ASTM D3720-90(2019)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3720 − 90 (Reapproved 2019)
Standard Test Method for
Ratio of Anatase to Rutile in Titanium Dioxide Pigments by
X-Ray Diffraction
This standard is issued under the fixed designation D3720; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Pigmented Coatings
1.1 This test method covers the determination of the ratio of
3. Summary of Test Method
anatase to rutile in titanium dioxide pigments. The method is
3.1 TheX-raydiffractionpatternobtainedfromamaterialis
also applicable to pigment mixtures and pigmented coatings
characteristic of that material. The intensity of a diffraction
containing titanium dioxide.
peak entirely due to one component of a mixture is dependent
1.2 The values stated in SI units are to be regarded as the
upon the amount of that substance in the mixture. To a minor
standard. The values given in parentheses are for information
extentthepeakintensityofthecomponentisalsodependenton
only.
the mass absorption coefficient of other materials present.
1.3 This standard does not purport to address all of the
Since the test method utilizes the ratio of the intensities of
safety concerns, if any, associated with its use. It is the
diffraction peaks of two chemically similar materials, it is
responsibility of the user of this standard to establish appro-
expected that the effects of other constituents will be the same
priate safety, health, and environmental practices and deter-
for both materials.
mine the applicability of regulatory limitations prior to use.
3.2 The intensity of the diffraction maxima for anatase and
1.4 This international standard was developed in accor-
rutile is measured by X-ray diffractometry. The intensity of the
dance with internationally recognized principles on standard-
anatase peak is converted to anatase content relative to rutile
ization established in the Decision on Principles for the
and the rutile content is determined by difference.
Development of International Standards, Guides and Recom-
3.3 The X-ray diffraction measurement is made on single
mendations issued by the World Trade Organization Technical
pigments, pigment mixtures, films of pigmented coatings, and
Barriers to Trade (TBT) Committee.
films prepared from liquid coatings, if interfering materials are
not present. When interfering materials are present, the pig-
2. Referenced Documents
ment is separated from the redissolved (or ignited film, or from
2.1 ASTM Standards:
the liquid coating and treated to isolate the titanium dioxide.
D215 Practice for the Chemical Analysis of White Linseed
Oil Paints (Withdrawn 2005)
4. Significance and Use
D2371 Test Method for Pigment Content of Solvent-
4.1 This test method is used by titanium dioxide pigment
Reducible Paints
manufacturers and users for process control and product
D2698 Test Method for Determination of the Pigment Con-
acceptance.
tent of Solvent-Reducible Paints by High-Speed Centri-
fuging
5. Interferences
D3925 Practice for Sampling Liquid Paints and Related
5.1 Calcium sulfate interferes, but its effect is eliminated by
chemical removal (see Practice D215). It is desirable to assure
by analysis that any residual CaSO is considerably less than
1 4
This test method is under the jurisdiction of ASTM Committee D01 on Paint
the level of anatase being sought. The insoluble residue after
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.31 on Pigment Specifications.
removal of calcium sulfate should be ignited above 700°C.
Current edition approved May 1, 2019. Published May 2019. Originally
Chrome yellow and the valentinite form of antimony trioxide
approved in 1978. Last previous edition approved in 2011 as D3720 – 90 (2011).
also interfere if not removed. High amounts of iron render
DOI: 10.1520/D3720-90R19.
analysis difficult due to increased background (see Note 1).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Additives, such as antimony and zinc, and impurities, such as
Standards volume information, refer to the standard’s Document Summary page on
niobium and zirconium, are generally present in solid solution
the ASTM website.
and thus would not have interfering diffraction peaks. Surface
The last approved version of this historical standard is referenced on
www.astm.org. treatments such as silica and alumina do not interfere. Extreme
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3720 − 90 (2019)
differences in particle size between the anatase and rutile 7.2 MixingReagents—Aseriesofrutilestandardsofvarying
portions affect the results. rutile content are prepared to cover the range of interest by
thoroughly mixing known amounts of 100 % rutile and 100 %
NOTE1—Backgroundscatterduetohighironlevelsinasamplemaybe
anatase together. The pigments are dispersed in a solvent such
reduced by use of a cobalt or molybdenum target tube in place of the
as isopropyl alcohol and then mixed, followed by air drying.
copper target tube. The background may be eliminated for all practical
purposes by use of a curved crystal monochromator equipped with a
This dry cake is ground up using a mortar and pestle to ensure
graphite crystal in conjunction with a copper target tube.
homogeneity.
5.2 In the calculation of converting the ratio to percent it is
8. Hazards
implicitly assumed that the sum of anatase and rutile is 100 %,
an assumption normally made in TiO pigment systems. Other
8.1 X-ray producing equipment can be dangerous to both
materials present would interfere to the extent that they dilute
theoperatorandpersonsintheimmediatevicinityunlesssafety
the sample. The third polymorphic form of TiO , brookite,
precautions are strictly observed. Refer to the manufacturer’s
would have such an effect. However, it reportedly does not
instruction manual. Exposure to excessive quantities of
occur in commercial titanium dioxide pigments.
X-radiation may be injurious to health.Therefore, users should
avoid exposing any parts of their bodies, not only to the direct
6. Apparatus
beam, but also to secondary or scattered radiation that occurs
when an X-ray beam strikes or has passed through any
6.1 X-Ray Diffractometer—The principle components of
material. It is strongly recommended that users check the
thisinstrumentare:(a)X-raygenerator,(b)coppertargetX-ray
degree of exposure by film carried on them or by the use of
tube, (c) goniometer, (d) detector, (e) electronic circuit panel,
dosimeters and that blood counts be made periodically. Before
(f) computer (if used), and (g) strip chart recorder or printer.
utilizing the equipment, all persons designated or authorized to
6.2 Operating Conditions—The X-ray tube voltage and
operate X-ray instrumentation or supervise its operation,
filament current and other settings are selected to record X-ray
should have a full understanding of its nature and should also
diffraction peaks of weak intensities.
become familiar with established safe exposure factors by a
6.2.1 Nickel Filter, to remove Cu K beta radiation if a
careful study of the National Bureau of Standards Handbook
monochromator is not used. Cu K beta radiation will produce
“X-Ray Recommendations of the International Roentgen Ray
a diffraction line from the rutile phase of
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