ASTM D6247-2018 Standard Test Method for Determination of Elemental Content of Polyolefins by Wavelength Dispersive X-ray Fluorescence Spectrometry.pdf

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1、Designation: D6247 18Standard Test Method forDetermination of Elemental Content of Polyolefins byWavelength Dispersive X-ray Fluorescence Spectrometry1This standard is issued under the fixed designation D6247; the number immediately following the designation indicates the year oforiginal adoption or

2、, 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. Scope*1.1 This test method covers a general procedure for thedetermination of elemental

3、content in polyolefins bywavelength-dispersive X-ray fluorescence (WDXRF)spectrometry, in mass fraction ranges typical of those contrib-uted by additives, catalysts, and reactor processes. The ele-ments covered by this test method include fluorine, sodium,magnesium, aluminum, silicon, phosphorus, su

4、lfur, calcium,titanium, chromium, and zinc in the composition ranges givenin Table 1.TABLE 1 Mass Fraction Ranges for Additive and Trace Elementsin PolyolefinsElement LowerLimit(mg/kg)UpperLimit(mg/kg)Fluorine 100 300Sodium 25 200Magnesium 10 600Aluminum 40 500Silicon 30 1000Phosphorus 5 200Sulfur 2

5、0 200Calcium 10 300Titanium 5 200Chromium 5 100Zinc 10 10001.1.1 This test method does not apply to polymers specifi-cally formulated to contain flame retardants including bromi-nated compounds and antimony trioxide.1.1.2 This test method does not apply to polymers formu-lated to contain high levels

6、 of compounds of vanadium,molybdenum, cadmium, tin, barium, lead, and mercury be-cause the performance can be strongly influenced by spectralinterferences or interelement effects due to these elements.NOTE 1Specific methods and capabilities of users may vary withdifferences in interelement effects a

7、nd sensitivities, instrumentation andapplications software, and practices between laboratories. Developmentand use of test procedures to measure particular elements, mass fractionranges or matrices is the responsibility of individual users.NOTE 2One general method is outlined herein; alternative ana

8、lyticalpractices can be followed, and are attached in notes, where appropriate.1.2 The values stated in SI units are to be regarded as thestandard.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 sta

9、ndard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Specific precautionary statements are given in Section 10.NOTE 3There is no known ISO equivalent to this standard.1.4 This international standard was de

10、veloped 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 D

11、ocuments2.1 ASTM Standards:2C1118 Guide for Selecting Components for Wavelength-Dispersive X-Ray Fluorescence (XRF) Systems (With-drawn 2011)3D883 Terminology Relating to PlasticsD4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or SheetsD6247 Test Method fo

12、r Determination of Elemental Contentof Polyolefins by Wavelength Dispersive X-ray Fluores-cence SpectrometryE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE1361

13、Guide for Correction of Interelement Effects inX-Ray Spectrometric AnalysisE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcomm

14、ittee D20.70 on Analytical Methods.Current edition approved Oct. 1, 2018. Published October 2018. Originallyapproved in 1998. Last previous edition approved in 2010 as D6247 - 10. DOI:10.1520/D6247-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servi

15、ce 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.*A Summary of Changes section appears at the end of this standardCopyright A

16、STM 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 St

17、andards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1E1621 Guide for Elemental Analysis by Wavelength Disper-sive X-Ray Fluorescence Spectrometry2.2 Other Documents:JCGM 100:2008 Guide to the Expression of Uncertainty inMeasurements3

18、. Terminology3.1 Definitions:3.1.1 Definitions of terms applying to XRF and plasticsappear in Terminology E135 and Terminology D883, respec-tively.3.2 Definitions of Terms Specific to This Standard:3.2.1 infinite thicknessor critical thickness: the thicknessof specimen which, if increased, yields no

19、 increase in countrate of secondary (fluorescent) X-rays. This thickness varieswith secondary X-ray energy or wavelength.3.2.2 polyolefinused in this context, refers to polyethylene(PE) and polypropylene (PP) thermoplastics.4. Summary of Test Method4.1 The test specimen is compression molded or inje

