1、Designation: D2702 05 (Reapproved 2011)Standard Practice forRubber ChemicalsDetermination of Infrared AbsorptionCharacteristics1This standard is issued under the fixed designation D2702; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This practice covers
3、a simple, rapid practice to prove theidentity of a rubber chemical before incorporation into a rubbermix by comparison of its infrared absorption spectrum withthat of a reference specimen.1.2 This technique can also be used to detect gross contami-nation or large differences in rubber chemicals. Thu
4、s, it canprovide a basis for producer-consumer agreement.1.3 Wherever “infrared spectrophotometer” is used, “Fou-rier Transform Infrared Spectrometer (FTIR)” may also beunderstood.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespo
5、nsibility 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:2E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of
6、Infrared Quanti-tative AnalysisE275 Practice for Describing and Measuring Performanceof Ultraviolet and Visible Spectrophotometers3. Terminology3.1 Definitions: For definitions of terms used in this practicerefer to Terminology E131.4. Summary of Practice4.1 A method of specimen preparation is selec
7、ted that iscompatible with the physical and chemical properties of therubber chemical that will provide the desired spectral informa-tion.4.2 The specimen is placed in the specimen beam of thespectrophotometer and scanned to obtain a spectrum over theregion of interest under specified instrument par
8、ameters.4.3 The spectrum is compared with that of a referencespecimen. It is understood that the reference specimen wasprepared and scanned in an identical manner and preferably onthe same infrared spectrophotometer.5. Significance and Use5.1 This procedure can be used for a variety of applications,
9、including identifying unlabeled material, process control, rawmaterial acceptance, product evaluation, and compositionalchange during environmental testing.5.2 Rubber chemicals vary widely in their chemical andphysical properties. Infrared spectrophotometers vary in thepresentation of a spectrum (so
10、me are linear with absorbance,others with transmittance, some use grating for energy disper-sion, others use a sodium chloride prism, some obtain aspectrum through a mathematical Fourier Transform, and thelike). For these reasons, a single universal method of specimenpreparation and set of instrumen
11、t parameters is not possible.5.3 By using a specific sampling procedure and operatingconditions, a given spectrophotometer will give an absorptioncurve that is characteristic of the rubber chemical or mixtureunder investigation.5.4 The ability to superimpose the infrared spectrum of thetest specimen
12、 upon that of a reference specimen, obtainedunder the same conditions, is evidence that the two areidentical.5.5 The presence of additional absorption bands in either thetest specimen or the reference specimen indicates the presenceof one or more additional components.1This practice is under the jur
13、isdiction ofASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.11 on Chemical Analysis.Current edition approved Nov. 1, 2011. Published January 2012. Originallyapproved in 1968. Last previous edition approved in 2005 as D2702 05. DOI:10.1520/D2702-05R11.2For referenced
14、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
15、ohocken, PA 19428-2959, United States.6. Apparatus6.1 Initial Specimen PreparationThe diverse physicalnature of rubber chemicals may require the use of one or moreof the following:6.1.1 Agate Mortar and Pestle, small.6.1.2 Wig-L-Bug Amalgameter.36.1.3 Mold and Press for KBr PelletsThe die size willd
16、epend on the disk holder available with the users infraredspectrophotometer. The hydraulic press should be capable ofexerting 140-MPa (20 000-psi) pressure.6.1.4 Vacuum Pump, operating at 250 Pa or less.6.2 Infrared Spectrophotometer:6.2.1 The spectral region from 2.5 to 15 m (4000 to 667cm1) is the
17、 region most often used for rubber chemicalidentification, although inorganic chemicals may have usefulbands down to 250 cm1.6.2.2 If the performance of the spectrophotometer must beevaluated, refer to Practice E275.6.3 Demountable CellsLiquid cells ranging from 0.025 to1.0 mm in specimen path lengt
