1、Designation: D6739 11 (Reapproved 2015)Standard Test Method forSilicapH Value1This standard is issued under the fixed designation D6739; 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 parenth
2、eses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is used to measure the pH of a 5 %silica/water suspension or mechanical dispersion and is indica-tive of the relative acidity or alkali
3、nity of the silica.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 standar
4、d 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:2E70 Test Method for pH of Aqueous Solutions With theGlass ElectrodeE177 Practice for Use of the Terms Precision and Bias inASTM T
5、est MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Significance and Use3.1 The pH level of silica, as measured by this test method,is known to affect the vulcanization of some rubber com-pounds. Refer to Test Method E70 for a fuller understa
6、nding ofpH and a more detailed procedure for making pH measure-ments.4. Apparatus4.1 pH Meter, (digital is recommended), having an accuracyof 60.05 pH and equipped with a combination electrode.4.2 Mortar and Pestle.4.3 Beaker, glass, 150 cm3with watch glass.4.4 Magnetic Stirring Bar and Stirrer.5. R
7、eagents5.1 Degassed, Neutral Water. Boil a container of eitherdistilled or deionized water for 10 min, cover, and allow to coolto room temperature, or purge the water with nitrogen gas for20 min using a fritted bubbler.5.2 Buffer Solutions, pH of 4.00, 7.00, and 10.00.6. Procedure6.1 Pulverize pelle
8、ted or granulated silica to a fine powder,using a mortar and pestle.6.2Weigh5gofsilica to the nearest 0.1 g into a 150 cm3glass beaker.6.3 Add 100 cm3of degassed, neutral water.6.4 Cover the glass beaker with a watch glass and stir themixture for 5 min at room temperature.6.5 Standardize the pH mete
9、r with two buffer solutions thatbracket the expected pH value of the silica. Rinse the electrodewith distilled water and wipe clean after each test.6.6 Place the electrode in the silica/water mixture, continu-ing to stir with the magnetic stirrer. When a constant pH isobtained, record the pH to the
10、nearest 0.05 pH unit.6.7 Rinse the electrode with distilled water. Store electrodein accordance with manufacturers instructions when not inuse.7. Report7.1 Report the following information:7.1.1 Identification of the sample, and7.1.2 Result obtained, reported to the nearest 0.1 unit.8. Precision and
11、 Bias38.1 The precision of this test method is based on aninterlaboratory study conducted in 2010. Eleven laboratories1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.20 on Compounding Materialsand Procedures.Current edit
12、ion approved Nov. 1, 2015. Published December 2015. Originallyapproved in 2001. Last previous edition approved in 2011 as D6739 11. DOI:10.1520/D6739-11R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AST
13、MStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D11-1108.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
14、ohocken, PA 19428-2959. United States1tested two types of silica samples. Every “test result” repre-sents an individual determination. Each laboratory was in-structed to report four replicate test results for each material.Practice E691 was followed for the design and analysis of thedata.8.1.1 Repea
15、tability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same
16、 equipment on the same day in the samelaboratory.8.1.1.1 Repeatability limits are listed in Table 1.8.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference betwee
17、n two test results for the same material,obtained by different operators using different equipment indifferent laboratories.8.1.2.1 Reproducibility limits are listed in Table 1.8.1.3 The above terms (repeatability limit and reproducibil-ity limit) are used as specified in Practice E177.8.1.4 Any jud
18、gment in accordance with statements 8.1.1and 8.1.2 would have an approximate 95 % probability ofbeing correct.8.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.8.3 The precisio
19、n statement was determined through statis-tical examination of 80 results, from ten laboratories, on twodifferent precipitated silica samples.9. Keywords9.1 pH; silicaASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin th
20、is standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and 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 b
21、e reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theres
22、ponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake 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, W
23、est Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained 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 ri
24、ghts to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 pHMaterialAverageARepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitxsrSRrRSilica A 6.61 0.01 0.07 0.04 0.21Silica B 6.74 0.01 0.08 0.01 0.22AThe average of the laboratories calculated averages.D6739 11 (2015)2
