1、Designation: D7253 06 (Reapproved 2011)1Standard Test Method forPolyurethane Raw Materials: Determination of Acidity asAcid Number for Polyether Polyols1This standard is issued under the fixed designation D7253; the number immediately following the designation indicates the year oforiginal adoption
2、or, in 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.1NOTEReapproved with editorial changes in September 2011.1. Scope1.1 This test method mea
3、sures the acidic constituents inpolyether polyols and reports the results as acid number. Thetypical acid number range is 0-0.1 mg KOH/g sample. (SeeNote 1.)1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard d
4、oes 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.NOTE 1There is no known ISO equiva
5、lent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions: For definitions of terms used in this testmethod see Terminology D883.3
6、.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 in1gofsample.4. Summary of Test Method4.1 The sample is dissolved in 2-propanol. The resultingsingle-phase solution i
7、s 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 is the indicator of choice based on publishedhydroxyl number methods that include an acid number correction
8、. 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 suitable for quality control, as aspecification test, and for research. Acid numbers indicate theextent of any ne
9、utralization 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. Interferences6.1 Samples or constituents that are highly-colored willinterfere with or prevent the use of this test met
10、hod.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved Sept. 1, 2011. Published October 2011. Originallyapproved in 2006. Last previous edition ap
11、proved in 2006 as D7253 - 06.DOI:10.1520/D7253-06R11E01.2For 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 page onthe ASTM website.1Copy
12、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 least 60.0001g.7.4 Erlenmeyer flask, at least 2
13、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
14、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.8.2 Phenolphthalein, Indicator Grade.8.3 Phenolphthalein Indicator SolutionDissolve1gofphenolp
15、hthalein 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 potassium hydrogen phtha-late.)9. Procedure9.1 Add 100 6 20 mL of 2-propan
16、ol 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 the same Erlenmeyer flaskand record the weight of the sample to the neares
17、t 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 seconds.10. Calculation or Interpretation of Results10.1 Calculate the acid numb
18、er, 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 used in g.11. Report11.1 Report results to the nearest 0.001 mg KOH/g.12. Pr
19、ecision and Bias412.1 Table 1 is based on a round robin involving sevenlaboratories and conducted in 2005 in accordance with PracticeE691. All labs used a colorimetric endpoint titration for thegeneration of the data used in this study. All the samples wereprepared at one source, but the individual
20、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 following explanations of r andR (12.2-12.2.3) are intended only to present a
21、 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 not representative of other lots,conditions, materials, or laboratories. Use
22、rs of this test methodare to apply the principles outlined in Practice E691 to generatedata specific to their laboratory and materials or betweenspecific laboratories. The principles of 12.2-12.2.3 are thenvalid for such data.)12.2 Precision12.2.1 Repeatability, (r)Comparing two replicates for thesa
23、me 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, (R)Comparing two results, eachthe mean of replicates, for the same material,
24、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 judgment in accordance with 12.2.1 and 12.2.2has an approximate 95 % (0.95) pr
25、obability 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; polyetherpolyols3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For sug
26、gestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K. and the United States Phamacopeia andNational Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.4Supporting data have been fi
27、led 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 E691Material 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.
28、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 co
29、ntributing valid data for this material.D7253 06 (2011)12ASTM 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 determination of the validity of any such paten
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