20、ctionmolded into a plaque having a clean, uniform surface.4.2 The plaque is irradiated in the WDXRF spectrometerwith a beam of primary X-rays that causes each element tofluoresce at specific wavelengths (lines). Choices of appropri-ate lines and spectrometer test conditions can vary according toeach

21、 element, and with factors such as detector response, massfraction range, and other elements present in the sample matrix.4.3 The secondary X-rays are dispersed by crystals andmultilayer structures of appropriate spacing, and measured byappropriate detectors configured at angles specific to lines of

22、interest.Additional considerations appear in Guides C1118 andE1621.4.4 Analyte mass fraction is determined by relation/comparison of measured count rate with a calibration curve.NOTE 4An alternative method utilizes a fundamental parameters typecalibration.5. Significance and Use5.1 Elemental analysi

23、s serves as a quality control measurefor post-reactor studies, for additive levels in formulated resins,and for finished products. X-ray fluorescence spectrometry isan accurate and relatively fast method to determine massfractions of multiple elements in polyethylene and polypropyl-ene materials.6.

24、Interferences6.1 Spectral InterferencesSpectral interferences resultfrom the behavior of the detector subsystem of the spectrom-eter and from scattering of X-rays by the specimen. Overlapsamong X-ray lines from elements in the specimen are causedby the limited resolution of the detection subsystem.

25、Thedegree of line overlap and the best method to account or correctfor it must be ascertained on an individual basis and must beconsidered when calibrating the instrument.6.1.1 The measurement of sodium as an analyte mustinclude correction for the line overlap of zinc L-series lines onsodium K-L2,3.

26、6.1.2 The measurement of fluorine as an analyte mustinclude correction for the overlap of magnesium K-series lineson background measurement angles near the fluorine K-L2,3peak.6.2 Interelement EffectsInterelement effects, also calledmatrix effects, exist among all elements as the result ofabsorption

27、 of fluorescent X-rays (secondary X-rays) by atomsin the specimen and the subsequent fluorescence of a fractionof those atoms. Three options exist for dealing with interele-ment effects.6.2.1 Mathematical MethodsA number of methods arecommonly utilized including full fundamental parameters (FP)treat

28、ments and mathematical models based on influence coef-ficient algorithms. The influence coefficients are calculatedeither from first principles, from the empirical data, or somecombination of the two approaches. See Guide E1361 forexamples of these approaches. Also, consult the softwaremanual for th

29、e spectrometer for information on the approachesprovided with the spectrometer. Any of these that will achievethe necessary analytical accuracy is acceptable. Examples ofcommon interelement effects are listed in Table 2.6.2.2 Internal Standard or Internal ReferenceThis ap-proach involves the correct

30、ion of interelement effects bynormalizing the measured count rate of an element to themeasured count rate of an internal standard element or aninternal reference line from the spectrometer.6.2.2.1 An internal standard element must be chosen care-fully and must be added during sample preparation to a

31、llspecimens in a completely homogeneous manner. The chosenline from the internal standard element can be used for anyanalyte as long as there are no absorption edges of majorconstituent elements between the measured line of the analyteand the measured line of the internal standard element.TABLE 2 Co

32、mmon Interelement Effects in Formulated PlasticsCause EffectPolymers of similar composition but differences in the relative mass fractions of hydrogen and carbon. Differences in C/H among calibrants and samples canresult in biases of a few percent (relative).Unmeasured elements boron, nitrogen, oxyg

33、en, and fluorine present in the matrix of the polymer, forexample, amide, fluorinated, and terephthalate compounds.If mass fractions differ significantly from the calibrants,these elements cause significant changes in both apparentsensitivity and background count rates.Absorption by elements in the

34、scope of the standard or unknown levels of elements outside the scopeof the standard (for example, molybdenum, cadmium, tin, and barium) included in the formulation.Reduction of apparent sensitivity for most analytes.D6247 1826.2.2.2 An internal reference line is a peak produced byscattering of prim

35、ary X-rays from the tube source from thespecimen into the monochromator. In most cases, it is appro-priate to use the Compton scatter peak, if available. Theinternal reference line can be used for any analyte as long asthere are no absorption edges of major constituent elementsbetween the measured l

