1、Designation: E 1858 03Standard 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 (e) 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 di
3、fferential scanningcalorimetry or pressure differential scanning calorimetry and isapplicable to hydrocarbons that oxidize exothermically in theiranalyzed form.1.2 Computer or electronic-based instruments, techniquesor data treatment equivalent to this test method may also beused.NOTE 1Since all ele
4、ctronic data treatments are not equivalent, theuser shall verify equivalency to this method.1.3 Test Method A A differential scanning calorimeter(DSC) is used at ambient pressure, for example, about 100 kPaof oxygen.1.4 Test Method B A pressure DSC (PDSC) is used at highpressure, for example, 3.5 MP
5、a (500 psig) oxygen.1.5 SI values are the standard.1.6 This test method is related to ISO 113576 but isdifferent in technical content. This test method is related toCEC L-85T but includes additional experimental conditions.1.7 This standard does not purport to address all of thesafety concerns, if a
6、ny, 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 limitations prior to use. Specific precau-tionary statements are given in Note 6 and Note 14.2. Referenced Documents2
7、.1 ASTM Standards:D 3350 Specification for Polyethylene Plastic Pipe andFitting Materials2D 3895 Test Method for Oxidative-Induction Time of Poly-olefins by Differential Scanning Calorimetry3D 4565 Test Method for Physical Environmental Perfor-mance Properties of Insulations and Jackets for Telecom-
8、munications Wire and Cable4D 5482 Test Method for Oxidation Induction Time of Lu-bricating Greases by Pressure Differential Scanning Calo-rimetry5D 5885 Test Method for Oxidative Induction Time of Poly-olefin Geosynthics By High Pressure Differential ScanningCalorimetry6D 6186 Test Method for Oxidat
9、ion Induction Time of Lu-bricating Oils by Pressure Differential Scanning Calorim-etry (PDSC) Polyolefin Geosynthics By High PressureDifferential Scanning Calorimetry7E 473 Terminology Relating to Thermal Analysis8E 691 Practice for Conducting and Interlaboratory Study ToDetermine the Precision of a
10、 Test Method8E 967 Practice for Temperature Calibration of DifferentialScanning Calorimeters8E 1860 Test Method for Elapsed Time Calibration of Ther-mal Analyzers82.2 Other Standards:ISO 113576 Plastice-Differential Scanning Calorimetry(DSC) Part 6: Oxidation Induction Time9CEC L-85T Hot Surface Oxi
11、dation103. 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 the referencealuminum pan are heated to a specified constant test tempera-ture in an oxygen environment. H
12、eat 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 relative measure ofoxidative stability at the test temperature, is determined from1This test method is under th
13、e direct jurisdiction of Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on TestMethods and Recommended Practices.Current edition approved March 10, 2003. Published April 2003. Originallyapproved in 1997. Last previous edition approved in 2000 as E 185800
14、.2Annual Book of ASTM Standards, Vol 08.03.3Annual Book of ASTM Standards, Vol 08.02.4Annual Book of ASTM Standards, Vol 10.02.5Annual Book of ASTM Standards, Vol 05.03.6Annual Book of ASTM Standards, Vol 04.09.7Annual Book of ASTM Standards, Vol 05.04.8Annual Book of ASTM Standards, Vol 14.02.9Avai
15、lable from ANSI, 11 W. 42nd Street, 13th Floor, New York, NY 10036.10Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.data recorded during the isothermal test. The OIT m
16、easurementis initiated upon reaching the isothermal test temperature.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 i
17、ncreasingthe pressure of oxygen purge gas, or both. Conversely, 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 w
18、ill beincreased (see Test Methods D 3895, D 4565, D 5482, D 6186,and Specification D 3350).NOTE 2For 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. Sig
19、nificance and Use5.1 Oxidative induction time is a relative measure 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 comp
20、ared fromone hydrocarbon to another or to a reference material to 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 P
21、ressure Differen-tial Scanning Calorimeter, the essential instrumentation 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 refe
22、rence to a constant temperature or at aconstant rate within the 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 refer
23、ence with a sensitivity of 5 W.6.1.1.4 A means of sustaining a Test 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 cha
24、nge of40 C/min constant to 1 % and an isothermal temperatureconstant to 60.4 CNOTE 3In 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 ope
25、rator is cautioned to verify (with apparatus manufac-turer) the maximum oxygen pressure at which the apparatus may be safelyoperated.6.1.3 Recording Device, capable of recording and display-ing any fraction of the heat flow signal on the Y-axis and timeFIG. 1 Hydrocarbon Oxidation by DSCE1858032on t
