1、Designation: D5885 06 (Reapproved 2012)Standard Test Method forOxidative Induction Time of Polyolefin Geosynthetics byHigh-Pressure Differential Scanning Calorimetry1This standard is issued under the fixed designation D5885; the number immediately following the designation indicates the year oforigi
2、nal adoption 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.1. Scope1.1 This test method covers a procedure for the determina-tion of th
3、e oxidative induction time (OIT) of polyolefingeosynthetics using high pressure differential scanning calo-rimetry.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 This test method mea
4、sures the oxidative induction timeassociated with a given test specimen at a specified temperatureand pressure.1.4 This is an accelerated test for highly stabilized materials.It is applicable only to material whose OIT values under 3.4MPa of oxygen is greater than 30 min at 150C.1.5 The values state
5、d in SI units are to be regarded as thestandard. The values stated in parentheses are provided forinformation only.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
6、safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2D3895 Test Method for Oxidative-Induction Time of Poly-olefins by Differential Scanning Calorimetr
7、yD4439 Terminology for GeosyntheticsD4491 Test Methods for Water Permeability of Geotextilesby PermittivityD4565 Test Methods for Physical and Environmental Per-formance Properties of Insulations and Jackets for Tele-communications Wire and CableD4703 Practice for Compression Molding ThermoplasticMa
8、terials into Test Specimens, Plaques, or SheetsE473 Terminology Relating to Thermal Analysis and Rhe-ologyE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzersE691 Practice for Conducting an Interlaboratory Study toDetermine the Preci
9、sion of a Test MethodG88 Guide for Designing Systems for Oxygen Service3. Terminology3.1 Definitions:3.1.1 differential scanning calorimetry (DSC), na tech-nique in which the difference in heat flow inputs into asubstance and a reference material is measured as a function oftemperature or time, whil
10、e the substance and reference materialare subjected to a controlled-temperature program. (See Ter-minology E473.)3.1.2 geomembrane, nan essentially impermeable geosyn-thetic composed of one or more synthetic sheets. (See Termi-nology D4439.)3.1.2.1 DiscussionIn this test method, essentially imper-me
11、able means that no measurable liquid flows through ageosynthetic when tested in accordance with Test MethodD4491.3.1.3 geosynthetic, na planar product manufactured frompolymeric material used with soil, rock, earth, or other geo-technical engineering-related material as an integral part of aman-made
12、 project, structure, or system. (See TerminologyD4439.)3.1.4 high-pressure differential scanning calorimetry(HPDSC) , ndifferential scanning calorimetry in which thesubstance and reference material are exposed to a controlledsuperambient atmosphere.3.1.5 index test, na test procedure that may be use
13、d toestablish an order for a set of specimens with respect to theproperty of interest.1This 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 July 1, 2012. Published Ju
14、ly 2012. Originally approvedin 1995. Last previous edition approved in 2006 as D5885 06. DOI: 10.1520/D5885-06R12.2For 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 th
15、e standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.6 oxidative induction time (OIT), n the elapsed timebetween first exposure to an oxidizing gas and the onset tooxidation of a mat
16、erial under isothermal conditions.3.1.6.1 DiscussionOxidative induction time is an indextest parameter dependent upon a wide range of experimentalconditions including temperature, pressure of oxygen, purgegas flow rate, and the presence or absence of catalysts.4. Summary of Test Method4.1 The specim
17、en to be tested and the corresponding refer-ence material are heated from room temperature at a constantrate in a non-purging, high-pressure oxygen environment at adefined pressure. When the specified temperature has beenreached, the specimen is then held at that temperature until theoxidative react
18、ion is displayed on the thermal curve. The OITis the time interval from the start of the temperature programtest to the onset of the oxidative reaction.4.2 In this procedure, an elevated pressure of oxygen is usedto accelerate the reaction and to reduce analysis time.4.3 Unless otherwise specified,
