6.2OzoneChamber—TheozonechambershallconformtotherequirementsspecifiedinTestMethodD1149.Itshallbeequippedtopermitflexingofthespecimensfrom0to2563%extensionsatarateof0.5Hz(30cpm).
6.3ApparatusforMeasuringOzonePartialPressure—TheapparatusformeasuringozonepartialpressureshallconformtotherequirementsspecifiedinTestMethodD4575.
7.TestSpecimens
7.1Thetestspecimensshallberectangularstrips10.0060.03mm(0.4060.01in.)wideby100625mm(461in.)inlength,cutfromtestsheetsthathavebeenpreparedinaccordancewithPracticeD3182.Thegrainordirectionofmillingofuncuredstockshallbeinthelengthwisedirectionofthespecimen.Duplicatetestspecimensshallbetestedwhen-everpossible.
NOTE2—Itisstronglysuggestedthatallrubbersheetsforozonetesting
MethodA
a—gearheadandeccentricdrive
b—travelingbarwithspecimenclamps,driventhroughroofofozonechamberc—stationarybarswithspecimenclampsd—specimens
FIG.1DynamicStrainOzoneTester
becuredbetweenaluminumfoilorpolyesterfilm40.1mminthickness.Thefoilwilladheremildlytomostcommercialrubbers.Atthetimespecimensarecutforozonetestingthefoilcanberemovedeasily.Thisfurnishesa“fresh”surfaceandthe24horotherpre-testconditioningperiod,canbereckonedfromtheformationofthisfresh“bloom-free”surface.
8.Procedure
8.1Pre-TestConditioning—NominalPeriod:
8.1.1Priortotesting,conditionallfree-surface(thatis,nofoilspecimens)for24.060.5hat2362°Cinasealedopaquecontainerthathasanozone-freeatmosphere.Differentcom-poundsaretobecontainedseparatelyinthesealedopaquecontainer.
8.1.2Selectotherpre-testconditioningperiodsconsistentwithcertaintechnicalrequirementsorpurchaserandselleragreements.
8.2OperationofTestApparatus:
8.2.1Byuseoftheslow-speedswitch,accuratelypositionthereciprocatingshaftatthemid-pointofitsstroke.Mountthetestspecimensandclamptheminplacesothatnodiscerniblebendorbowisevident.Closethedoortotheozonechamberandallowashortperiod(5min)fortheozonepartialpressuretostabilize.Startthetest,notingthetimeanddateofstarting(61min).
8.2.2Thestandardozonepartialpressureshallbe5065mPa(equivalentto50pphmat100kPaatmosphericpressure).Otherpartialpressuresmaybeselectedaccordingtotheparticularobjectivesofanytestingprogram.Refertotheseasoptionalpartialpressures.Measuretheozonepartialpressureonceadayforroutineworkandmoreoftenforspecialtestconditions.Conductthisanalysiswiththechambercontainingtestspecimens.Ifthenumberofspecimensiskeptataminimum,“empty”and“loaded”ozonepartialpressureswillcloselyagree.Determinethemagnitudeofthereductionofozonepartialpressurefor“empty”versus“loaded”foreachsetofoperatingvariablesemployed.Thiswillvaryforeachlaboratory.RefertoTestMethodD4575forozoneanalysisprocedures.
8.2.3Thestandardtemperatureshallbe4061°C(10462°F).Highertemperaturescauseanaccelerationintherateofozoneattack.Thesehighertemperaturesshallbeoptional.8.2.4Makeobservationsfordetectingtheappearanceofcrackingatmaximumextensionandwithsufficientfrequencytobeabletodetectthefirstappearanceofozonecracking.Thisfrequencywilldependontheresistancetoozoneattackoftherubbersbeingtested.Recommendedobservationmagnificationis73.Whencomparisonsarebeingmadewithastandardreferencematerial,exposuresmaybemadeforafixedtimeandthedegreeofcrackingevaluated.Makeobservationsinsuchawayastominimizeozonepartialpressurechanges(thatis,removespecimensquicklyandkeepdoorclosedasmuchaspossible).
9.Report
9.1Thereportshallincludethefollowing:
9.1.1Identificationofthematerialstestedanddatesoftesting,
4A200Mylar,oritsequivalent,hasbeenfoundsatisfactoryforthismethod.
9.1.2Ozonepartialpressure,bothnominalandthatactuallymeasuredonadailybasis,
9.1.3Temperatureofthetest,
9.1.4Timeornumberofextensioncyclestothefirstobservedcrackingoradescriptionofthecharacteroftheozonecracksatvariousperiodsofexposure,and
9.1.5Pre-conditioninginformation(thatis,numberofhoursofozone-freeconditioning)at2362°C.
METHODB—BELTFLEXTEST
10.Apparatus
10.1BeltFlexDevice:
10.1.1Thetestapparatusshallconsistofasuitablemetalframeworktoaccommodatethebeltandpulleysasspecifiedbelow.Theframeworkshallbeequippedtoaccepteitheroftwosetsofpulleys;oneset,63.5mm(21⁄2in.)indiameterandoneset,102mm(4in.)indiameter.Theupperpulleyofeachsetoftwoshallbepoweredtorotatethetestbeltatacyclicfrequencyof0.67Hz(40rpm)withthe63.5-mmdiameterpulleys,andat1.04Hz(62.5rpm)whenusingthe102-mmdiameterpulleys.Alternatively,thedriveshaftmayberotatedat3.75Hz(225rpm)toobtainthespecifiedbeltrotationrate.Thelowerpulleyshaftshallbeallowedtomoveupanddown,havingan18-kg(40-lb)masssuspendedfromittomaintainsufficienttensiononthespecimenbelttoachievemaximumconformationofthetestspecimensandbeltaroundeachpulley.
