1、Designation: D3168 85 (Reapproved 2016)Standard Practice forQualitative Identification of Polymers in Emulsion Paints1This standard is issued under the fixed designation D3168; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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 U.S. Department of Defense.1. Scope1.1 This practice describes a
3、procedure for the qualitativeidentification in emulsion paints of most types of polymerspresent as major components of the paint vehicle. Limitationsare discussed in Sections 5 and 10.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informa
4、tiononly.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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Ref
5、erenced Documents2.1 ASTM Standards:2D16 Terminology for Paint, Related Coatings, Materials, andApplicationsD1193 Specification for Reagent WaterD2621 Test Method for Infrared Identification of VehicleSolids From Solvent-Reducible PaintsE275 Practice for Describing and Measuring Performance ofUltrav
6、iolet and Visible Spectrophotometers3. Terminology3.1 DefinitionsFor definitions of terms, refer to Terminol-ogy D16.4. Summary of Practice4.1 The vehicle is extracted from the dried paint and afterfiltering is cast on a salt plate. The infrared spectrum isobtained and compared with reference spectr
7、a for identificationof major components.4.2 The paint is applied to a filament and pyrolyzed todepolymerize the vehicle.An internal standard is added and thepyrolyzate is separated into its components by gas-liquidchromatography. Monomers are identified by comparison ofrelative retention times.5. Si
8、gnificance and Use5.1 Identification of specific acrylic polymers in emulsionpaints is often difficult or impossible by infrared alone. This isparticularly true when the acrylic is present in a small amountas a comonomer with vinyl acetate, or when blended withalkyds or other ester systems. If ident
9、ification of an acryliccomponent is required in such a system, it may often beaccomplished by gas-liquid chromatographic analysis of thepyrolyzed paint film. The presence of a number of otherpolymers may often also be confirmed by pyrolysis since theyproduce characteristic and reproducible pyrograms
10、.5.2 The pyrograms obtained from unknown samples vary incomplexity according to the sample composition. It is neces-sary to establish the presence or absence of as many compo-nents as possible from a study of the infrared spectra obtainedin the first part of this practice. The gas-liquid chromatogra
11、phyresults may then be used to help identify any unknowncomponents present and to confirm identifications made byinfrared.6. Interferences6.1 Dibutyl maleate and dibutyl fumarate monomers are notsuccessfully recovered by this procedure. If their presence issuspected as comonomer in a vinyl acetate c
12、opolymer system,n-butyl alcohol should be found in the pyrolyzate. Thisevidence, together with the absence of butyl acrylate or butylmethacrylate monomer peaks, is an indirect indication of thepresence of one or both of these monomers.6.2 The presence of relatively low quantities of copolymer-ized a
13、cids may not be successfully established by thisprocedure, due to some unavoidable decomposition of acrylateand methacrylate esters to acrylic or methacrylic acid and thecorresponding alcohols during the pyrolysis. The infraredspectrum and an acid number determination, both run on the1This practice
14、is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1973
15、. Last previous edition approved in 2011 as D3168 85 (2011).DOI: 10.1520/D3168-85R16.2For 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 to the standards Document Summary
16、page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1polymer solids, may usually be relied upon to establish thepresence or absence of acid groups in the polymer.6.3 In the case where the polymer being analyzed is s
17、imple(such as a vinyl acetate-alkyl ester copolymer, or a singleacrylate-methacrylate copolymer), it might be advantageous toexamine the total pyrolyzate directly by infrared (as a solutionin carbon disulfide).7. Apparatus7.1 Spectrophotometer, recording, double-beam, infrared,with a range from at l
18、east 2.5 m to 15 m and a spectralresolution of at least 0.04 m over that range. For checking theperformance of the infrared spectrophotometer, see PracticeE275.7.2 Cell Mount, demountable.7.3 Halide Salt Crystals, for use with demountable cellmount.7.4 Oven, gravity or forced-draft, maintained at 10
