Standard Test Methods for Testing Polyurethane Raw ...

1 Designation: D 4274 99 Standard Test Methods for TestingPolyurethane Raw Materials: determination of HydroxylNumbers of Polyols1 This 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 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 Scope * These test Methods measure the hydroxyl groups inpolyester and polyether polyols containing primary and sec-ondary hydroxyl groups. They also apply to many otherhydroxyl-containing Method A Acetic Anhydride Pressure Bottle,recommended for Method B Phthalic Anhydride Pressure Bottle,recommended for polyethers and Method C Phthalic Anhydride Reflux, recom-mended for polyethers and Method D Imidazole Catalyzed Phthalic Anhy-dride Pressure Bottle, recommended for polyethers, polyesters,polymer polyols, and amine-initiated Method E2 Imidazole-Catalyzed PyromelliticDianhydride Esterification, recommended for polyols used forflexible and rigid Polyurethane foams and urethane is recommended for polyester polyols, polyether polyols,amine-started polyols, and polymer polyols (polyacrylonitrile/copolystyrene-based).

2 Other ASTM test Methods for measuring hydroxylgroups are Test Methods D 1957, E 222, E 326, and E 335 (seeNote 1).NOTE1 Test 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 The values stated in SI units are to be regarded as 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 of regulatory limitations prior to Referenced standards :D 883 Terminology Relating to Plastics3D 1193 Specification for Reagent Water2D 1957 Test Method for Hydroxyl Value of Fatty Oils andAcids4E 180 Practice for Determining the Precision of ASTMM ethods for Analysis and Testing of Industrial Chemicals5E 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis5E 203 Test Method for Water Using Karl Fischer Reagent5E 222 Test Methods for Hydroxyl Groups by Acetic Anhy-dride Acetylation5E 326 Test Method for Hydroxyl Groups by Phthalic Anhy-dride Esterification5E 335 Test Method for Hydroxyl Groups by PyromelliticDianhydride Esterification5E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Standard :7 ISO6791-1981 PolyglycolsforIndustrialUse determination of Hydroxyl Number Phthalic AnhydrideEsterification Method3.

3 The terminology in these test methodsfollows the Standard terminology defined in TerminologyD of Terms Specific to This Standard Thereare no terms in these test Methods that require new or otherthan dictionary test Methods are under the jurisdiction of ASTM Committee D-20 onPlastics and are the direct responsibility of Subcommittee on CellularPlastics. These test Methods were recommended to ASTM by the Society of thePlastics Industry Polyurethane Raw material Analysis edition approved Nov. 10, 1999. Published February 2000. Originallypublished as D 4274 88. Last previous edition D 4274 Book of ASTM standards ,Vol Book of ASTM standards , Vol Book of ASTM standards ,Vol Book of ASTM standards ,Vol Book of ASTM standards , Vols , , and from American National standards Institute, 11 W. 42nd St., 13thFloor, New York, NY *A Summary of Changes section appears at the end of this ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Summary of Test Method A The sample is acetylated with a solu-tion of acetic anhydride (Caution:see Note 2) in pyridine in apressure bottle at 98 C.

4 The excess reagent is hydrolyzed withwater and the acetic acid is titrated with Standard sodiumhydroxide solution. The hydroxyl content is calculated fromthe difference in titration of the blank and sample Caution:Acetic anhydride and pyridine are toxic and flam-mable. In addition, acetic anhydride is corrosive. Proper precautionsshould be taken in handling these Method B The hydroxyl group is esterified with asolution of phthalic anhydride in pyridine in a pressure bottleat 98 C. The excess reagent is titrated with Standard sodiumhydroxide Method C The hydroxyl group is esterified with asolution of phthalic anhydride in pyridine under reflux condi-tions at 115 C. The excess reagent is titrated with standardsodium hydroxide Method D The hydroxyl group is esterified byreaction with phthalic anhydride in a pyridine medium atapproximately 100 C. The esterification reaction is catalyzedby imidazole.

