1、Designation: D5629 11D5629 16Standard Test Method forPolyurethane Raw Materials: Determination of Acidity inLow-Acidity Aromatic Isocyanates and PolyurethanePrepolymers1This standard is issued under the fixed designation D5629; the number immediately following the designation indicates the year ofor
2、iginal adoption 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.1. Scope*1.1 This test method measures the acidity, expressed as ppm of h
3、ydrochloric acid (HCl), in aromatic isocyanate or polyurethaneprepolymer samples of below 100 ppm acidity. The test method is applicable to products derived from toluene diisocyanate andmethylene di(phenylisocyanate) (see Note 1). Refer toTest Method D6099 for determination of acidity in moderate- t
4、o high-acidityaromatic isocyanates.1.2 The values stated in SI units are to be regarded as the standard.1.3 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
5、health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1This standard is equivalent to ISO 14898, Method B.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD6099 Test Method for Polyurethane Raw Materials: Determination of Acidity i
6、n Moderate to High Acidity AromaticIsocyanatesE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 ISO Standards:
7、4ISO 14898 PlasticsAromatic Isocyanates for Use in the Production of PolyurethaneDetermination of Acidity3. Terminology3.1 DefinitionsThe terminology in this test method follows the standard terminology defined in Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity, nth
8、e acid strength of a sample expressed in ppm HCl.4. Summary of Test Method4.1 The isocyanate is mixed with an excess of n-propanol, a cosolvent and a known amount of HCl.Additional acid is releasedinto the solvent system during urethane formation. The acid is then titrated potentiometrically with me
9、thanolic KOH. The sameprocedure is performed with a blank solution and the difference in titer is used to calculate the acidity present in the isocyanatesample.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Ce
10、llular Materials - Plasticsand Elastomers.Current edition approved Feb. 1, 2011April 1, 2016. Published March 2011April 2016. Originally approved in 1994. Last previous edition approved in 20052011 asD5629 - 05.D5629 - 11. DOI: 10.1520/D5629-11.10.1520/D5629-16.2 For referencedASTM standards, visit
11、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 last approved version of this historical standard is referenced on www.astm.org.4 Available f
12、rom 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 standard an indication of what changes have been made to the previous version. Becauseit may n
13、ot 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 Changes section appears at the e
14、nd of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 This test method can be used is suitable for research or for quality control to characterize aromatic isocyanates andlow-acidity prepolymers
15、. Acidity correlates with performance in some polyurethane systems.6. Apparatus6.1 Disposable Beakers, 250 mL.6.2 Repipet, pipet or buret, 50 mL.6.3 Pipet, 100 mL, class A volumetric; or a 100-mL buret with a dosing unit; or a 100-mL repipet, class A volumetric.6.4 Potentiometric Titrator:6.4.1 Refe
16、rence ElectrodeElectrode, bridge-type electrolyte (double junction), sleeve-type diaphragm, having saturatedLiCl/ethanol solution in both chambers, or equivalent.6.4.2 pH Glass Electrode (see Note 2).NOTE 2A combination pH electrode with internal reference is acceptable.6.5 Magnetic Stirrer.6.6 Poly
17、tetrafluoroethylene-Coated Stir Bars.6.7 Watch Glasses.6.8 Analytical Balance, capable of weighing to the nearest 0.1 mg.7. Reagents and Materials7.1 0.01 N KOH in Methanol, for example, 0.66 g 87.7 % KOH/1000 mL methanol, standardized with potassium hydrogenphthalate (KHP).7.2 Toluene or THF (dried
18、 for 24 h over 5 A molecular sieves).7.3 n-Propanol, acidified with 120 L concentrated hydrochloric acid per 4-L bottle.Allow this solution to stand for at least 24h before use to allow equilibration. The solution is to be mixed well before dispensing.8. Sampling8.1 Since organic isocyanates react w
19、ith atmospheric moisture, take special precautions in sampling. Usual sampling methods,even when conducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dryair or nitrogen at all times. (WarningMany diisocyanates are known or suspected sensiti
20、zers. Over-exposure to diisocyanatescan lead to adverse health effects which include the development of occupational asthma and other respiratory, skin and eye effects.Engineering controls and/orDiisocyanates are eye, skin and respiratory irritants at concentrations above the occupational exposureli
21、mit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people. Once sensitized, it isessential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal protective equipment,including respiratory, skin and eye protection
22、, are to be used when there is a potential for to prevent over-exposure to diisocyanates.The Consult the product suppliersMaterialSafety Data Safety Sheet (MSDS) provides(SDS) for more detailed information aboutpotential adverse health effects and other importantspecific safety and handling informat
23、ion.Always follow the specific instructionsprovided on the MSDS.instructions for the product.)9. Calibration9.1 Calibrate the electrodes using pH 4 and 7 aqueous buffers.10. Test Conditions10.1 Since isocyanates react with moisture, keep samples protected against moisture until immediately before te
24、sting. laboratoryhumidity low, preferably around 50 % relative humidity. For further information, see 8.1.11. Procedure11.1 Make a blank determination in conjunction with each series of samples. Prepare the blank in the same manner as a sample,only omitting the sample. All samples and blanks are to
25、be made in duplicate.11.2 Accurately weigh, to the nearest 0.1 mg, 20 g of sample into a 250-mL beaker.11.3 Add 50 mL of dried toluene (dried over 5-A molecular sieves).NOTE 3For prepolymers, THF is an acceptable substitute for toluene.NOTE 4If a sample is difficult to get into solution, it is accep
