Designation:D4575–09
Standard Test Methods for
Rubber Deterioration—Reference and Alternative Method(s) for Determining Ozone Level in Laboratory Test Chambers1 This standard is issued under thefixed designation D4575;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Numerous techniques exist for the analysis of gaous ozone in ozone-air mixtures ud for ozone crack testing of rubber.The include wet chemical procedures,electrochemical cells,UV absorption, and chemiluminescence with ethylene.See Refs(1-4).2
Wet chemical methods(the absorption of ozone in a potassium iodide solution and titration of the iodine relead with sodium thiosulfate)have been in traditional u in the rubber industry,but they are not suitable for continuous operation,and in recent years they have been shown to be nsitive to small variations in test procedures and concentration and purity of reagents.Interlaboratory tests have indicated that different procedures do not give equivalent results,and most of them differ from an absolute UV method.Frequently,wet chemical methods yield higher ozone concentrations due to the oxidizing capacity of other components of the ozone-air mixture.
Certain nonreference instrumental methods are amenable to automatic operation and for this reason they are included in this standard.They may be ud for routine testing once calibrated against the reference UV method.
UV absorption is adopted as the reference method against which the others shall be calibrated.It is an absolute test method and is in common u by environmental protection agencies for the determination of pollutant ozone in air(e2.3).焖猪肉
Although the test methods are concerned with ozone analysis,it also draws attention to the influence of atmospheric pressure on the rate of cracking of rubber at constant ozone concentration as normally expresd in terms of parts by volume.As described in Appendix X2,the variation in ozone resistance that can result between laboratories operating at significantly different atmospheric pressures can be eliminated by specifying ozone concentration in terms of the partial pressure of ozone.
1.Scope
1.1The test methods cover the following three types of methods for the determination of ozone content in laboratory test chambers.Method A(UV absorption)is specified for reference or referee purpos and as a means of calibration for the alternative methods;Method B,instrumental device(elec-trochemical or chemiluminescence);and Method C,wet chemical techniques(e Appendix X1).The methods are primarily intended for u with tests for determining rubber ozone cracking resistance and thus are applicable over the ozone level range from25to200mPa.
N OTE1—Prior to1978,ozone concentrations were expresd in ASTM D11Standards in parts per hundred million(pphm)of air by volume.See Appendix X2for an explanation of the change to partial pressure in millipascals(mPa).
1.2The values stated in SI units are to be regarded as standard.No other units of measurement are included in this standard.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.For a specific hazard statement,e Note2and5.1.
N OTE2—Warning—Ozone is a hazardous chemical.
1The test methods are under the jurisdiction of ASTM Committee D11on
Rubber and are the direct responsibility of Subcommittee D11.15on Degradation
Tests.
Current edition approved July1,2009.Published August2009.Originally
approved in1986.Last previous edition approved in2005as D4575–99(2005).
2The boldface numbers in parenthes refer to the list of references at the end of
this standard.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
2.Referenced Documents 2.1ASTM Standards:3
D 518Test Method for Rubber Deterioration—Surface Cracking 4wps求和怎么操作
D 1149Test Methods for Rubber Deterioration—Cracking in an Ozone Controlled Environment
D 1171Test Method for Rubber Deterioration—Surface Ozone Cracking Outdoors or Chamber (Triangular Speci-mens)
D 3395Test Methods for Rubber Deterioration—Dynamic Ozone Cracking in a Chamber 42.2ISO Standard:5
ISO-1431/I,II and III Rubber Ozone Testing;Static,Dy-namic and Analysis Methods (respectively)2.3Federal Standard:6
Code of Federal Regulations (Protection of Environment)Title 40Parts 1to 51,July 1,1984,Appendix D (Ozone in Atmosphere)pp.550–5623.Summary of Methods
3.1This standard includes the following three types of independent methods.
