1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS ISO 974:2000 ICS 83.08
2、0.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Plastics Determination of the brittleness temperature by impactThis British Standard, having been prepared under the direction of the Sector Committee for Materials and Chemicals, was published under the authority of the Sta
3、ndards Committee and comes into effect on 15 May 2000 BSI 05-2000 ISBN 0 580 34260 3 BS ISO 974:2000 Amendments issued since publication Amd. No. Date Comments National foreword This British Standard reproduces verbatim ISO 974:2000 and implements it as the UK national standard. The UK participation
4、 in its preparation was entrusted to Technical Committee PRI/21, Testing of plastics, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK inter
5、ests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications refer
6、red to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a c
7、ontract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank p
8、age, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.Referencenumber ISO974:2000(E) INTERNATIONAL STANDARD ISO 974 Secondedition 2000-01-15 PlasticsDeterminationofthebrittleness temperaturebyimpact Plastiques Dtermination
9、 de la temprature de fragilit au chocISO974:2000(E) ii ISO974:2000(E)iii Contents 1 Scope1 2 Normativereferences1 3 Termsanddefinitions.1 4 Principle2 5 Apparatus.2 6 Testspecimens3 7 Conditioning.5 8 Procedure.5 9 Expressionofresults6 9.1 Graphicalmethod6 9.2 Calculationmethod.6 10 Testreport7ISO97
10、4:2000(E) iv Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenes
11、tablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmattersofelectrotechnicalstandardization. InternationalStandardsaredra
12、ftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. Attentionisdrawntothepossibilitythatsomeoft
13、heelementsofthisInternationalStandardmaybethesubjectof patentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights. InternationalStandardISO974waspreparedbyTechnicalCommitteeISO/TC61, Plastics, Subcommittee SC 2, Mechanical properties. Thissecondeditioncancelsandreplacesthefirste
14、dition(ISO974:1980),whichhasbeentechnicallyrevised.ISO974:2000(E)v Introduction Plasticsareusedinmanyapplicationsrequiringlow-temperatureflexingwithorwithoutimpact.Polymerbrittleness isaffectedbyanyorientationproducedduringfabrication,bythermalhistoryandbytheapplicationofstresstothe material,especia
15、llytherateofappliedstressasinimpact.Brittlenesstemperaturedatamaybeusedtopredictthe behaviourofplasticmaterialsatlowtemperatureonlyinapplicationsinwhichtheconditionsofdeformationare similar.Thebrittlenesstemperaturetestwasoriginallydevelopedtomeasurethetemperatureatwhichapolymer ceasestobeflexiblean
16、dbecomes“glasslike”.INTERNATIONALSTANDARD ISO974:2000(E)1 PlasticsDeterminationofthebrittlenesstemperaturebyimpact 1 Scope ThisInternationalStandardspecifiesamethodforthedeterminationofthetemperatureatwhichplasticsthatare notrigidatnormalambienttemperatureexhibitbrittlefailureunderspecifiedimpactcon
17、ditions.Asupplementary techniqueusingnotchedspecimensdevelopsbrittlenessvaluesatamuchhighertemperaturethanareobserved forunnotchedspecimensofthesameplasticmaterial.Themethodutilizesastatisticaltechniquetoquantifythe brittlenessfailuretemperature.Provisionsaremadeforthetestingofsufficientspecimenstop
18、ermitthecalculation ofthebrittlenesstemperatureonastatisticalbasis.Statisticaltechniqueshavebeendevelopedtoquantifythe brittlenesstemperatureasisdefinedin3.1. Themethodestablishesthetemperatureatwhichthereisa50%chanceoffailureineitherunnotchedornotched specimens.Thismethodhasbeenfoundusefulforspecif
19、icationpurposes,althoughitdoesnotnecessarily measurethelowesttemperatureatwhichthematerialmaybeused.Inthemeasurementofthebrittleness temperature,theprecisionofthemeasurementshouldpreferablybe 5Cattheworstwhenestablishingvalues usedinmaterialspecifications. 2 Normativereferences Thefollowingnormative
20、documentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsof thisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedto investigatethepossibilityof
21、applyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.For undatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidInternationalStandards. ISO175:1999, Plastics Methods of test for the determination of the effects of i
22、mmersion in liquid chemicals. ISO291:1997, Plastics Standard atmospheres for conditioning and testing. 3 Termsanddefinitions ForthepurposesofthisInternationalStandard,thefollowingtermsanddefinitionsapply: 3.1 brittlenesstemperature thetemperatureatwhichthereisa50%probabilityoffailureinaspecimenwhent