26、table to gently heat and stir to ensure homogeneity.11.4 Pipet 100 mL of acidified n-propanol into the solution so that the volume can be is reproduced to 0.05 mL.D5629 16211.5 Add a stir bar, cover with a watch glass and stir for 20 min. Allow the sample to cool to room temperature after stirring.N
27、OTE 5Samples must be at room temperature before titration.11.6 Titrate the mixture with 0.01 N methanolic KOH through the titration endpoint as determined potentiometrically. Continuethe titration through an apparent pH of 8.NOTE 6If the results indicate a drift in the data or a slow electrode respo
28、nse, the pH electrode is to be cleaned by soaking in 2:1 sulfuric:nitric acidsfor 10 min, followed by soaking in water for 20 min and then rinsing with acetone.11.7 Record the titrant volume for the potentiometric endpoint. If more than one potentiometric endpoint is found, record theone at the high
29、est apparent pH below 7.NOTE 7The inflection point is typically at an apparent pH between 4 and 5.12. Calculation12.1 Calculate the acidity, as ppm HCl, as follows:acidity5Vsam 2Vblank!3KOHnormality!3Fsample weight g! (1)where:Vsam = volume of titrant needed for the sample, mL,Vblank = volume of tit
30、rant needed for the blank, mL,KOHnormality = normality of the titrant solution, andF = 36465 = 36.456 (mol weight of HCl) 1000 (factor to change mg/g to g/g, that is, ppm).NOTE 8Acidity is typically calculated as meq/Kg for prepolymers. For this calculation, F = 1000.13. Report13.1 Report the result
31、 as the average of duplicates, expressed as ppm HCl, to the nearest 1 ppm. See also Note 8.14. Precision and Bias5NOTE 9The estimate of precision below was determined using reference and pH glass electrode systems.14.1 PrecisionTable 1 is based on a round robin conducted in 1993 per Practice E180, i
32、nvolving six materials tested by ninelaboratories. All of the samples for each material were prepared at one source, but the individual specimens were prepared at thelaboratories that tested them. Each test result was the average of two individual determinations. Each laboratory obtained two testres
33、ults for each material on each of two days. (WarningThe following explanations of r and R (14.1 14.1.3) are intended onlyto present a meaningful way of considering the approximate precision of this test method. The data in Table 1 are not to be appliedrigorously to the acceptance or rejection of mat
34、erial, as those data are specific to the round robin and may not be representativeof other lots, conditions, materials, or laboratories. Users of this test method are to apply the principles outlined in Practice E691to generate data specific to their laboratory and materials or between specific labo
35、ratories. The principles of 14.1.1 14.1.3 wouldthen be valid for such data.)14.1.1 Repeatability, (r)(Comparing two replicates for the same material, obtained by the same operator using the sameequipment on the same day.) The two replicate results are to be judged not equivalent if they differ by mo
36、re than the r value forthat material.5 Supporting data are available from ASTM Headquarters. Request RR:D20-1186.TABLE 1 Round Robin Acidity Data According to Practice E180Values in ppm HClAverage SrA SRB rC RD nETD-80 Grade B 73.81 3.14 7.80 8.79 21.84 8TD-80 Grade A 39.47 1.44 4.28 4.03 11.98 8Adi
37、prene L-100 23.56 0.99 4.00 2.77 11.20 8Vibrathane B836 3.37 0.82 2.27 2.30 6.36 7Isonate 143L 1.12 1.53 2.41 4.28 6.75 7Mondur M 1.07 0.74 2.53 2.07 7.08 7A Sr = within-laboratory standard deviation of the replicates.B SR = between-laboratory standard deviation of the average.C r = within-laborator
38、y repeatability limit = 2.8 Sr.D R = between-laboratory reproducibility limit = 2.8 SR.E n = number of laboratories contributing valid data for this material.D5629 16314.1.2 Reproducibility, (R)(Comparing two results for the same material, obtained by different operators using differentequipment on
39、different days.) The two test results are to be judged not equivalent if they differ by more than the R value for thatmaterial.14.1.3 Any judgement per 14.1.1 and 14.1.2 would have an approximate 95 % (0.95) probability of being correct.14.2 BiasThere are no recognized standards by which to estimate
40、 the bias of this test method.15. Keywords15.1 acidity; aromatic isocyanates; isocyanates; methylene-bis-(4-phenylisocyanate); methylene di(phenylisocyanate); methyl-ene diphenyldiisocyanate; MDI; prepolymer; polyurethane; raw materials; test method; TDI; titration; toluene diisocyanateSUMMARY OF CH
41、ANGESCommittee D20 has identified the location of selected changes to this standard since the last issue(D5629 - 05D5629 - 11) that may impact the use of this standard. (February(April 1, 2011)2016)(1) Changed the nomenclature in Section Various edits throughout 1to be consistent with the commonly-r
42、ecognized industrialterms, and to be more descriptive of all the MDI isomers.remove non-mandatory language.(2) ChangedRevised 9.1the format of to remove non-mandatory language and updated with input from the Center for Note 1 tocomply with the format specified in Guide D4968.the Polyurethanes Indust
43、rys (CPI) Product Stewardship Committee.(3) Replaced manufacture-specific terminology in Section 6.(4) Changed the format of Note 2, Note 3, Note 4 to comply with ASTMs non-mandatory language requirement.(3) Removed reference to sampling with a thief redundant information from Section 810 because th
44、is apparatus is no longercommonly used. The new statement is consistent with the requirements of ASTMs Form and Style Manual(6) Changed subsection 10.1 to more directly address the sensitivity of the samples to moisture.(7) Removed reference to a specific manufacturer in Section 11.(8) Added Note 9
45、in Section 14 for informational purposes.(9) Replaced Practice E180 with Practice E691 in subsection 14.1 (Warning section) as recommended by Guide D4968.(10) Added methylene di(phenylisocyanate) to keywords.ASTM International takes no position respecting the validity of any patent rights asserted i
46、n connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the r
47、esponsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive care
48、ful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Internationa
49、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 164