3.1.1Method A Reference Method (UV Instrument)—For UV absorption instruments,the ozonized air is pasd through a flow cell.UV energy (wavelength 254nm)pass through the cell and the resultant energy is detected at the other end.The degree of absorption is dependent on the number of ozone molecules in the path.The absorption is compared to the absorption with zero ozone and the difference in energy received at the detector is converted into an electrical output and measured.See Appendix X2for more details and infor-mation.
3.1.2Method B—Secondary Method (Instrumental De-vices):
3.1.2.1For chemiluminescent instruments,the ozonized air is pasd through an analysis chamber,it contacts a stream of ethylene and the two gas undergo a chemiluminescent reaction with the emis
sion of photons at about 430nm.This emission is measured on a photomultiplier and converted to an electrical output.
3.1.2.2For electrochemical methods,the ozonized air is bubbled at a fixed rate through a coulometric (Pt-Hg)cell containing a buffered solution of potassium iodide.The iodine liberated from the solution is ionized at the cathode and is transported to the anode by turbulence.At the anode,insoluble HgI is formed with the relea of ionic charges equivalent to the ozone content of the O 3-air stream.
3.1.3Method C—Secondary Method (Wet Chemical Tech-nique):
3.1.3.1Procedure C-1—An ozonized air sample is pasd through an efficient absorption device containing an aqueous buffered solution of KI.After a fixed absorption time,the I 2relead is titrated with Na 2S 2O 3and the ozone concentration is calculated from the thiosulfate consumed.
3.1.3.2Procedure C-2—An air sample is pasd through a solution in an efficient absorption container with an electrode end point device.The solution contains buffered KI and an amount of sodium thiosulfate to permit exhaustive absorption in 20to 30min (total consumption of the sodium thiosulfate).At the endpoint,the voltage across the electrodes abruptly increas and the time of this increa is recorded.The time is related inverly to the ozone content.
4.Significance and U
4.1General purpo and many specialty rubbers will un-dergo ozone cracking when expod to ozone containing atmospheres,when the test specimens or actual u products are under a certain degree of tensile strain.Certain additives such as antiozonants and waxes inhibit or prevent this crack-ing.Various rubbers and rubber formulations containing such additives are customarily evaluated under static or dynamic tensile strain in laboratory ozone chambers.This standard provides for an accurate asssment of the ozone content of such chambers ud in Test Methods D 518,D 1149,D 1171,D 3395and ISO Standard 1431I/II/III.For additional infor-mation on ozone analysis,refer to Code of Federal Regula-tions;Title 40Parts 1to 51.
5.Hazards
5.1Warning —Ozone is a hazardous substance.Consult and follow all applicable laws,rules,and regulations regarding exposure to ozone.
6.Calibration of Nonreference Methods
6.1The condary (c)methods shall be calibrated with respect to one of two reference ozone systems;
6.1.1Reference O 3System No.1,consisting of (1)stable O 3generator with adjustable output in the range from 0to 500mPa and (2)a reference UV ozone analyzer (Method A type).6.1.2Reference O 3System No.2,consisting of a UV photometric O 3calibration system (calibration O 3/air supply).This system generates reference levels of ozone,but it does not function as an analyzer.See Appendix X2for more informa-tion.
6.2Apparatus Required for Reference O 3System No.1:6.2.1Adjustable Level ,stable,generator of ozonized air.This is normally a UV lamp,flow rate,and containment system.
6.2.2System ,permitting the output from the ozone genera-tor to be lectively switched to inputs for (1)the reference UV ozone measuring device and (2)the (condary)ozone mea-suring device to be calibrated.The tubing for the ozonized air should be clean,PTFE or glass,and be as short as possible.A PTFE cock for switching is mandatory to prevent O 3decom-position.
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6.3Calibration Procedure :
6.3.1Select at least three (preferably five)ozone levels that span the range of interest.Select the lowest level and adjust the
3
For referenced ASTM standards,visit the ASTM website,www.astm,or contact ASTM Customer Service at rvice@astm.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.4
圆白菜炒肉Withdrawn.The last approved version of this historical standard is referenced on www.astm.5
Available from American National Standards Institute (ANSI),25W.43rd St.,4th Floor,New York,NY 10036.6
Available from U.S.Government Printing Office Superintendent of Documents,732N.Capitol St.,NW,Mail Stop:SDE,Washington,DC
20401.
