1、Designation: D 5885 06Standard Test Method forOxidative Induction Time of Polyolefin Geosynthetics byHigh-Pressure Differential Scanning Calorimetry1This standard is issued under the fixed designation D 5885; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of 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 covers a procedure for the determina-tion of the oxidative ind
3、uction 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 measures the oxida
4、tive 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 stated in SI units a
5、re 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 safety and heal
6、th 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:2D 3895 Test Method for Oxidative-Induction Time of Poly-olefins by Differential Scanning CalorimetryD 4439 Termin
7、ology for GeosyntheticsD 4491 Test Methods for Water Permeability of Geotextilesby PermittivityD 4565 Test Methods for Physical and Environmental Per-formance Properties of Insulations and Jackets for Tele-communications Wire and CableD 4703 Practice for Compression Molding ThermoplasticMaterials in
8、to Test Specimens, Plaques, or SheetsE 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 967 Test Method for Temperature Calibration of Differ-ential Scanning Calorimeters and Differential ThermalAnalyzersE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a
9、 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, while the sub
10、stance and reference materialare subjected to a controlled-temperature program. (See Ter-minology E 473.)3.1.2 geomembrane, nan essentially impermeable geo-synthetic composed of one or more synthetic sheets. (SeeTerminology D 4439.)3.1.2.1 DiscussionIn this test method, essentially imper-meable mean
11、s that no measurable liquid flows through ageosynthetic when tested in accordance with Test MethodD 4491.3.1.3 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 project
12、, structure, or system. (See TerminologyD 4439.)3.1.4 high-pressure differential scanning calorimetry (HP-DSC), ndifferential scanning calorimetry in which the sub-stance and reference material are exposed to a controlledsuperambient atmosphere.3.1.5 index test, na test procedure that may be used to
13、establish 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 Oct. 1, 2006. Published Novemb
14、er 2006. Originallyapproved in 1995. Last previous edition approved in 2004 as D 5885 04.2For 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 Summ
15、ary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.6 oxidative induction time (OIT), nthe elapsed timebetween first exposure to an oxidizing gas and the onset tooxidation of a material under isothermal co
16、nditions.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 specimen to be tested and the c
17、orresponding 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 reaction is displayed on the t
18、hermal 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, the temperature used in t
19、histest 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 type and amount of addit
20、ives 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 formulations containing different a
21、ntioxidantpackages, 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 shallit be used for this
22、 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 temperature and the proper
23、-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 versa.5.4 This test method ca
24、n 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, theshorter the oxidation inductio
25、n 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 not significant at end-use
26、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 measurements suchas Test Method
27、 D 3895 or Test Methods D 4565.6. Apparatus6.1 Differential Scanning CalorimeterThermal 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 equipmentmust be capable of me
28、asuring 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 output device capable of
29、 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 CellA unit capable of maintain-ing pressure up to 3.4 MPa (500 psig). The system shall beequipped with a pressure gage to monitor the internal pressureof
30、 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 Cylinder RegulatorA pr
31、essureregulator 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 diameter.6.7 Core Ho
32、le 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 8.2 and 8.3.7.3 Indium
33、(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.8.2 The stainless steel tube connecting the hig
34、h-pressurecell to the oxygen cylinder must be thoroughly cleaned byhexane (or acetone) and then dried before being connected tothe cell.D58850628.3 All specimen holders should be cleaned by washingwith hexane (or acetone) and then drying before being used inthe test.8.4 The use of pressurized oxygen
35、 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-thetic test sample.9.2 Compressio
36、n mold these assembled parts into a uniformplaque to a thickness of 0.25 mm (10 mil) (see PracticeD 4703).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 induce a negative bias into OIT
37、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 E 967, temperature calibrate thedifferential scanning calor
38、imeter 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 different polyolefin geosynthe
39、tic products, for example, geomem-branes, 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 test method.11.4 Secure t
40、he 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 C until the oxidativeexoth
41、ermic 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 material and 170 C for polypropyl
42、ene-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 with stabilizer packagean
43、d 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 the outlet valve is opene
44、d.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 the cell for 2 min.NOTE 10R
45、apid 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, close the outlet valve, allow
46、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 of 400C for 3 min under air
47、 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. A full-scale sensitivity
48、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.12.2.3 Draw a tangent at
49、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. Report13.1 Report the follo
