ASTM D6247-98
(Test Method)Standard Test Method for Analysis of Elemental Content in Polyolefins By X-Ray Fluorescence Spectrometry
Standard Test Method for Analysis of Elemental Content in Polyolefins By X-Ray Fluorescence Spectrometry
SCOPE
1.1 This test method covers a general procedure for the determination of elemental content in polyolefins by X-ray fluorescence spectrometry, in concentration levels typical of those contributed by additives and reactor processes. Note 1-Specific methods and capabilities of users may vary with differences in interelement effects and sensitivities, instrumentation and applications software, and practices between laboratories. Development and use of test procedures to measure particular elements, concentration ranges or matrices is the responsibility of individual users. Note 2-One general method is outlined herein; alternative analytical practices can be followed, and are attached in notes, where appropriate.
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 10. Note 3-There is no similar or equivalent ISO standard.
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Designation: D 6247 – 98
Standard Test Method for
Analysis of Elemental Content in Polyolefins By X-Ray
Fluorescence Spectrometry
This standard is issued under the fixed designation D 6247; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Determine the Precision of a Test Method
E 1361 Guide for Correction of Interelement Effects in
1.1 This test method covers a general procedure for the
X-Ray Spectrometric Analysis
determination of elemental content in polyolefins by X-ray
E 1621 Guide for X-Ray Emission Spectrometric Analysis
fluorescence spectrometry, in concentration levels typical of
those contributed by additives and reactor processes.
3. Terminology
NOTE 1—Specific methods and capabilities of users may vary with
3.1 Definitions:
differences in interelement effects and sensitivities, instrumentation and
3.1.1 Definitions of terms applying to XRF and plastics
applications software, and practices between laboratories. Development
appear in Terminology E 135 and Terminology D 883, respec-
and use of test procedures to measure particular elements, concentration
tively.
ranges or matrices is the responsibility of individual users.
3.2 Definitions of Terms Specific to This Standard:
NOTE 2—One general method is outlined herein; alternative analytical
practices can be followed, and are attached in notes, where appropriate.
3.2.1 element—used in this context, refers to any chemical
element that can be determined by XRF; and is often used
1.2 The values stated in SI units are to be regarded as the
synonymously with the term metal.
standard. The inch-pound units given in parentheses are for
3.2.2 infinite thickness—or critical thickness: the thickness
information only.
of specimen which, if increased, yields no increase in intensity
1.3 This standard does not purport to address all of the
of secondary x-rays, due to absorption by the polymer matrix.
safety concerns, if any, associated with its use. It is the
This thickness varies with secondary x-ray energy, or wave-
responsibility of the user of this standard to establish appro-
length.
priate safety and health practices and determine the applica-
3.2.3 polyolefin—used in this context, refers to PE and PP
bility of regulatory limitations prior to use. Specific precau-
thermoplastics.
tionary statements are given in Section 10.
NOTE 3—There is no similar or equivalent ISO standard. 4. Summary of Test Method
4.1 The test specimen is compression molded or injection
2. Referenced Documents
molded into a plaque having a clean, uniform surface.
2.1 ASTM Standards:
4.2 The plaque is irradiated in the WDXRF with a beam of
C 1118 Guide for Selecting Components for Wavelength-
primary X-rays, that causes each element to fluoresce at
Dispersive X-Ray Fluorescence (XRF) Systems
specific wavelengths (lines). Choice of appropriate lines and
D 883 Terminology Relating to Plastics
spectrometer test conditions can vary according to each ele-
D 4703 Practice for Compression-Molding Thermoplastic
ment, and with factors such as detector response, concentration
Materials into Test Specimens, Plaques or Sheets
range, and other elements present in the sample matrix.
E 135 Terminology Relating to Analytical Chemistry for
4.3 These secondary X-rays are dispersed with diffraction
Metals, Ores, and Related Materials
crystals of appropriate spacing, and measured by appropriate
E 691 Practice for Conducting an Interlaboratory Study to
detectors configured at angles specific to lines of interest.
Additional considerations appear in Guides C 1118 and
E 1621.
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
4.4 Analyte concentration is determined by relation/
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
comparison of line intensity with a calibration curve.
Current edition approved April 10, 1998. Published February 1999.
Annual Book of ASTM Standards, Vol 12.01.
Annual Book of ASTM Standards, Vol 08.01.
4 6
Annual Book of ASTM Standards, Vol 08.03. Annual Book of ASTM Standards, Vol 14.02.
5 7
Annual Book of ASTM Standards, Vol 03.05. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 6247
NOTE 4—An alternative method utilizes a fundamental parameters type
8.2 Nitrogen, prepurified grade or equivalent, for purging
calibration.
the melt fusion chamber.
8.3 Elemental Standards—Compounds or additives, or
5. Significance and Use
both, to be melt homogenized into polymer calibration stan-
5.1 X-ray fluorescence spectrometry is an accurate and
dards. Material should be certified as to elemental purity and
relatively fast method to determine multielement concentra-
should be dried and desiccated prior to use.
tions in polyethylene or polypropylene materials, or both. It
9. Reference Materials
can be used as a quality control measure for post-reactor
studies, for additive levels in formulated resins, and for
9.1 Reference Materials, can be prepared by users, as in
finished products.