花生汤generator.Allow it to become stable in output to within65% variation for veral measurements made in a short time span by monitoring the output ozone with the reference UV device. Record the average ozone level.
6.3.2Switch the ozone output to the condary ozone measuring device,and measure the ozone veral times over a time period sufficient to get an average value with individual deviations no great
er than65%.Record the average ozone level measured with the condary device.
6.3.3Take care to execute6.3.1and6.3.2until the indicated repeatability(precision)of65%is attained;this indicates stable output and good condary measurement procedure. 6.3.4Repeat the procedure of6.3.1and6.3.2for the other two(or four)levels in ascending order.
6.3.5Plot the average concentrations,O3(Sec)versus O3(Ref),and determine linear regression parameters b0and b1.
O3~Sec!5b01b1O3~Ref!(1)
O3~Ref!5O3~Corr!5O3~Sec!2b0
b1(2)
6.3.6To obtain true or reference O3concentration in routine daily work,u Eq2.The value as calculated from Eq2is called the corrected ozone concentration,O3(corr).
6.3.7The uncertainty of the corrected routine daily ozone level or concentration as calculated from Eq2will depend on the number of average values,reference and condary,ud in establishing the li
near regression calibration line,upon the number of measurements forming each plotted average,and upon the basic measurement error of the condary method.If five ozone levels are ud to establish the linear regression line, an estimate of the standard deviation of the corrected ozone concentration(SD,O3(corr))that is,the standard error of the estimate,with three degrees of freedom,may be obtained by the u of Eq3.
SD~O3~corr!!5S N21N22~S y22b12S x2!D1/2(3)
where:
N=number of plotted points,
b1=slope of regression curve of Eq1,
S y2=variance among plotted(average)condary method O3concentrations,and
S x2=variance among plotted(average)reference method O3concentrations.
6.3.8Thus the(6)90%confidence limits on the corrected ozone concentrations are61.64SD(O3(corr))for a linear regression curve obtained with5reference and condary levels of ozone.
6.4Apparatus Required for Reference O3System No.2: 6.4.1A UV photometric ozone calibration system shall be ud.Various commercial systems may be ud provided they indicate ozone concentration to the same accuracy and preci-sion as specified in8.2for the direct reading UV ozone analyzer.
6.5Calibration Procedure:
6.5.1Follow the general procedure as outlined in6.3.The procedure with the No.2Reference System varies from the No. 1system only in the n that the ozone generation and reference analysis are conducted in a lf-contained system.
TEST METHOD A
7.Sampling
7.1The sampling line shall be polytetrafluoroethylene (PTFE),or glass,or PTFE-lined material,or any other demon-strably unreactive and impermeable material.The line shall be as short as practicable and,unless otherwi specified,shall be no longer than1m in length.The line shall be designed so as to prevent ingress of contaminants.The combination of length and bore of the sampling line should be such as to minimize residence time of the sample without producing undue pressure drop.
8.Preparation of Apparatus
8.1A direct-reading UV ozone analyzer or instrument shall be ud.
8.2When the instrument is ud over the0to500-mPa range,the parameters shall conform to the performance re-quirements given in Table1.
8.3Initial UV Instrument Calibration—The calibration pro-cedure shall be as follows:
8.3.1Set up the instrument in accordance with the manu-facturer’s instructions and allow a sufficient stabilization pe-riod.Set the instrument zero using zero air produced by suitably removing contaminants with a calibration O3/air supply(e X2.1).Feed the zero air directly to the instrument and adjust the zero control after allowing sufficient stabiliza-tion time.See Table1.
8.3.2Span the instrument measuring circuit using a lf-contained calibration atmosphere system as described in6.1.1. See also X2.2.
