Designation: D3194 − 17Standard Test Method forRubber From Natural Sources—Plasticity Retention Index(PRI) 1This standard is issued under the f i xed 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 specif i ed 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 Sources—Sampling and Sample PreparationD3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing (Withdrawn1987) 3D3182 Practice for Rubber—Materials, Equipment, and Pro-cedures for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsE145 Specif i cation for Gravity-Convection and Forced-Ventilation Ovens3. Summary of Test Method3.1 A homogenized sample of raw rubber is prepared by aspecif i ed procedure to create a sheet from which six cylindricalpellets of specif i ed dimensions are cut, three to be tested inoriginal condition and three to be aged under specif i ed condi-tions.3.2 Plasticity on both the original and aged samples ismeasured as the median f i nal thickness of each set of samplesafter a compressive force of 100 N 6 1 N is applied for aspecif i ed time. The PRI is the ratio expressed as a percentageof the aged to the original plasticity.4. Signif i cance 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 Plastometer 4 , with a 10 mm diameterplaten. The platen temperature shall be 100 6 1°C 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, specif i ed in Specif i cation E145,Type IIA. The oven must be capable of maintaining 140 60.5°C.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.1 This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materials and is the direct responsibility of Subcommittee D11.22on Natural Rubber.Current edition approved Jan. 1, 2017. Published January 2017. Originallyapproved in 1973. Last previous edition approved in 2009 as D3194 – 04 (2009).DOI: 10.1520/D3194-17.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 The last approved version of this historical standard is referenced onwww.astm.org.4 The 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, 1 which you may attend.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1 Copyright by ASTM Int'l (all rights reserved); Sat Sep 30 12:39:18 EDT 2017Downloaded/printed byUniversity of Edinburgh (University of Edinburgh) pursuant to License Agreement. No further reproductions authorized.
