ASTM_D_2765_-_11.pdf

Designation:D276511Standard Test Methods forDetermination of Gel Content and Swell Ratio ofCrosslinked Ethylene Plastics1This standard is issued under the fixed designation D2765;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 The gel content(insoluble fraction)produced in ethyl-ene plastics by crosslinking is determined by extracting withsolvents such as decahydronaphthalene or xylenes.The meth-ods described herein are applicable to crosslinked ethyleneplastics of all densities,including those containing fillers,andall provide corrections for the inert fillers present in some ofthose compounds.1.2 Test MethodA,which permits most complete extractionin least time,is to be used for referee tests,but two alternativenonreferee Test Methods B and C are also described.TestMethod B differs from the referee test method only in samplepreparation;that is,it requires use of shavings taken at selectedpoints in cable insulation,for example,rather than the groundsample required by the referee test method.Because the shavedparticles are larger,less total surface per sample is exposed tothe extractant,so this test method ordinarily yields extractionvalues about 1 to 2%lower than the referee method.TestMethod C requires that a specimen in one piece be extracted inxylenes at a constant temperature of 110C.At this temperatureand with a one-piece specimen,even less extraction occurs(from 3 to 9%less than the referee test method),this methodpermits swell ratio(a measure of the degree of crosslinking inthe gel phase)be determined.1.3 Extraction tests are made on articles of any shape.Theyhave been particularly useful for electrical insulations sincespecimens may be selected from those portions of the insula-tion most susceptible to insufficient crosslinking.1.4 The values stated in SI units are to be regarded asstandard.The inch-pound units in brackets are for informationonly.NOTE1Method B of this test method is equivalent to ISO 10147.1.5 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.Specific precau-tionary statements are given in Sections 6,10,and 25.2.Referenced Documents2.1 ASTM Standards:2D297 Test Methods for Rubber ProductsChemical Analy-sisD618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1603 Test Method for Carbon Black Content in OlefinPlasticsD1998 Specification for Polyethylene Upright Storage TanksD3351 Test Method for Gel Count of Plastic Film(With-drawn 2000)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 10147 Pipes and Fittings Made of Crosslinked Poly-ethylene(Pe-X)Estimation of the Degree of Crosslink-ing by Determination of the Gel Content3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 gel contentthe percentage by mass of polymerinsoluble in a specified solvent after extraction under thespecified conditions.3.1.2 solublecapable of being loosened or dissolved,sus-ceptible of being dissolved in or as if in a fluid.(See WebstersNinth New Collegiate Dictionary,1988.)3.1.3 swell ratiothe ratio of the gel volume in the swollenstate to its volume in the unswollen state.3.2 Terms as shown in Terminology D883 are applicable tothis test method.1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterials.Current edition approved Sept.1,2011.Published September 1,2011.Originallyapproved in 1968.Last previous edition approved in 2006 as D2765 01(2006).DOI:10.1520/D2765-11.2For 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.3The last approved version of this historical standard is referenced onwww.astm.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 States1 4.Summary of Test Methods4.1 Specimens of the crosslinked ethylene plastic areweighed and then immersed in the extracting solvent at thetemperature specified by the procedure selected and for thetime designated by that procedure.After extraction,the speci-mens are removed,dried,and reweighed as directed.Theamount of material extracted is calculated and,if desired,swellratio determined by the means described in alternative TestMethod C.5.Significance and Use5.1 M