1、Designation: D8036 16Standard Test Method forPolyurethane Raw Materials: Determination of Dimer Ratioin Pure MDI1This standard is issued under the fixed designation D8036; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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. Scope1.1 This test method determines the ratio of the infraredabsorbance of uretidinedione (dimer) in methylene-4,4- di-(pheny
3、lisocyanate) to an infrared absorbance at a referencewavelength within the same material. It is applicable tomonomeric methylene-di(phenylisocyanate), or “Pure MDI,”containing 95 % or greater methylene-4,4-di(phenylisocyanate).1.2 This standard does not purport to address all of thesafety concerns,
4、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 use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM
5、Standards:2D883 Terminology Relating to PlasticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Terminology in this test method is in accordance withTerminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 dimer, nure
6、tidinedione, with the structure in Fig. 1,is an undesirable reaction product of two or more isocyanategroups.4. Summary of Test Method4.1 The infrared spectrum of a dichloromethane solution ofthe sample is recorded in the 1600 to 2000 cm1region. Theabsorbance ratio of the peak maximum at approximate
7、ly 1778cm1, corresponding to the carbonyls present in uretidinedione,to the para-substituted ring combination peak maximum atapproximately 1900 cm1is calculated.5. Significance and Use5.1 This test method can be used for research or for qualitycontrol to determine the dimer ratio of Pure MDI.5.2 Ure
8、tidinedione begins forming in Pure MDI with therate of formation increasing with increasing temperature. Highlevels can affect the appearance of Pure MDI and the quality ofproducts made from it.6. Apparatus6.1 SpectrometerA Fourier-Transform infrared spectrom-eter accurate to 0.2 % transmission and
9、capable of resolvingthe dimer peak maximum at approximately 1778 cm1andreference peak maximum at approximately 1900 cm1.6.2 Cell, sealed sodium chloride (NaCl) liquid absorptioncell with 0.5-mm path length.6.3 Glassware, 25-mL, glass-stoppered, volumetric flaskand an all-glass syringe.7. Reagents an
10、d Materials7.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise noted, all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society where such specifications areavailable.3It is acceptable to use other grades, provided i
11、t isascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.7.2 Dichloromethane, reagent grade.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.2
12、2 on Cellular Materials -Plastics and Elastomers.Current edition approved May 1, 2016. Published May 2016. DOI: 10.1520/D8036-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informati
13、on, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemic
14、als, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States18. Sampling8.1 Since organic isocya
15、nates react with atmosphericmoisture, 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 all times. (WarningDiisocyanates are eye, skin and resp
16、iratory irritants at concen-trations above the occupational exposure limit (TLV or PEL).Diisocyanates can cause skin and respiratory sensitization(asthma) in some people. Once sensitized, it is essential to limitfurther exposure to diisocyanates. Use a combination ofengineering controls and personal
17、 protective equipment, in-cluding respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product suppliersSafety Data Sheet (SDS) for more detailed information aboutpotential health effects and other specific safety and handlinginstructions for the product.)9. T
18、est Conditions9.1 Since isocyanates react with moisture, keep laboratoryhumidity low, preferably around 50 % relative humidity. Seethe Warning note in 8.1.10. Calibration10.1 Because the result of the analysis is a ratio ofabsorbances, no calibration standards are necessary. This ratiois independent
19、 of the type and brand of infrared instrumentused.11. Procedure11.1 Scan an open-path background (the light path clear ofany cell). Use a resolution of 4 cm1or better and take at least16 scans to average. All scans shall be ratioed to this back-ground scan.11.2 Transfer 4.5 to 5.5 grams of sample in
20、to a dry, 25-mL,glass-stoppered, volumetric flask. Dilute to volume withdichloromethane, stopper, and mix thoroughly. Fill the cellwith this solution using the glass syringe and record theabsorbance spectrum from 1600 to 2000 cm1using the sameresolution and number of scans as the background.12. Calc
21、ulation12.1 Measure the height of the reference peak maximum atapproximately 1900 cm1using baseline points at about 1949and 1848 cm1. Measure the height of the dimer peak maxi-mum at approximately 1778 cm1using baseline points atabout 1812 and 1760 cm1. (see Fig. 2)12.2 Calculate the 1778/1900-cm1ab
22、sorbance height ratio,and express the result to two decimal places.13. Precision and Bias13.1 PrecisionThe repeatability standard deviation hasbeen determined to be 0.0024 (see Table 1). The reproducibil-ity of this test method is being determined and will be availableon or before January 2021.FIG.
23、1 Dimer StructureFIG. 2 IR Spectrum of Pure MDI Showing the Uretidinedione Peak at 1781 cm1and the Reference Peak at 1904 cm1D8036 16213.2 BiasThere are no recognized standards by which toestimate the bias of this test method.14. Keywords14.1 FTIR; infrared; IR; dimer; polyurethane raw material;Pure
24、 MDI; uretidinedione; monomer; methylene-4,4- di(phe-nylisocyanate); MDIASTM 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
25、 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 responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments ar
26、e invited either for revision of this standard 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 rec
27、eived 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies)
28、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:/ 1 Repeatability Standard DeviationAnalysis # Dimer Ratio1 0.45192 0.45183 0.45294 0.45145 0.45306 0.44777 0.44838 0.44749 0.450410 0.4544Average 0.4509Standard Deviation 0.0024D8036 163
