1、Designation: E 1858 08Standard Test Method forDetermining Oxidation Induction Time of Hydrocarbons byDifferential Scanning Calorimetry1This standard is issued under the fixed designation E 1858; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 describes the determination of theoxidative properties of hydrocarbons by dif
3、ferential scanningcalorimetry or pressure differential scanning calorimetry and isapplicable to hydrocarbons that oxidize exothermically in theiranalyzed form.1.2 Test Method A A differential scanning calorimeter(DSC) is used at ambient pressure, for example, about 100 kPaof oxygen.1.3 Test Method B
4、Apressure 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 This test method is related to ISO 113576 but isdifferent in technical content. This te
5、st method is 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 theresponsibility of the user of this standard to establish appro-priate safety and health practices and de
6、termine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Note 5 and Note 13.2. Referenced Documents2.1 ASTM Standards:2D 3350 Specification for Polyethylene Plastics Pipe andFittings MaterialsD 3895 Test Method for Oxidative-Induction Time of
7、 Poly-olefins by Differential Scanning CalorimetryD 4565 Test Methods for Physical and Environmental Per-formance Properties of Insulations and Jackets for Tele-communications Wire and CableD 5482 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini MethodAtmospheric)D 5885 Test Method for Ox
8、idative Induction Time of Poly-olefin Geosynthetics by High-Pressure Differential Scan-ning CalorimetryD 6186 Test Method for Oxidation Induction Time of Lu-bricating Oils by Pressure Differential Scanning Calorim-etry (PDSC)E 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 691 Practice
9、for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 967 Test Method for Temperature Calibration of Differ-ential Scanning Calorimeters and Differential ThermalAnalyzersE 1860 Test Method for Elapsed Time Calibration of Ther-mal Analyzers2.2 Other Standards:ISO 113576
10、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 this test method aregiven in Terminology E 473.4. Summary of Test Method4.1 The test specimen in an aluminum pan and t
11、he 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 oxidativereaction is manifested by heat evolution on the thermal curve.The oxidative induction time (OIT), a relati
12、ve measure ofoxidative stability at the test temperature, is determined fromdata recorded during the isothermal test. The OIT measurementis initiated upon reaching the isothermal test temperature.4.2 For some particularly stable materials, the OIT may bequite long ( 120 min) at the specified elevate
13、d 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, reac-tions that proceed too rapidly, with a short OIT, may be1This test method is under the direct jurisdicti
14、on of Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on ThermalTest Methods and Practices.Current edition approved Sept. 1, 2008. Published October 2008. Originallyapproved in 1997. Last previous edition approved in 2003 as E 185803.2Supporting data have
15、 been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: E371018.3Available from ANSI, 11 W. 42nd Street, 13th Floor, New York, NY 10036.4Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096.1Copyright ASTM International, 100 Barr Harbor Drive,
16、PO Box C700, West Conshohocken, PA 19428-2959, United States.extended 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 D 3895, D 4565, D 5482, D 6186
17、,and Specification D 3350).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 meas
18、ure of 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 t
19、o obtainrelative 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 instru
20、mentation re-quired to provide the minimum differential scanning calorimet-ric capability for this test method 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
21、applicable temperature range of thistest method.6.1.1.2 A Temperature Sensor, to provide an indication ofthe specimen/furnace temperature to 60.4 C.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 T
22、est 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 of40 C/min constant to 1 % and an isothermal temperaturecons
23、tant to 60.4 CNOTE 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
24、maximum 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 are heatflow, temperature and time.NOTE 3The capability to record t
25、he 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 materials.
26、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 this test method.6.3.1.2 A source of pressurized oxygen or air capable ofsustaining a regulated gas pre
27、ssure 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 pressu
28、re 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 the te
29、st 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 supplier
30、of flowmeters for specific details on calibration, see Note 10, follow-ing Section 11.4.NOTE 5Caution: Use metal or fluoropolymer tubing with oxygenrather than the commonly used rubber or polyvinyl chloride plastic tubing.There have been hazardous situations with prolonged use of certainpolymer tubi
31、ng in oxygen service.NOTE 6Gas 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
32、 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
33、1.7. Materials7.1 Oxygen, extra dry, purity of not less than 99.50 % byvolume.NOTE 7Warning: Oxidizer. 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. PrecautionsNOTE 8Caution: Oxygen is a strong oxidizer and vigorously accel-erates combusti
34、on. Keep surfaces clean.NOTE 9Caution: Oxygen is a strong oxidizer and may react withaluminum pans.8.1 If the specimen is heated to decomposition, toxic orcorrosive products may be released.E18580828.2 For certain types of PDSC, it is recommended that theflow be set up with a “reverse flow” implemen
35、tation 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 b
36、eanalyzed 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 Cali
37、brate the temperature output of the instrumentusing Test Method E 967 except that a heating rate of 1 C/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
38、 conditions.NOTE 10This assumes known temperature calibration with depen-dence on pressure. If the temperature calibration varies with pressure bymore than 0.4 C, then the calibration should be performed at the testpressure.10.2 Obtain the melting temperatures observed in the instru-ment calibration
39、 from extrapolated onset temperatures.10.3 Confirm the time scale conformance of the differentialscanning calorimeter to better than 1 % using Test MethodE 1860.11. Procedure11.1 Weigh 3.00 to 3.30 mg of sample to a precision of 60.01 mg into a clean specimen capsule. For accurate compari-sons, spec
40、imens should have equivalent masses to within 10 %to avoid mass-dependent effects on the oxidative properties.Do not place lid on specimen pan or capsule.NOTE 11Other specimen sizes may be used if used consistently.However, the OIT values obtained may differ from those obtained with 3mg.Also, vented
41、 specimen covers 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 th
42、at the pans are 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 6 4 %. Other flow rates may be used, but shall benoted in the report.NOTE 12Many flowmeters are not rated for h
43、igh pressure operationand may burst if excess pressure is applied. In these cases, the flow rateshould be 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 flo
44、w rate (forexample, 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 mi
45、n, to ensureexchange 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 40 C/min fromambient temperature to the isothermal temperatures, 175 or195 C. Wait until temperature reaches isother
46、mal conditionsand record the thermal curve.11.7.1 Continue heating until the isothermal test tempera-ture 6 0.4 C 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
47、 heat from room temperature 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
48、the test temperature be 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 0.4 C.11.8.2 When using PDSC Test Method B, pressurize slowly,adjust
49、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 0.4 C.11.8.3 Other temperatures in the range of 170 to 210 C maybe used for Test Method A and in the range of 150 to 200 Cfor Test Method B, but must be reported. The same temperaturemust be used by all participants intending to compare data andfor all specimens to be compared.11.9 Continue isothermal operation until the peak of theoxidation exotherm is observed or until an inflection point isobserved and the total displacement
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