19、the temperature used in thistest method shall be 150C, and the chamber pressure is to bemaintained at 3.4 MPa (500 psi) using a constant volume testcondition.5. Significance and Use5.1 The oxidative induction time is a characteristic of acompounded polyolefin product that is dependent not only onthe
20、 type and amount of additives present, but also on the typeof resin. In well-behaved systems, this test method can be usedas a quality control measure to monitor the stabilization ingeosynthetics as received from a supplier.5.2 When this test method is used to compare differentgeomembrane formulatio
21、ns containing different antioxidantpackages, then those results shall be considered valid only atthe temperature of test.5.3 This test method is intended as an geosynthetic test. Useof the OIT value to estimate the lifetime of the geomembranefrom which the test specimen is taken is not addressed nor
22、 shallit be used for this purpose.5.3.1 The OIT measurement is an accelerated thermal agingtest and, as such, interpretation of resulting data may bemisleading if done by an inexperienced operator. Cautionshould be exercised in data interpretation since oxidationreaction kinetics are a function of t
23、emperature and the proper-ties of the additives contained in the geosynthetic sample. Forexample, OIT values are often used to select optimum resinformulations. Certain antioxidants, however, may generatepoor OIT results even though they may be adequate at theirintended use temperature and vice vers
24、a.5.4 This test method can be used for other purposes such asmanufacturing control and research and development.5.5 Oxidation induction time is strongly dependent upontest temperature and the partial pressure of oxygen. The higherthe test temperature or the oxygen partial pressure, or both, theshort
25、er the oxidation induction time.5.5.1 The use of high test temperature, however, may havedeleterious effects. The first of these is the potential volatiliza-tion of additive packages used to stabilize the test materials.The second is the potential for the influence of chemicalmechanisms which are no
26、t significant at end-use operationconditions.5.5.2 This test method uses high oxygen pressure to accel-erate the test period while making use of lower test tempera-tures to protect additive packages.5.6 The results from this test method may or may notcorrelate with those obtained by other OIT measur
27、ements suchas Test Method D3895 or Test Methods D4565.6. Apparatus6.1 Differential Scanning Calorimeter Thermal analysisequipment capable of heating rates up to 20 6 1C/min and ofautomatically recording the differential heat flow between thetest sample and a reference sample is necessary. The equipm
28、entmust be capable of measuring sample temperature to 61Cwhile maintaining a set temperature to 60.5C.NOTE 1Modern computer-based instrumentation equipped with “iso-track” modes provide adequate specimen temperature control.6.2 Data Presentation DeviceA printer, plotter, recorder,or other recording
29、output device capable of displaying heatflow on the Y-axis versus time on the X-axis as output signalsfrom differential scanning calorimeters in 6.1.6.3 High-Pressure DSC CellAunit capable of maintainingpressure up to 3.4 MPa (500 psig). The system shall beequipped with a pressure gage to monitor th
30、e internal pressureof the cell to permit manual release of pressure to maintaindesired level.NOTE 2The gage shall be accurate to 2 % at 3.4 MPa (500 psig).NOTE 3All pressures in this test method are indicated relative toatmosphere pressurethat is, they are “gage” pressures.6.4 High-Pressure Oxygen C
31、ylinder RegulatorA pressureregulator capable of regulating a pressure up to 5.5 MPa (800psi). The outlet of the cylinder is to be linked to the high-pressure cell using a clean stainless steel tube.6.5 Analytical Balance, 0.1-mg sensitivity.6.6 Specimen Holders, degreased aluminum pans, 6.0 to7.0-mm
32、 diameter.6.7 Core Hole Borer, cork borer or arch punch producing6.3-mm (0.25-in.) disks.7. Reagents and Materials7.1 All chemical reagents used in this test method shall beanalytical grade unless otherwise specified.7.2 Hexane or Acetone, for cleaning specimen pans andstainless steel tubing, see 8.
