1、Designation: D 4575 99 (Reapproved 2005)Standard Test Methods forRubber DeteriorationReference and Alternative Method(s)for Determining Ozone Level in Laboratory Test Chambers1This standard is issued under the fixed designation D 4575; the number immediately following the designation indicates the y
2、ear oforiginal adoption or, 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.INTRODUCTIONNumerous techniques exist for the analysis of gaseou
3、s ozone in ozone-air mixtures used for ozonecrack testing of rubber. These include wet chemical procedures, electrochemical cells, UV absorption,and chemiluminescence with ethylene. See Refs (1-4).2Wet chemical methods (the absorption of ozone in a potassium iodide solution and titration of theiodin
4、e released with sodium thiosulfate) have been in traditional use in the rubber industry, but theyare not suitable for continuous operation, and in recent years they have been shown to be sensitive tosmall variations in test procedures and concentration and purity of reagents. Interlaboratory tests h
5、aveindicated that different procedures do not give equivalent results, and most of them differ from anabsolute UV method. Frequently, wet chemical methods yield higher ozone concentrations due to theoxidizing capacity of other components of the ozone-air mixture.Certain nonreference instrumental met
6、hods are amenable to automatic operation and for this reasonthey are included in this standard. They may be used for routine testing once calibrated against thereference UV method.UV absorption is adopted as the reference method against which the others shall be calibrated. It isan absolute test met
7、hod and is in common use by environmental protection agencies for thedetermination of pollutant ozone in air (see 2.3).Although these test methods are concerned with ozone analysis, it also draws attention to theinfluence of atmospheric pressure on the rate of cracking of rubber at constant ozone co
8、ncentration asnormally expressed in terms of parts by volume.As described inAppendix X2, the variation in ozoneresistance that can result between laboratories operating at significantly different atmosphericpressures can be eliminated by specifying ozone concentration in terms of the partial pressur
9、e ofozone.1. Scope1.1 These test methods cover the following three types ofmethods for the determination of ozone content in laboratorytest chambers. Method A (UV absorption) is specified forreference or referee purposes and as a means of calibration forthe alternative methods; Method B, instrumenta
10、l device (elec-trochemical or chemiluminescence); and Method C, wetchemical techniques (see Appendix X1). These methods areprimarily intended for use with tests for determining rubberozone cracking resistance and thus are applicable over theozone level range from 25 to 200 mPa.NOTE 1Prior to 1978, o
11、zone concentrations were expressed inASTMD11 Standards in parts per hundred million (pphm) of air by volume. SeeAppendix X2 for an explanation of the change to partial pressure inmillipascals (mPa).1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport
12、 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. For a specifichazard statement, see Note 2 and 5
13、.1.1These test methods are under the jurisdiction of ASTM Committee D11 onRubber and are the direct responsibility of Subcommittee D11.15 on DegradationTests.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1986. Last previous edition approved in 1999 as D 4575 - 99.2T
14、he boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 2WarningOzone is a hazardous chemical.2. Referenced Documents2.1 ASTM Standards:3D 518
15、 Test Method for Rubber DeteriorationSurfaceCrackingD 1149 Test Method for Rubber DeteriorationSurfaceOzone Cracking in a ChamberD 1171 Test Method for Rubber DeteriorationSurfaceOzone Cracking Outdoors or Chamber (Triangular Speci-mens)D 3395 Test Methods for Rubber DeteriorationDynamicOzone Cracki
16、ng in a Chamber2.2 ISO Standard:4ISO-1431/I, II and III Rubber Ozone Testing; Static, Dy-namic and Analysis Methods (respectively)2.3 Federal Standard:5Code of Federal Regulations (Protection of Environment)Title 40 Parts 1 to 51, July 1, 1984, Appendix D (Ozonein Atmosphere) pp. 5505623. Summary of
