1、Designation: D4274 11D4274 16Standard 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 the case of
2、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 containing pr
3、imary 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 Method CPhthali
4、c 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 Esterification,
5、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).1.2 Another ASTM test method for measuring hydroxyl groups is T
6、est Method E222.1.3 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 standard to establish appropriate safety and health practices an
7、d determine the applicability of regulatorylimitations prior to use.NOTE 1This standard standard, ISO 14900 and ISO 6796 address the same subject matter, but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1193 Specification for Reagent Wa
8、terE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3E200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical AnalysisE203 Test Method for Water Using Volumetric
9、 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:4ISO 6796 Polyglycols for Industrial UseDetermination of Hydroxyl NumberPhthalic Anhydride
10、Esterification MethodISO 14900 PlasticsPolyols for Use in the Production of PolyurethaneDetermination of Hydroxyl Number3. Terminology3.1 DefinitionsThe terminology in these test methods follows the standard terminology defined in Terminology D883.1 These test methods are under the jurisdiction ofAS
11、TM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand Elastomers.Current edition approved Feb. 1, 2011April 1, 2016. Published March 2011April 2016. Originally approved in 1988. Last previous edition approved in 20052011 asD4274 - 05
12、.D4274 - 11. DOI: 10.1520/D4274-11.10.1520/D4274-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The las
13、t approved version of this historical standard is referenced on www.astm.org.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM stan
14、dard an indication of what changes have been made to the previous 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 AST
15、M is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This StandardThere are no terms in these
16、 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 is hydrolyzed with water and the acetic acid is titrated with standard
17、 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 corrosive. Proper precautions must be taken in handling these reagents.).4.
18、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 hydrolyzed with water and the acidic species are titrated with standard sodium hydroxide solution.4.3 Test Method CThe hydroxyl group is esterified with
19、 a solution of phthalic anhydride in pyridine under reflux conditionsat 115C. The excess reagent is hydrolyzed with water and the acidic species are titrated with standard sodium hydroxide solution.4.4 Test Method DThe hydroxyl group is esterified by reaction with phthalic anhydride in a pyridine me
20、dium at approximately100C. The 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
21、titration of the blank and the 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 hydrolyzed with water and the acidic speciesare titrated
22、with standard sodium hydroxide solution.5. Significance and Use5.1 These test 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. ReagentsNOTE 2Test methods A through D
23、 use pyridine as a solvent, which is a suspected teratogen. Avoid contact with skin and inhalation of vapors. Useonly in a well-ventilated area, such as a fume hood. Use a combination of engineering controls and personal protective equipment, including respiratory,skin and eye protection, to prevent
24、 over-exposure to pyridine. In the event a non-pyridine method is required, use test method E.6.1 Purity of ReagentsUse reagent-grade chemicals in all tests. Unless otherwise indicated, all reagents must conform to thespecifications of the Committee on Analytical Reagents of the American Chemical So
25、ciety, where such specifications areavailable.5 Other grades can be used, are allowed, provided they are pure enough to be used without lowering accuracy.6.2 Purity of WaterUnless otherwise indicated, use Type II water conforming to Specification D1193.7. Sampling7.1 Polyesters and polyethers usuall
26、y 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 highertemperature than necessary) and mix the resin well before removing a sample for anal
27、ysis. 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 0.2 % water. More than that will interfere by destroying the esterification reagents.
