrawn1987)3D3182 Practice for RubberMaterials,Equipment,and Pro-cedures for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsE145 Specification for Gravity-Convection and Forced-Ventilation Ovens3.Summary of Test Method3.1 A homogenized sample of raw rubber is prepared by aspecified procedure to create a sheet from which six cylindricalpellets of specified dimensions are cut,three to be tested inoriginal condition and three to be aged under specified condi-tions.3.2 Plasticity on both the original and aged samples ismeasured as the median final thickness of each set of samplesafter a compressive force of 100 N 6 1 N is applied for aspecified time.The PRI is the ratio expressed as a percentageof the aged to the original plasticity.4.Significance and Use4.1 This test method may be used to evaluate the heat and/oroxidation stability(aging)of raw rubber under controlledconditions.High original and aged plasticity values usuallycorrespond to good aging properties.The ratio of the aged tooriginal plasticity values expressed as a percentage,the PRI,isused as an indication of aging.5.Apparatus5.1 Parallel Plate Plastometer4,with a 10 mm diameterplaten.The platen temperature shall be 100 6 1C and theplastometer shall have a timer unit capable of giving a 15 6 1s initial conditioning period during which the sample shall becompressed to 1 6 0.01 mm and a test period of 15 6 1 s undera compression force of 100 N 61 N.The plastometer shall alsohave a measuring device gauge reading to 0.01 mm.Calibra-tion procedures recommended by the manufacturer of theplastometer should be followed.5.2 Punch,that will die out cylindrical specimens approxi-mately 13 mm in diameter from a prepared sheet of rubber.5.3 Circulating Air Oven,specified in Specification E145,Type IIA.The oven must be capable of maintaining 140 60.5C.5.4 Dishes or Tray,aluminum,for test specimens,light-weight aluminum dishes approximately 38 mm(1.5 in.)indiameter or an aluminum tray approximately 150 by 150 mm(7 by 7 in.)for aging specimens in the oven.1This method is under the jurisdiction of ASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.22 on Natural Rubber.Current edition approved Sept.1,2009.Published December 2009.Originallyapproved in 1973.Last previous edition approved in 2004 as D3194 04.DOI:10.1520/D3194-04R09.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4The sole source of supply of the Wallace Rapid Plastimeter known to thecommittee at this time is Leverett A.Anderson Co.,P.O.Box 5400,Akron,OH44313.If you are aware of alternative suppliers,please provide this information toASTM International Headquarters.Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.5 Tissue paper or cigarette paper,approximately 40 by 40mm(1.5 by 1.5 in.).This paper shall be bleached,unglazedacid-free tissue paper,of approximately 1.7 g/m2.6.Precautions6.1 The initial thickness of the prepared sheet can affect thefinal thickness after testing.Ascertain the required mill openingby preliminary trial;it will vary with the rubber and the mill.6.2 The temperature and speed of the testi