ASTM_D_3157_-_05_2020.pdf

Designation:D315705(Reapproved 2020)Standard Test Method forRubber from Natural SourcesColor1This standard is issued under the fixed designation D3157;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 covers a method of classifying thecolor of raw rubber according to a standard color scale.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D926 Test Method for Rubber PropertyPlasticity andRecovery(Parallel Plate Method)D1485 Practice for Rubber from Natural SourcesSampling and Sample PreparationD3182 Practice for RubberMaterials,Equipment,and Pro-cedures for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsD3767 Practice for RubberMeasurement of Dimensions3.Summary of Test Method3.1 The raw rubber is prepared in the form of a molded diskof specified thickness,and the color of this disk is comparedand matched as closely as possible with that of colored glassdisks referred to as standard glasses.The standard glasses usedare calibrated according to the intensity of their amber color.Occasionally the color of the rubber cannot be matched due tothe presence of strong yellow,green,or gray tints.Colormatching is carried out under diffuse daylight illuminationagainst a matt white background,preferably by use of acomparator that suitably locates and shrouds the test specimenand standard glass.The standard glasses used are calibratedaccording to the intensity of their color to provide a color indexscale in which higher index values correspond to deeper color.4.Significance and Use4.1 Color of material rubber is of importance in compoundswhere product color is determined by the color of the rawrubber.5.Apparatus5.1 Laboratory Mill,as described in Practice D3182.5.2 Hydraulic Press,capable of giving a molding pressureof not less than 3.5 MPa(500 psi)over the platen surface andplaten temperatures of 150 6 3C(302 6 5F).5.3 Mold,stainless steel or aluminum,1.60 6 0.05 mm(0.063 6 0.002 in.)thick having holes approximately 14 mm(0.55 in.)in diameter in accordance with Fig.1.5.4 Mold Plates,two,of similar material,1.60 6 0.05 mm(0.063 6 0.002 in.)in thickness.5.5 Comparator or Standard Glass Disks3Standard col-ored glasses with color index scale:1 to 5 in half-integral stepsand 5 to 16 in integral steps.5.6 Test Specimen Cutting Die,as described in Test MethodD926.5.7 Thickness Gage,capable of measuring the test specimento the nearest 0.02 mm(0.001 in.)in accordance with PracticeD3767,Procedure A1.1This 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 June 1,2020.Published July 2020.Originally approvedin 1973.Last previous edition approved in 2015 as D3157 05(2015).DOI:10.1520/D3157-05R20.2For 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.3Lovibond Comparator disks 4/19A for 1 to 5 units and 4/19B for 5 to 16 unitshave been found to be satisfactory.The sole source of supply of the LovibondComparator disks known to the committee at this time is Wilkens Anderson Co.(WACO),4525 W.Division Street,Chicago,Illinois 60651,.Ifyou are aware of alternative suppliers,please provide this information to ASTMInternational Headquarters.Your comments will receive careful consideration at ameeting 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 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.15.8 Polyester or Cellulose Film,transparent of 0.02