1、Designation: D 6099 03Standard 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 (e) 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
3、HCl, 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:
4、D 883 Terminology Relating to Plastics2E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method42.2 ISO Standards:ISO 14898 PlasticsAro
5、matic isocyanates for use in theproduction of polyurethaneDetermination of acidity53. 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 hydr
6、ochloric 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 samp
7、le 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
8、.6.2 50-mL Pipet or Repipet, Class A volumetric.6.3 100-mL Pipet or Repipet, Class A volumetric.6.4 Automatic Titration Equipment, such as:6.4.1 Titroprocessor6, and6.4.2 Dosimat6, with magnetic stirrer.6.4.3 Reference Electrode7, with saturated LiCl/ethanol so-lution in both chambers.6.4.4 pH Glass
9、 Electrode8, (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 Materials7.1 0.02 N KOH in Methanol1.32 g KOH pellets (85 %KOH)/1000
10、mL methanol, standardized with potassium hydro-gen phthalate (KHP).1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular MaterialsPlastics and Elastomers.Current edition approved March 10, 2003. Published Apri
11、l 2003. Originallyapproved in 1997. Last previous edition approved in 1997 as D 6099 - 97.2Annual Book of ASTM Standards, Vol. 08.01.3Annual Book of ASTM Standards, Vol. 15.05.4Annual Book of ASTM Standards, Vol. 14.02.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th
12、Floor, New York, NY 10036.6Instruments similar to and including the Metrohn 686 Titroprocessor with aMetrohn 665 Dosimat/magnetic stirrer as supplied by Brinkman Instruments Co.,Cantiague Road, Westbury, NY 11590-9974, or an equivalent instrument, have beenfound to be satisfactory for this analysis.
13、7The Brinkman CAT. #020-94-400-5, or its equivalent: bridge electrolyte(double junction), sleeve-type diaphragm, has been found satisfactory for thisanalysis. See Footnote 5 for the address to Brinkman Instruments Co.8The Brinkman CAT. #020-91-012-7, or its equivalent, has been found satisfac-tory f
14、or this analysis. See Footnote 5 for the address to Brinkman Instruments Co.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.7.2 Toluene or 1,2,4Trichlorobenzene (TCB),
15、 dried for 24 hover molecular sieves.7.3 Anhydrous Methanol.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take special precautions in sampling. (WarningOrganicisocyanates are toxic when they are absorbed through the skinor when the vapors are breathed.) (WarningProvide a
16、d-equate ventilation and wear protective gloves and eyeglasses.)Usual sampling methods, for example, sampling with an opendrum thief, even when carried out rapidly, can cause contami-nation of the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times.9. Calib
17、ration9.1 Calibrate the electrodes using pH 4 and pH 7 aqueousbuffer.10. Test Conditions10.1 Since isocyanates react with moisture, keep laboratoryhumidity low, preferably around 50 % relative humidity.11. Procedure11.1 All samples should be done in duplicate.11.2 Accurately weigh to the nearest 1 m
18、g, 10 g of sampleinto a 250-mL beaker.11.3 Add 50 mL of dried toluene or TCB dried overmolecular sieves.NOTE 3If 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
19、 4Samples must be at room temperature before titration. Warmsamples cause more frequent electrode clogging.11.6 Titrate the mixture with 0.02 N methanolic KOHthrough the titration end point between apparent pH 4 and 9 asdetermined potentiometrically.NOTE 5If results indicate a drift in the data or a
20、 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 the titrant volume for the potentiometric endpoint. If more than one potentiometric end point is found,rec
21、ord the one at highest apparent pH less than 7.NOTE 6The inflection point typically is at apparent pH between 4 and5.11.7.1 If no clear end point can be identified, calculateresults using the end point at apparent pH 7.0, and report theresult as acidity at apparent pH 7.0.12. Calculation12.1 Calcula
22、te 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= 36.465 (mol weight of HCl) 3 1000 (factorto change mg/g to g/g, that is, ppm).13. Report13.1 The result is
23、 reported as the average of duplicates,expressed as ppm HCl, to the nearest 1 ppm. Any unusualconditions during the operation also should be reported, suchas any heating required to effect solution before titration, orend point identified different from that described in 11.7.14. Precision and Bias1
24、4.1 Table 1 is based on a round robin conducted in 1995 inaccordance with Practice E 180, involving twelve laboratories.For each material, all the samples were prepared at one source,but the individual specimens were prepared at the laboratoriesthat tested them. Some laboratories generated a set of
25、resultsfor each of two solvents (toluene and TCB), and somelaboratories generated a set of results for each of two differentelectrode types. Neither change in experimental conditions wasfound to be a significant source of increased variability. Eachof these combinations of conditions was treated as
26、a differentlaboratory for purposes of calculating the precision data. Eachtest result was the average of two individual determinations.Each laboratory obtained two test results for each material foreach combination of electrode and solvent used. (WarningThe following explanations of r and R (14.1.1
27、and 14.1.3) areintended only to present a meaningful way of considering theapproximate precision of this test method. The data in Table 1should not be applied rigorously to the acceptance or rejectionof material, as those data are specific to the round robin andmay not be representative of other lot
28、s, conditions, materials,or laboratories. Users of the test method should apply theprinciples outlined in Practice E 691 or E 180 to generate dataspecific to their laboratory and materials, or between specificlaboratories. The principles of 14.1.1 through 14.1.3 thenwould be valid for such data.)14.
29、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, (R)Comparing two resul
30、ts, eachthe mean of replicates, for the same material, obtained byTABLE 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 27.5 9.5 76.9 11 20ASr= within-laboratory standard deviation of the replica
31、tes.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 for this material.Fdf = degrees of freedom in the data after incorporating
32、multiple data sets frommost laboratories due to different combinations of solvent and electrode.D6099032different 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 thatmate
33、rial.14.1.3 Any 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
34、 diphenyldiisocyanate; polyurethane; raw materials;TDI; titration; toluene diisocyanateSUMMARY OF CHANGESThis section identifies the location of selected changes to these test methods. For the convenience of the user,Committee D20 has highlighted those changes that may impact the use of these test m
35、ethods. This section mayalso include descriptions of the changes or reasons for the changes, or both.D 6099 03:(1) Updated Note 1 to reflect recent ISO publication.(2) Corrected misspelled term in Footnote 5.(3) Corrected standard citation in paragraph 14.1. Changedreference from Practice E 691 to P
36、ractice E 180.(4) Added Practice E 180 to the Warning statement at the endof paragraph 14.1.(5) Editorially changed the placement of Warning, Caution,and Precaution statements to conform with ASTMs Form andStyle.ASTM International takes no position respecting the validity of any patent rights assert
37、ed in connection with any item mentionedin this standard. Users of this standard are expressly advised that 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 t
38、he responsible technical committee and must be reviewed every five years andif not revised, either reapproved 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
39、 careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel 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 Interna
40、tional, 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).D6099033
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