36、ine of the analyte and the internalreference line.6.2.3 Restricted Calibration RangeIn this option, theanalyst chooses to restrict the maximum mass fractions of theanalytes to values below which there are no significant biasesdue to absorption. The analyst must demonstrate by experimentthat interele

37、ment effects have been controlled completely.NOTE 5Differences in specimen thickness may be a source of biaswhen the energy of the measured X-ray line is high. Internal standard andinternal reference procedures can be used to correct for the effects of thesedifferences. See Section 13.NOTE 6The back

38、ground count rate near the peak of interest can serveas an internal reference measurement in the same way as a peak fromscattered primary radiation.7. Apparatus7.1 Calibration Standards Formulation:7.1.1 Batch Compounding Equipment, with temperatureregulation capabilities, for melt homogenization of

39、 elementalcompounds or additives into polyolefin reference standards.Equipment can range from small scale torque rheometersequipped with mixing head, to large-scale batch mixers.Nitrogen purge capabilities are recommended.NOTE 7An alternative method utilizes a single-screw or twin-screwlaboratory-sc

40、ale extruder in place of the melt-fusion head, however, morematerial is required for formulation. Dry homogenization techniques thatdo not require the use of melt-compounding apparatus have been used;however, such are not recommended.7.1.2 Analytical Balance, 0.1-mg sensitivity7.2 Specimen Preparati

41、on:7.2.1 Thermal Press, for compression-molding of plaques,and capable of obtaining temperatures, pressures and coolingrates, as recommended for PE and PP in Practice D4703 and inSection 11 of this test method.7.2.2 Flash Type Mold, picture-frame type, described inPractice D4703: stainless-steel cha

42、se to mold test plaques,uncoated polyester film parting sheets, and smooth, stainlesssteel backing plates of minimum 2.5 mm thickness.NOTE 8Injection molding apparatus have also been employed, inplace of the thermal press and flash mold.NOTE 9One laboratory has prepared plaques using standard steel

43、dies(designed for preparing briquettes of powder materials) in a hydraulicpress. Aluminum pressing caps served as molds. The loaded die washeated in an oven for 2 h prior to pressing. During pressing, a laboratoryvacuum was drawn on the side port of the die. In the press, the pressurewas rapidly inc

44、reased to 12 tons and the die was allowed to cool to roomtemperature. The pressing cap was removed from the cooled plaque.7.3 SpectrometerRequirements for a wavelength-dispersive XRF spectrometer are outlined in Guides C1118 andE1621.7.3.1 Source of X-ray Excitation, capable of exciting therecommend

45、ed lines listed in Table 3, typically an X-ray tube.7.3.2 X-ray Detectors, with sufficient sensitivity to detectthe recommended lines listed in Table 3. Typical spectrometersinclude proportional counters, sealed or flow designs, and ascintillation counter.7.3.3 Signal Conditioning and Data Handling

46、Electronicsthat include the functions of X-ray counting and peak process-ing.7.3.4 Vacuum PumpThe X-ray optical path must beevacuated using a mechanical pump.7.3.5 The following spectrometer features and accessoriesare optional.7.3.5.1 Beam FiltersUsed on the primary X-ray beam tomake the excitation

47、 more selective and to reduce backgroundcount rates.7.3.5.2 Specimen SpinnerUse is recommended to reducethe effect of surface irregularities of the specimen.7.4 Drift Correction Monitor(s)Due to instability of themeasurement system, the sensitivity and background of thespectrometer will drift with t

48、ime. Drift correction monitors canbe used to correct for this drift. The optimum drift correctionmonitor specimens are permanent materials that are stable withtime and repeated exposure to X-rays.NOTE 10Suitable drift correction monitors can be fused bead speci-mens containing the relevant elements

49、or elements that have fluorescencewith the same energies as the elements of interest. It is recommended thatmonitors provide count rates near to the low and high ends of the rangestypically encountered from plastic specimens.7.5 GlovesDisposable cotton gloves are recommended forhandling all specimens to minimize contamination.7.6 Personal Protective EquipmentAppropriate personalprotective equipment for the handling of reagents and hotequipment.8. Reagents and Materials8.1 P-10 Gas, a mixture of 90 % argon and 10 % methane,ultra-high purity or equivalent, for u