ASTM D8117-17 Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by Differential Scanning Calorimetry.pdf

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1、Designation: D8117 17Standard Test Method forOxidative Induction Time of Polyolefin Geosynthetics byDifferential Scanning Calorimetry1This standard is issued under the fixed designation D8117; 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 a procedure for the determina-tion of the oxidative induction time (OIT)

3、 of polyolefingeosynthetics using differential scanning calorimetry.1.2 The focus of the test is on geomembranes, but geogrids,geonets, geotextiles, and other polyolefin-related geosyntheticsare also suitable for such evaluation.1.3 The values stated in SI units are to be regarded as thestandard.NOT

4、E 1This standard and ISO 11357-6 2013 address the same subjectmatter, but differ in technical content.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 he

5、alth practices and determine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,

6、Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for GeosyntheticsD4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or SheetsE473 Termin

7、ology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzers3. Terminology3.1 Definitions:3.1.1 F

8、or definitions of terms applying to thermal analysis,refer to Terminology E473.3.1.2 For definitions of terms related to geosynthetics, referto Terminology D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 oxidative induction timea relative measure of amaterials resistance to oxidative

9、decomposition; it is deter-mined by the thermoanalytical measurement of the timeinterval to onset of exothermic oxidation of a material at aspecified temperature in an oxygen atmosphere.3.3 Abbreviations:3.3.1 HDPEhigh-density polyethylene.3.3.2 LDPElow-density polyethylene.3.3.3 LLDPElinear low-den

10、sity polyethylene.3.3.4 OIToxidative induction time.4. Summary of Test Method4.1 The sample to be tested is heated at a constant rate in aninert gaseous environment (nitrogen). When the specifiedtemperature has been reached, the atmosphere is changed tooxygen maintained at the same flow rate. The sp

11、ecimen is thenheld at constant temperature until the oxidative reaction isdisplayed on the thermal curve. The OIT is determined fromthe data recorded during the isothermal period. The timeinterval from when the oxygen flow is first initiated to theoxidative reaction is referred to as the induction p

12、eriod.4.1.1 The end of the induction period is signaled by anabrupt increase in the specimens evolved heat or temperatureand will be recorded as an exothermic event by a differentialscanning calorimeter (DSC).4.2 The test is conducted in open aluminum pans.5. Significance and Use5.1 The OIT is a qua

13、litative assessment of the level (ordegree) of stabilization of the material tested. This test has the1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-ance Properties.Current edition approved June 1, 20

14、17. Published June 2017. Originallyapproved in 2017. DOI: 10.1520/D8117-17.2For 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

15、 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 recognized principles on standardization established in the Decision on Principles for theDevelo

16、pment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1potential to be used as a quality control measure to monitor thestabilization level in formulated resin as received from asupplier, prior to extrusion.NOTE

17、 2The OIT measurement is an accelerated thermal-aging test,and as such can be misleading. Caution should be exercised in datainterpretation since oxidation reaction kinetics are a function of tempera-ture and the inherent properties of the additives contained in the sample.For example, OIT results a

18、re often used to select optimum resinformulations. Volatile antioxidants may generate poor OIT results eventhough they may perform adequately at the intended use temperature ofthe finished product.NOTE 3There is no accepted sampling procedure, nor have anydefinitive relationships been established fo

19、r comparing OIT values on fieldsamples to those on unused products, hence the use of such values fordetermining life expectancy is uncertain and subjective.6. Apparatus6.1 Differential Scanning CalorimeterAs a minimumrequirement, the thermal analysis equipment shall be capableof measuring heat flow

20、of at least 10 mW full scale. Theinstrument recorder shall be capable of displaying heat flow ortemperature differential on the y-axis and time on the x-axis.The time base must be accurate to 61 % and be readable to0.1 min.NOTE 4The OIT test is a function of a particular compoundsstabilizer system a

21、nd should not be used as a basis of comparison betweenformulations that might contain different resins, stabilizers, additivepackages, or all of these.6.2 Gas Selector Switch and Regulators, for high-puritynitrogen and oxygen. The distance between the gas-switchingpoint and the instrument cell shall