33、2 and 8.3.7.3 Indium (99.999 % Purity) , for calibration purposes, see9.1.7.4 Oxygen, purity 99.5 % for the test atmosphere.8. Precautions8.1 Oxygen is a strong oxidizer that vigorously acceleratescombustion. Keep oil and grease away from equipment usingor containing oxygen.D5885 06 (2012)28.2 The s
34、tainless steel tube connecting the high-pressurecell to the oxygen cylinder must be thoroughly cleaned byhexane (or acetone) and then dried before being connected tothe cell.8.3 All specimen holders should be cleaned by washingwith hexane (or acetone) and then drying before being used inthe test.8.4
35、 The use of pressurized oxygen requires appropriate andcareful handling procedures. The user of this test method shallbe familiar with the precautions described in Guide G88.9. Sampling9.1 Using a bore hole cutter, cork borer, or punch, cutseveral 6.3-mm (0.25-in.) round specimen from the geosyn-the
36、tic test sample.9.2 Compression mold these assembled parts into a uniformplaque to a thickness of 0.25 mm (10 mil) (see PracticeD4703).NOTE 4The temperature at which molding takes place may be at orabove the test temperature of this test method. Prolonged exposure to airat these temperatures may ind
37、uce a negative bias into OIT measurement.Molding should be performed at as low a temperature and as quickly aspossible to minimized this bias.9.3 Cut test specimens from the plaque using a 6.3-mm(0.25-in.) bore hole cutter or punch.10. Calibration10.1 Using Test Method E967, temperature calibrate th
38、edifferential scanning calorimeter using indium metal and aheating rate of 1C/min from 145 to 165C.10.1.1 Perform the calibration step at least once a month orwhenever changes have occurred in the experimental setup.11. ProcedureNOTE 5Procedures for preparing the test specimen may be differentfor di
39、fferent polyolefin geosynthetic products, for example,geomembranes, geonets, geogrids, or geotextiles.11.1 Prepare a specimen with a mass of 5 6 1 mg.11.2 Place the weighed specimen into the cleaned specimenpan.11.3 Place the specimen and reference pans into the cell.NOTE 6Open pans are used in this
40、 test method.11.4 Secure the top plate of the test chamber and tighten thecell system.11.5 Commence programmed heating of the specimen fromambient temperature to 150 C at a rate of 20 C/min. Zerotime is taken at the initiation of the temperature program. Thenhold the temperature isothermally at 150
41、C until the oxidativeexothermic peak is detected. At the same time, the thermalcurve of the entire test is being recorded. Other test tempera-ture may be used, with the agreement of all parties concerned,but must be reported.NOTE 7150 C is the temperature typically used for polyethylenebased materia
42、l and 170 C for polypropylene-based materials.NOTE 8A slight gain in pressure at the beginning of the test isanticipated as the temperature of the cell increases. Decrease the pressureback to 3.4 MPa (500 psi) by slightly opening the pressure release valve.NOTE 9The time to onset of oxidation varies
43、 with stabilizer packageand may be more than 900 min. For a first-time specimen, the isothermaltime period of 1000 min. is suggested.11.6 Operate and test under constant volume conditionsaccording to the following procedure:11.6.1 Close the pressure release valve and the inlet valve ofthe cell. Only
44、 the outlet valve is opened.11.6.2 Adjust the pressure of the cylinder regulator todeliver 3.4-MPa (500-psi) test pressure. Other pressures maybe used with the agreement of all parties concerned but must bereported. See Note 8.11.6.3 Slowly open the inlet valve of the cell and allowoxygen to purge t
45、he cell for 2 min.NOTE 10Rapid pressurization may cause a temperature increase dueto adiabatic compression (see Guide G88). The user shall observe thetemperature of the test specimen and adjust the pressurization rate so thata temperature rise of no more than 5 C is observed.11.6.4 After 2-min, clos
46、e the outlet valve, allow the cell toreach full pressure, then turn off the inlet valve. Also turn offthe oxygen supplied from the cylinder.11.7 Record the sample temperature 5 min after isothermalconditions have been reachedNOTE 11The DSC cell should be cleaned by holding the cell at atemperature o
47、f 400C for 3 min under air or oxygen atmosphere.12. Analysis Response12.1 Plot the data with the heat flow signal on the y-axis,versus time on the x-axis.12.2 Determine the value for OIT in the following manner:12.2.1 Plot data with a y-axis sensitivity sufficient to showthe full oxidative exotherm.
48、 A full-scale sensitivity of 5 W/g isusually adequate.12.2.2 Extend the horizontal baseline generated prior to theonset to oxidation.NOTE 12For the oxidation exotherm containing a small shoulder peakat the beginning of oxidation, a sigmoidal baseline may be moreappropriate than the straight baseline
49、.12.2.3 Draw a tangent at the inflection point of the exother-mic peak and extend this tangent to intersect with the baseline.12.2.4 The time at the intersection, measured from theinitiation of the temperature program from ambient tempera-ture is the onset of oxidative degradation and is taken as theOIT value.12.2.5 Measure the OIT as shown in Fig. 1.12.3 Report the OIT for a single specimen.NOTE 13If replicate tests are required by the parties involved, a meanvalue shall be calculated as being representative of the material beingevaluated.13.
