1、Designation: D 5721 08Standard Practice forAir-Oven Aging of Polyolefin Geomembranes1This standard is issued under the fixed designation D 5721; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a means for estimating the resis-tance of polyolefin geomembranes to thermal aging in thepresence of air. Only the procedur
3、e for heat exposure isspecified, not the test method or specimen. The effect of heaton any particular property may be determined by selection ofthe appropriate test method and specimen.1.2 This practice should be used as a guide to comparethermal aging characteristics of materials as measured by the
4、change in some property of interest. This practice does notpredict thermal aging characteristics where interactions be-tween stress, environment, temperature, and time controlfailure.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisst
5、andard.1.4 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 determine the applica-bility of regulatory limitations prior to use.2. Refer
6、enced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 638 Test Method for Tensile Properties of PlasticsD 746 Test Method for Brittleness Temperature of Plasticsand Elastomers by ImpactD 1238 Test Method for Melt Flow Rates of Thermoplasticsby Extrusion Plastometer
7、D 1505 Test Method for Density of Plastics by the Density-Gradient TechniqueD 1525 Test Method for Vicat Softening Temperature ofPlasticsD 1790 Test Method for Brittleness Temperature of PlasticSheeting by ImpactD 1822 Test Method for Tensile-Impact Energy to BreakPlastics and Electrical Insulating
8、MaterialsD 1870 Practice for Elevated Temperature Aging Using aTubular Oven3D 3045 Practice for Heat Aging of Plastics Without LoadD 4439 Terminology for GeosyntheticsE 145 Specification for Gravity-Convection and Forced-Ventilation OvensF 412 Terminology Relating to Plastic Piping Systems3. Termino
9、logy3.1 Definitions:3.1.1 For definitions of general terms used in this standard,refer to Terminology D 4439.3.1.2 aging, nthe process of exposing materials to anenvironment for an interval of time.3.1.3 polyolefin, na polymer prepared by the polymeriza-tion of an olefin(s) as the sole monomer(s). (
10、F 412)3.1.4 Vicat softening pointthe temperature at which aflat-ended needle of 1 mm2circular cross section will penetratea thermoplastic specimen to a depth of 1 mm under a specifiedload using a selected uniform rate of temperature rise.(D 1525)4. Significance and Use4.1 Under the severe conditions
11、 of this test, the specimensundergo degradation at a rate that is a function of the thermalendurance of the geomembrane under examination.4.2 The elevated temperature for this practice should repre-sent conditions that are sufficiently severe to induce failure ofpolyolefin geomembranes within an abb
12、reviated period oftime.4.3 The rate of change of a particular property as a functionof temperature may be evaluated using the temperatures andtimes outlined in Practice D 3045.4.4 Any correlation between this practice and natural life ofthese materials must be determined for the particular applica-t
13、ion in which the materials are to be used.1This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subcommittee D35.02 on EnduranceProperties.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 1995. Last previ
14、ous edition approved in 2002 as D 572195(2002).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.3Withdrawn.1Co
15、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.5 Air-oven aging can be used to evaluate and compare theperformance of various heat stabilizer packages.5. Apparatus5.1 OvenA controlled, forcedventilation oven with sub-stantial fresh a
16、ir intake is recommended. Oven apparatus shallbe in accordance with Type 11B in Specifications E 145.NOTE 1Cross contamination has been known to occur in rubberproducts. It is not known if it can occur in semi-crystalline thermoplastics.When it is necessary to avoid contamination among specimens orm
17、aterials, a tubular oven method such as Practice D 1870 may bedesirable.5.2 Temperature Measuring DeviceA thermocouple orthermometer adequate to cover the range being tested andaccurate to at least 60.5C.6. Sampling6.1 Sampling shall be in accordance with the ASTM testmethods for the specific proper
18、ties to be determined.7. Conditioning7.1 Conduct initial tests in the standard laboratory atmo-sphere as specified in Practice D 618, and with specimensconditioned in accordance with the requirements of the ASTMtest method for determining the specific property or propertiesrequired.7.2 When required
19、, conditioning of specimens followingexposure at elevated temperature and prior to testing, unlessotherwise specified, shall be in accordance with PracticeD 618.8. Procedure8.1 Allow the oven to equilibrate at the test temperature.The temperature shall be below the Vicat softening point of themateri
20、al.8.2 Suspend the specimens for exposure below an ovenshelf in a way to maintain a distance of at least 20 mm betweenspecimens and to allow for the entire shelf with specimens tobe removed. Age for the specified time and temperature.NOTE 2Certain metals are known to affect the thermal endurance ofs
21、ome polyolefins. Therefore, direct contact of the specimens with metalshall be minimized.8.3 Inspect the specimens weekly to ensure that the speci-mens have remained properly mounted. Note any visualchanges of the specimens.8.4 Rotate the shelves from top to bottom and from front toback once a week
22、to ensure even exposure.8.5 At the end of an aging interval, remove a set ofspecimens and allow them to cool. Test the specimens for theselected property in accordance with the appropriate testmethod, including provisions for conditioning.9. Potential Tests9.1 The following properties may be appropr
23、iate for evalu-ating the effects of oven exposure:9.1.1 Tensile properties (see Test Method D 638),9.1.2 Melt flow index (see Test Method D 1238),9.1.3 Density (see Test Method D 1505),9.1.4 Tensile impact (see Test Method D 746), and9.1.5 Brittleness temperature (see Test Method D 1790).10. Calcula
24、tion10.1 Express the results of the aging test as a percentage ofthe change in each physical property, calculated as follows:change,%5 A 2 O!/O 3 100 (1)where:O = original value, andA = value after aging.NOTE 3Since the values of some properties may increase as afunction of exposure time, a positive
25、 change shows an increase while anegative change shows a decrease in the property value.10.2 Alternatively, the time to failure can be determinedbased on a failure criteria such as brittleness, or on a percent-age change of a given property.11. Report11.1 Report the following information:11.1.1 Geom
26、embrane type, thickness and specimen prepa-ration procedure,11.1.2 Pre-conditioning and post-conditioning proceduresfollowed,11.1.3 Test methods utilized for evaluation of each property,11.1.4 Observations of any visible changes in the testspecimens,11.1.5 Type of oven used,11.1.6 Exposure temperatu
27、re and times used,11.1.7 Mean and standard deviation for results calculatedaccording to 10.1, and11.1.8 Mean time to failure and failure criteria for resultsgenerated in 10.2.12. Keywords12.1 geomembrane; oven aging; polyolefinD5721082ASTM International takes no position respecting the validity of a
28、ny patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to re
29、vision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. You
30、r comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copy
31、righted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D5721083
