1、Designation: D5629 11Standard 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 oforiginal a
2、doption 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 ppmof hydrochlor
3、ic acid (HCl), in aromatic isocyanate or polyure-thane prepolymer samples of below 100 ppm acidity. The testmethod is applicable to products derived from toluene diiso-cyanate and methylene di(phenylisocyanate) (see Note 1).Refer to Test Method D6099 for determination of acidity inmoderate- to high-
4、acidity aromatic isocyanates.1.2 The values stated in SI units are to be regarded as thestandard.1.3 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
5、practices and determine the applica-bility of regulatory limitations 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: De-termination of Acidity in Mo
6、derate to High Acidity Aro-matic IsocyanatesE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:4ISO 14898 Plastics
7、Aromatic Isocyanates for Use in theProduction of PolyurethaneDetermination of Acidity3. Terminology3.1 DefinitionsThe terminology in this test method fol-lows the standard terminology defined in Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity, nthe acid strength of
8、a sample expressed inppm HCl.4. Summary of Test Method4.1 The isocyanate is mixed with an excess of n-propanol, acosolvent and a known amount of HCl. Additional acid isreleased into the solvent system during urethane formation.The acid is then titrated potentiometrically with methanolicKOH. The same
9、 procedure is performed with a blank solutionand the difference in titer is used to calculate the acidity presentin the isocyanate sample.5. Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize aromatic isocyanates and low-acidityprepolymers. Acidit
10、y correlates with performance in somepolyurethane 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 buretwith a dosing unit; or a 100-mL repipet, class A volumetric.6.4 Potentiometric Titrator:6.4.1 Reference Elec
11、trodebridge-type electrolyte (doublejunction), sleeve-type diaphragm, having saturated LiCl/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 accept-able.1This test method is under the jurisdiction of AS
12、TM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved Feb. 1, 2011. Published March 2011. Originallyapproved in 1994. Last previous edition approved in 2005 as D5629 - 05. DOI:10.1520/D5629-11.2For
13、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 to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard
14、is referencedon www.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho
15、hocken, PA 19428-2959, United States.6.5 Magnetic Stirrer.6.6 Polytetrafluoroethylene-Coated Stir Bars.6.7 Watch Glasses.6.8 Analytical Balance, capable of weighing to the nearest0.1 mg.7. Reagents and Materials7.1 0.01 N KOH in Methanol, for example, 0.66 g 87.7 %KOH/1000 mL methanol, standardized
16、with potassium hydro-gen phthalate (KHP).7.2 Toluene or THF (dried for 24 h over 5 A molecularsieves).7.3 n-Propanol, acidified with 120 L concentrated hydro-chloric acid per 4-L bottle. Allow this solution to stand for atleast 24 h before use to allow equilibration. The solution is tobe mixed well
17、before dispensing.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take special precautions in sampling. Usual samplingmethods, even when conducted rapidly, can cause contamina-tion of the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at
18、all times. (WarningManydiisocyanates are known or suspected sensitizers. Over-exposure to diisocyanates can lead to adverse health effectswhich include the development of occupational asthma andother respiratory, skin and eye effects. Engineering controlsand/or personal protective equipment, includi
19、ng respiratory,skin and eye protection, are to be used when there is a potentialfor over-exposure to diisocyanates. The product suppliersMaterial Data Safety Sheet (MSDS) provides more detailedinformation about potential adverse health effects and otherimportant safety and handling information. Alwa
20、ys follow thespecific instructions provided on the MSDS.)9. Calibration9.1 Calibrate the electrodes using pH 4 and 7 aqueousbuffers.10. Test Conditions10.1 Since isocyanates react with moisture, keep samplesprotected against moisture until immediately before testing.11. Procedure11.1 Make a blank de
21、termination in conjunction with eachseries of samples. Prepare the blank in the same manner as asample, only omitting the sample. All samples and blanks areto be made in duplicate.11.2 Accurately weigh, to the nearest 0.1 mg, 20 g ofsample into a 250-mL beaker.11.3 Add 50 mL of dried toluene (dried
22、over 5-A molecularsieves).NOTE 3For prepolymers, THF is an acceptable substitute for toluene.NOTE 4If a sample is difficult to get into solution, it is acceptable togently heat and stir to ensure homogeneity.11.4 Pipet 100 mL of acidified n-propanol into the solutionso that the volume can be reprodu
23、ced to 0.05 mL.11.5 Add a stir bar, cover with a watch glass and stir for 20min. Allow the sample to cool to room temperature afterstirring.NOTE 5Samples must be at room temperature before titration.11.6 Titrate the mixture with 0.01 N methanolic KOHthrough the titration endpoint as determined poten
24、tiometrically.Continue the titration through an apparent pH of 8.NOTE 6If the results indicate a drift in the data or a slow electroderesponse, the pH electrode is to be cleaned by soaking in 2:1 sulfuric:nitricacids for 10 min, followed by soaking in water for 20 min and then rinsingwith acetone.11
