ASTM_D_3720_-_90_2011.pdf

Designation:D372090(Reapproved 2011)Standard Test Method forRatio of Anatase to Rutile in Titanium Dioxide Pigments byX-Ray Diffraction1This standard is issued under the fixed designation D3720;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 the determination of the ratio ofanatase to rutile in titanium dioxide pigments.The method isalso applicable to pigment mixtures and pigmented coatingscontaining titanium dioxide.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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D215 Practice for the Chemical Analysis of White LinseedOil Paints(Withdrawn 2005)3D2371 Test Method for Pigment Content of Solvent-Reducible PaintsD2698 Test Method for Determination of the Pigment Con-tent of Solvent-Reducible Paints by High-Speed Centri-fugingD3925 Practice for Sampling Liquid Paints and RelatedPigmented Coatings3.Summary of Test Method3.1 The X-ray diffraction pattern obtained from a material ischaracteristic of that material.The intensity of a diffractionpeak entirely due to one component of a mixture is dependentupon the amount of that substance in the mixture.To a minorextent the peak intensity of the component is also dependent onthe mass absorption coefficient of other materials present.Since the test method utilizes the ratio of the intensities ofdiffraction peaks of two chemically similar materials,it isexpected that the effects of other constituents will be the samefor both materials.3.2 The intensity of the diffraction maxima for anatase andrutile is measured by X-ray diffractometry.The intensity of theanatase peak is converted to anatase content relative to rutileand the rutile content is determined by difference.3.3 The X-ray diffraction measurement is made on singlepigments,pigment mixtures,films of pigmented coatings,andfilms prepared from liquid coatings,if interfering materials arenot present.When interfering materials are present,the pig-ment is separated from the redissolved(or ignited film,or fromthe liquid coating and treated to isolate the titanium dioxide.4.Significance and Use4.1 This test method is used by titanium dioxide pigmentmanufacturers and users for process control and productacceptance.5.Interferences5.1 Calcium sulfate interferes,but its effect is eliminated bychemical removal(see Practice D215).It is desirable to assureby analysis that any residual CaSO4is considerably less thanthe level of anatase being sought.The insoluble residue afterremoval of calcium sulfate should be ignited above 700C.Chrome yellow and the valentinite form of antimony trioxidealso interfere if not removed.High amounts of iron renderanalysis difficult due to increased background(see Note 1).Additives,such as antimony and zinc,and impurities,such asniobium and zirconium,are generally present in solid solutionand thus would not have interfering diffraction peaks.Surfacetreatments such as silica and alumina do not interfere.Extremedifferences in particle size between the anatase and rutileportions affect the results.NOTE1Background scatter due to high iron levels in a sample may bereduced by use of a cobalt or molybdenum target tube in place of thecopper target tube.The background may be eliminated for all practical1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved June 1,2011.Published June 2011.Originallyapproved in 1978.Last previous edition approved in 2005 as D3720-90(2005).DOI:10.1520/D3720-90R11.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 purposes by use of a curved crystal monochromator equipped with agraphite crystal in conjunction with a copper target tube.5.2 In the calculation of converting the ratio to percent it isimplicitly assumed that the sum of anatase and rutile is 100%,an assumption normally made in TiO2pigment systems.Othermaterials present would interfere to the extent that they dilut