18、h and KBr pellet holder shouldbe available. On occasion, a variable-path cell is useful.6.4 KBr or NaCl Plates, of suitable size for spectrophotom-eter.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shal
19、l conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy
20、of the determination.7.2 Observe all health and safety recommendations forhandling the chemicals in this practice.7.3 Any of the following reagents may be required depend-ing on the method chosen for sample preparation:7.3.1 Carbon Disulfide, spectro quality.7.3.2 1,2-Dichlorobenzene.7.3.3 Ether, an
21、hydrous.7.3.4 Hexachlorobutadiene.7.3.5 Refined Mineral Oil.57.3.6 Perfluorocarbon Oil.7.3.7 Potassium Bromide (KBr), infrared quality.7.3.8 Tetrahydrofuran, (without inhibitor).7.3.9 Acetone, infrared quality.8. Sampling and Sample Preparation8.1 Generally, the physical nature of the specimen willd
22、etermine the specimen preparation procedure. In some cases,where alternative procedures could be used, agreement be-tween the chemical producer and consumer would be required.In choosing a specimen preparation procedure, certain poten-tial sources of error should be considered. These are listed inth
23、e preparation procedures 8.2-8.5. The techniques are alsodescribed in Practices E168.8.2 LiquidsFixed-thickness absorption cells of 0.025 to0.5 mm are used for the analysis of low-viscosity liquids.Demountable cells are used with more viscous liquid speci-mens. Spacers can be used to adjust specimen
24、 thickness, butthe usual practice is to spread a film of viscous liquid over onesalt plate, overlay a second plate, and squeeze out the excessuntil the desired film thickness has been reached. Initially, thedesired thickness may be obtained by trial and error. Aspecimen thickness of 0.02 to 0.1 mm u
25、sually gives a goodspectrum. The experienced spectroscopist can usually judge anadequate film thickness with minimum effort.8.3 SolidsSpecimens that are solid (amorphous, poly-meric, or crystalline) may be handled by one or more of severaltechniques:8.3.1 Mulling Techniques:8.3.1.1 Perhaps the most
26、common method for infrared studyof solid powders is to grind a few milligrams of powder in anagate mortar and add a suspending agent to make a mull (seePractices E168). Scan the resultant paste in a demountable cell.8.3.1.2 Mineral Oil5is a mulling agent, which in thethickness used, is quite transpa
27、rent in the infrared, except forthe CH absorption frequencies at 3.3, 6.9, 7.3, and 13.9 m(3000, 1450, 1375, and 720 cm1). If information is desired inthese regions, alternative mulling materials are hexachlorob-utadiene or perfluorocarbon oil.8.3.1.3 It is desirable to grind the specimen thoroughly
28、 withmortar and pestle before adding the mulling agent to minimizelight scattering and reduce window scratching. A minimum ofmulling agent should be used to wet the powder.8.3.1.4 Polymeric specimens are usually better handled byother techniques because of the grinding difficulty. Freezingthis type
29、of specimen with dry ice or the use of a freezer millmay help, but it can also introduce water condensate contami-nation.8.3.2 Melted Film Technique:8.3.2.1 This method can be used for polymeric or highlyviscous materials. It consists of melting the specimen andspreading a thin film across the face
30、of a salt plate.8.3.2.2 Advantages are that no solvent or mulling agentinterference bands are introduced. Possible disadvantages arethermal or oxidation breakdown, loss of volatile components,or spurious bands due to crystal orientation in the case ofcrystalline materials.8.3.3 Solution Technique:8.
31、3.3.1 Dissolving the specimen in a suitable solvent andscanning the solution in a fixed path cell is a technique that isfrequently used.8.3.3.2 The solution technique is used in resolving OH andNH bands in the 3.3 to 2.5-m (3000 to 4000-cm1) region.3The sole source of supply of the apparatus known t
32、o the committee at this timeis Crescent Dental and Manufacturing, 7750 W. 47th St., Lyons IL 60534. If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical
33、 committee,1which you may attend.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K.