23、estedbythemethodspecified ItmaybedesignatedT 50 . 3.2 testspeed therelativevelocitybetweenthestrikingedgeofthetestapparatusandatestspecimenheldinthespecimen clampISO974:2000(E) 2 4Principle Testspecimens,supportedascantileverbeams,areimmersedinaheat-transfermediumwhosetemperatureis accuratelyknownan
24、dpreciselycontrolled.Thespecimensareconditionedforaspecifiedperiodoftimeandthen impactedbyasingleswingofthestrikingedgeoftheapparatusataspecifiedconstantspeed.Asufficientnumber ofspecimensaretestedtopermitthecalculationofthebrittlenesstemperatureonastatisticalbasis.The temperatureatwhich50%ofthespec
25、imensfailisdefinedasthebrittlenesstemperature. 5 Apparatus 5.1 Testmachine,consistingofaclampingdevicetoholdthetestspecimens,astrikingedgeandamechanical arrangementappropriatetoensurethatthesearemaintainedinproperrelationtoeachotherandthatthestriking edgemovesataconstantspeedrelativetothetestspecime
26、ns. NOTE1 DetailsofthestrikingedgeandclampingdeviceareshowninFigures1and2,andaphotographoftheclampwith mountedspecimensisshowninFigure3. Theprincipaldimensionsoftheapparatusshallbeasfollows: a) radiusofstrikingedge:1,6mm 0,1mm; b) radiusoflowerjawofclampingdevice:4,0mm 0,1mm; c) distancebetweenpoint
27、ofimpactofstrikingedgeandclampingdevice:3,6mm 0,1mm; d) clearancebetweenoutsideofstrikingedgeandclampingdevice:2,0mm 0,1mm; Thetestspeedshallbe200cm/s 20cm/satimpactandduringatleastthenext0,5cmoftravel. NOTE2 Commercialapparatusisavailablemeetingtherequirementsofthissubclause,inwhichthestrikingedgei
28、sdriven byamotor,byasolenoid,bygravityorbyaspring. 5.2 Temperature-measuringsystem:Anysuitabledevicemaybeused.Itshallbecalibratedovertherequired rangeandaccuratetowithin 0,5C.Thetemperature-measuringdeviceshallbeplacedasneartothespecimen aspossible. 5.3 Liquidorgaseousheat-transfermedium,preferablyl
29、iquid,whichremainsfluidatthetesttemperatureand whichdoesnotappreciablyaffectthematerialbeingtested.Themediumshallbemaintainedatthetest temperaturetowithin 0,5C. NOTE Giventhatthetimeofcontactbetweentheliquidandtheplasticspecimensisshortandthetemperaturelow,the useofamethanol/solid-CO 2 mixturehasbee
30、nfoundsuitableformostplastics.Thismixturecanbeusedsuccessfullydownto 76C.Belowthistemperature,otherheat-transfermediaareneeded,forexamplesiliconeoils,dichlorodifluoromethane/liquid nitrogen,oranairbath. Shouldanydoubtexistregardingtheinertnessoftheplasticstothemixtureused,measureselectedphysical pro
31、pertiesbeforeandafter15minexposureatthehighesttemperatureused(seeISO175).Thevaluesobtained shouldnotdiffersignificantly. 5.4 Tank,insulated. 5.5 Stirrer,toprovidethoroughcirculationoftheheat-transfermedium.ISO974:2000(E)3 Dimensionsinmillimetres Key 1 Strikingedge 2 Clampingdevice 3 Testspecimen Fig
32、ure1Dimensionaldetailsofstrikingedgeandclampingdevice (positioningofunnotchedtestspecimen) 6 Testspecimens 6.1 Formanypolymers,theresultsofthistestdependtoalargedegreeontheconditionsusedforsample preparationandonthemethodofspecimenpreparation.Unlessotherwisespecified,therelevantISOmaterial specifica
33、tionshallbeusedforthepreparationofthetestsamplefromwhichthespecimensarecut.Cleaneredge cutsandthereductionoreliminationofaccidentalnotcheswillresultinlowerobservedbrittlenesstemperatures. Itisessentialthatthespecimensbepreparedinareproducibleway.Arazorbladeorothersharptoolshallbeused tocutthespecime
34、ns,preferablyinasinglesmoothstroke.Die-cutspecimensarenotrecommended.Althoughitis possibletopreparesatisfactoryspecimensbyhand,itisstronglyrecommendedthatanautomaticmethodbeused. Whatevermethodisused,itisessentialthatthecutterbeinspectedfrequentlyandmaintained.Sharpcuttersmust beusedinthepreparation
35、ofspecimensforthistestifreliableresultsaretobeobtained. Theconditionofthediemaybejudgedbyinvestigatingtherupturepointonanyseriesofbrokenspecimens.When brokenspecimensareremovedfromtheclampsofthetestmachine,itisconvenienttomakeapileofthese specimensandnoteifthereisanytendencytobreakatornearthesamepoi
36、ntoneachspecimen.Rupturepoints consistentlyatthesameplacemaybeanindicationthatthedieisdull,nickedorbentatthatparticularposition. NOTE Fortheuseofanautomaticcutterforspecimenpreparation,seeBestelink,P.N.,andTurner,S.: Low-temperature brittleness testing of polyethylene, ASTM Bulletin No. 231, 68 (195
37、8). 6.2 Testspecimens20,00mm 0,25mmlongby2,50mm 0,05mmwideand2,0mm 0,1mmthick(see Figure4)shallbecutfromatestsheet.Specimenscanbeconvenientlycuttothespecifieddimensionsfromastrip ofmaterial20,00mm 0,25mminwidthandoftherequiredthickness.Thisispreferablyaccomplishedusingan automaticmachine(seenoteto6.
