1、Designation: D 2702 05Standard Practice forRubber ChemicalsDetermination of Infrared AbsorptionCharacteristics1This standard is issued under the fixed designation D 2702; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 a simple, rapid
3、 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. Thus, it canprovid
4、e 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 theresponsibility of th
5、e 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:2E 131 Terminology Relating to Molecular SpectroscopyE 168 Practices for General Techniques of Infrared Quan
6、ti-tative AnalysisE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near-Infrared Spectrophotom-eters3. Terminology3.1 Definitions: For definitions of terms used in this practicerefer to Terminology E 131.4. Summary of Practice4.1 A method of specimen preparation is
7、 selected 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 instrume
8、nt parameters.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 applica
9、tions,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 spectr
10、um (some 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 ins
11、trument 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 sp
12、ecimen 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 t
13、he jurisdiction ofASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.11 on Chemical Analysis.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1968. Last previous edition approved in 2004 as D 2702 04.2For referenced ASTM standards, visit t
14、he 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 Conshohocken, PA 19428-2959,
15、 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 willdepend on the disk holde
16、r 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 region most often used
17、 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 E 275.6.3 Demountable CellsLiquid cells ranging from 0.025 to1.0 mm in specimen path length and KBr pellet holde
18、r 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 shall conform to the speci
19、fications 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 of the determination.7
20、.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, anhydrous.7.3.4 Hexachlo
21、robutadiene.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 willdetermine the specimen
22、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 inthe preparation procedur
23、es 8.2-8.5. The techniques are alsodescribed in Practices E 168.8.2 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 thickness, butthe us
24、ual 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 usually gives a goodsp
25、ectrum. 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 common method for inf
26、rared studyof solid powders is to grind a few milligrams of powder in anagate mortar and add a suspending agent to make a mull (seePractices E 168). Scan the resultant paste in a demountablecell.8.3.1.2 Mineral Oil5is a mulling agent, which in thethickness used, is quite transparent in the infrared,
27、 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 withmortar and pestl
28、e 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 of specimen with dry
29、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 of a salt plate.8.3.2
30、.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:8.3.3.1 Dissolving the
31、specimen in a suitable solvent andscanning the solution in a fixed path cell is a technique that isfrequently used.3The sole source of supply of the apparatus known to the committee at this timeis Crescent Dental and Manufacturing, 7750 W. 47th St., Lyons IL60534. If you areaware of alternative supp
32、liers, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee,1which you may attend.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC
33、. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Nujol has been fou
34、nd satisfactory for this purpose.D27020528.3.3.2 The solution technique is used in resolving OH andNH bands in the 3.3 to 2.5-m (3000 to 4000-cm1) region.Hydrogen-bonding effects in this region are reduced by dis-solving the rubber chemical in a solvent.8.3.3.3 One problem with this technique is tha
35、t 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 use of a variable-path referen
36、ce 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 problem is that solubility of pola
37、r 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 solution is poured on a salt pl
38、ateleaving 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 orientation.8.3.5 KBr Pellet Technique:8
39、.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 described in Practices E 168.8.3.5
40、.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:8.4.1 A variety of reflectance app
41、aratuses 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 the reflectance crystal, eith
42、er 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 them with spectra generated by ot
43、hersampling 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 theinterference.8.5.1.2 Some rubber chemical
44、s 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 inwhich two or three of the stro
45、nger 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 to 10 times or15 to110 the ori
46、ginal 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 manual of the spectrophotomet
47、er 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 superimposable, compare theloca
48、tion, 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 length, or solution concentrati
49、ondifferences 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 samematerial.11.3.2 If extra absorption ban
