1、Designation:D427405 Designation: D4274 11Standard Test Methods for TestingPolyurethane Raw Materials: Determination of HydroxylNumbers of Polyols1This standard is issued under the fixed designation D4274; the number immediately following the designation indicates the year oforiginal adoption or, in
2、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 These test methods measure the hydroxyl groups in polyester and polyether polyols c
3、ontaining primary and secondaryhydroxyl groups. They also apply to many other hydroxyl-containing substances.1.1.1 Test Method AAcetic Anhydride Pressure Bottle, recommended for polyesters.1.1.2 Test Method BPhthalic Anhydride Pressure Bottle, recommended for polyethers and polyesters.1.1.3 Test Met
4、hod CPhthalic Anhydride Reflux, recommended for polyethers and polyesters.1.1.4 Test Method DImidazoleCatalyzed Phthalic Anhydride Pressure Bottle, recommended for polyethers, polyesters,polymer polyols, and amine-initiated polyols.1.1.5 Test Method EImidazole-Catalyzed Pyromellitic Dianhydride Este
5、rification, recommended for polyols used for flexibleand rigid polyurethane foams and urethane elastomers. It is recommended for polyester polyols, polyether polyols, amine-startedpolyols, and polymer polyols (polyacrylonitrile/copolystyrene-based).1.2Other ASTM test methods for measuring hydroxyl g
6、roups are Test Methods D1957 and1.2 Another ASTM test method for measuring hydroxyl groups is Test Method E222(see Note 1).NOTE1Test Method C is essentially similar to ISO 6796-1981, but there are some differences in the concentrations used and some procedural details.There are currently no data ava
7、ilable for comparing the results of Test Method C to those of ISO 6796-1981.1.3 The values stated in SI units are to be regarded as the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this stan
8、dard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1This standard and ISO 6796 address the same subject matter, but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to Pl
9、asticsD1193 Specification for Reagent Water D1957Test Method for Hydroxyl Value of Fatty Oils and AcidsE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty ChemicalsE200 Practice for Preparation, Standardization, and Storage of Standard and
10、 Reagent Solutions for Chemical AnalysisE203 Test Method for Water Using Volumetric Karl Fischer TitrationE222 Test Methods for Hydroxyl Groups Using Acetic Anhydride AcetylationE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 ISO Standard:3ISO 679
11、6-1981ISO 6796 Polyglycols for Industrial UseDetermination of Hydroxyl NumberPhthalic Anhydride Esterifi-cation Method1These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on CellularMaterialsPlastics and Elastomers.C
12、urrent edition approved July 1, 2005. Published August 2005. Originally approved in 1988. Last previous edition approved in 1999 as D4274-99. DOI:10.1520/D4274-05.on Cellular Materials - Plastics and Elastomers.Current edition approved Feb. 1, 2011. Published March 2011. Originally approved in 1988.
13、 Last previous edition approved in 2005 as D4274 - 05. DOI:10.1520/D4274-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on
14、the ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the pre
15、vious version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Ch
16、anges 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.3. Terminology3.1 DefinitionsThe terminology in these test methods follows the standard terminology defined in Terminology D883.3.2 Defi
17、nitions of Terms Specific to This StandardThere are no terms in these test methods that require new or other thandictionary definitions.4. Summary of Test Methods4.1 Test Method AThe sample is acetylated with a solution of acetic anhydride in pyridine in a pressure bottle at 98C. Theexcess reagent i
18、s hydrolyzed with water and the acetic acid is titrated with standard sodium hydroxide solution. The hydroxylcontent is calculated from the difference in titration of the blank and sample solutions. (WarningAcetic anhydride and pyridineare toxic and flammable. In addition, acetic anhydride is corros
19、ive. Proper precautions must be taken in handling these reagents.).4.2 Test Method BThe hydroxyl group is esterified with a solution of phthalic anhydride in pyridine in a pressure bottle at98C. The excess reagent is titrated with standard sodium hydroxide solution.4.3 Test Method CThe hydroxyl grou