10.1.2Thesizeofthistestapparatusrequiresthatalargerectangularboxbeusedtohousethedevice.Fig.2showsatypicalozonechamberusedforthistestdevice.Thedimen-sionsofthisboxare1370by310by4380mm(54by121⁄4by15in.)withavolumeof0.16m3(10in.3).Fig.3isaschematicdiagramofthetestapparatus.10.2TestChamber:
10.2.1ThematerialforconstructingthetestchamberandequipmentformeasuringozonepartialpressureshallconformtothosedescribedinTestMethodD1149.
10.2.2Thestandardozonepartialpressureshallbe5065mPa.Otherpartialpressuresmaybeselectedforspecialresearchtestprograms.
11.TestSpecimens
11.1Thespecimenbelt,towhichthesamplesareeithercuredorcemented,shallbeaone-plybeltof1.1-kg/m2(32-oz/yd2)squarewovencottonduck,100mm(4in.)wideand2300625mm(9061in.)incircumference.Thebeltshouldbecoatedwithatypicalrubberfrictionorcoatcompound,0.2mm(0.08in.)thick.Ifthebeltcontainscutedges,theseshouldbecoatedwithaflexiblecuringtypecementorothermaterialinerttoozone.Thiswillreduceozonedecompositionbycontactwiththesesurfaces.Therubbercoatsoappliedshouldbecured.Thetestspecimensshallbepreparedbyeithercuttingaspecimen100by25mm(4by1in.)fromastandardtensionsheetandcementingtothebeltwiththemilledgrainbeingparalleltothe100-mm(4-in.)specimenlength;oraspecimenshallbecuredonthebeltusingaspecialmold.Thelatteristhepreferredmethod,sincethereislessdifficultyinpreventingseparationofthetestspecimenfromthebeltduringflexing.Thetestiscarriedoutwithduplicatespecimens.
MethodB(DoorOpen)a—belt
b—attachedtestspecimenc—upperpulley
d—UVozonegeneratortube
FIG.2DynamicStrainOzoneTester
11.2Fig.4showsadrawingofamulticavitymoldusedtopreparemoldedspecimens.
11.3Thecuredspecimenshallbe100by50by360.20mm(4by2by0.13in.),protectedduringcurebytheuseofaluminumfoilorpolyesterfilmonthesurfacetobeexposed.12.Procedure
12.1Priortotest,conditionallfree-surfacetestspecimensseparatelyfor24.060.5hat2362°Cinasealedopaquecontainerthathasanozone-freeatmosphere.
12.2Installthebelt,withtheadheredspecimens,onthepulleysinthetestchamber.Startthebeltwhenthedoorisclosed.Forachamberoftheinternalvolumeasmentionedin10.1.2,aperiodof30minisrequiredfortheozonepartialpressuretostabilize.Alsoforachamberofthissizethe“empty”(nobeltortestspecimens)ozonepartialpressure
FIG.3SchematicDiagramofMethodBTester
shouldbesetapproximately20%higherthantheintended“test”ozonelevel(thatis,setchamberat60mPaforatestpressureof50mPa).Makeminoradjustmentsofpressureasthetestproceeds.Additionally,amorestableozonelevelwillbeobtainedifvoltageregulationismaintainedontheozonegenerationequipment.Exposethespecimensforaperiodof48hasdescribedinTestMethodD1149at4061°C(10462°F).
12.3Duringthe48-hperiod,observetheexposedspeci-mensatmaximumteststrainatintervalsof1hforthefirst6h,andthereafterat24,30,and48-hperiods.Examinewitha73magnifierandrecordthetimeofinitialcracking.Duringthisexaminationtakeprecautionstominimizeozonepartialpressurechanges(thatis,quickobservationperiod,dooropenforaminimumtime).
12.4Ifdesired,theexposuremaybecontinuedforthepurposeofobservingtherateofgrowthofthecracksorthedevelopmentofanycharacteristicsorunusualsurfaceeffects.13.Report
13.1Thereportshallincludethefollowing:
13.1.1Descriptionofthespecimens,identifyingtherubbercompounds,timeandtemperatureofvulcanization,curedorcementedtypeofspecimenmounting,sizeofspecimen,andconditioninginformation,
13.1.2Dateandtimeofstartofexposure,
13.1.3Ozonepartialpressurewithbeltrunning(dailyormorefrequently),
13.1.4Temperatureofchamber,
13.1.5Timeorcyclestoinitialcracking,
13.1.6Totalexposuretime,ornumberoftestcycles,and13.1.7Sizeofpulleysused.
13.2Ifdesired,aphotographmaybetakentoprovideapermanentrecordforevaluation.
mm(a)584(b)457(c)292(d)228(e)102(f)76(g)51(h)38in.(23.0)(18.0)(11.5)(9.0)(4.0)(3.0)(2.0)(1.5)mm(i)27.78(j)25(k)19.05(m)18.92(n)12.7(p)6.3(q)3.17(r)1.65in.(1.094)(1.0)(0.750)(0.745)(0.50)(0.25)(0.125)(0.065)
FIG.4MoldDrawingLegend
14.PrecisionandBias
14.1Precisionandbiasstatementsareintheprocessofbeingprepared.Theywillbeaddedtothismethodwhentheyarecompleted.
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