ASTM D6645-2001(2010) 1875 Standard Test Method for Methyl (Comonomer) Content in Polyethylene by Infrared Spectrophotometry《红外光谱法测定聚乙烯中甲基(共聚单体)含量的标准试验方法》.pdf
《ASTM D6645-2001(2010) 1875 Standard Test Method for Methyl (Comonomer) Content in Polyethylene by Infrared Spectrophotometry《红外光谱法测定聚乙烯中甲基(共聚单体)含量的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM D6645-2001(2010) 1875 Standard Test Method for Methyl (Comonomer) Content in Polyethylene by Infrared Spectrophotometry《红外光谱法测定聚乙烯中甲基(共聚单体)含量的标准试验方法》.pdf(4页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: D6645 01 (Reapproved 2010)Standard Test Method forMethyl (Comonomer) Content in Polyethylene by InfraredSpectrophotometry1This standard is issued under the fixed designation D6645; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 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 test method covers the determination of methylgroups (that is, comonomer content) in polye
3、thylenes byinfrared spectrophotometry. The test method is applicable tocopolymers of ethylene with 1-butene, 1-hexene, or 1-octenehaving densities above 900 kg/m3. High-pressure low-densitypolyethylenes (LDPE) and terpolymers are excluded.1.2 The values stated in SI units, based on IEEE/ASTM SI-10,
4、are to be regarded as the standard.1.3 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 limit
5、ations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD1505 Test Method for Density of Plastics by the Density-Gradient TechniqueD1898 Pr
6、actice for Sampling of Plastics3D2238 Test Methods for Absorbance of Polyethylene Dueto Methyl Groups at 1378 cm1D3124 Test Method for Vinylidene Unsaturation in Poly-ethylene by Infrared SpectrophotometryD5576 Practice for Determination of Structural Features inPolyolefins and Polyolefin Copolymers
7、 by Infrared Spec-trophotometry (FT-IR)E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE932 Practice for Describing and Measuring Performanceof Dispersi
8、ve Infrared SpectrometersE1421 Practice for Describing and Measuring Performanceof Fourier Transform Mid-Infrared (FT-MIR) Spectrom-eters: Level Zero and Level One TestsIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI): The Modern System3. Terminology3.1 TerminologyThe units,
9、 symbols, and abbreviationsused in this test method appear in Terminology E131 orIEEE/ASTM SI-10.3.2 comonomera-olefin monomer. In this test method,comonomer refers to 1-butene, 1-hexene, and 1-octene only.4. Summary of Test Method4.1 The band located between 1377 cm-1and 1379 cm-1isdue to a deforma
10、tion vibration of the CH3group. Bands atapproximately 772 cm-1(branch methylene rocking mode), 895cm-1(methyl rocking mode), and 785 cm-1(branch methylenerocking mode) are characteristic of ethyl (that is, butenecopolymer), butyl (that is, hexene copolymer), and hexyl (thatis, octene copolymer) bran
11、ches, respectively.44.2 This test method determines the methyl (that is,comonomer) content of a polyethylene copolymer based on theIR absorbance at 1378 cm-1from a pressed plaque. Thecomonomer type has to be known and a calibration curve hasto be available prior to the analysis. If the comonomer is
12、notknown a priori, the presence of bands at 772 cm-1, 895 cm-1,and 785 cm-1can be used to identify ethyl (minimum of 1branch per 1000 carbons), butyl (minimum of about 5 branchesper 1000 carbons), and hexyl (minimum of about 5 branchesper 1000 carbons) branches, respectively. A more sensitive andles
13、s ambiguous identification is obtained by C13 NMR spec-troscopy. The latter technique is also used as a referencetechnique to provide polymer standards for the generation ofcalibration curves.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibilit
14、y of Subcommittee D20.70 on Analytical Methods.Current edition approved Jan. 1, 2010. Published January 2010. Originallyapproved in 2001. Last previous edition approved in 2001 as D6645 - 01. DOI:10.1520/D6645-01R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
15、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Blitz, J. P., and McFadden, D. C., “The Characterization of Short ChainBranching in Polyethylene Using Fourier Transform Infrared Spe
16、ctroscopy,” J.Appl. Pol. Sci., 51, 13 (1994).1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 2For comonomer identification, it is recommended, for maxi-mum sensitivity, to view the second derivative of the IR spectrum.4.3 The me
17、thod is calibrated by plotting absorbance at 1378cm-1per unit area of the methylene combination band at 2019cm-1(that is, internal thickness correction approach) or per unitof spectral cross-section (that is, the reciprocal of the productof plaque thickness and density) versus number of branches per
18、1000 carbons as determined by C13 NMR spectroscopy.Although both approaches give equivalent results, the oneusing internal thickness correction is recommended in this testmethod since it is considerably simpler to execute.5. Significance and Use5.1 This method determines the number of branches (that
19、 is,comonomer content) in copolymers of ethylene with 1-butene,1-hexene or 1-octene. This information can be correlated withphysical properties such as melting point, density, and stiffness,all of which depend on the degree of crystallinity of thepolymer. Differences in the comonomer content thus ma
20、y havea significant effect on the final properties of products madefrom these resins.6. Interferences6.1 A conformational CH2wagging absorbance at 1368cm-1overlaps the methyl absorbance at 1378 cm-1, but does notcause significant interference in this test method since itsintensity is not significant
21、ly affected by the comonomer con-tent, but rather by the plaque thickness. The result of notcorrecting for this overlap is a positive ordinate intercept forthe calibration curve (see 10.4). Another conformational CH2wagging absorbance at 1352 cm-1does not significantlyoverlap the 1378 cm-1absorbance
22、.6.2 The presence of most pigments will interfere with thismethod.6.3 The presence of low molecular weight hydrocarbonswill produce high results in this method due to absorbance bytheir end methyl groups at 1378 cm-1.6.4 The secondary antioxidant Irgafos 1685shows an absor-bance at 768 cm-1which int
23、erferes with the identification oflow levels (that is, typically less than 5 branches per 1000carbons or less) of ethyl branches.6.5 Vinylidene groups absorb at 888 cm-1and thus mayinterfere with a conclusive identification of a hexene copoly-mer from its 895 cm-1resonance, depending on the relative
24、intensities of the two peaks.7. Apparatus7.1 Infrared Spectrophotometer, either double beam or aFourier transform (FTIR).7.1.1 Dispersive Infrared Spectrophotometer, capable ofachieving a spectral bandwidth of 4 cm-1(see Practice E932).The instrument should be capable of scale expansion along thewav
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