20、p is esterified with a solution of phthalic anhydride in pyridine under reflux conditionsat 115C. The excess reagent is titrated with standard sodium hydroxide solution.4.4 Test Method DThe hydroxyl group is esterified by reaction with phthalic anhydride in a pyridine medium at approximately100C. Th
21、e esterification reaction is catalyzed by imidazole. The excess anhydride is hydrolyzed with water, and the phthalic acidformed is titrated to the phenolphthalein end point with standard sodium hydroxide solution. The hydroxyl content is calculatedfrom the difference in titration of the blank and th
22、e sample solution.4.5 Test Method EThe hydroxyl group is esterified with a solution of imidazole (IMDA) and pyromellitic dianhydride(PMDA) in dimethylformamide in an iodine flask at 70 to 80C. The excess reagent is titrated with standard sodium hydroxidesolution.5. Significance and Use5.1 These test
23、 methods are suitable for research and as quality control and specification tests. It is necessary to know thehydroxyl contents of polyols in order to formulate polyurethane systems.6. Reagents6.1 Purity of ReagentsUse reagent-grade chemicals in all tests. Unless otherwise indicated, all reagents mu
24、st conform to thespecifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications areavailable.4Other grades can be used, provided they are pure enough to be used without lowering accuracy.6.2 Purity of WaterUnless otherwise indicated, use Type II wa
25、ter conforming to Specification D1193.7. Sampling7.1 Polyesters and polyethers usually contain molecules covering an appreciable range of molecular weights. These have atendency to fractionate during solidification. Unless the material is a finely-ground solid it is necessary to melt (using no highe
26、rtemperature than necessary) and mix the resin well before removing a sample for analysis. Many polyols are hygroscopic, and careis to be taken to provide minimum exposure to atmospheric moisture during the sampling.TEST METHOD AACETYLATION8. Interferences8.1 Dry the sample if it contains more than
27、0.2 % water. More than that will interfere by destroying the esterification reagents.8.2 Primary and secondary amines and long-chain fatty acids react with the reagent to form stable compounds that would beincluded in the analysis.9. Apparatus9.1 Bottle, pressure, heat-resistant, approximately 350 m
28、L.9.2 Bag, , heavy fabric with draw string to hold bottle. As an alternative, a stainless steel mesh jacket fitted to cover the bottle can be used.9.3 Buret, 100-mL total capacity, range of graduated portion 50 mL, 0.1-mL graduations.NOTE 2As a substitute, if the 100-mL buret is not available, the f
29、irst 50 mL of titrant can be added by pipet (uniform drainage time for all aliquots)and the titration completed with a 50-mL buret.9.4 Water Bath,986 2C, containing enough water to cover the liquid in the sample bottles. The water level must be asprescribed, and the temperature must be within the pr
30、escribed range and uniform throughout the bath.4“Reagent Chemicals, American Chemical Society Specifications,” Am. Chemical Soc., Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society, see “Reagent Chemicals and Standards,” by Joseph Rosin, D. Van Nost
31、rand Co., Inc., New York, NY, and the “United States Pharmacopeia.”D4274 11210. Reagents10.1 Acetic Anhydride.10.2 Acetylation ReagentMix 127 mL of acetic anhydride with 1000 mL of pyridine (10.5). Prepare the reagent fresh dailyand keep it in a dark bottle. Do not use it if it is darker than pale y
32、ellow.10.3 Hydrochloric Acid, Standard (0.5 N)Prepare and standardize in accordance with Sections 20 to 24 of Practice E200.Determine and record the temperature at which the standardization was performed. The concentration of the solution shall becorrected to the temperature at which the determinati
33、on is performed as described in 10.6. The factor for the thermal expansionof this solution is 0.00014. This solution is required only if a correction is to be applied for the presence of strong base in the samplebeing analyzed.10.4 Phenolphthalein Indicator SolutionDissolve1gofphenolphthalein in 100
34、 mL of pyridine.10.5 Pyridine, containing from 0.30 to 0.45 % water. Determine the water content of the pyridine using Test Method E203.Addthe required amount of water. The volume of water to add, mL,mL per litre of pyridine can be calculated as follows:Water to add 5 4.0 2 9A (1)where A = percent o
35、f water in pyridine.10.6 Sodium Hydroxide, Standard Solution (0.5 N)Prepare and standardize in accordance with Sections 14 to 19 of PracticeE200. Determine and record the temperature at which the standardization was performed. The factor for thermal expansion of thissolution is 0.00014. For calculat
36、ion of the hydroxyl content, the normality of the solution shall be corrected to the temperature atwhich the determination is performed by the following:Nt25 Nt11 t12 t2!F! (2)where:Nt1= normality when standardized,Nt2= normality during analysis of samples,t1= temperature of solution during standard
37、ization, C,t2= temperature of solution during analysis of samples, C, andF = factor to correct for thermal expansion of the solution (see each solution for appropriate factor).11. Procedure11.1 Pipet 20.0 mL of the acetylation reagent to each pressure bottle for the blank and sample determinations (
38、in duplicate). Usethe same drainage time for each aliquot.11.2 Reserve two of the bottles for the blank determinations; weigh samples to the nearest 0.1 mg into the other bottles.Determine the sample weight, g, as follows:Sample weight 5 561 3 0.98!/approximate hydroxyl number(3)Since the calculated
39、 weight will be near the maximum permitted by the test method, adhere closely to the indicated weight.11.3 Stopper the bottle and swirl it until the sample is completely dissolved. Enclose each bottle in a fabric bag and place allbottles as close together as possible in the water bath at 98 6 2C for
40、 2 h. Keep enough water in the bath to cover the level ofliquid in the bottles.11.4 Remove the bottles from the bath and allow them to cool to room temperature. Untie the bags, uncap the bottles to releaseany pressure, and then remove the bags.11.5 Carefully rinse any liquid on the stopper into the
41、bottle and rinse the walls of the flask with 20 to 30 mL of water. Addclean crushed ice to each of the bottles until about half full.11.6 Add 1 mL of the phenolphthalein indicator solution and titrate immediately with the 0.5 N NaOH solution to the first faintpink end point that persists for 15 s. T
42、he solution is to be swirled during the titration, with vigorous swirling as the end point isreached. Record the volume of titrant to 0.02 mL (Note 3). Record the temperature of the NaOH solution.NOTE 3If the volume of 0.5 N NaOH solution required for the sample is less than 80 % of that required fo
43、r the blank, the sample was too large andthe analysis must be repeated with a smaller sample.11.7 Acidity or Alkalinity CorrectionIf the sample contains significant acidity or alkalinity, correct the result as follows.Weigh into a 400-mL Erlenmeyer flask the same amount of sample used before for the
44、 hydroxyl determination. Add to the flask75 mL of redistilled pyridine, 75 mL of distilled water, and 0.5 mL of phenolphthalein indicator solution.11.8 Acidity CorrectionIf the solution is colorless, titrate with standard 0.1 N NaOH to a pink end point that persists for atleast 15 s. Make a blank ti
45、tration on the reagent mixture described in 11.7, omitting the sample. The acidity correction, mg KOH/g,is calculated as follows:Acidity correction 5 A 2 B!N 3 56.1/W (4)D4274 113Wwhere:A = NaOH solution required for titration of the blank,sample, mL,B = NaOH solution required for titration of the b
46、lank, mL,N = normality of the NaOH solution, andW = sample used, g.56.1 = Eq weight of KOH, mg/meq11.9 Alkalinity CorrectionIf the solution in 11.7 is pink, titrate to the disappearance of the pink color with 0.1 N HCl, andthen add 1.0 mL excess. Back-titrate with standard 0.1 N NaOH to a pink end p
47、oint that persists for at least 15 s. Titrate withstandard 0.1 N NaOH a blank containing exactly the same amount of added 0.1 N HCl and the reagent mixture described in 11.7omitting the sample. The alkalinity correction, mg KOH/g, is calculated as follows:Alkalinity correction 5 B 2 A!N 3 56.1/W (5)
48、where the terms are as defined as in 11.8.12. Calculation12.1 Calculate the hydroxyl number, mg KOH/g, of sample as follows:Hydroxyl number 5 B 2 A!N 3 56.1/W (6)where:A = NaOH required for titration of the sample, mL,B = NaOH required for titration of the blank, mL,N = normality of the NaOH, andW =
49、 sample used, g.12.2 If the sample contains free acidity or alkalinity as measured in 11.7-11.9, the result in 12.1 must be corrected as follows:Hydroxyl number corrected!5hydroxyl number 1 acidity, or(7)Hydroxyl number corrected!5hydroxyl number 2 alkalinity(8)13. Report13.1 Report the corrected hydroxyl number to the nearest 0.1.14. Precision and Bias514.1 PrecisionAttempts to develop a precision and bias statement for this test method have not been successful. For thisreason, data on precision and bias cannot be given. Cont