22、 be such that the timerequired to transition to an oxygen environment is less than1 min. At a flow rate of 50 mL/min, this equates to a maximumswitching volume of less than 50 mL.6.3 Analytical Balance, 0.1-mg sensitivity.6.4 Bore Hole Cutter, 6.4-mm diameter.6.5 Specimen-Encapsulating Press.6.6 For

23、ceps, Scalpel, and Cutting Board.6.7 Electronic Mass Flow Controller, Rotometer(Calibrated), or Soap-Film Flowmeter, for gas flow calibration.6.8 Specimen HoldersDegreased aluminum pans (6.0- to7.0-mm diameter, 1.5-mm height).NOTE 5The material composition of the specimen holder can influ-ence the O

24、IT test result significantly (that is, including any associatedcatalytic effects).6.9 Compression-Molding Device with Heated Platens.6.10 Spacer Plates, Shim Stock, Caul Plates, etc.6.11 Polyethylene Terephthalate Film (PET) or Polytetra-fluoroethylene (PTFE)-Coated Cloth, for sample-plaque prepa-ra

25、tion.6.12 Thickness Gauge.6.13 Forced-Air Oven.7. Reagents and Materials7.1 All chemical reagents used in this procedure shall beanalytical grade unless otherwise specified.7.2 Oxygen, ultra-high purity grade (extra dry).7.3 Nitrogen, ultra-high purity grade (extra dry).7.4 Aluminum Pan Degreasing S

26、olvent.7.5 Indium, 99.999 % purity.7.6 Tin, 99.999 % purity.8. Hazards8.1 Oxygen is a strong oxidizer that vigorously acceleratescombustion. Keep oil and grease away from equipment usingor containing oxygen.8.2 The use of pressurized gas requires safe and properhandling.9. Sampling9.1 Compression mo

27、ld the sample into sheet format (thick-ness of 250 6 15 m) prior to analysis and weight. Specimendisks (6.4-mm diameter) cut from the sheet will have a weightof approximately 5 to 10 mg, depending on sample density.NOTE 6If the sample requires homogenization prior to analysis, oneof the procedures g

28、iven in Appendix X1, Appendix X2,orAppendix X3is recommended. Poor sample uniformity will adversely affect testprecision.NOTE 7If the sample contains a layer or layers of polymers other thanpolyolefins, the polyolefin may be tested separately from the entirecross-section. A recommended procedure is

29、given in Appendix X4.9.1.1 Place the assembly into the compression-moldingdevice. The preheat and pressing temperature is 160 C forpolyethylene and 190 C for polypropylene.9.1.2 Heat the sample with appropriate pressure and timesettings to obtain a plaque with uniform thickness.9.1.3 Remove the plaq

30、ue assembly and place it between twothick steel plates (heat sink) and cool the plaque to ambienttemperature. Alternatively, quench the plaque in ice water.9.1.4 Determine the average thickness of the sheet to ensurethat it is within the allowable tolerances.9.1.5 Use the bore hole cutter to punch o

31、ut a disk from theplaque and record the specimen weight.9.1.6 Place the specimen disk into the appropriate pan type.Use an identical empty pan as the reference. (Do not crimp orseal the pans.)NOTE 8If controlled cooling is not necessary, the option to prepare thetest sample using Practice D4703, Ann

32、ex A1 (Procedure C), is acceptable.10. Procedure10.1 Instrument CalibrationThis procedure uses a two-point calibration step. Indium and tin are used as the calibrantssince their respective melting points encompass the specifiedanalysis temperature range (180 to 220 C). Calibrate theinstrument in acc

33、ordance with the manufacturers instructionsusing the following procedure. Calibrate the instrument at leastonce per month or before use if longer than one month.10.1.1 Place 5 6 0.5 mg of indium/tin into an aluminumsample pan. Place an aluminum cover over the pan, and sealusing the encapsulating pre

34、ss. Prepare an empty sealed pan tobe used as the reference. Place the specimen and reference pansinto their respective locations in the instrument cell.D8117 17210.1.2 Turn on the nitrogen gas flow at a rate of 50 mL min(with an absolute pressure of 140 kPa).10.1.3 Use the following melting profiles

35、:Indium ambient to 145 C at 10 C min, 145 to 165 C at 1 C minTin ambient to 220 C at 10 C min, 220 to 240 C at 1 C minNOTE 9The specified heating rates are for calibration use only.10.1.4 Adjust the temperature-calibration software (or po-tentiometer) to set the melting point at 156.63 and 231.97 C(

