ASTM_D_6738_-_15.pdf

Designation:D673815Standard Test Method forPrecipitated SilicaVolatile Content1This standard is issued under the fixed designation D6738;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 procedure to determine thevolatile content of precipitated hydrated silicas.These volatilesare generally excess water adsorbed onto the surface of thesilica.This test method does not determine water of hydrationof the silica.1.2 The values stated in SI units are to be regarded as thestandard.The values in parentheses are for information only.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:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Significance and Use3.1 The volatiles content of a precipitated silica may affectthe processing properties of a rubber mixture containing silicaand the properties of the final product.4.Apparatus4.1 Oven,gravity-convection type,capable of maintaining105 6 5C.4.2 Ground-glass stoppered low-form weighing bottle,ap-proximately 30 mm in height by 60 mm in diameter.4.3 Analytical Balance,sensitive to 0.1 mg.4.4 Desiccator.NOTE1It is important that the desiccant is very dry,or moisture maybe drawn from the desiccant into the sample during cooling.5.Procedure5.1 Weigh a weighing bottle with stopper to the nearest 0.1mg and record its weight(W1).5.2 Add approximately 2 g of the silica sample to theweighing bottle and reweigh to the nearest 0.1 mg(W2).5.3 Place the weighing bottle with the silica sample into the105C oven for 2 h 6 5 min.Place the stopper nearby theweighing bottle.5.4 Transfer the weighing bottle containing the silica sampleand closed with the stopper from the oven into a desiccator andcool for 2 h or until room temperature.5.5 Remove the weighing bottle containing the silica samplefrom the desiccator and reweigh to the nearest 0.1 mg(W3).NOTE2An aluminum pan may be substituted for the weighing bottlein this test method.The results are systematically lower due to moisturepick-up from the atmosphere.The thermal transfer of glass differs fromthat of aluminum,so cooling time may be shortened using an aluminumpan.6.Calculation6.1 The volatile material is given by the following equation:%Volatiles5W22 W3!/W22 W1!#3100(1)where:W1=mass of weighing bottle,g,W2=mass of weighing bottle and silica sample beforeheating,g,andW3=mass of weighing bottle and silica sample afterheating,g.7.Report7.1 Report the following information:7.1.1 Identification of the sample,and7.1.2 Result reported to the nearest 0.1%.1This 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 edition approved Nov.1,2015.Published December 2015.Originallyapproved in 2001.Last previous edition approved in 2011 as D6738 11.DOI:10.1520/D6738-15.2For 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 States1 8.Precision and Bias38.1 The precision of this test method is based on aninterlaboratory study of conducted in 2010.Eleven laboratoriestested 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 Repeatability 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”is theinterval representing the critical difference between two testresults for the same material,obtained by the same operatorusing the same 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 between 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(repeat