188宝金博页面版

Designation: D5629 − 16Standard Test Method forPolyurethane Raw Materials: Determination of Acidity inLow-Acidity Aromatic Isocyanates and PolyurethanePrepolymers 1This standard is issued under the f i xed designation D5629; 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 (´) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method measures the acidity, expressed as ppmof hydrochloric 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-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 practices and determine the applica-bility of regulatory limitations prior to use.N OTE 1—This 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: Deter-mination ofAcidity in Moderate to HighAcidityAromaticIsocyanatesE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009) 3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards: 4ISO 14898 Plastics—Aromatic Isocyanates for Use in theProduction of Polyurethane—Determination of Acidity3. Terminology3.1 Def i nitions—The terminology in this test method fol-lows the standard terminology def i ned in Terminology D883.3.2 Def i nitions of Terms Specif i c to This Standard:3.2.1 acidity, n—the acid strength of 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 procedure is performed with a blank solutionand the difference in titer is used to calculate the acidity presentin the isocyanate sample.5. Signif i cance and Use5.1 This test method is suitable for research or for qualitycontrol to characterize aromatic isocyanates and low-acidityprepolymers. Acidity 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 Electrode, bridge-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).1 This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1994. Last previous edition approved in 2011 as D5629 - 11. DOI:10.1520/D5629-16.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 The last approved version of this historical standard is referenced onwww.astm.org.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http://www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1