1、Designation: D 7253 06Standard Test Method forPolyurethane Raw Materials: Determination of Acidity asAcid Number for Polyether Polyols1This standard is issued under the fixed designation D 7253; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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. Scope1.1 This test method measures the acidic constituents inpolyether polyols and reports the results
3、 as acid number. Thetypical acid number range is 0-0.1 mg KOH/g sample. (SeeNote 1.)1.2 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
4、 determine the applica-bility of regulatory limitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Met
5、hod3. Terminology3.1 Definitions: For definitions of terms used in this testmethod see Terminology D 883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acid numberthe quantity of base, expressed inmilligrams of potassium hydroxide, that is required to titrateacidic constituents in1gofsampl
6、e.4. Summary of Test Method4.1 The sample is dissolved in 2-propanol. The resultingsingle-phase solution is titrated at room temperature with 0.02N methanolic potassium hydroxide solution to an end pointindicated by the color change (pink endpoint) of the addedphenolphthalein.NOTE 2Phenolphthalein i
7、s the indicator of choice based on publishedhydroxyl number methods that include an acid number correction. Otherindicators can be chosen if specific acids are of interest. Bromothymolblue (green endpoint) can be used for stronger acids (pKas 7).5. Significance and Use5.1 This test method is suitabl
8、e for quality control, as aspecification test, and for research. Acid numbers indicate theextent of any neutralization reaction of the polyol with acids.The results of this method measure batch-to-batch uniformityand are used as correction factors in calculating true hydroxylnumbers.6. Interferences
9、6.1 Samples or constituents that are highly-colored willinterfere with or prevent the use of this test method.7. Apparatus7.1 Buret, 10 mL, can be manual or automatic.7.2 Graduated cylinder, 10 mL, maximum.7.3 Balance, analytical with sensitivity of at least60.0001 g.7.4 Erlenmeyer flask, at least 2
10、50 mL.7.5 Stirring bars or stirring rods.8. Reagents and Materials8.1 Purity of ReagentsUse reagent-grade chemicals in alltests. Unless otherwise indicated, it is intended that all reagentsconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society where suc
11、hspecifications are available.3Other grades can be used pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct
12、 responsibility of Subcommittee D20.22 on Cellular MaterialsPlastics and Elastomers.Current edition approved April 1, 2006. Published April 2006.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
13、volume information, refer to the standards Document Summary page onthe ASTM website.3Reagent 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
14、LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K. and the United States Phamacopeia andNational Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.2 Phenolphthalein
15、, Indicator Grade.8.3 Phenolphthalein Indicator SolutionDissolve1gofphenolphthalein in 100 mL of methanol.8.4 Potassium Hydroxide Standard Solution (0.02 N)Prepare and standardize a 0.02 N methanolic potassium hy-droxide solution. (1.32 g KOH pellets (85 % KOH) per 1000mL methanol, standardized with
16、 potassium hydrogen phtha-late.)9. Procedure9.1 Add 100 6 20 mL of 2-propanol and 1 mL of phenol-phthalein indicator solution to an Erlenmeyer flask.9.2 Titrate the stirred solution with 0.02 N KOH solution tothe first faint pink endpoint that persists for 30 seconds.9.3 Weigh 50-60 g of sample into
17、 the same Erlenmeyer flaskand record the weight of the sample to the nearest 0.1 g.9.4 Stir or swirl the solution in the flask until the sample iscompletely dissolved.9.5 Titrate the clear sample solution with standardized 0.02N KOH solution to the first faint pink endpoint that persists for30 secon
18、ds.10. Calculation or Interpretation of Results10.1 Calculate the acid number, in milligrams of KOH/gram of sample as follows:Acid Number 5 A 3 N 3 56.1/W (1)where:A = volume of KOH solution for the titration of the samplein mL,N = the normality of the KOH solution, andW = the weight of the sample u
19、sed in g.11. Report11.1 Report results to the nearest 0.001 mg KOH/g.12. Precision and Bias412.1 Table 1 is based on a round robin involving sevenlaboratories and conducted in 2005 in accordance with PracticeE 691. All labs used a colorimetric endpoint titration for thegeneration of the data used in
20、 this study. All the samples wereprepared at one source, but the individual specimens wereprepared at the laboratories that tested them. Each test resultwas the average of two individual determinations. Each labo-ratory made duplicate determinations on each material on eachof two days. (WarningThe f
21、ollowing explanations of r andR (12.2-12.2.3) are intended only to present a meaningful wayof considering the approximate precision of this test method.The data in Table 1 is not to be rigorously applied to theacceptance or rejection of material, as those data are specific tothe round robin and are
22、not representative of other lots,conditions, materials, or laboratories. Users of this test methodare to apply the principles outlined in Practice E 691 togenerate data specific to their laboratory and materials orbetween specific laboratories. The principles of 12.2-12.2.3 arethen valid for such da
23、ta.)12.2 Precision12.2.1 Repeatability, (r)Comparing two replicates for thesame material, obtained by the same operator, using the sameequipment on the same day. The two replicate results are to bejudged not equivalent if they differ by more than the r value forthat material.12.2.2 Reproducibility,
24、(R)Comparing two results, eachthe mean of replicates, for the same material, obtained bydifferent operators, using different equipment in differentlaboratories on different days. The two test results are to bejudged not equivalent if they differ by more than the R valuefor that material.12.2.3 Any j
25、udgment in accordance with 12.2.1 and 12.2.2has an approximate 95 % (0.95) probability of being correct.12.3 There are no recognized standards by which to esti-mate the bias of this test method.13. Keywords13.1 acidity; acid number; hydroxyl number; polyetherpolyolsASTM International takes no positi
26、on respecting the validity of any patent rights asserted 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
27、.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 reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM
28、International Headquarters. Your comments will receive 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 sh
29、own 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), 610-83
30、2-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D20-1244.TABLE 1 Round Robin Data for Acid Number (mg KOH/g) inAccordance with Practice E 691M
31、aterial Average SrASRBrCRDnE1 0.026 0.001 0.005 0.003 0.013 72 0.015 0.001 0.005 0.004 0.014 73 0.016 0.002 0.005 0.005 0.013 74 0.105 0.001 0.008 0.004 0.022 6ASr= within-laboratory standard deviation of the replicates.BSR= between-laboratory standard deviation of the averages.Cr = within-laboratory repeatability limit = 2.8*Sr.DR = between-laboratory reproducibility limit = 2.8*SR.En = number of laboratories contributing valid data for this material.D7253062