19、5 6 2C.7.5 Linear Programmed Temperature Gas Chromatograph,equipped with a thermal conductivity detector.7.6 Pyrolysis AccessoryAny suitable apparatus for achiev-ing pyrolysis external to the chromatograph, that results in therecovery of sufficient pyrolyzate for identification purposes.The apparatu
20、s described in the Annex has been found to meetthese requirements.7.7 Gas Chromatographic Column, 3 m (10 ft) in length, 6.4mm (14 in.) in outside diameter copper tubing packed with10 % silicone resin3on 80 to 100-mesh acid-washed, dimethyl-dichlorosilane treated calcined diatomaceous earth.47.8 Ste
21、am Bath or Low-Temperature Hot Plate.7.9 Flask, small Dewar.8. Reagents8.1 Purity of ReagentsReagent grade chemicals 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 Che
22、mical Society,where such specifications are available.5Other 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.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall
23、be understood to mean reagent water conformingto Type II of Specification D1193.8.3 Extraction Solvent MixtureEqual volumes of o-dichlorobenzene, dimethylformamide, and tetrahydrofuran.8.4 Liquid Nitrogen.8.5 Petroleum Ether (30 to 60C boiling range) or heptane.9. ProcedureInfrared Analysis9.1 Trans
24、fer 1 to 2 g of emulsion paint to a 100-mLborosilicate glass beaker. Add approximately 2 mL of waterand swirl or use a clean glass rod to spread the paint uniformlyover the bottom of the beaker.9.2 Place the beaker in an oven at 105 to 6 2C for at least2 h, breaking up any skins that form so that co
25、mplete drying isensured.9.3 Add 50 mL of water, cover with a watchglass, and placeon a steam bath or low-temperature hotplate for 1 h. Thisprocess removes emulsifiers, protective colloids, and otherwater-soluble components that might interfere with interpreta-tion of the infrared spectrum. Decant of
26、f the clear water layerand discard. If the addition of the distilled water to the driedpaint film produces a milky dispersion, the drying step in 9.2was not complete and should be repeated.NOTE 1If there is an interest in characterization of the emulsifiersystem used, the water should be filtered th
27、rough a fine-texture filter paperand taken to dryness. The solids may then be examined by infrared.9.4 Dry for 15 to 20 min in an oven at 105 to 6 2C. Add50 mL of petroleum ether or heptane, cover with a watchglass,and bring to a slow boil for approximately 5 min. This processremoves most emulsified
28、 plasticizers, oils, and other waterinsoluble, nonpolymeric organic materials, which might alsointerfere with the interpretation of the infrared spectrum.Decant off the solvent and discard.NOTE 2If there is an interest in characterizing the water-insolublepetroleum ether-soluble fraction, it should
29、also be filtered throughfine-texture paper, taken to dryness, and examined by infrared.9.5 Add 10 mL of the extraction solvent mixture (8.3) andplace on a steam bath or low-temperature hotplate for approxi-mately 1 h. Filter, while still hot, through a fine-texture filterpaper. If the polymer soluti
30、on is viscous, it may be dilutedfurther with extraction solvent mixture and warmed prior tofiltration. Alternatively, the pigment may be removed from thepolymer solution by centrifuging. Evaporate the solution on thesteam bath or hotplate to a volume of 1 mL or less.9.6 Place the concentrated polyme
31、r solution on a halide saltcrystal and spread to form a uniform film. The thickness of thefilm should be such that when the infrared spectrum isrecorded, the transmittance of the strongest band falls between5 and 15 %. Dry the film in an oven at 105 6 2C for 1 h andcool in a desiccator.9.7 Record th
32、e infrared spectrum from 2.5 to 15 m so thata spectral resolution of 0.04 m is maintained throughout thatrange. (Methods for achieving this resolution will vary accord-ing to the directions of the manufacturer of the instrumentused.)3The sole source of supply of silicone resin SE-30, known to the co
33、mmittee atthis time is General Electric Co. If you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments willreceive careful consideration at a meeting of the responsible technical committee,1which you may attend.4The sole source of supp
34、ly of Chromosorb W, known to the committee at thistime is Manville Sales Corp., Filtration and Minerals, P.O. Box 5108, Denver, CO80217-5108. If you are aware of alternative suppliers, please provide this informa-tion to ASTM International Headquarters. Your comments will receive carefulconsideratio