Section 11.
5.2 Further elaboration appears in Guide E 1621.
9.2 Other Materials, appear in Guide E 1621.
9.3 Monitor Samples—To account for instrument drift (for
6. Interferences
example, electronic variations or long term X-ray source
6.1 Potential interferences are explained in Guide E 1621. degradation).
NOTE 8—Monitor samples are selected for their long-term durability,
7. Apparatus
and should ideally contain elements near to high and low ends of
7.1 Calibration Standards Formulation:
analytical range(s) of interest. Prefabricated glass discs outside range(s) of
7.1.1 Batch Compounding Equipment, with temperature
interest are often used. They are measured before measurement of
calibration standards, and are remeasured periodically (for example,
regulation capabilities, for melt homogenization of elemental
daily). Any drift from original measurements can be accounted for, and
compounds or additives into polyolefin reference standards.
necessary corrections can be applied to maintain calibrations relative to
Equipment can range from small scale torque rheometers
initial conditions.
equipped with mixing head, to larger-scale batch mixers.
Nitrogen purge capabilities are recommended.
10. Safety Precautions
NOTE 5—An alternative method requires a single-screw or twin-screw 10.1 Occupational Health and Safety Standards for X-Rays,
laboratory-scale extruder in place of the melt-fusion head, however, more
and ionizing radiation shall be observed. It is also recom-
material is required for formulation. Dry homogenization techniques
mended that proper practices be followed, as shown in Guide
which do not require the use of melt-compounding apparatus have been
E 1621.
used, however, such are not recommended.
NOTE 9—X-rays are dangerous and can cause serious personal injury.
7.1.2 Analytical Balance, 0.1-mg sensitivity
X-ray beams can be very narrow and difficult to detect. Precautions taken
7.2 Specimen Preparation:
minimize potential radiation exposure include an increase in protective
7.2.1 Thermal Press, for compression-molding of plaques,
shielding, an increase of distance, and a decrease of time near any
and capable of obtaining temperatures, pressures and cooling
suspected source of leakage.
rates, as recommended for PE and PP in Practice D 4703 and
10.2 Chemical—Appropriate precautions for chemical haz-
in Section 11 of this test method.
ards shall be observed for any chemicals and materials used in
7.2.2 Flash Type Mold, picture-frame type, described in
preparing calibration standards. Consult the suppliers’ Material
Practice D 4703: stainless-steel chase to mold test plaques 3.2
Safety Data Sheets for specific hazards and safety practices.
mm (0.125 in.) thick, uncoated Mylar (polyester film) parting
10.3 Pressurized Gas requires safe and proper handling
sheets, and smooth, stainless steel backing plates of minimum
practices.
2.5 mm thickness.
10.4 Specimen Preparation—Follow appropriate precau-
NOTE 6—Injection molding apparatus have also been employed, in tions when using hot equipment for homogenization and
place of the thermal press and flash mold.
specimen preparation. Consult manufacturer’s recommenda-
NOTE 7—The recommended thickness of 3.2 mm may vary with user
tions for specific practices.
preference. Other material may be used for parting sheets, provided it does
not adhere to the polymer under such thermal conditions. Some techniques
11. Preparation of Reference Materials and Test
use polished steel backing plates, with chromed surfaces, and no parting
Specimens
sheets. The apparatus used should not introduce contamination of ele-
11.1 Specimen Plaques—Consistent preparation of refer-
ments of interest, and should yield specimens with a plane surface of
ence materials and test specimens is essential. Variations in
adequate smoothness.
sample thickness, surface finish and homogeneity can affect
7.3 Excitation Source, Spectrometer, and Measuring
reliability of results.
System—Requirements for a wavelength-dispersive XRF are
11.1.1 Reference Materials—A technique that offers consis-
outlined in Guides C 1118 and E 1621.
tent elemental dispersion throughout the calibration standard
should be followed. Melt homogenization to ensure uniformity
8. Reagents and Materials
is recommended; see Annex A1.
8.1 P-10 Gas, a mixture of 90 % argon and 10 % methane,
NOTE 10—Resins from actual production runs have been used for
ultra-high purity or equivalent, for use with gas-flow propor-
calibration standards, after verification by independent analytical methods.
tional detectors.
11.1.2 Test Specimens—If elemental dispersion is poor,
homogenize the sample according to Annex A1, Section 2. If
Mylar is a registered trademark of DuPont. elemental dispersion is acceptable, proceed to 11.2.
D 6247
11.2 Compression Molding—Both calibration standards and 14. Procedure
test specimens are pressed into plaques having a suggested
14.1 Refer to Guide E 1621.
thickness of 3.2 mm (0.125 in.). Each plaque should have a
NOTE 19—The effects of poor surface finish on test accuracy can
smooth, plane surface, and no voids. Refer to Practice D 4703.
become more adverse at longer wavelengths (lower atomic numbers) and
NOTE 11—Techniques using no polymer-based calibration have been at lower analyte concentrations. The use of a sample spinner is recom-
used. mended.
NOTE 12—Some users employ a laboratory-scale injection molding
14.2 It is recommended to measure monitor sample(s) daily,
technique as an alternative to this suggested compression molding
for elements of interest, and to apply any required drift
method.
correct
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