1、Designation: E1858 08 (Reapproved 2015)1Standard Test Methods forDetermining Oxidation Induction Time of Hydrocarbons byDifferential Scanning Calorimetry1This standard is issued under the fixed designation E1858; the number immediately following the designation indicates the year oforiginal adoption
2、 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.1NOTEWarning notes were editorially updated throughout in May 2015.1. Scope1.1 These tes
3、t methods describe the determination of theoxidative properties of hydrocarbons by differential scanningcalorimetry or pressure differential scanning calorimetry and isapplicable to hydrocarbons that oxidize exothermically in theiranalyzed form.1.2 Test Method AA differential scanning calorimeter(DS
4、C) is used at ambient pressure, for example, about 100 kPaof oxygen.1.3 Test Method BA pressure DSC (PDSC) is used at highpressure, for example, 3.5 MPa (500 psig) oxygen.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 T
5、hese test methods are related to ISO 113576 but isdifferent in technical content. These test methods are related toCEC L-85T but includes additional experimental conditions.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
6、ty 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 6.4 and 11.10.2. Referenced Documents2.1 ASTM Standards:2D3350 Specification for Polyethylene
7、 Plastics Pipe and Fit-tings MaterialsD3895 Test Method for Oxidative-Induction Time of Poly-olefins by Differential Scanning CalorimetryD4565 Test Methods for Physical and Environmental Per-formance Properties of Insulations and Jackets for Tele-communications Wire and CableD5482 Test Method for Va
8、por Pressure of Petroleum Prod-ucts (Mini MethodAtmospheric)D5885 Test Method for Oxidative Induction Time of Poly-olefin Geosynthetics by High-Pressure Differential Scan-ning CalorimetryD6186 Test Method for Oxidation Induction Time of Lubri-cating Oils by Pressure Differential Scanning Calorimetry
9、(PDSC)E473 Terminology 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-lyzersE1860 Test Method fo
10、r Elapsed Time Calibration of Ther-mal Analyzers2.2 Other Standards:ISO 113576 Plastice-Differential Scanning Calorimetry(DSC) Part 6: Oxidation Induction Time3CEC L-85T Hot Surface Oxidation43. Terminology3.1 Definitions:3.1.1 Specific technical terms used in these test methods aregiven in Terminol
11、ogy E473.4. Summary of Test Method4.1 The test specimen in an aluminum pan and the referencealuminum pan are heated to a specified constant test tempera-ture in an oxygen environment. Heat flow out of the specimenis monitored at an isothermal temperature until the oxidative1These test methods are un
12、der the direct jurisdiction of Committee E37 onThermal Measurements and is the direct responsibility of Subcommittee E37.01 onCalorimetry and Mass Loss.Current edition approved May 1, 2015. Published May 2015. Originallyapproved in 1997. Last previous edition approved in 2008 as E1858 08. DOI:10.152
13、0/E1858-08R15E01.2For 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.3Available from American National Standards
14、Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,PA 15096-0001, http:/www.sae.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United Sta
15、tes1reaction is manifested by heat evolution on the thermal curve.The oxidative induction time (OIT), a relative measure ofoxidative stability at the test temperature, is determined fromdata recorded during the isothermal test. The OIT measurementis initiated upon reaching the isothermal test temper
16、ature.4.2 For some particularly stable materials, the OIT may bequite long (120 min) at the specified elevated temperatures ofthe experiment. Under these circumstances, the OIT may bereduced by increasing the isothermal temperature or increasingthe pressure of oxygen purge gas, or both. Conversely,
17、reac-tions that proceed too rapidly, with a short OIT, may beextended by decreasing the test temperature or reducing thepartial pressure of oxygen, or both. By admixing oxygen gaswith a suitable diluent, for example, nitrogen, the OIT will beincreased (see Test Methods D3895, D4565, D5482, D6186,and
18、 Specification D3350).NOTE 1For some systems, the use of copper pans to catalyzeoxidation will reduce the oxidation induction time for a particulartemperature. The results, however, will not correlate with non-catalyzedtests.5. Significance and Use5.1 Oxidative induction time is a relative measure o
19、f thedegree of oxidative stability of the material evaluated at theisothermal temperature of the test. The presence, quantity oreffectiveness of antioxidants may be determined by thismethod. The OIT values thus obtained may be compared fromone hydrocarbon to another or to a reference material to obt