25、.7 Record the titrant volume for the potentiometric end-point. If more than one potentiometric endpoint is found,record the one at the highest apparent pH below 7.NOTE 7The inflection point is typically at an apparent pH between 4and 5.12. Calculation12.1 Calculate the acidity, as ppm HCl, as follow
26、s:acidity 5Vsam2 Vblank! 3 KOHnormality! 3 Fsample weight g!(1)where:Vsam= volume of titrant needed for the sample,mL,Vblank= volume of titrant needed for the blank,mL,KOHnormality= normality of the titrant solution, andF = 36465 = 36.456 (mol weight of HCl) 31000 (factor to change mg/g to g/g, that
27、is, ppm).NOTE 8Acidity is typically calculated as meq/Kg for prepolymers.For this calculation, F = 1000.13. Report13.1 Report the result as the average of duplicates, ex-pressed as ppm HCl, to the nearest 1 ppm. See also Note 8.14. Precision and Bias5NOTE 9The estimate of precision below was determi
28、ned usingreference and pH glass electrode systems.14.1 PrecisionTable 1 is based on a round robin con-ducted in 1993 per Practice E180, involving six materialstested by nine laboratories.All of the samples for each materialwere prepared at one source, but the individual specimens wereprepared at the
29、 laboratories that tested them. Each test resultwas the average of two individual determinations. Each labo-ratory obtained two test results for each material on each of twodays. (WarningThe following explanations of r and R(14.1-14.1.3) are intended only to present a meaningful way ofconsidering th
30、e approximate precision of this test method. Thedata in Table 1 are not to be applied rigorously to theacceptance or rejection of material, as those data are specific tothe round robin and may not be representative of other lots,5Supporting data are available from ASTM Headquarters. Request RR:D20-1
31、186.D5629 112conditions, materials, or laboratories. Users of this test methodare to apply the principles outlined in Practice E691 to generatedata specific to their laboratory and materials or betweenspecific laboratories. The principles of 14.1.1-14.1.3 wouldthen be valid for such data.)14.1.1 Rep
32、eatability, (r)(Comparing two replicates for thesame material, obtained by the same operator using the sameequipment on the same day.) The two replicate results are to bejudged not equivalent if they differ by more than the r value forthat material.14.1.2 Reproducibility, (R)(Comparing two results f
33、or thesame material, obtained by different operators using differentequipment on different days.) The two test results are to bejudged not equivalent if they differ by more than the R valuefor that material.14.1.3 Any judgement per 14.1.1 and 14.1.2 would have anapproximate 95 % (0.95) probability o
34、f being correct.14.2 BiasThere are no recognized standards by which toestimate the bias of this test method.15. Keywords15.1 acidity; aromatic isocyanates; isocyanates; methylene-bis-(4-phenylisocyanate); methylene di(phenylisocyanate);methylene diphenyldiisocyanate; MDI; prepolymer; polyure-thane;
35、raw materials; test method; TDI; titration; toluenediisocyanateSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D5629 - 05)that may impact the use of this standard. (February 1, 2011)(1) Changed the nomenclature in Section 1 to be
36、 consistentwith the commonly-recognized industrial terms, and to bemore descriptive of all the MDI isomers.(2) Changed the format of Note 1 to comply with the formatspecified in Guide D4968.(3) Replaced manufacture-specific terminology in Section 6.(4) Changed the format of Note 2, Note 3, Note 4 to
37、 complywith ASTMs non-mandatory language requirement.(5) Removed reference to sampling with a thieffrom Section8 because this apparatus is no longer commonly used. The newstatement is consistent with the requirements of ASTMs Formand Style Manual.(6) Changed subsection 10.1 to more directly address
38、thesensitivity of the samples to moisture.(7) Removed reference to a specific manufacturer in Section11.(8) Added Note 9 in Section 14 for informational purposes.(9) Replaced Practice E180 with Practice E691 in subsection14.1 (Warning section) as recommended by Guide D4968.(10) Added methylene di(ph
39、enylisocyanate) to keywords.ASTM International takes no position respecting the validity of any patent rights asserted in 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 infr
40、ingement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible 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 standa
41、rd or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful 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 vie
42、ws known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 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 contacti
43、ng 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 ASTM website (www.astm.org/COPYRIGHT/).TABLE 1 Round Robin Acidity Data Accordi
44、ng to Practice E180Values in ppm HClAverage SrASRBrCRDnETD-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 8Adiprene 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
45、Sr= within-laboratory standard deviation of the replicates.BSR= between-laboratory standard deviation of the average.Cr = within-laboratory repeatability limit = 2.8 3 Sr.DR = between-laboratory reproducibility limit = 2.8 3 SR.En = number of laboratories contributing valid data for this material.D5629 113
