1、Designation: D 4274 05Standard Test Methods for TestingPolyurethane Raw Materials: Determination of HydroxylNumbers of Polyols1This standard is issued under the fixed designation D 4274; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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 These test methods measure the hydroxyl groups inpolyester and polyether polyols containing primary
3、and sec-ondary hydroxyl groups. They also apply to many otherhydroxyl-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 CPhthalic Anhyd
4、ride Reflux, recom-mended for polyethers and polyesters.1.1.4 Test Method DImidazoleCatalyzed Phthalic Anhy-dride Pressure Bottle, recommended for polyethers, polyesters,polymer polyols, and amine-initiated polyols.1.1.5 Test Method E2Imidazole-Catalyzed PyromelliticDianhydride Esterification, recom
5、mended for polyols used forflexible and rigid polyurethane foams and urethane elastomers.It is recommended for polyester polyols, polyether polyols,amine-started polyols, and polymer polyols (polyacrylonitrile/copolystyrene-based).1.2 Other ASTM test methods for measuring hydroxylgroups are Test Met
6、hods D 1957 and E 222 (see Note 1).NOTE 1Test Method C is essentially similar to ISO 6796-1981, butthere are some differences in the concentrations used and some proceduraldetails. There are currently no data available for comparing the results ofTest Method C to those of ISO 6796-1981.1.3 The value
7、s stated in SI units are to be regarded as thestandard.1.4 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 determine the applica-bility
8、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 1193 Specification for Reagent WaterD 1957 Test Method for Hydroxyl Value of Fatty Oils andAcidsE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Test
9、ing of Industrial ChemicalsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysisE 203 Test Method for Water Using Karl Fischer ReagentE 222 Test Methods for Hydroxyl Groups by Acetic Anhy-dride AcetylationE 691 Practice for Conducting an
10、 Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:3ISO 6796-1981 Polyglycols for Industrial UseDetermination of Hydroxyl NumberPhthalic AnhydrideEsterification Method3. Terminology3.1 DefinitionsThe terminology in these test methodsfollows the standard terminology def
11、ined in TerminologyD 883.3.2 Definitions of Terms Specific to This StandardThereare no terms in these test methods that require new or otherthan dictionary definitions.4. Summary of Test Methods4.1 Test Method AThe sample is acetylated with a solu-tion of acetic anhydride in pyridine in a pressure b
12、ottle at 98C.The excess reagent is hydrolyzed with water and the acetic acidis titrated with standard sodium hydroxide solution. Thehydroxyl content is calculated from the difference in titration ofthe blank and sample solutions. (WarningAcetic anhydrideand pyridine are toxic and flammable. In addit
13、ion, aceticanhydride is corrosive. Proper precautions must be taken inhandling these reagents.)1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.22 on CellularMaterialsPlastics and Elastomers.Current edition approved
14、July 1, 2005. Published August 2005. Originallyapproved in 1988. Last previous edition approved in 1999 as D 4274 - 99.2For 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
15、to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
16、st Conshohocken, PA 19428-2959, United States.4.2 Test Method BThe hydroxyl group is esterified with asolution of phthalic anhydride in pyridine in a pressure bottleat 98C. The excess reagent is titrated with standard sodiumhydroxide solution.4.3 Test Method CThe hydroxyl group is esterified with as
17、olution of phthalic anhydride in pyridine under reflux condi-tions at 115C. The excess reagent is titrated with standardsodium hydroxide solution.4.4 Test Method DThe hydroxyl group is esterified byreaction with phthalic anhydride in a pyridine medium atapproximately 100C. The esterification reactio
18、n is catalyzedby imidazole. The excess anhydride is hydrolyzed with water,and the phthalic acid formed is titrated to the phenolphthaleinend point with standard sodium hydroxide solution. Thehydroxyl content is calculated from the difference in titration ofthe blank and the sample solution.4.5 Test
