1、Designation: D3157 05 (Reapproved 2015)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
2、 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
3、 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 and health
4、 practices and determine the applica-bility of regulatory limitations prior to use.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
5、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 dis
6、k 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,
7、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
8、 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 Hyd
9、raulic 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 accordan
10、ce 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
11、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 A1.5.8 Polyester or Cellulose Film, transparent of 0.025-mm(0.001-in.) thickness.6. Sampling6.1 Sampling shall be carried out in accordance with Te
12、stMethods D1485.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.22 on Natural Rubber.Current edition approved Aug. 1, 2015. Published September 2015. Originallyapproved in 1973. Last previous edition approved in 2010 as
13、D3157 05 (2010)1.DOI: 10.1520/D3157-05R15.2For 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 Comparato
14、r 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 alternativ
15、e 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
16、. United States17. Test Specimen and Sample7.1 Homogenize the piece to be tested in accordance withTest Methods D1485, omitting the weighing procedure unlessthat is required for other tests.7.2 Take a test portion of about 30 g from the homogenizedpiece and pass not more than three times (doubling t
17、he sheetbetween passes) between the mill rolls at room temperaturewith the nip adjusted so that the final sheet thickness is 1.6 to1.8 mm (0.06 to 0.07 in.). Immediately double the sheet, whichshould be uniform in texture and free of holes, and press thetwo halves lightly together by hand, avoiding
18、the formation ofair bubbles. From the sheet, which is 3.2 to 3.6 mm (0.10 to0.15 in.) thick, punch two pellets (each weighing about 0.3 g)and laminate together by lightly pressing with the fingers. Pressthe rubber specimen in the mold between sheets of polyester(or cellophane) using mold plates at n
19、ot less than 3.5 MPa (500psi) pressure on the mold surface for 5 min at 150C (302F).The molded test piece should be 1.4 to 1.8 mm (0.05 to 0.07in.) thick. The sample should be smooth, free of air bubbles,mold lubricant, rust, grease, soot, or other contaminants and thetransparent polyester sheet lef
20、t in place.8. Procedure8.1 Compare the test specimen with the standard glasses.Take its color index as that of the glass giving the closest colormatch. Color matching should be carried out under diffusedaylight illumination against a matt white background, viewingin a direction normal to the major s
21、urface of the test specimen.If the comparator shown in Fig. 2 is used, first place a sheet ofmatt white paper (with holes to accommodate the projectionsshown) on the base plate. Fit the disk of standard glasses andthe filled mold (with transparent cover films attached) over theprojections and place
22、the cover plate in position. Carry outcolor matching for each test specimen in turn.9. Report9.1 The color index of the rubber should be reported to thenearest half unit for index values 1 to 5 and to the nearest unitfor higher values. Occasionally the color of the rubber cannotbe matched due to the
23、 presence of strong yellow, green, or graytints. In this case, the rubber fails to test, and a note to thiseffect should be recorded.10. Precision and Bias10.1 No statement is made about either the precision or thebias of Test Method D3157, for measuring color of a rawrubber from natural sources, si
24、nce the results merely statewhether there is conformance to the criteria for the parameterin terms of an index using a comparative standard.11. Keywords11.1 color; color index; comparator discs; Lovibond; naturalrubberFIG. 1 Mold for Color Index TestFIG. 2 Comparator Mounting (for use with Commercia
25、l Lovibond Comparator Disks)D3157 05 (2015)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and
26、 the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revisio
27、n of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you sho
28、uldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obta
29、ined by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 05 (2015)3