38、1).ISO974:2000(E) 4 Dimensionsinmillimetres Key a Twoholes, 3,7mm, countersunk 6,4mm 90 b Removesharpcornersonserrations c Twoinsertedbushes d Twoholes,48A e Twoholes, 3,7mm Figure2Detailsofoneformofclampmeetingtherequirementsof5.1ISO974:2000(E)5 Figure3Assembledclampwithtestspecimens Dimensionsinmi
39、llimetres Figure4Specimensize 7 Conditioning Thetestspecimensshallbeconditionedasspecifiedinthestandardforthematerialtested.Intheabsenceofthis information,selectthemostappropriateconditionsfromISO291,unlessotherwiseagreeduponbytheinterested parties,e.g.fortestingathighorlowtemperatures. 8 Procedure
40、8.1 Inestablishingthebrittlenesstemperatureofamaterial,itisrecommendedthatthetestbestartedata temperatureatwhich50%failureisexpected.Testaminimumoftenspecimensatthistemperature.Ifallofthe specimensfail,increasethetemperatureofthebathby10Candrepeatthetestusingnewspecimens.Ifnoneof thespecimensfail,de
41、creasethebathtemperatureby10Candrepeatthetestusingnewspecimens.Ifthe approximatebrittlenesstemperatureisnotknown,choosethestartingtemperaturearbitrarily. 8.2 Priortobeginningatest,prepareabathandbringtheapparatustothedesiredstartingtemperature.Ifthe bathiscooledusingdryice,placeasuitableamountofpowd
42、ereddryiceintheinsulatedtankandslowlyaddthe heat-transfermediumuntilthetankisfilledtoalevel30mmto50mmfromthetop.Iftheapparatusisequipped withaliquid-nitrogenorCO 2 coolingsystemandautomatictemperaturecontrol,followtheinstructionsprovidedby themanufactureroftheinstrumentforpreparingandoperatingthebat
43、h. 8.3 Mountthetestspecimensfirmlyintheclampingdeviceandsecurethelatterinthetestmachine(see Figure3). NOTE Excessiveclampingforcesmaypre-stresssomematerials,causingprematurefailureduringthetest.Atorque wrenchmaybeusedsothattheforcenecessarytoholdthespecimensintheclampscanbemonitoredandtheminimumforc
44、e applieduniformlytoeachspecimen.Itisrecommendedthatatorqueof2,8Nmbeusedtosecurethespecimensintheclamps.ISO974:2000(E) 6 8.4 Lowertheclampingdeviceintotheheat-transfermedium.Ifdryiceisbeingusedasacoolant,maintaina constanttemperaturebythejudiciousadditionofsmallquantitiesofdryice.Iftheapparatusisequ
45、ippedwitha liquid-nitrogenorCO 2 coolingsystemandautomatictemperaturecontrol,followthemanufacturersinstructionsfor settingandmaintainingthetemperature. 8.5 Afterwaitingfor3min 0,5minwhenusingaliquidmedium,or20min 0,5minwhenusingagaseous medium,recordthetemperatureanddeliverasingleimpactonthespecimen
46、s. 8.6 Removetheclampingdevicefromthetestapparatusandremovetheindividualspecimensfromthe clampingdevice.Examineeachspecimentodeterminewhetherornotithasfailed.Failureisdefinedasthe divisionofaspecimenintotwoormorecompletelyseparatedpiecesorasanycrackinthespecimenwhichis visibletotheunaidedeye.Whereas
47、pecimenhasnotcompletelyseparated,itshallbebenttoanangleof90 in thesamedirectionasthebendcausedbytheimpactandthenbeexaminedforcracksatthebend.Recordthe numberoffailuresandthetemperatureatwhichthespecimensweretested. NOTE Thetemperatureofaspecimenwhenitisbentwillbesubstantiallyabovethetemperatureatwhi
48、chthespecimen wasimpacted. Increaseordecreasethetemperatureofthebathinuniformincrementsof2Cor5Candrepeattheprocedure untilthelowesttemperatureatwhichnoneofthespecimensfailandthehighesttemperatureatwhichallofthe specimensfailisdetermined.Usenewtestspecimensforeachtest. 8.7 Carryouttestsatfourormorete
49、mperaturesintherangeincluding10%to90%failure(0%and100% failurearenotusefulindeterminingT 50 bythegraphicalmethodgivenin9.1). 9 Expressionofresults ThetemperatureT 50 maybedeterminedbyeitherofthefollowingmethods: 9.1 Graphicalmethod Plotthepercentagefailureatanytemperatureagainstthetesttemperatureonarithmeticprobabilitypaperand drawthebeststraightlinethroughtheresults.Readthebrittlenesstemperaturefromthegraphwherethisline intersectsthatfor50%probability. 9.2 Calculationmethod CalculateT 50 usingfollowingequation: TTT S 50 100 1 2 F H
