1、Designation: D7214 07a (Reapproved 2012)Standard Test Method forDetermination of the Oxidation of Used Lubricants by FT-IRUsing Peak Area Increase Calculation1This standard is issued under the fixed designation D7214; the number immediately following the designation indicates the year oforiginal ado
2、ption 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.INTRODUCTIONThis test method was jointly developed with “Groupement Francais de Coo
3、rdination” (GFC),technical committee LM5 and “Coordinating European Council” (CEC) Surveillance Group T-048 forthe purpose of monitoring the oxidation stability of artificially aged automotive transmission fluids.This test method has been used in the CEC L-48-A-00 method as an end of test measuremen
4、tparameter.1. Scope1.1 This test method covers the determination of the oxida-tion of used lubricants by FT-IR (Fourier Transform InfraredSpectroscopy). It measures the concentration change of con-stituents containing a carbonyl function that have formedduring the oxidation of the lubricant.1.2 This
5、 test method may be used to indicate relativechanges that occur in an oil under oxidizing conditions. Thetest method is not intended to measure an absolute oxidationproperty that can be used to predict performance of an oil inservice.1.3 This test method was developed for transmission oilswhich have
6、 been degraded either in service, or in a laboratorytest, for example a bulk oxidation test. It may be used for otherin-service oils, but the stated precision may not apply.1.4 The results of this test method may be affected by thepresence of other components with an absorbance band in thezone of 16
7、001800 cm-1. Low PAI values may be difficult todetermine in those cases. Section 6 describes these possibleinterferences in more detail.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to ad
8、dress 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:2D4057 Practi
9、ce for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceE131 Terminology Relating to M
10、olecular SpectroscopyE1421 Practice for Describing and Measuring Performanceof Fourier Transform Mid-Infrared (FT-MIR) Spectrom-eters: Level Zero and Level One TestsE1866 Guide for Establishing Spectrophotometer Perfor-mance Tests2.2 CEC Standard:CEC L-48-A-00 Oxidation Stability of Lubricating Oils
11、Used in Automotive Transmissions by Artificial Aging33. Terminology3.1 DefinitionsFor terminology relating to molecularspectroscopic methods, refer to Terminology E131.3.2 Definitions of Terms Specific to This Standard:3.2.1 carbonyl region, nregion of the FT-IR spectrumcorresponding to the absorban
12、ce of compounds containing a1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.96 on In-Service Lubricant Testing and Condition Monitoring Services.Current edition approved Nov. 1, 2012. Published
13、November 2012. Originallyapproved in 2006. Last previous edition approved in 2007 as D721407a. DOI:10.1520/D7214-07AR12.2For 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
14、 to the standards Document Summary page onthe ASTM website.3Available from Coordinating European Council (CEC), c/o Interlynk Admin-istrative Services, Ltd., P.O. Box 6475, Earl Shilton, Leicester, LE9 9ZB, U.K.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
15、9428-2959. United States1carbonyl function. Depending on the nature of the carbonylcompounds, this region is usually located between approxi-mately 1820 cm-1and 1650 cm-1.3.2.2 differential spectrum, nFT-IR absorbance spectrumresulting from the subtraction of the fresh oil from the used oil.3.2.3 PA
16、I (peak area increase), narea of the carbonylregion of the differential FT-IR spectrum, divided by the cellpathlength in millimetres. In this standard, PAI refers to arelative measurement of the oxidation of a used lubricant byFT-IR.4. Summary of Test Method4.1 FT-IR spectra of the fresh oil and of
17、the used oil arerecorded in a transmission cell of known pathlength. Bothspectra are converted to absorbance and then subtracted. Usingthis resulting differential spectrum, a baseline is set under thepeak corresponding to the carbonyl region around 1650 cm-1and 1820 cm-1and the area created by this
18、baseline and thecarbonyl peak is calculated. The area of the carbonyl region isdivided by the cell pathlength in millimetres and this result isreported as Peak Area Increase (PAI).5. Significance and Use5.1 The PAI is representative of the quantity of all thecompounds containing a carbonyl function
19、that have formed bythe oxidation of the lubricant (aldehydes, ketones, carboxylicacids, esters, anhydrides, etc.). The PAI gives representativeinformation on the chemical degradation of the lubricant whichhas been caused by oxidation.5.2 This test method was developed for transmission oilsand is use
20、d in the CEC L-48-A-00 test (Oxidation Stability ofLubricating Oils Used in Automotive Transmissions by Artifi-cial Aging) as a parameter for the end of test evaluation.6. Interferences6.1 Some specific cases (very viscous oil, use of ester asbase stock, high soot content) may require a dilution of
