1、Designation: D 6099 08Standard Test Method forPolyurethane Raw Materials: Determination of Acidity inModerate to High Acidity Aromatic Isocyanates1This standard is issued under the fixed designation D 6099; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n 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 determines the acidity, expressed asparts per million (ppm) of H
3、Cl, in aromatic isocyanate samplesof greater than 100ppm acidity. The test method is applicableto products derived from toluene diisocyanate and methylene-bis-(4phenylisocyanate) (see Note 1).NOTE 1This test method is equivalent to ISO 14898, Test Method A.2. Referenced Documents2.1 ASTM Standards:2
4、D 883 Terminology Relating to PlasticsE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty ChemicalsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:ISO 14898 PlasticsAromat
5、ic isocyanates for use in theproduction of polyurethaneDetermination of acidity33. Terminology3.1 DefinitionsTerms used in this test method are inaccordance with Terminology D 883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity, nthe acid strength of a sample expressed inppm hydroch
6、loric acid.4. Summary of Test Method4.1 The isocyanate is mixed with an excess of methanol anda cosolvent. Additional acid is released into the solvent systemduring urethane formation. The acid then is titrated potentio-metrically with methanolic KOH, and the acidity present in theisocyanate sample
7、is calculated from the titer.5. Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize aromatic isocyanates and prepolymersof moderate to high acidity. Acidity correlates with perfor-mance in some polyurethane systems.6. Apparatus6.1 250-mL Beakers.6.
8、2 50-mL Pipet or Repipet, Class A volumetric.6.3 100-mL Pipet or Repipet, Class A volumetric.6.4 Automatic Titration Equipment, capable of inflectiondetection and stirring the sample while, titrating, such as:6.4.1 Commerically-available Automatic Titration Appara-tus,6.4.2 Reference Electrode, with
9、 saturated LiCl/ethanol so-lution in both chambers.6.4.3 pH Glass Electrode, (see Note 2).NOTE 2A combination pH electrode with internal reference also maybe used.6.5 Magnetic Stirrer.6.6 Stir Bars.6.7 Watch Glasses.6.8 Analytical Balance, capable of weighing to the nearest 1mg.7. Reagents and Mater
10、ials7.1 0.02 N KOH in Methanol1.32 g KOH pellets (85 %KOH)/1000 mL methanol, standardized with potassium hydro-gen phthalate (KHP).7.2 Toluene or 1,2,4Trichlorobenzene (TCB), dried for 24 hover molecular sieves.7.3 Anhydrous Methanol.1This test method is under the jurisdiction of ASTM Committee D20
11、on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved Nov. 15, 2008. Published November 2008. Originallyapproved in 1997. Last previous edition approved in 2003 as D 6099 - 03.2For referenced ASTM standards, visit t
12、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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY
13、 10036, http:/www.ansi.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take special prec
14、autions in sampling. Usual samplingmethods, even when conducted rapidly, can cause contamina-tion of the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times.NOTE 3Warning: Many diisocyanates are known or suspected sen-sitizers. Over-exposure to diisocyanate
15、s can lead to adverse health effectswhich may include the development of occupational asthma and otherrespiratory, skin and eye effects. Engineering controls and/or personalprotective equipment, including respiratory, skin and eye protection,should be used when there is a potential for over-exposure
16、 to diisocyan-ates. The product suppliers Material Data Safety Sheet (MSDS) providesmore detailed information about potential adverse health effects and otherimportant safety and handling information. Always follow the specificinstructions provided on the MSDS.9. Calibration9.1 Calibrate the electro
17、des using pH 4 and pH 7 aqueousbuffers.10. Test Conditions10.1 Since isocyanates react with moisture, keep laboratoryhumidity low, preferably around 50 % relative humidity.11. Procedure11.1 All samples shall be done in duplicate.11.2 Accurately weigh to the nearest 1 mg, 10 g of sampleinto a 250-mL
18、beaker.11.3 Add 50 mL of dried toluene or TCB.NOTE 4If this test method is used for prepolymers, substitute THF asthe solvent.11.4 Add 100 mL of methanol into the solution.11.5 Add a stir bar, cover with a watch glass, and stir for 20min.NOTE 5Samples must be at room temperature before titration. Wa
19、rmsamples cause more frequent electrode clogging.11.6 With uniform stitrring of the sample, automaticallytitrate the mixture with 0.02 N methanolic KOH through thepotentiometrically-determined inflection end point betweenapparent pH 4 and 9. Follow manufacturers instructions forinstrument-specific p
20、arameters for set-up, calibration andanalysis of samples.NOTE 6If results indicate a drift in the data or a slow electroderesponse, the pH electrode should be cleaned by soaking in 2:1 sulfuric:nitric acids for 10 min, followed by soaking in water for 20 min, and thenrinsing with acetone.11.7 Record