35、n at a meeting of the responsible technical committee,1which you mayattend.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for Laborator
36、yChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D3168 85 (2016)29.8 Compare the spectrum obtained with reference spectraprepared in a similar manner from emulsion paints of knowncomposition
37、or with published collections of polymer spectrasuch as Test Method D2621. Other sources are listed in thereferences (1-7).610. ProcedurePyrolysis-Gas Liquid Chromatography10.1 Coat the resistance wire filament of the pyrolysis unitby dipping it into the original paint sample to be tested.Remove the
38、 volatiles either by drying the filament in an ovenfor about 30 min at 105 6 2C or by heating it electrically withthe power supply set at 1 or 2 A (100 to 200C) forapproximately 10 min. If a larger volume of pyrolyzate isrequired than would be produced by the initial amount ofsample deposited, addit
39、ional layers of coating may be added byrepeating the dipping and drying steps.10.2 Place the coated filament-vial cap assembly in a smallbeaker. Extract with water, followed by petroleum ether orheptane, as outlined in 9.3 and 9.4.10.3 Add a few drops of liquid nitrogen to the vial or flushwith nitr
40、ogen gas to prevent oxidation reactions from occurringduring the pyrolysis.NOTE 3If the infrared spectrum obtained in 9.8 shows poly(vinylacetate) or poly(vinyl chloride) to be present, the pyrolysis step should bemodified to prevent the acetic or hydrochloric acid formed from degradingother monomer
41、s that may be present in the pyrolyzate. Addition of a dropof concentrated ammonium hydroxide to the vial just prior to pyrolysis,neutralizes the acid as it is formed. The pyrolyzate may then be recoveredby dissolving in diethyl ether just before sampling.10.4 Tightly screw the coated filament-cap a
42、ssembly ontothe glass vial and connect the filament leads to the powersupply.10.5 Submerge the entire vial in liquid nitrogen contained ina small Dewar flask. Allow to equilibrate for several minutes,then apply a predetermined current for approximately 10 to 15min.NOTE 4The optimum temperature which
43、 varies for different polymertypes may be determined experimentally from known polymer systems.Six amperes (approximately 600C) has been found to be close tooptimum for the types tested. A study of the pyrolysis of acrylic polymersshowed that heating times varying from 10 to 30 min produced nosignif
44、icant differences in the composition of the pyrolyzate.10.6 Turn off the power supply and allow the filament tocool for several minutes. Remove the vial from the liquidnitrogen and substitute a standard screw cap for the filament-cap.10.7 Using a syringe, add n-butyl acetate to the pyrolyzateequal t
45、o approximately 20 % of the pyrolyzate volume.10.8 Install the silicone resin column in the chromatographand allow it to condition to 200C. Set up the followingconditions on the chromatograph:Temperatures, CInjection port 270Detector block 270Column (programmed):Initial 70Final 200T, C/min 6Carrier
46、gas: heliumFlow rate, mL/min 60Detector current, mA 15010.9 Inject 5 L of pyrolyzate into the chromatograph,engage the chart drive, and start the temperature programmer.Attenuate as necessary during the run.NOTE 5The use of the method described minimizes the tendency ofpyrolysis products to undergo
47、secondary reactions while still in the vaporstate. This simplifies the chromatograms obtained, making interpretationeasier.10.10 Calculate retention times relative to the n-butyl ac-etate internal standard peak for each major peak obtained.Compare relative retention times obtained with known valuesf
48、or monomers of interest (see Table 1).10.11 If any doubt remains concerning an identificationbased on the pyrogram obtained, it is recommended that thepeak of interest be trapped as it is eluted from the chromato-graph for subsequent positive identification by infrared spec-troscopy or mass spectrom
49、etry.10.12 Burn off any remaining organic residue by applying 8or 9 A for a few seconds. Disconnect the filament from thepower supply; then clean off any adhering pigment by gentlybrushing with a test tube brush while holding the filamentunder running water. The same filament may be reused manytimes.6The boldface numbers in parentheses refer to the list of references at the end ofthis practice.TABLE 1 Relative Retention TimesAMonomer or Alcohol Relative RetentionMethanol 0.13Ethanol 0.16Acrylonitrile 0.25Vinyl acetate 0.37Methyl acrylate 0.45Isobutanol