21、thesample and a specific area calculation, which are described in14.1-14.3. In those cases, the result is corrected by a dilutionfactor, which is applied to the sample.7. Apparatus7.1 FT-IR Spectrophotometer, suitable for recording mea-surements between 1650 cm-1and 1820 cm-1and with aresolution of
22、4 cm-1.7.2 Transmission Cell, with windows of potassium bromide,having a known pathlength of approximately 0.025 to 0.1 mm.7.3 Syringe, or Other Automated or Semi-AutomatedDevice, with adequate volume to fill the cell, for example, 2mL.8. Reagents and Materials8.1 Purity of ReagentsReagent grade che
23、micals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beused, provided it is first ascertain
24、ed that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Heptane, used as cleaning solvent. Other solvents andsolvent mixtures may be used provided they adequately cleanthe cell(s) between samples. A 50/50 mixture of cyclohexaneand to
25、luene has been found to be useful in cleaning cells afterhighly contaminated and degraded samples have been run.(WarningFlammable.)8.3 PAO4, used as dilution oil (PAO4: PolyAlphaOlefinwith a kinematic viscosity at 100C of approximately 4 mm2/s)9. Calibration and Standardization9.1 Calculation of the
26、 Cell PathlengthUse a cell with aknown pathlength of approximately 0.025 to 0.1 mm. Calibratethe infrared cell pathlength using the interference fringemethod:9.1.1 Acquire the single beam background infrared spec-trum. Using the empty infrared cell in the infrared spectrometersample compartment, acq
27、uire the cell single beam infraredspectrum. Calculate the transmittance spectrum by dividing thecell single beam spectrum by the background single beamspectrum. Optionally, convert the transmittance spectrum to anabsorbance spectrum by taking the negative logarithm (base10) of the transmittance spec
28、trum. The fringe calculation maybe done on either the transmittance or absorbance. spectrum.The final spectrum is obtained by subtraction of the back-ground spectrum from the cell spectrum.NOTE 1This computation is generally an integral part of the infraredspectrometer software.9.1.2 Choose 2 minima
29、 separated by about 20 measurableinterference fringes as shown in Fig. 1. Count the number ofinterference fringes between the lower and the higherwavenumbers, referred to as 1and 2.NOTE 2The spectral range may be chosen freely in an area where thefringes are regular.9.1.3 The cell pathlength is calc
30、ulated by the formula:e 55n12 2!(1)where:e = the pathlength in mm, andn = the number of fringes between 1and 2.9.2 Instrument Performance Checks:9.2.1 Periodically, the performance of the FT-IR instrumentshould be monitored using the Level 0 procedure of PracticeE1421. If significant change in perfo
31、rmance is noted, thentesting should be suspended until the cause of the performancechange is diagnosed and corrected.9.2.2 Alternative instrument performance tests conformingto the recommendations of Guide E1866 may be substituted forthe Practice E1421 test.10. Conditioning10.1 Before using the infr
32、ared cell ensure that it is clean bywashing through with a suitable solvent, for example, heptane.D7214 07a (2012)2Dry the cell using dry air or nitrogen, if necessary. Calibratethis cell as described in Section 9.11. Preparation of Sample of Used Oil11.1 Refer to Practice D4057 (Manual Sampling) or
33、 Prac-tice D4177 (Automatic Sampling) for proper sampling tech-niques.11.2 When sampling used lubricants, the specimen shall berepresentative of the system sampled and shall be free ofcontamination from external sources. As used oil can changeappreciably in storage, test samples as soon as possible
34、afterremoval from the lubricating system and note the dates ofsampling and testing.11.3 If the sample of used oil contains visible sediment, heatto 60 6 5C in the original container and agitate until all of thesediment is homogeneously suspended in the oil. If the originalcontainer is a can or if it
35、 is glass and more than three-fourthsfull, transfer the entire sample to a clear-glass bottle having acapacity at least one third greater than the volume of thesample. Transfer all traces of sediment from the originalcontainer to the bottle by vigorous agitation of portions of thesample in the origi
36、nal container.12. Procedure12.1 Acquire a single beam background spectrum. Thisbackground spectrum may be used in the conversion of allsubsequent spectra for at least one day.12.2 With a syringe or other injection device, fill the cellwith the fresh oil, and record its single beam sample spectrum.Co
37、nvert this spectrum to a transmittance spectrum by dividingit by the single beam background spectrum and to a fresh oilabsorbance spectrum by taking the negative logarithm (base10) of the transmittance spectrum. Accumulate an adequatenumber of scans for a satisfactory noise level of 2 mAbs2000 cm-1.
