ASTM_D_6579_-_11_2015.pdf

Designation:D657911(Reapproved 2015)Standard Practice forMolecular Weight Averages and Molecular WeightDistribution of Hydrocarbon,Rosin and Terpene Resins bySize-Exclusion Chromatography1This standard is issued under the fixed designation D6579;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.Scope1.1 This practice covers the determination of apparentmolecular weight(MW)averages and molecular weight distri-butions(MWD)for THF-soluble hydrocarbon,rosin and ter-pene resins by size-exclusion chromatography(SEC).Thistechnique is not absolute;it requires calibration with standardsof known molecular weight.This practice is applicable toresins containing molecular-weight components that have elu-tion volumes falling within the elution volume range definedby polystyrene standards.NOTE1SEC is also known as gel permeation chromatography(GPC).1.2 SEC systems employ low-volume liquid chromatogra-phy components and columns packed with relatively small(generally 3 to 20 m)microporous particles.High-performance liquid chromatography instrumentation and auto-mated data handling systems for data acquisition and process-ing are also required.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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.2.Referenced Documents2.1 ASTM Standards:2D804 Terminology Relating to Pine Chemicals,IncludingTall Oil and Related ProductsD3016 Practice for Use of Liquid Exclusion Chromatogra-phy Terms and RelationshipsD6440 Terminology Relating to Hydrocarbon Resins3.Terminology3.1 For definitions of size-exclusion chromatography terms,see Practice D3016.3.2 For definition of terpene resin,see Terminology D804.3.3 For definitions of resin terms,see Terminology D6440.4.Summary of Practice4.1 In this practice,a dilute solution of a hydrocarbon,rosinor terpene resin sample is injected into a liquid mobile phasecontaining the same solvent used to prepare the resin solution.The mobile phase transports the resin into and through achromatography column(or set of columns connected inseries)packed with a rigid or semirigid,porous substrate thatseparates the molecules according to their size in solution.Adetector monitors the eluate as a function of elution volume(ortime).Upon emerging from the column(s),the fractions ofsize-separated molecules are detected and their elution vol-umes(or times)and(usually)concentrations recorded.Through calibration,the elution volumes(or times)are con-verted to apparent molecular weights,and various molecularweight parameters for the sample resin are calculated from themolecular weight/concentration data.5.Significance and Use5.1 The MW averages and the MWD are important charac-teristics of a resin.They may be used for a variety ofcorrelations for fundamental studies,processing,or productapplications.The MW and MWD values may also be used forproduction quality control of resins.5.2 LimitationsComparison of SEC molecular weight val-ues should be made only if the data were obtained underidentical chromatographic conditions.6.Apparatus6.1 Solvent ReservoirThe solvent reservoir must holdsufficient solvent to ensure consistency of composition for a1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.34 on Pine Chemicals and Hydrocarbon Resins.Current edition approved Dec.1,2015.Published December 2015.Originallyapproved in 2000.Last previous edition approved in 2011 as D6579 11.DOI:10.1520/D6579-11R15.2For referenced ASTM standards,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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 number of analyses.The reservoir should isolate the solventfrom the atmosphere,permit control of the environment incontact with the solvent,and be inert to the solvent employed.Some means of agitation(for example,magnetic stirring)isrecommended to ensure uniform composition.6.2 Solvent Pumping SystemThe principal requirement ofthe pumping system is production of a relatively constant andpulseless flow of solvent through the columns.In general,therate of flow should be adjustable between 0.1 and 5.0 mL/min,and back pressures should not exceed limits specified by thecolumn manufacturer.If the