28、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 mL.9.2 Bag, heavy fabric with draw string to hold bottle. As an alternative, a stainle
29、ss steel mesh jacket fitted to cover the bottlecan be is used.9.3 Buret, 100-mL total capacity, range of graduated portion 50 mL, 0.1-mL graduations.5 “Reagent Chemicals, American Chemical Society Specifications,” Am. Chemical Soc., Washington, DC. For suggestions on the testing of reagents not list
30、ed by theAmerican Chemical Society, see “Reagent Chemicals and Standards,” by Joseph Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States Pharmacopeia.”D4274 162NOTE 3As a substitute, if the 100-mL buret is not available, the first 50 mL of titrant can be is added by pipet (uniform
31、 drainage time for all aliquots)and the titration completed with a 50-mL buret.9.4 Water Bath, 986 98 6 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 prescribed range and uniform throughout the bath
32、.10. Reagents10.1 Acetic Anhydride.10.2 Acetylation ReagentMix 127 mL of acetic anhydride with 1000 mL of pyridine (10.5).(10.5). Prepare the reagent freshdaily and keep it in a dark bottle. Do not use it if it is darker than pale yellow.10.3 Hydrochloric Acid, Standard (0.5 N)Prepare and standardiz
33、e 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 determination is performed as described in 10.6. The factor for the thermal exp
34、ansionof 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 SolutionDissolve 1 g of phenolphthalein in 100 mL of pyridine.10.5 Pyridine, containing from 0.30 to 0.45 % wat
35、er. Determine the water content of the pyridine using Test Method E203.Addthe required amount of water. The volume of water to add, mL per litre of pyridine can be is calculated as follows:Water to add54.029A (1)where A = percent of water in pyridine.10.6 Sodium Hydroxide, Standard Solution (0.5 N)P
36、repare 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 calculation of the hydroxyl content, the normality of the solution shall be c
37、orrected to the temperature atwhich the determination is performed by the following:Nt2 5Nt1 1t1 2t2!F! (2)where:Nt1 = normality when standardized,Nt2 = normality during analysis of samples,t1 = temperature of solution during standardization, C,t2 = temperature of solution during analysis of samples
38、, C, andF = factor to correct for thermal expansion of the solution (see each solution for appropriate factor).11. Procedure11.1 Pipet 20.0 mLof the acetylation reagent to each pressure bottle for the blank and sample determinations (in duplicate). Usethe same drainage time for each aliquot.11.2 Res
39、erve 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 weight556130.98!/approximate hydroxyl number (3)Since the calculated weight will be near the maximum permitted by the test method, adhere
40、 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 2 h. Keep enough water in the bath to cover the level ofliquid in th
41、e 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 bottle and rinse the walls of the flask with 20 to 30 mL of water. Ad
42、dclean 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. The solution is to be swirled during the titration, with vigorous swir
43、ling as the end point isreached. Record the volume of titrant to 0.02 mL (Note 34). Record the temperature of the NaOH solution.NOTE 4If the volume of 0.5 N NaOH solution required for the sample is less than 80 % of that required for the blank, the sample was too large andthe analysis must be repeat
44、ed with a smaller sample.D4274 16311.7 Acidity or Alkalinity CorrectionIf the sample contains significant acidity or alkalinity, correct the result as follows.Weighinto a 400-mL Erlenmeyer flask the same amount of sample used before for the hydroxyl determination. Add to the flask 75 mLof redistille
45、d 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 titration on the reagent mixture described in 11.7, omitting t
46、he sample. The acidity correction, mg KOH/g,is calculated as follows:Acidity correction5A 2B!N 356.1#/W (4)where:A = NaOH solution required for titration of the sample, mL,B = NaOH solution required for titration of the blank, mL,N = normality of the NaOH solution, andW = sample used, g.56.1 = Eq we
47、ight 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, and thenadd 1.0 mL excess. Back-titrate with standard 0.1 N NaOH to a pink end point that persists for at least 15 s. Titrate with standard0.1 N NaOH a blank c
48、ontaining exactly the same amount of added 0.1 N HCl and the reagent mixture described in 11.7 omittingthe sample. The alkalinity correction, mg KOH/g, is calculated as follows:Alkalinity correction5B 2A!N 356.1#/W (5)where the terms are as defined as in 11.8.12. Calculation12.1 Calculate the hydrox
49、yl number, mg KOH/g, of sample as follows:Hydroxyl number5B 2A!N 356.1#/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 = 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 number1acidity,or (7)Hydroxyl number corrected!5hydroxyl number1acidity correction,or (7)Hydroxyl number corrected!5hydroxyl number2alk