8.3.3U three tofive concentrations corresponding to the spread over the measuring range.Steady indicated values shall agree to within2%of the calibration value.
8.4Operational Recalibration—The following procedure shall be carried out ideally on a daily basis,but at least weekly: 8.4.1Check the instrument ozone level using zero air and take appropriate action,if necessary.
TABLE1Performance Requirements for UV Instruments Ud in the Determination of Ozone in Ambient Air
Parameter Requirements
Range0to500mPa
Noi0.5mPa
Lower detectable limit 1.0mPa
Interference equivalent:
Each interferent62mPa
Total interferent66mPa
Zero drift,12h and24h62mPa
Span drift,24h
20%of upper range limit620.0%,max
80%of upper range limit65.0%,max
Lag time2min,max
Ri time2min,max
Fall time2min,max
Precision:
20%of upper range limit
80%of upper range limit
1.0mPa,max
1.5mPa,
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8.4.2Check the span of the instrument measuring circuit as described in8.3.2but using a single,reprentative,reference test atmosphere in accordance with 6.1.2.Recalibrate the instrument through that part of the sampling system dedicated to the instrument.The indicated value shall conform propor-tionally to the value of span drift given in Table1.
TEST METHOD B
9.Preparation of Apparatus
9.1A direct reading instrument shall be provided.This may be a chemiluminescence or an electrochemical device.
9.2When the instrument is ud over the range from0to 500mPa,the performance requirements shall
be comparable to tho listed in Table1.
10.Calibration
10.1Set up the instrument in accordance with the manufac-turer’s instructions,and allow the instrument to stabilize. 10.2Set the instrument to zero by the u of a calibration O3/air supply.
10.3Span the instrument measuring circuit or system using
a calibration test atmosphere or O3/air volume as in8.3,and calibrate as specified in8.3.
10.4Recalibration Operation—This procedure shall be car-ried out ideally on a daily basis but at least weekly.See8.4for exact details.
10.5Sampling—See7.1for sampling procedure.
TEST METHOD C
11.General Theory
11.1The absorption of ozone is an aqueous neutral buffered KI solution yields free iodine by oxidatio
n.
O312KI1H2O→O212KOH1I2(4) 11.1.1The addition of sodium thiosulfate solution caus an immediate reaction of free iodine and thiosulfate.
I212Na2S2O3→Na2S4O612NaI(5) 11.1.2Thus,one O3is equivalent to2Na2S2O3.
11.2Method C contains two alternative absorption proce-dures,C-1and C-2;either may be ud.
12.Reagents
12.1Reagent grade chemicals and distilled water shall be ud in all tests.
12.2Buffer Solution:
12.2.1The recommended buffer is0.1M boric acid (H3BO4).This is prepared by dissolving in1L of distilled water;6.18g of H3BO4,10g of KI.The solution shall have a pH value of560.2.Before using,take10cm3of the buffer solution and add a few drops of(2mol/dm3or litre alterna-tively or73mg HCl cm3)HCl and0.5cm3of starch solution. No color should develop.Store H3BO4buffer in a brown stoppered bottle in a cool place.
12.2.2The cond choice buffer is the customary sodium, potassium hydrogen phosphate buffer.Prepare a0.025-M solution of anhydrous hydrogen phosphate(Na2HPO4)and a 0.025-M solution of anhydrous potassium dihydrogen phos-phate(KH2PO4).To prepare the buffer solution having a pH of 6.7to7.1,add1.5volumes of0.025M Na2HPO4solution to1 volume of0.025M KH2PO4solution.Shake thoroughly. 12.3Potassium Iodide(KI)—U pure analytical grade KI.
12.4Sodium Thiosulfate Solution(0.020N)—Prepare a10 mol/m3(0.020N)sodium thiosulfate(Na2S2O3)solution.This may be standardized by using a standard0.0200N potassium bromate(KBrO3)solution to oxidize an excess quantity of potassium iodide(KI)in acid solution.Titrate the liberated iodine immediately with the Na2S2O3solution.The titration equipment for the Microammeter Method(or Null Method) may be ud to determine the end point in this titration.Store the prepared10mol/m3(0.020N)Na2S2O3solution in a cool dark place.