19、Method EThe hydroxyl group is esterified with asolution of imidazole (IMDA) and pyromellitic dianhydride(PMDA) in dimethylformamide in an iodine flask at 70 to80C. The excess reagent is titrated with standard sodiumhydroxide solution.5. Significance and Use5.1 These test methods are suitable for res
20、earch and asquality control and specification tests. It is necessary to knowthe hydroxyl contents of polyols in order to formulate poly-urethane systems.6. Reagents6.1 Purity of ReagentsUse reagent-grade chemicals in alltests. Unless otherwise indicated, all reagents must conform tothe specification
21、s of the Committee on Analytical Reagents ofthe American Chemical Society, where such specifications areavailable.4Other grades can be used, provided they are pureenough to be used without lowering accuracy.6.2 Purity of WaterUnless otherwise indicated, use TypeII water conforming to Specification D
22、 1193.7. Sampling7.1 Polyesters and polyethers usually contain moleculescovering an appreciable range of molecular weights. Thesehave a tendency to fractionate during solidification. Unless thematerial is a finely-ground solid it is necessary to melt (usingno higher temperature than necessary) and m
23、ix the resin wellbefore removing a sample for analysis. Many polyols arehygroscopic, and care is to be taken to provide minimumexposure 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 inte
24、rfere by destroying the esterificationreagents.8.2 Primary and secondary amines and long-chain fattyacids react with the reagent to form stable compounds thatwould be included in the analysis.9. Apparatus9.1 Bottle, pressure, heat-resistant, approximately 350 mL.9.2 Bag,5,6heavy fabric with draw str
25、ing to hold bottle. Asan alternative, a stainless steel mesh jacket fitted to cover thebottle can be used.9.3 Buret, 100-mLtotal capacity, range of graduated portion50 mL, 0.1-mL graduations.NOTE 2As a substitute, if the 100-mL buret is not available, the first50 mL of titrant can be added by pipet
26、(uniform drainage time for allaliquots) and the titration completed with a 50-mL buret.9.4 Water Bath,986 2C, containing enough water to coverthe liquid in the sample bottles. The water level must be asprescribed, and the temperature must be within the prescribedrange and uniform throughout the bath
27、.10. Reagents10.1 Acetic Anhydride.10.2 Acetylation ReagentMix 127 mL of acetic anhydridewith 1000 mL of pyridine (10.5). Prepare the reagent freshdaily and keep it in a dark bottle. Do not use it if it is darkerthan pale yellow.10.3 Hydrochloric Acid, Standard (0.5 N)Prepare andstandardize in accor
28、dance with Sections 20 to 24 of PracticeE 200. Determine and record the temperature at which thestandardization was performed. The concentration of the solu-tion shall be corrected to the temperature at which thedetermination is performed as described in 10.6. The factor forthe thermal expansion of
29、this solution is 0.00014. This solutionis required only if a correction is to be applied for the presenceof strong base in the sample being analyzed.10.4 Phenolphthalein Indicator SolutionDissolve1gofphenolphthalein in 100 mL of pyridine.10.5 Pyridine, containing from 0.30 to 0.45 % water. Deter-min
30、e the water content of the pyridine using Test MethodE 203.Add the required amount of water. The volume of waterto add, mL, per litre of pyridine can be calculated as follows:Water to add 5 4.0 2 9A (1)where A = percent of water in pyridine.10.6 Sodium Hydroxide, Standard Solution (0.5 N)Prepare and
31、 standardize in accordance with Sections 14 to 19of Practice E 200. Determine and record the temperature atwhich the standardization was performed. The factor forthermal expansion of this solution is 0.00014. For calculationof the hydroxyl content, the normality of the solution shall becorrected to
32、the temperature at which the determination isperformed by the following:4“Reagent Chemicals,American Chemical Society Specifications,”Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed bytheAmerican Chemical Society, see “Reagent Chemicals and Standards,” by Jo
33、sephRosin, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”5The sole source of supply of the apparatus known to the committee at this timeis Flaherty Filter Media, Inc., 16 Passaic Ave., P.O. Box 357, Spring Lake, NJ07762.6If you are aware of alternative suppliers, pleas
