1、Designation:D223822Standard Test Methods forAbsorbance of Polyethylene Due to Methyl Groups1at 1378cm1This standard is issued under the fixed designation D2238;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision
2、.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 These test methods cover measurement by infraredabsorption spectrophotometry of the 1378 cm1(7.25 m)bandin polyethylene due to methyl gr
3、oups.(1,2,3-6)2Two testmethods are covered:1.1.1 Test Method A uses compensation with a standardsample film of known methyl content.1.1.2 Test Method B uses compensation with a wedge ofpolymethylene or a polyethylene of known low methyl content.1.2 These test methods are applicable to polyethylenes
4、ofTypes I(density 0.910 to 0.925 g/cm3),II(density 0.926 to0.940 g/cm3),and III(density 0.941 to 0.965 g/cm3).NOTE1For determination of density,see Specifications D1505.NOTE2In cases of Type III polyethylene with densities greater than0.950 g/cm3,different results are obtained with the two test meth
5、ods.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 app
6、ro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Specific hazards statements are given in Section 7.NOTE3There is no known ISO equivalent to this standard.1.5 This international standard was developed in accor-dance with inte
7、rnationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:3D618 Pra
8、ctice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1505 Test Method for Density of Plastics by the Density-Gradient TechniqueE131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE177 Practice for Use
9、of the Terms Precision and Bias inASTM Test MethodsIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units(SI):The Modern Metric System3.Terminology3.1 For definitions of terms used in these test methods andassociated with plastics issues refer to the terminology con-tained in Terminolo
10、gy D883.3.2 Units,symbols,and abbreviations used in this testmethod appear in Terminology E131 or Practice IEEE/ASTMSI-10.4.Significance and Use4.1 When interpreted with the aid of appropriate calibrationdata,either test method is acceptable for use to compare thetotal methyl contents of polyethylen
11、es made by similar pro-cesses.Data on infrared absorption at certain other wave-lengths is potentially useful for information on certain otherwavelengths(7).NOTE4The bias of determination of the concentration of total alkylgroups depends on knowing the concentrations of methyl and ethylbranches pres
12、ent,since these branches have anomalously high absorptivi-ties per group at 1378 cm1(7.25 m).4.2 Knowledge of total methyl groups in polyethylene,when combined with data on molecular weight and on reactiveend groups such as vinyl,is potentially useful so as to lead to1These test methods are under th
13、e jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.70 on AnalyticalMethods(Section D20.70.08).Current edition approved Sept.1,2022.Published September 2022.Originallyapproved in 1964.Last previous edition approved in 2012 as D2238-92(2012)1,which wa
14、s withdrawn January 2021 and reinstated in September 2022.DOI:10.1520/D2238-22.2The boldface numbers in parentheses refer to the list of references at the end ofthese test methods.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.Fo
15、r 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 StatesThis international standard was developed in accordance with internationally r
16、ecognized 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.1assignment of end-group structures and to shed light uponpolymerization mechanisms.4.3 Qualitative correlations are possible between data ontotal methyl groups in polyethylene with certain polymerproperties such as melting point,density,stiffness,and othermechani