20、ainrelative oxidative stability information.5.2 Typical uses include the oxidative stability of edible oilsand fats (oxidative rancidity), lubricants, greases, and polyole-fins.6. Apparatus6.1 Differential Scanning Calorimeter or Pressure Differen-tial Scanning Calorimeter, the essential instrumenta
21、tion re-quired to provide the minimum differential scanning calorimet-ric capability for these test methods include:6.1.1 DSC Test Chamber, composed of:6.1.1.1 A Furnace(s), to provide uniform controlled heatingof a specimen and reference to a constant temperature or at aconstant rate within the app
22、licable temperature range of thesetest methods.6.1.1.2 A Temperature Sensor, to provide an indication ofthe specimen/furnace temperature to 60.4C.6.1.1.3 Differential Sensors, to detect a heat flow differencebetween specimen and reference with a sensitivity of 5 W.6.1.1.4 A means of sustaining a Tes
23、t Chamber Environmentof a purge gas of 50 mL/min within 5 %.6.1.2 Temperature Controller, capable of executing a spe-cific temperature program by operating the furnace(s) betweenselected temperature limits at a rate of temperature change of40C/min constant to 1 % and an isothermal temperatureconstan
24、t to 60.4CNOTE 2In certain cases when the sample under study is of highvolatility (for example, low molecular weight hydrocarbons), either theuse of pressures in excess of one atmosphere or lower temperatures maybe required. The operator is cautioned to verify (with apparatus manufac-turer) the maxi
25、mum oxygen pressure at which the apparatus may be safelyoperated.6.1.3 A Data Collection Device, to provide a means ofacquiring, storing, and displaying measured or calculatedsignals, or both. The minimum output signals required for DSCare heat flow, temperature and time.NOTE 3The capability to reco
26、rd the first derivative of the heat flowcurve will be helpful in cases where the baseline is not constant.6.2 Containers (pans, crucibles, etc.), that are inert to thespecimen and reference materials and that are of a suitablestructural shape and integrity to contain the specimen andreference materi
27、als.6.3 For use in Test Method B.6.3.1 Pressure System, consisting of:6.3.1.1 A Pressure Vessel, or similar means of sealing thetest chamber at any applied oxygen pressure within thepressure limits of these test methods.6.3.1.2 A source of pressurized oxygen or air capable ofsustaining a regulated g
28、as pressure in the test chamber of up to3.2 MPa.6.3.1.3 A Pressure Transducer, or similar device to measurethe pressure inside the test chamber to 60.2 MPa, includingany temperature dependence of the transducer.NOTE 4The link between the test chamber and the pressure transducershould allow for fast
29、pressure equilibrium to ensure accurate recording ofthe pressure above the specimen during testing.6.3.1.4 A Pressure Regulator, or similar device to adjust theapplied pressure in the test chamber to 60.2 MPa of thedesired value.6.3.1.5 A Ballast, or similar means to maintain the appliedpressure in
30、the test chamber constant to 60.2 MPa.6.3.1.6 Valves, to control the gas in the test chamber or toisolate components of the pressure system.6.4 Flow meter, capable of reading 50 mL/min or anotherselected flow rate, accurate to within 6 5 %. Ensure theflowmeter is calibrated for oxygen. Contact a sup
31、plier of flowmeters for specific details on calibration, see Note 6, followingSection 11.4.(WarningUse metal or fluoropolymer tubingwith oxygen rather than the commonly used rubber or polyvi-nyl chloride plastic tubing. There have been hazardous situa-tions with prolonged use of certain polymer tubi
32、ng in oxygenservice.)NOTE 5Gas delivery tubing should be kept as short as possible tominimize “dead” volume.6.5 Analytical Balance with a capacity of at least 100 mgand capable of weighing to the nearest 0.01 mg or less than 1 %of the specimen mass.6.6 Specimen Containers, and sample holders are the
33、 alu-minum sample pans and should be inert to the sample and theoxidizing gas. The pans shall be clean, dry, and flat. A typicalcylindrical pan has the following dimensions: height, 1.5 to 2.5mm and outer diameter, 5.0 to 6.0 mm.6.6.1 New sample pans shall be cleaned by the procedurefound in Annex A
34、1.E1858 08 (2015)127. Materials7.1 Oxygen, extra dry, purity of not less than 99.50 % byvolume. (WarningOxidizer. Gas under pressure.)7.2 Indium, of not less than 99.9 % by mass.7.3 Tin, of not less than 99.9 % by mass.8. Precautions8.1 WarningOxygen is a strong oxidizer and vigorouslyaccelerates co