12.5Sodium Thiosulfate Solution(1mol/m3)(0.0020N)—Prepare1mol/m3(0.0020N)Na2S2O3solution for u in the ozone analysis by diluting the10mol/m3(0.020N)solution10 to1,using a10-cm3pipet and100-cm3volumetricflask. Redeterminations of the normality of the10mol/m3(0.020N) Na2S2O3solution should be carried out weekly.
13.Preparation of Apparatus
13.1The arrangement of the ozone analysis train is shown in a generalized format in Fig.1.The quence of devices is shown and is the same for all three alternative methods or absorption devices as depicted in Figs.2-4.The pressure differential as measured at manometer(4of Fig.1)shall be subtracted from the barometric pressure to obtain the air sample pressure,as follows:
P5P B2P M(6) where:
P=air sample pressure,
P B=barometric pressure,and
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P M=manometer pressure differential,all pressures in kPa (mm Hg30.133).
The temperature of the air sample shall be obtained from the thermometer at point2of Fig.1.An alternativeflowmeter(3of Fig.1)may be ud,that is,the differential manometer type.
1—Ozone chamber
2—Thermometer
3—Flowmeter(rotameter type)
4—Manometer(mercury)
5—Absorption device
6—Cold trap(optional)
7—(Air)Vacuum pump
8—Bleeder valve to adjustflow
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FIG.1Generalized Analysis Train
Format
13.2One of the two alternative absorption devices shall be provided.The first is the spray-jet device,and the cond is the single column solution absorption device.13.3Spray-Jet Device :
13.3.1The spray-jet device is shown in Fig.2.The glass tube,A,is approximately 9.5mm (0.375in.)in diameter and 100mm (4in.)long,terminating at B in a short length of capillary tubing with a ba of 1to 2mm (0.04to 0.08in.).Concentric within A is a smaller glass tube.C.(Fig.2(a)is an enlarged view of this part.)The end of C is heated in a flame until the bore is reduced in size so as just to admit a wire or drill 0.75mm (0.03in.)in diameter.At this thickened end two
flats are ground off on a sheet of fine alumina abrasive paper as at D in Fig.2(b).When in position in t
ube A,end D fits snugly against the hole in capillary B.A rubber tubing connection at E holds the two tubes in position.F is a trap about 50mm (2in.)in diameter and 100mm (4in.)long,and G is an enlargement in the exit tube about 40mm (1.5in.)in diameter,containing glass wool to trap spray passing F.F is connected to the side tube of A.H is a 1-L three-neck round-bottom flask in which A and F are cured by standard-taper ground joints.A occupying the center opening with B protruding just below the neck and J reaching to within 13mm (0.5in.)of the bottom of the bottle.The third opening rves to introduce and remove the reagent.A is connected through plasticized poly(vinyl chloride)tubing and glass tubing to a rotameter 7graduated from 0to 1.0m 3(0to 35ft 3)of air/h.The entrance to the rotameter is connected with glass tubing to the sampling tube,and the exit of F is connected through a regulating valve to a vacuum line.When properly regulated and a vacuum applied at F,most of the reagent enters F,furnishing a head of reagent at B,where the entering air resolves it into a fine mist that fills the entire bottle.The absorption flask shall be mounted in a light-tight box to protect it from light during the time a run is being made.
13.4Single Column Absorption Device :
13.4.1This technique us a single absorption column that is shown in Fig.4.The dimensions are noted on the diagram.
7
The sole source of supply of the rotameter known to the committee at this time is the Fischer &Porter Rotameter,obtainable from Fischer &Porter Co.,Warminster,PA.If you are aware of alternative suppliers,plea provide this information to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,1which you may
attend.
FIG.2Ozone Absorbing Device (Spray
Jet)
FIG.3Modified Spray-Jet
Apparatus
FIG.4Ozone Absorption
Column