21、 the titrant volume for the potentiometric endpoint. If more than one potentiometric end point is found,record the one at highest apparent pH less than 7.NOTE 7The inflection point typically is at apparent pH between 4 and5.11.7.1 If no clear end point can be identified, calculateresults using the e
22、nd point at apparent pH 7.0, and report theresult as acidity at apparent pH 7.0.12. Calculation12.1 Calculate the acidity as ppm HCl as follows:Acidity ppm HCl! 5Vsam!3N 3 Fsample weight g!#(1)where:Vsam = volume of titrant needed for the sample, mL,N = normality of the titrant solution, andF=36465=
23、 36.465 (mol weight of HCl) 3 1000 (factorto change mg/g to g/g, that is, ppm).13. Report13.1 The result is reported as the average of duplicates,expressed as ppm HCl, to the nearest 1 ppm. Any unusualconditions during the operation shall also be reported, such asany heating required to effect solut
24、ion before titration, or endpoint identified different from that described in 11.7.14. Precision and Bias414.1 Table 1 is based on a round robin conducted in 1995 inaccordance with Practice E 180, involving two materials testedby twelve laboratories. For each material, all the samples wereprepared a
25、t one source, but the individual specimens wereprepared at the laboratories that tested them. Some laboratoriesgenerated a set of results for each of two solvents (toluene andTCB), and some laboratories generated a set of results for eachof two different electrode types. Neither change in experimen-
26、tal conditions was found to be a significant source of increasedvariability. Each of these combinations of conditions wastreated as a different laboratory for purposes of calculating theprecision data. Each test result was the average of twoindividual determinations. Each laboratory obtained two tes
27、tresults for each material for each combination of electrode andsolvent used. (WarningThe following explanations of r andR (14.1.1 and 14.1.2) are intended only to present a meaningfulway of considering the approximate precision of this testmethod. The data in Table 1 should not be applied rigorousl
28、y tothe acceptance or rejection of material, as these data apply onto the materials tested in the round robin and may not berepresentative of other lots, conditions, materials, or laborato-ries. Users of this test method should apply the principlesoutlined in Practice E 691 or E 180 to generate data
29、 specific to4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D201195.TABLE 1 RoundRobin Acidity Data in Accordance With PracticeE 180Values, ppm HClAverage SrASRBrCRDnEdfFRubinate M 189 5.8 13.5 16.2 37.9 11 23Mondur MR 414 3.4
30、27.5 9.5 76.9 11 20ASr= within-laboratory standard deviation of the replicates.BSR= between-laboratory standard deviation of the average.Cr = within-laboratory repeatability limit = 2.8 3 Sr.DR = between-laboratory reproducibility limit = 2.8 3 SR.En = number of laboratories contributing valid data
31、for this material.Fdf = degrees of freedom in the data after incorporating multiple data sets frommost laboratories due to different combinations of solvent and electrode.D6099082their laboratory and materials (or between specific laborato-ries). The principles of 14.1.1 through 14.1.2 would then be
32、valid for such data.)14.1.1 Repeatability, (r)Comparing two replicates for thesame material, obtained by the same operator using the sameequipment on the same day, the two replicate results should bejudged not equivalent if they differ by more than the r value forthat material.14.1.2 Reproducibility
33、, (R)Comparing two results, eachthe mean of replicates, for the same material, obtained bydifferent operators using different equipment in different labo-ratories on different days, the two test results should be judgednot equivalent if they differ by more than the R value for thatmaterial.14.1.3 An
34、y judgment made in accordance with 14.1.1 and14.1.2 would have an approximate 95 % (0.95) probability ofbeing correct.14.2 BiasThere are no recognized standards by which toestimate the bias of this test method.15. Keywords15.1 acidity; aromatic isocyanates; isocyanates; MDI; me-thylene diphenyldiiso
35、cyanate; polyurethane; raw materials;TDI; titration; toluene diisocyanateSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue(D 6099 - 03) that may impact the use of this standard. (November 15, 2008)(1) Modified sampling statement in
36、8.1 to better reflectthoughts of industry experts.(2) Replaced non-mandatory language in 11.1, 13.1, and 14.1.(3) Made editorial changes in 14.1 for clarity or to removeredundancy.(4) Editorially changed 6.4 for clarity.(5) Made warning in 8.1 into a note and renumbered subse-quent notes.(6) Editori
37、ally changed 11.6 for clarity.(7) Removed footnotes 6, 7, 8. Removed unnecessary vendor-specific details.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that
38、 determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapprov
39、ed or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you fee
40、l that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D6099083
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