38、NOTE 3Assuming there are no absorbance peaks in the range from2050 to 1950 cm-1for the sample, the noise level may be estimated as thestandard deviation of the absorbance data over this spectral range.12.3 Empty and clean the cell. Heptane may be used. Fillthe cell with the aged oil, and record its
39、single beam samplespectrum. Convert this spectrum to a transmittance spectrumby dividing by the single beam background spectrum, and to anaged oil absorbance spectrum by taking the negative logarithm(base 10) of the transmittance spectrum.NOTE 4It may happen that the aged oil is too viscous to fill
40、the cell.Then it is possible to proceed to a dilution as described in 12.4.1.12.4 Generate a differential spectrum by subtracting thefresh oil absorbance spectrum from the aged oil absorbancespectrum (see Fig. 2). Locate and zoom on the carbonyl regioncentered at 1720 cm-1. Processing may continue i
41、f the maxi-mum absorbance of this carbonyl region is lower than 1.5.NOTE 5Since the carbonyl region absorption minima (close to 1820cm-1and 1650 cm-1) can vary with the type of oil sample being tested, itwas decided not to use fixed baseline limits for calculating the area A.FIG. 1 Example of Interf
42、erence Fringes for Cell Pathlength CalculationD7214 07a (2012)3NOTE 6The carbonyl band may consist of more than one peakmaxima.NOTE 7Do not calculate the differential peak area by difference of thepeak area of the aged oil with the peak area of the fresh oil.12.4.1 If the maximum absorbance of the c
43、arbonyl region ofthe differential spectrum is higher than 1.5: dilute with 1 %accuracy by weight both fresh and aged oils with the samedilution factor, D (PAO 4 is recommended as dilution oil). Forexample,D=2fora50%(1:1) wt/wt dilution. Record the twospectra, convert them to absorbance and subtract
44、them. If themaximum absorbance of the carbonyl region is still higher than1.5, then use a higher dilution factor. This occurrence couldhappen in the case of ester or soot-containing oils.NOTE 8The cell pathlength may be changed to 0.05 mm or 0.025 mmif absorbance in the assessment area is greater th
45、an 1.5.NOTE 9Dilution factors are commonly chosen between 2 and 10.12.4.2 If the maximum absorbance of the carbonyl region ofthe differential spectrum is lower than 1.5: draw a base lineconnecting the absorption minima located at each side of thisregion as shown on the spectrum in Fig. 2. These mini
46、ma areusually close to 1820 cm-1and 1650 cm-1within 6 20 cm-1.Calculate and record the differential peak area as area A. (Thismay be done automatically with the spectrometer software.)13. Calculation of Results13.1 The results are reported as PAI (peak area increase):carbonyl region area, A multipli
47、ed by the dilution factor, D anddivided by the cell pathlength, e in mm:PAI 5area Ae mm!3 D (2)13.1.1 If no dilution was needed, the dilution factor, D is 1.14. Procedures for Interferences14.1 The results of this test method may be affected by thepresence of other components with an absorbance band
48、 in thezone of 16001800 cm-1. Low PAI values may be difficult todetermine in those cases. The following procedures may beused if interferences are present.14.2 Soot-Containing OilsThe presence of soot degradesthe spectra by decreasing the transmittance level. This casemay require a dilution as descr
49、ibed in 12.4 in order to obtain anabsorbance lower than 1.5.14.3 Ester-Containing OilsThe ester functions containedin some lubricants, especially those formulated with ester baseoil, interfere with the oxidation peak. Dilution may be neededwith these types of lubricants and it is recommended to use acell with a small pathlength (0.05 mm maximum). Check theshape of the spectrum before interpreting it. The residualpositive or negative peaks at 1740 cm-1showing the presenceof ester function may make it difficult to correctly perform thesubtraction opera