17、 Methods3.1 This standard includes the following three types ofindependent methods.3.1.1 Method A Reference Method (UV Instrument)ForUV absorption instruments, the ozonized air is passed througha flow cell. UVenergy (wavelength 254 nm) passes through thecell and the resultant energy is detected at t
18、he other end. Thedegree of absorption is dependent on the number of ozonemolecules in the path. The absorption is compared to theabsorption with zero ozone and the difference in energyreceived at the detector is converted into an electrical outputand measured. See Appendix X2 for more details and in
19、for-mation.3.1.2 Method BSecondary Method (Instrumental De-vices):3.1.2.1 For chemiluminescent instruments, the ozonized airis passed through an analysis chamber, it contacts a stream ofethylene and the two gases undergo a chemiluminescentreaction with the emission of photons at about 430 nm. Thisem
20、ission is measured on a photomultiplier and converted to anelectrical output.3.1.2.2 For electrochemical methods, the ozonized air isbubbled at a fixed rate through a coulometric (Pt-Hg) cellcontaining a buffered solution of potassium iodide. The iodineliberated from the solution is ionized at the c
21、athode and istransported to the anode by turbulence.At the anode, insolubleHgI is formed with the release of ionic charges equivalent tothe ozone content of the O3-air stream.3.1.3 Method CSecondary Method (Wet Chemical Tech-nique):3.1.3.1 Procedure C-1An ozonized air sample is passedthrough an effi
22、cient absorption device containing an aqueousbuffered solution of KI. After a fixed absorption time, the I2released is titrated with Na2S2O3and the ozone concentrationis calculated from the thiosulfate consumed.3.1.3.2 Procedure C-2An air sample is passed through asolution in an efficient absorption
23、 container with an electrodeend point device. The solution contains buffered KI and anamount of sodium thiosulfate to permit exhaustive absorptionin 20 to 30 min (total consumption of the sodium thiosulfate).At the endpoint, the voltage across the electrodes abruptlyincreases and the time of this in
24、crease is recorded. The time isrelated inversely to the ozone content.4. Significance and Use4.1 General purpose and many specialty rubbers will un-dergo ozone cracking when exposed to ozone containingatmospheres, when the test specimens or actual use productsare under a certain degree of tensile st
25、rain. Certain additivessuch as antiozonants and waxes inhibit or prevent this crack-ing. Various rubbers and rubber formulations containing suchadditives are customarily evaluated under static or dynamictensile strain in laboratory ozone chambers. This standardprovides for an accurate assessment of
26、the ozone content ofsuch chambers used in Test Methods D 518, D 1149, D 1171,D 3395 and ISO Standard 1431 I/II/III. For additional infor-mation on ozone analysis, refer to Code of Federal Regula-tions; Title 40 Parts 1 to 51.5. Hazards5.1 WarningOzone is a hazardous substance. Consultand follow all
27、applicable laws, rules, and regulations regardingexposure to ozone.6. Calibration of Nonreference Methods6.1 The secondary (sec) methods shall be calibrated withrespect to one of two reference ozone systems;6.1.1 Reference O3System No. 1, consisting of (1) stable O3generator with adjustable output i
28、n the range from 0 to 500mPa and (2) a reference UV ozone analyzer (Method A type).6.1.2 Reference O3System No. 2, consisting of a UVphotometric O3calibration system (calibration O3/air supply).This system generates reference levels of ozone, but it does notfunction as an analyzer. See Appendix X2 f
29、or more informa-tion.6.2 Apparatus Required for Reference O3System No. 1:6.2.1 Adjustable Level, stable, generator of ozonized air.This is normally a UV lamp, flow rate, and containmentsystem.6.2.2 System, permitting the output from the ozone genera-tor to be selectively switched to inputs for (1) t
30、he reference UVozone measuring device and (2) the (secondary) ozone mea-suring device to be calibrated. The tubing for the ozonized airshould be clean, PTFE or glass, and be as short as possible. APTFE cock for switching is mandatory to prevent O3decom-position.6.3 Calibration Procedure:6.3.1 Select
31、 at least three (preferably five) ozone levels thatspan the range of interest. Select the lowest level and adjust the3For 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
32、 the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.5Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.