34、, and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Nujol has been found satisfactory for this purpose.D2702 05 (2011)2Hydrogen-bonding effects in this region are reduced by dis-solving the rubber chemical in a solvent.8.3.3.3 One pro
35、blem with this technique is that no singlesolvent is completely transparent in the infrared region. Two ormore solvents are thus necessary to provide “windows” acrossthe infrared region so that solvent interference peaks do notoccur.8.3.3.4 Minor solvent interference bands can often be can-celled by
36、 use of a variable-path reference cell containing puresolvent. However, if major solvent bonds are compensated inthis manner, there is little or no available energy left in thespectrophotometer. Therefore, little or no useful informationcan be obtained in these wavelength regions.8.3.3.5 Another pro
37、blem is that solubility of polar rubberchemicals is very limited in the better nonpolar solvents, suchas carbon disulfide. Some rubber chemicals will also react withcarbon disulfide.8.3.4 Film Cast from Solution:8.3.4.1 In this technique, the specimen is dissolved in asuitable volatile solvent. The
38、solution is poured on a salt plateleaving a film, or, on a glass plate, where the dried film may belifted from the surface and placed in a specimen holder forsubsequent infrared analysis.8.3.4.2 Difficulties with this method may be incompletesolvent removal or spurious bands due to crystal orientati
39、on.8.3.5 KBr Pellet Technique:8.3.5.1 The specimen is intimately mixed with KBr powderand pressed into a pellet for measurement of the infraredspectrum.NOTE 1The Wig-L-Bug is useful in intimately mixing the specimenwith KBr using a vial and pestle and a vibrating motion.8.3.5.2 This technique is des
40、cribed in Practices E168.8.3.5.3 This technique should be used only when there isagreement between the producer and the consumer because thespectrum obtained by this means may contain extra crystallinebands or the specimen may react with KBr to produce spuriousbands.8.4 Reflectance Measurements:8.4.
41、1 A variety of reflectance apparatuses are available foruse with IR and FTIR spectrometers. The most common isAttenuated Total Reflectance (ATR), but several other configu-rations are available, including Horizontal ATR (H-ATR). Thesample must be such that it can be pressed into intimate contactwith
42、 the reflectance crystal, either by a holder, or by pressingthe sample into the crystal.8.4.2 The use of reflectance spectroscopy may cause distor-tion of the shape of the bands or of the shape of the baseline,or both. Care must be taken in the interpretation of reflectancespectra when comparing the
43、m with spectra generated by othersampling techniques.8.5 Special Handling:8.5.1 Some specimens require pretreatment before exami-nation by the infrared technique. For example:8.5.1.1 Specimens containing water, carbon, or other highlyactive infrared absorbers must be treated to remove theinterferenc
44、e.8.5.1.2 Some rubber chemicals are dispersed on inert mate-rials such as diatomaceous earth or clay. In this case, solventextraction and subsequent evaporation of the solvent mayseparate the rubber chemical from the inert material.9. Test Specimen9.1 The specimen thickness normally chosen is one in
45、which two or three of the stronger bands fall within about 10 %transmittance range.9.2 For FTIR spectrometers, the spectrum is obtained froma minimum of 32 scans (interferograms).9.3 Sometimes this does not provide complete informationon the very weak or very strong bands, and a second spectrumat 5
46、to 10 times or15 to110 the original thickness is run throughportions of the spectrum.10. Procedure10.1 Scan the spectrum at median values of the operatingrange, resolution, and signal to noise ratio of the particularinstrument employed.10.2 For detailed instrument operation, refer to the instru-ment
47、 manual of the spectrophotometer used.11. Interpretation of Results11.1 The objective of this practice is to determine whetherthe test specimen is the same as a reference specimen. If thespectrum of the two can be superimposed over each other, thematerials are identical.11.2 If the spectra are not s
48、uperimposable, compare thelocation, shape, and relative absorbance of every absorptionband in each of the spectra. If the materials are identical, thesefactors should agree. Furthermore, there should be no extrane-ous bands in either spectrum. However, crystallinity, sampleoxidation, specimen path l
49、ength, or solution concentrationdifferences may cause the absorbance of the absorption bandsin one spectrum to be different from those in the other. If thematerials are identical, these differences will be proportionalthroughout the spectra.11.3 If discrepancies exist between the spectrum of the testspecimen and that of the reference specimen, one of thefollowing conclusions may be drawn:11.3.1 If one or more major bands in the spectrum of thereference specimen is missing from the spectrum of the testspecimen, the probability is that the two are not the samemateria