34、e provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.D4274052Nt25 Nt11 t12 t2!F! (2)where:Nt1= normality when standardized,Nt2= normality during analysis of samples,t1
35、= temperature of solution during standardization, C,t2= temperature of solution during analysis of samples,C, andF = factor to correct for thermal expansion of thesolution (see each solution for appropriate factor).11. Procedure11.1 Pipet 20.0 mL of the acetylation reagent to eachpressure bottle for
36、 the blank and sample determinations (induplicate). Use the 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 h
37、ydroxyl number (3)Since the calculated weight will be near the maximumpermitted by the test method, adhere closely to the indicatedweight.11.3 Stopper the bottle and swirl it until the sample iscompletely dissolved. Enclose each bottle in a fabric bag andplace all bottles as close together as possib
38、le in the water bathat 98 6 2C for 2 h. Keep enough water in the bath to cover thelevel of liquid in the bottles.11.4 Remove the bottles from the bath and allow them tocool to room temperature. Untie the bags, uncap the bottles torelease any pressure, and then remove the bags.11.5 Carefully rinse an
39、y liquid on the stopper into the bottleand 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 solutionand titrate immediately with the 0.5 N NaOH solution to thefirst faint pink end
40、point that persists for 15 s. The solution isto be swirled during the titration, with vigorous swirling as theend point is reached. 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 sampleis less t
41、han 80 % of that required for the blank, the sample was too largeand the analysis must be repeated with a smaller sample.11.7 Acidity or Alkalinity CorrectionIf the sample con-tains significant acidity or alkalinity, correct the result asfollows. Weigh into a 400-mL Erlenmeyer flask the sameamount o
42、f sample used before for the hydroxyl determination.Add to the flask 75 mL of redistilled pyridine, 75 mL ofdistilled water, and 0.5 mL of phenolphthalein indicator solu-tion.11.8 Acidity CorrectionIf the solution is colorless, titratewith standard 0.1 N NaOH to a pink end point that persists forat
43、least 15 s. Make a blank titration on the reagent mixturedescribed 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)where:A = NaOH solution required for titration of the blank, mL,B = NaOH solution required for titration
44、 of the blank, mL,N = normality of the NaOH solution, andW = sample used, g.11.9 Alkalinity CorrectionIf the solution in 11.7 is pink,titrate to the disappearance of the pink color with 0.1 N HCl,and then add 1.0 mL excess. Back-titrate with standard 0.1 NNaOH to a pink end point that persists for a
45、t least 15 s. Titratewith standard 0.1 N NaOH a blank containing exactly the sameamount of added 0.1 N HCl and the reagent mixture describedin 11.7 omitting the sample. The alkalinity correction, mgKOH/g, is calculated as follows:Alkalinity correction 5 B 2 A!N 3 56.1/W (5)where the terms are as def
46、ined as in 11.8.12. Calculation12.1 Calculate the hydroxyl number, mg KOH/g, of sampleas 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 = sample used, g.12.2 If the
47、 sample contains free acidity or alkalinity asmeasured in 11.7-11.9, the result in 12.1 must be corrected asfollows: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 nearest0
48、.1.14. Precision and Bias714.1 PrecisionAttempts to develop a precision and biasstatement for this test method have not been successful. Forthis reason, data on precision and bias cannot be given. Contactthe Chairman, Subcommittee D20.22,ASTM, 100 Barr HarborDrive, West Conshohocken, PA 194282959 to
49、 participate inthe development of precision and bias data.14.2 It is estimated that duplicate results by the same analystare to be considered suspect if they differ by more than 1 unit(where the measured hydroxyl number 120).14.3 BiasThere are no recognized standards on which tobase an estimate of bias for this test method.7Supporting data are available from ASTM Headquarters. Request RR: D20-1089.D4274053TEST METHOD BPRESSURE-BOTTLEPHTHALATION15. Interferences15.1 Excessive amounts of water in the sample will interfereby destruc