5 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 Method E The hydroxyl group is esterified with asolution of imidazole (IMDA) and pyromellitic dianhydride(PMDA) in dimethylformamide in an iodine flask at 70 to80 C. The excess reagent is titrated with Standard sodiumhydroxide Significance and These test Methods are suitable for research and asquality control and specification tests . It is necessary to knowthe hydroxyl contents of polyols in order to formulate poly-urethane of Reagents Use reagent-grade chemicals in alltests. Unless otherwise indicated, all reagents must conform tothe specifications of the Committee on Analytical Reagents ofthe American Chemical Society, where such specifications grades may be used, provided they are pureenough to be used without lowering of Water Unless otherwise indicated, use TypeII water conforming to Specification D Polyesters and polyethers usually contain moleculescovering an appreciable range of molecular weights.

6 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 mix the resin wellbefore removing a sample for analysis. Many polyols arehygroscopic, and care should be taken to provide minimumexposure to atmospheric moisture during the METHOD A ACETYLATION8. Dry the sample if it contains more than % than that will interfere by destroying the Primary and secondary amines and long-chain fattyacids react with the reagent to form stable compounds thatwould be included in the ,9pressure, heat-resistant, approximately 350 ,10heavy fabric with draw string to hold bottle. Asan alternative, a stainless steel mesh jacket fitted to cover thebottle may be , 100-mL total capacity, range of graduated portion50 mL, As a substitute, if the 100-mL buret is not available, the first50 mL of titrant may be added by pipet (uniform drainage time for allaliquots) and the titration completed with a 50-mL Bath,9862 C, containing enough water to coverthe liquid in the sample bottles.

7 The water level must be asprescribed, and the temperature must be within the prescribedrange and uniform throughout the Reagent Mix 127 mL of acetic anhydridewith 1000 mL of pyridine ( ). Prepare the reagent freshdaily and keep it in a dark bottle. Do not use it if it is darkerthan pale Acid, Standard ( ) Prepare andstandardize in accordance 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 The factor forthe thermal expansion of this solution is This solutionis required only if a correction is to be applied for the presenceof strong base in the sample being Indicator Solution Dissolve1gofphenolphthalein in 100 mL of , containing from to % water. Deter-mine the water content of the pyridine using Test MethodE 203.

8 Add the required amount of water. The volume of waterto add, mL, per litre of pyridine may be calculated as follows:8 Reagent Chemicals, American Chemical Society Specifications, Am. Chemi-cal Soc., Washington, DC. For suggestions on the Testing of reagents not listed bythe American Chemical Society, see Reagent Chemicals and standards , by JosephRosin, D. Van Nostrand Co., Inc., New York, NY, and the United StatesPharmacopeia. 9A suitable bottle is available from B. Preiser Co., Inc., Charleston, WV, CatalogNo. 10-5485; Chemical Rubber Co., Cleveland, OH, Catalog No. 33052A; andScientific Glass Co., Bloomfield, NJ, Catalog No. from Flaherty Filter Media, Inc., 16 Passaic Ave., Box 357,Spring Lake, NJ 42742 Water to (1)whereA= percent of water in Hydroxide, Standard Solution( ) Prepare and standardize in accordance with Sections 14 to 19of Practice E 200. Determine and record the temperature atwhich the standardization was performed.

9 The factor forthermal expansion of this solution is For calculationof the hydroxyl content, the normality of the solution shall becorrected to the temperature at which the determination isperformed by the following:Nt25Nt11~t12t2!~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, C, andF= factor to correct for thermal expansion of thesolution (see each solution for appropriate factor).11. Pipet mL of the acetylation reagent to eachpressure bottle for the blank and sample determinations (induplicate). Use the same drainage time for each Reserve two of the bottles for the blank determinations;weigh samples to the nearest mg into the other the sample weight, g, as follows:Sample weight5~ !/approximate hydroxyl number(3)Since the calculated weight will be near the maximumpermitted by the test method, adhere closely to the Stopper the bottle and swirl it until the sample iscompletely dissolved.

10 Enclose each bottle in a fabric bag andplace all bottles as close together as possible in the water bathat 9862 C for 2 h. Keep enough water in the bath to cover thelevel of liquid in the 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 Carefully rinse any 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 Add 1 mL of the phenolphthalein indicator solutionand titrate immediately with the solution to thefirst faint pink end point that persists for 15 s. The solutionshould be swirled during the titration, with vigorous swirling asthe end point is reached. Record the volume of titrant to (Note 4). Record the temperature of the NaOH If the volume of solution required for the sampleis less than 80 % of that required for the blank, the sample was too largeand the analysis must be repeated with a smaller or Alkalinity Correction If the sample con-tains significant acidity or alkalinity, correct the result asfollows.