33、D 4575 99 (2005)2generator. Allow it to become stable in output to within 65%variation for several measurements made in a short time spanby monitoring the output ozone with the reference UV device.Record the average ozone level.6.3.2 Switch the ozone output to the secondary ozonemeasuring device, an
34、d measure the ozone several times over atime period sufficient to get an average value with individualdeviations no greater than 65 %. Record the average ozonelevel measured with the secondary device.6.3.3 Take care to execute 6.3.1 and 6.3.2 until the indicatedrepeatability (precision) of 65 % is a
35、ttained; this indicatesstable output and good secondary measurement procedure.6.3.4 Repeat the procedure of 6.3.1 and 6.3.2 for the othertwo (or four) levels in ascending order.6.3.5 Plot the average concentrations, O3(Sec) versusO3(Ref), and determine linear regression parameters b0and b1.O3Sec!5b0
36、1 b1O3Ref! (1)O3Ref!5O3Corr!5O3Sec!2b0b1(2)6.3.6 To obtain true or reference O3concentration in routinedaily work, use Eq 2. The value as calculated from Eq 2 iscalled the corrected ozone concentration, O3(corr).6.3.7 The uncertainty of the corrected routine daily ozonelevel or concentration as calc
37、ulated from Eq 2 will depend onthe number of average values, reference and secondary, used inestablishing the linear regression calibration line, upon thenumber of measurements forming each plotted average, andupon the basic measurement error of the secondary method. Iffive ozone levels are used to
38、establish the linear regression line,an estimate of the standard deviation of the corrected ozoneconcentration (SD, O3(corr) that is, the standard error of theestimate, with three degrees of freedom, may be obtained bythe use of Eq 3.SDO3corr! 5SN 2 1N 2 2Sy22 b12Sx2!D1/2(3)where:N = number of plott
39、ed points,b1= slope of regression curve of Eq 1,Sy2= variance among plotted (average) secondary methodO3concentrations, andSx2= variance among plotted (average) reference methodO3concentrations.6.3.8 Thus the (6)90 % confidence limits on the correctedozone concentrations are 61.64 SD (O3(corr) for a
40、 linearregression curve obtained with 5 reference and secondarylevels of ozone.6.4 Apparatus Required for Reference O3System No. 2:6.4.1 A UV photometric ozone calibration system shall beused. Various commercial systems may be used provided theyindicate ozone concentration to the same accuracy and p
41、reci-sion as specified in 8.2 for the direct reading UV ozoneanalyzer.6.5 Calibration Procedure:6.5.1 Follow the general procedure as outlined in 6.3. Theprocedure with the No. 2 Reference System varies from the No.1 system only in the sense that the ozone generation andreference analysis are conduc
42、ted in a self-contained system.TEST METHOD A7. Sampling7.1 The sampling line shall be polytetrafluoroethylene(PTFE), or glass, or PTFE-lined material, or any other demon-strably unreactive and impermeable material. The line shall beas short as practicable and, unless otherwise specified, shall beno
43、longer than1minlength. The line shall be designed so asto prevent ingress of contaminants. The combination of lengthand bore of the sampling line should be such as to minimizeresidence time of the sample without producing undue pressuredrop.8. Preparation of Apparatus8.1 A direct-reading UV ozone an
44、alyzer or instrument shallbe used.8.2 When the instrument is used over the 0 to 500-mParange, the parameters shall conform to the performance re-quirements given in Table 1.8.3 Initial UV Instrument CalibrationThe calibration pro-cedure shall be as follows:8.3.1 Set up the instrument in accordance w
45、ith the manu-facturers instructions and allow a sufficient stabilization pe-riod. Set the instrument zero using zero air produced bysuitably removing contaminants with a calibration O3/airsupply (see X2.1). Feed the zero air directly to the instrumentand adjust the zero control after allowing suffic
46、ient stabiliza-tion time. See Table 1.8.3.2 Span the instrument measuring circuit using a self-contained calibration atmosphere system as described in 6.1.1.See also X2.2.8.3.3 Use three to five concentrations corresponding to thespread over the measuring range. Steady indicated values shallagree to
47、 within 2 % of the calibration value.8.4 Operational RecalibrationThe following procedureshall be carried out ideally on a daily basis, but at least weekly:8.4.1 Check the instrument ozone level using zero air andtake appropriate action, if necessary.TABLE 1 Performance Requirements for UV Instrumen
48、ts Used inthe Determination of Ozone in Ambient AirParameter RequirementsRange 0 to 500 mPaNoise 0.5 mPaLower detectable limit 1.0 mPaInterference equivalent:Each interferent 62 mPaTotal interferent 66 mPaZero drift, 12 h and 24 h 62 mPaSpan drift, 24 h20 % of upper range limit 620.0 %, max80 % of u
49、pper range limit 65.0 %, maxLag time 2 min, maxRise time 2 min, maxFall time 2 min, maxPrecision:20 % of upper range limit80 % of upper range limit1.0 mPa, max1.5 mPa, maxD 4575 99 (2005)38.4.2 Check the span of the instrument measuring circuit asdescribed in 8.3.2 but using a single, representative, referencetest atmosphere in accordance with 6.1.2. Recalibrate theinstrument through that part of the sampling system dedicatedto the instrument. The indicated value shall conform propor-tionally to the value of span drift given in Table 1.TEST METHOD B9. Pre
