ASTM_D_6739_-_20.pdf

Designation:D673920Standard 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 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 is used to measure the pH of a 5%mass per volume(m/V)silica/water suspension or mechanicaldispersion and is indicative of the relative acidity or alkalinityof 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 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:2D4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesE70 Test Method for pH of Aqueous Solutions With theGlass Electrode3.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 understanding 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.Reagents5.1 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 pelleted or granulated silica to a fine powder,using a mortar and pestle.6.2 Weigh 5 g of silica 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 meter 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 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.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materials and is the direct responsibility of Subcommittee D11.20on Compounding Materials and Procedures.Current edition approved June 1,2020.Published June 2020.Originallyapproved in 2001.Last previous edition approved in 2015 as D6739 11(2015).DOI:10.1520/D6739-20.2For 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.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.8.Precision and Bias38.1 These precision statements have been prepared in ac-cordance with Practice D4483.Refer to this practice forterminology and other statistical details.8.2 A type 1 inter-laboratory precision program was con-ducted in 2010 using two different types of silica material.Datawas received from eleven laboratories.In each laboratory foursingle tests were performed on each of the two materials on thesame day(total of four replicates).A test result is the valueobtained from a single determination.Both repeatability andreproducibility represent short-term(daily)testing conditions.Acceptable difference values were not measured.8.3 In the initial outlier evaluation at the 95%confidencelevel,one laboratory was an outlier for mean and var