1、Designation: D 5629 05Standard Test Method forPolyurethane Raw Materials: Determination of Acidity inLow-Acidity Aromatic Isocyanates and PolyurethanePrepolymers1This standard is issued under the fixed designation D 5629; the number immediately following the designation indicates the year oforiginal
2、 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 reapproval.1. Scope*1.1 This test method measures the acidity, expressed as ppmof hydroch
3、loric 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-bis-(4-phenylisocyanate) (see Note 1).Refer to Test Method D 6099 for determination of acidity inmoderate-
4、to high-acidity aromatic isocyanates.NOTE 1ISO 14898, Method B is technically equivalent to this testmethod.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 theresponsib
5、ility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 6099 Test Method for Polyurethane Raw Materials: De-term
6、ination of Acidity in Moderate- to High-Acidity Aro-matic IsocyanatesE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals2.2 ISO Standards:3ISO 14898 PlasticsAromatic Isocyanates for Use in theProduction of PolyurethaneDeterminat
7、ion of Acidity3. Terminology3.1 DefinitionsThe terminology in this test method fol-lows the standard terminology defined in Terminology D 883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity, nthe acid strength of a sample expressed inppm HCl.4. Summary of Test Method4.1 The isocyana
8、te 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 procedure is performed with a blank solutionand the difference in tit
9、er 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. Acidity correlates with performance in somepolyurethane systems.6. Apparatus
10、6.1 Disposable Beakers, 250 mL.6.2 Repipet,50mL.6.3 Pipet, 100 mL, class A volumetric; or a 100-mL buretwith a dosimat; or a 100-mL repipet, class A volumetric.6.4 Automatic Titration Equipment, such as the following:6.4.1 Titroprocessor.46.4.2 Dosimat, with magnetic stirrer.41This test method is un
11、der the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.Current edition approved March 1, 2005. Published March 2005. Originallyapproved in 1994. Last previous edition approved in 1999 as D 5629 - 99.2For referenced ASTM stan
12、dards, 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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor
13、, New York, NY 10036.4The sole source of supply of instruments similar to and including the Metrohn686 Titroprocessor with a Metrohn 665 Dosimat/magnetic stirrer known to thecommittee at this time is Brinkman Instruments Company, Division of SybronCorporation, Cantiague Road, Westbury, NY 11590-9974
14、, have been found to besatisfactory for this analysis. If you are aware of alternative suppliers, please providethis information to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee1, whichyou may attend.1*A Summary o
15、f Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.4.3 Reference Electrode (Brinkman Catalogue No. 020-94-400-5 or equivalent: bridge electrolyte (double junction),sleeve-type diaph
16、ragm), having saturated LiCl/ethanol solutionin both chambers.6.4.4 pH Glass Electrode (Brinkman Catalogue No. 020-91-012-7 or equivalent) (see Note 2).NOTE 2A combination pH electrode with internal reference can alsobe used.6.5 Magnetic Stirrer.6.6 Polytetrafluoroethylene-Coated Stir Bars.6.7 Watch
17、 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 with potassium hydro-gen phthalate (KHP).7.2 Toluene or THF (dried for 24 h over 5 A molecularsieves).7.3 n-Prop
18、anol, 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 before dispensing.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take special precau
19、tions in sampling. Usual samplingmethods (for example, sampling from an open drum with athief), even when conducted rapidly, can cause contaminationof the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times. (WarningOrganic isocyanates are toxic when they a
20、re absorbed throughthe skin or when the vapors are breathed. Provide adequateventilation, and wear protective gloves and eye glasses.)9. Calibration9.1 Calibrate the electrodes using pH 4 and 7 aqueousbuffers.10. Test Conditions10.1 Since isocyanates react with moisture, keep the labo-ratory humidit
21、y low, preferably at approximately 50 % relativehumidity.11. Procedure11.1 Make a blank determination 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
22、nearest 0.1 mg, 20 g ofsample into a 250-mL beaker.11.3 Add 50 mL of dried toluene (dried over 5-A molecularsieves).NOTE 3Substitute THF for toluene for prepolymers.NOTE 4If a sample is difficult to get into solution, it may be gentlyheated and stirred for a longer period of time to ensure homogenei
23、ty.11.4 Pipet 100 mL of acidified n-propanol into the solutionso that the volume can be reproduced 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 T
24、itrate the mixture with 0.01 N methanolic KOHthrough the titration endpoint as determined potentiometrically.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:
25、nitricacids for 10 min, followed by soaking in water for 20 min and then rinsingwith acetone.11.7 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
26、 an apparent pH between 4and 5.12. Calculation12.1 Calculate the acidity, as ppm HCl, as follows: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 titran
27、t solution, andF = 36465 = 36.456 (mol weight of HCl) 31000 (factor to change mg/g to g/g, thatis, 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
28、1 ppm. See also Note 8.14. Precision and Bias514.1 PrecisionTable 1 is based on a round robin con-ducted in 1993 per Practice E 180, involving six materialstested by nine laboratories.All of the samples for each materialwere prepared at one source, but the individual specimens wereprepared at the la
29、boratories 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 the a
30、pproximate 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: D20-118
31、6.D5629052conditions, materials, or laboratories. Users of this test methodare to apply the principles outlined in Practice E 180 togenerate data specific to their laboratory and materials orbetween specific laboratories. The principles of 14.1.1-14.1.3would then be valid for such data.)14.1.1 Repea
32、tability, (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 for
33、 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 of
34、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 diphenyldiisocyanate;MDI; prepolymer; polyurethane; raw materials; test method;TDI; tit
35、ration; toluene diisocyanateSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue,D 5629 - 99, that may impact the use of this standard. (March 1, 2005)(1) Added Test Method D 6099 to 1.1 and 2.1.(2) Added reference to ISO 14898 in Note
36、 1 and 2.2.(3) Corrected volume for consistency in 6.3.(4) Editorially changed 7.1, 7.2, 8.1, 11.5 and Note 4 forclarity.(5) Removed non-mandatory language from 11.1, 14.1, 14.1.1,14.1.2, Note 2, Note 4 and Note 6.(6) Added keyword: methylene-bis-(4-phenylisocyanate).ASTM International takes no posi
37、tion 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 infringement of such rights, are entirely their own responsibili
38、ty.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 standard or for additional standardsand should be addressed to AST
39、M 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 views known to the ASTM Committee on Standards, at the address
40、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 contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-
41、832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).TABLE 1 Round Robin Acidity Data According to Practice E 180Values 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
42、.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 7ASr= 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.D5629053