26、he X-axis (see Fig. 1). Time base shall be accurate to 6 0.1min and be readable to 0.1 min.NOTE 4The capability to record 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 thespeciment and
27、reference materials and that are of a suitablestructural shape and integrity to contain the specimen andreference materials.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 t
28、hepressure limits of this test method.6.3.1.2 A source of pressurized oxygen or air capable ofsustaining a regulated gas 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
29、dependence of the transducer.NOTE 5The link between the test chamber and the pressure transducershould allow for fast 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 th
30、e test chamber to 60.2 MPa of thedesired value.6.3.1.5 A Ballast, or similar means to maintain the appliedpressure in 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/m
31、in or anotherselected flow rate, accurate to within 6 5 %. Ensure theflowmeter is calibrated for oxygen. Contact a supplier of flowmeters for specific details on calibration, see Note 13, follow-ing Section 11.4.NOTE 6Caution: Use metal or fluoropolymer tubing with oxygenrather than the commonly use
32、d rubber or polyvinyl chloride plastic tubing.There have been hazardous situations with prolonged use of certainpolymer tubing in oxygen service.NOTE 7Gas delivery tubing should be kept as short as possible tominimuze “dead” volume.6.5 Analytical Balance with a capacity of at least 100 mgand capable
33、 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 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: he
34、ight, 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 A1.7. Materials7.1 Oxygen, extra dry, purity of not less than 99.50 % byvolume.NOTE 8Warning: Oxidizer. Gas under pressure.7.2 Indium, of not less than 99.9 % by mass.7.3 Tin, o
35、f not less than 99.9 % by mass.8. PrecautionsNOTE 9Caution: Oxygen is a strong oxidizer and vigorously accel-erates combustion. Keep surfaces clean.NOTE 10Caution: Oxygen is a strong oxidizer and may react withaluminum pans.8.1 If the specimen is heated to decomposition, toxic orcorrosive products m
36、ay be released.8.2 For certain types of PDSC, it is recommended that theflow be set up with a “reverse flow” implementation 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
37、the sample is a liquid or powder, mix thoroughly priorto sampling.9.2 In the absence of information, samples are to beanalyzed 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 treatm
38、ent isused prior to oxidative testing, then record any mass loss as aresult of the treatment.10. Calibration10.1 Calibrate the temperature output of the instrumentusing Test Method E 967 except that a heating rate of 1C/minshall be used to approach the isothermal conditions of this test.Use indium a
39、nd tin calibration material to bracket the tempera-ture used in this test. Perform calibration under ambientpressure conditions.NOTE 11This assumes known temperature calibration with depen-dence on pressure. If the temperature calibration varies with pressure bymore than 0.4C, then the calibration s
40、hould be performed at the testpressure.10.2 Obtain the melting temperatures observed in the instru-ment calibration 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
41、3.00 to 3.30 mg of sample to a precision of60.01 mg into a clean specimen capsule. For accurate compari-sons, specimens 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 12Other specimen sizes may
42、be used if used consistently.However, the OIT values obtained may differ from those obtained with 3mg. Also, vented 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 i
43、n the sampleposition of the instrument and an empty specimen pan, withoutlid, in the reference position. Be sure that the pans are centeredon the sensors.11.3 Clean and replace all DSC covers in accordance withappropriate recommendations.E185803311.4 Adjust flow rate of oxygen gas to 50.0 6 2 mL/min
44、accurate to 6 4 %. Other flow rates may be used, but shall benoted in the report.NOTE 13Many flowmeters are not rated for high 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, ifrecomme
45、nded by the instrument manufacturer. If measured at elevatedpressure, the flow rate should be corrected to a comparable flow 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 t
46、o 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 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 heat
47、ing at 40C/min fromambient temperature to the isothermal temperatures, 175 or195C. Wait until temperature reaches isothermal conditionsand record the thermal curve.11.7.1 Continue heating until the isothermal test tempera-ture 6 0.4C is reached. Discontinue programmed heating andequilibrate sample a
48、t the constant isothermal temperature. Zerotime is recorded at the initiation of the OIT measurement andincludes time to 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
49、 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 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 0.4C.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 Ot