36、see Practice E967) for indium and tin, respectively. Themelting point of the calibrant is defined as the intercept of theextended baseline and the extended tangent to the first slope ofthe endotherm (that is, the onset). See Fig. 1.NOTE 10An inadequate melting thermal curve is occasionally ob-tained

37、 due to poor surface contact of the calibrant material to the pansurface. If this occurs, repeat the calibration step. (After one melting/crystallization cycle the calibrant material should coat the bottom of thepan evenly.)10.2 Instrument Operation:10.2.1 Load the specimen and reference pans into t

38、he cell.10.2.2 Allow 5 min for a nitrogen pre-purge prior to begin-ning the heating cycle to eliminate any residual oxygen.Commence programmed heating of the specimen (under nitro-gen flow of 50 6 5 mL min) from ambient temperature to200 C (set point) at a rate of 20 C min.10.2.3 When the set temper

39、ature has been reached, discon-tinue programmed heating and equilibrate the sample for 5 minat the set temperature. Turn on the recorder. If the instrumentbeing used does not have an isothermal temperature-controlmode feature, ensure accurate temperature control by monitor-ing and adjusting continua

40、lly, as required.10.2.4 Once the equilibrium time has expired, change thegas to oxygen at a flow rate of 50 6 mL min. (Record thisevent.) This changeover point to oxygen flow is considered thezero time of the experiment.10.2.5 Continue isothermal operation until the maximumexotherm has been reached

41、to allow a complete examination ofthe entire exotherm. (See Figs. 2 and 3). At the testersdiscretion, it is acceptable to terminate the test at a predeter-mined heat flow change provided that data are available tosupport the alternative. It is also acceptable to terminate the testif time requirement

42、s stated in the products specification havebeen met.10.2.6 Upon completion of the test, switch the gas selectorback to nitrogen and cool the instrument to ambient tempera-ture. If additional testing is being conducted, cooling theinstrument cell below 60 to 70 C is sufficient to avoid anypremature t

43、hermal oxidation of the sample.10.2.7 Test frequency is established by the user. As aminimum requirement, samples are tested in duplicate with themean value reported.10.2.8 Clean the DSC cell of contamination by heating to500 C for 5 min in air (or oxygen) prior to conductingmeasurements and between

44、 the testing of different formula-tions.10.3 Thermal Curve AnalysisThe data is plotted with theheat-flow signal normalized to sample mass (that is, W/g) onthe y-axis, versus time on the x-axis. Expand the x-axis as muchas possible to facilitate analysis.10.3.1 Extend the recorded baseline beyond the

45、 oxidativereactive exotherm. Extrapolate the steepest linear slope of thisexotherm to intercept the extended baseline (see Fig. 3).10.3.2 The OIT is measured to within 60.1 min from zerotime to the intercept point.10.3.3 The tangent method used to measure the oxidationtime is the preferred method, b

46、ut the selection of the appropri-ate tangent to the exotherm sloped line is, at times, difficult ifthe exothermic peak has a leading edge. It is possible thatexothermic peaks with leading edges occur if the oxidationreaction is slow.NOTE 11The oxidation may not occur as a smooth transition andmultip

47、le steps or slopes may be produced. When this occurs, resamplingand retesting is recommended. Use of one of the homogenization methodsmentioned in the appendixes of this standard may be used to obtain ahomogeneous specimen and a single exothermic peak.NOTE 12If multiple slopes result from the oxidat

48、ion process, OITneeds to be defined to accurately reflect the oxidation of the polymer. It isup to the user to determine which slope best represents the materialproperty for an application. It must be noted in the report if the tangentline is not drawn from the first steep slope.NOTE 13If the select

49、ion of the appropriate baseline is not obvioususing the tangent method, try the offset method. Draw a second baselineparallel to the first baseline at a distance of 0.05 W g above the firstbaseline. The intersection of this second line with the exotherm signal isdefined as the onset of oxidation. The time from this intersection to zerotime is the OIT.NOTE 14Other gas flow rates or specimen weights, or both, may beused if shown to be equivalent.11. Report11.1 Report the following information:11.1.1 Identification of t