【英文标准名称】:StandardTestMethodforDeterminationofWeight-AverageMolecularWeightofPolymersByLightScattering
【原文标准名称】:用低扩散法测定聚合物分子量和平均分子量的标准试验方法
【标准号】:ASTMD4001-1993(2006)
【标准状态】:现行
【国别】:
【发布日期】:1993
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D20.70
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:高聚物;塑料;测定;工艺;分子量
【英文主题词】:lightscattering;polymers;weight-averagemolecularweight
【摘要】:Theweight-averagemolecularweightisafundamentalstructureparameterofpolymers,whichisrelatedtomanyphysicalpropertiesofthebulkmaterial,suchasitsrheologicalbehavior.Inaddition,knowledgeoftheweight-averagemolecularweight,togetherwithknowledgeofthenumber-averagemolecularweightfromosmometry,providesausefulmeasureofthebreadthofthemolecular-weightdistribution.Otherimportantusesofinformationontheweight-averagemolecularweightarecorrelationwithdilute-solutionormelt-viscositymeasurementsandcalibrationofmolecular-weightstandardsforuseinliquid-exclusion(gel-permeation)chromatography.Totheextentthatthelight-scatteringphotometerisappropriatelycalibrated,lightscatteringisanabsolutemethodandmaythereforebeappliedtononionichomopolymersthathavenotpreviouslybeensynthesizedorstudied.1.1Thistestmethoddescribesthetestproceduresfordeterminingtheweight-averagemolecularweightMwofpolymersbylightscattering.Itisapplicabletoallnonionichomopolymers(linearorbranched)thatdissolvecompletelywithoutreactionordegradationtoformstablesolutions.Copolymersandpolyelectrolytesarenotwithinitsscope.Theprocedurealsoallowsthedeterminationofthesecondvirialcoefficient,A2,whichisameasureofpolymer-solventinteractions,andtheroot-mean-squareradiusofgyration(s2)1/2,whichisameasureofthedimensionsofthepolymerchain.1.2Themolecular-weightrangeforlightscatteringis,tosomeextent,determinedbythesizeofthedissolvedpolymermoleculesandtherefractiveindicesofsolventandpolymer.Arangefrequentlystatedis10,000to10,000,000,butthismaybeextendedineitherdirectionwithsuitablesystemsandbytheuseofspecialtechniques.1.2.1Thelowerlimittomolecularweightresultsfromlowlevelsofexcesssolutionscatteringoverthatofthesolvent.Thegreaterthespecificrefractiveincrementdn/dc(differenceinrefractiveindicesofsolutionandsolventperunitconcentration),thegreaterthelevelofsolutionscatteringandthelowerthemolecularweightthatcanbedeterminedwithagivenprecision.1.2.2Theupperlimittomolecularweightresultsfromtheangulardependenceofthesolutionscattering,whichisdeterminedbythemolecularsize.Forsufficientlylargemolecules,measurementsmustbemadeatsmallscatteringangles,whichareultimatelyoutsidetherangeofthephotometerused.1.3ThevaluesstatedinSIunitsaretoberegardedasstandard.Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.TherearenosimilarorequivalentISOstandards.
【中国标准分类号】:G31
【国际标准分类号】:83_080_01
【页数】:12P.;A4
【正文语种】: