1、Designation:D 4664 93An American National StandardStandard Test Method forPolyurethane Raw Materials:Determination of FreezingPoint of Toluene Diisocyanate Mixtures1This standard is issued under the fixed designation D 4664;the number immediately following the designation indicates the year oforigin
2、al 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.Scope1.1 This test method determines the freezing points ofmixturesoftoluene-2,4
3、-diisocyanateandtoluene-2,6-diisocyanate.It should not be used to measure the isomercontent of the mixture.(See Note 1.)1.2 This standard does not purport to address all of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priat
4、e safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specificwarning and precautionary statements see Note 2 and Note 3.NOTE1There is no equivalent ISO standard.2.Referenced Documents2.1 ASTM Standards:D 883 Terminology Relating to Plastics23.Term
5、inology3.1 Definitions:For definitions of terms used in this testmethod see Terminology D 883.4.Summary of Test Method4.1 The toluene diisocyanate(TDI isomer)mixture iscooled slowly by stirring until it crystallizes.Since super-cooling occurs,the temperature first falls,then rises to amaximum,and th
6、en falls again.This maximum temperature isthe freezing point of the mixture.5.Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize isocyanates used in polyurethane prod-ucts.5.2 For toluene diisocyanate,the test methods for assay,freezing point,and
7、specific gravity help determine purity,whilethe other test methods(isomer content,total chlorine,hydro-lyzable chlorine,acidity,and color)may relate to reactivity orperformance in polyurethane systems.6.Apparatus6.1 Air Jacket,glass test tube,50-mm outside diameter and175 mm long.6.2 Freezing Point
8、Tube,glass test tube,25-mm outsidediameter and 150 mm long.6.3 Ice Bath,1-L beaker or other container 180 mm deep.6.4 Stirrer,made from a 2-mm glass rod(or 1-mm stainlesssteel wire)with one end made into a circle perpendicular to theshaft so that it moves freely between the thermometer stem andthe f
9、reezing point tube.Operate the stirrer either manually ormechanically.6.5 Thermometer,graduated to 0.1C and calibratedfrom 5 to+30C.36.6 Timer,read to the nearest 1 s.7.Sampling7.1 Since organic isocyanates react with atmospheric mois-ture,take special precautions in sampling(Warning:PrecautionNote
10、2).Usual sampling methods(for example,sampling an open drum thief),even when carried out rapidly,can cause contamination of the sample with insoluble urea.Therefore,blanket the sample with dry air or nitrogen at alltimes.NOTE2:WarningOrganic isocyanates are toxic when they areabsorbed through the sk
11、in,or when the vapors are breathed.PrecautionProvide adequate ventilation and wear protective gloves and eyeglasses.8.Test Conditions8.1 Since isocyanates react with moisture,keep laboratoryhumidity low,preferably around 50%relative humidity.9.Procedure(Note 3)9.1 Fit the small test tube with a two-
12、hole cork stopper,andinsert the thermometer through the center hole and shaft of thestirrer through the other hole.Place two 3-mm layers ofabsorbent cotton in the bottom of the large test tube.Insert thesmall test tube up to its lip into a cork stopper or cork ring thatjust fits into the large test
13、tube.9.2 Fill the ice bath with ice water,and sodium chloride(NaCl)if necessary,to bring the temperature to about 10Cbelow the expected freezing point of the test sample.1This test method is under the jurisdiction ofASTM Committee D-20 on Plasticsand is the direct responsibility of Subcommittee D20.
14、22 on Cellular Plastics.Current edition approved June 15,1993.Published August 1993.Originallypublished as part of D 1638 59 T.Last previous edition D 1638 87.2Annual Book of ASTM Standards,Vol 08.01.3Athermometer of this range may be purchased from the Walter H.Kessler Co.,219 Westbury Ave.,Carle P
15、lace,Long Island,NY.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMNOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.ast
16、m.org)for the latest information.9.3 Add the sample to the small test tube to a height of 90to 100 mm.NOTE3:PrecautionCarry out this test method in an exhaust hoodand run the test method quickly to avoid reaction of toluene diisocyanatewith atmospheric moisture.9.4 Insert the cork carrying the stirrer and thermometer intothe small test tube and adjust the thermometer so that itsimmersion mark is just level with the top of the sample.Coolthe small test tube in the ice bath,while stirring,to about