35、mbustion. Keep surfaces clean.8.2 WarningOxygen is a strong oxidizer and may reactwith aluminum pans.8.3 If the specimen is heated to decomposition, toxic orcorrosive products may be released.8.4 For certain types of PDSC, it is recommended that theflow be set up with a “reverse flow” implementation
36、 to ensurethere is no contact of decomposed hydrocarbons with incomingoxygen within the instrument. See instrument designers rec-ommendation on “reverse flow.”9. Sampling9.1 If the sample is a liquid or powder, mix thoroughly priorto sampling.9.2 In the absence of information, samples are to beanaly
37、zed as received. If some heat or mechanical treatment isapplied to the sample prior to analysis, this treatment should bein nitrogen and noted in the report. If some heat treatment isused prior to oxidative testing, then record any mass loss as aresult of the treatment.10. Calibration10.1 Calibrate
38、the temperature output of the instrumentusing Test Method E967 except that a heating rate of 1C/minshall be used to approach the isothermal conditions of this test.Use indium and tin calibration material to bracket the tempera-ture used in this test. Perform calibration under ambientpressure conditi
39、ons.NOTE 6This assumes known temperature calibration with dependenceon pressure. If the temperature calibration varies with pressure by morethan 0.4C, then the calibration should be performed at the test pressure.10.2 Obtain the melting temperatures observed in the instru-ment calibration from extra
40、polated onset temperatures.10.3 Confirm the time scale conformance of the differentialscanning calorimeter to better than 1 % using Test MethodE1860.11. Procedure11.1 Weigh 3.00 to 3.30 mg of sample to a precision of60.01 mg into a clean specimen capsule. For accuratecomparisons, specimens should ha
41、ve equivalent masses towithin 10 % to avoid mass-dependent effects on the oxidativeproperties. Do not place lid on specimen pan or capsule.NOTE 7Other specimen sizes may be used if used consistently.However, the OIT values obtained may differ from those obtained with 3mg.Also, vented specimen covers
42、 may be used, but OIT values may differfrom those obtained in open pans. The following procedure assumes theuse of open pans.11.2 Place the uncovered prepared specimen in the sampleposition of the instrument and an empty specimen pan, withoutlid, in the reference position. Be sure that the pans are
43、centeredon the sensors.11.3 Clean and replace all DSC covers in accordance withappropriate recommendations.11.4 Adjust flow rate of oxygen gas to 50.0 6 2 mL/minaccurate to 64 %. Other flow rates may be used, but shall benoted in the report.NOTE 8Many flowmeters are not rated for high pressure opera
44、tion andmay burst if excess pressure is applied. In these cases, the flow rate shouldbe measured at atmospheric pressure at the exit of the DSC cell, ifrecommended by the instrument manufacturer. If measured at elevatedpressure, the flow rate should be corrected to a comparable flow rate (forexample
45、, 1.4 mL/min at 3.5 MPa).11.5 Set the instrument sensitivity as required to retain theoxidation exotherm on the recorded range. A pre-analysis maybe required to determine this value. A sensitivity of 2 W/g fullscale is typically acceptable.11.6 Purge the specimen area for 3 to 5 min, to ensureexchan
46、ge of air with oxygen at atmospheric pressure. Checkthe flow rate at elevated pressure and re-adjust to 50 6 2mL/min, if required.11.7 Commence programmed heating at 40C/min fromambient temperature to the isothermal temperatures, 175 or195C. Wait until temperature reaches isothermal conditionsand re
47、cord the thermal curve.11.7.1 Continue heating until the isothermal test tempera-ture 60.4C is reached. Discontinue programmed heating andequilibrate sample at the constant isothermal temperature. Zerotime is recorded at the initiation of the OIT measurement andincludes time to heat from room temper
48、ature to the specifiedisothermal temperature. The OIT is the total time from the startof the experiment at room temperature in oxygen to theextrapolated onset time of the exothermic process.11.7.2 To ensure that the sample is at the proper testtemperature, it is suggested that the test temperature b
49、e readand reported at 5 min into the isothermal portion of the run.11.8 Test Methods:11.8.1 When using DSC Test Method A, maintain flow rateof 50 mL/min (see 11.6) of oxygen and isothermal temperatureof 195 6 0.4C.11.8.2 When using PDSC Test Method B, pressurize slowly,adjust and maintain pressure of oxygen at 3.5 6 0.2 MPa,maintain flow rate of 50 mL/min (see 11.6) and isothermaltemperature of 1756 0.4C.11.8.3 Other temperatures in the range of 170 to 210C maybe used for Test MethodAand in the range of 150 to 200C forTest Method B, but must
