1、ReproducedByGLOBAL ENGINEERING DOCUMENTSIHS Under License WithASTMCopyright American SoeietyFDrTesting And Miterillis1916ReleStreet,PlIiledelphia,Pennsylvania19103lDesignation:D2236-81AMERICANSOCIETYFORTESTINGANDMATERIALS,Standard Test Method forDYNAMIC MECHANICAL PROPERTIES OF PLASTICS BYMEANS OF A
2、 TORSIONAL PENDULUM1This standardisissued under the fixed designation D 2236;thenumberimmediately following the designation indicates theyearofonglOal adoptIOn or,10the caseofreVlSlon,the yearoflastreVISIOn.Anumberin parentheses indicates theyearoflastreapproval.A superscript epsilon(E)indicatesaned
3、itorial change since the last revisionorreapproval.1.Scope1.1This method covers determinationoftheelasticandnonelastic componentsofthe com-plex shear modulusofplasticsoflogarithmicdecrement less thanorequal to1.Themethodisprimarily useful when conducted over arangeoftemperaturesandisknown to be vali
4、dat frequencies from at least0.1to 10.0 Hz(cyclespersecond).1.2Themethodisintended for materialsthathave tensile moduli in the range from345MPato13.8GPa(5X104to 2X106psi),asdetermined by Method D 638.1.3Thescopeofthe method does not in-clude tests in a region where the logarithmicdecrementofa materi
5、alisgreaterthana valueofI.This limitationisnota functionofthetechnique,butwilldependon the massoftheparticular specimenandthe apparatus inertialmemberandgripping arrangement.Thetesthas been shown to be validanduseful wherethe logarithmicdecrement is greaterthanIandfor materialsoftensile modulusupto3
6、4.SGPa(5X106psi).1.4Thevalues stated in SI units are to beregarded as the standard.2.Applicable Documents2.1ASTMStandards:D 618 Conditioning PlasticsandElectricalInsulating Materials for Testing2D 638 Test for Tensile PropertiesofPlastics3D1898Recommended Practice for Sam-plingofPlastics33.Summaryof
7、Method3.1This method is intended to provide ameansofdetermining the elasticandloss mod-ulusofplastics over a rangeoftemperatures bya free decay technique ataboutI Hz(cycle persecond).A plotofthese moduli is indicativeofthe thermo-mechanicalcharacteristicsofa plas-tic.Thespecimen isanintegralpartofan
8、inertial system,thus determining the frequencyandrateofdecayofthe system from whichmoduli may be determined.These moduli area functionoftemperatureandfrequency inplasticsandchangerapidlyatparticular tem-peraturesinthetorsionpendulumanalysis.Thetemperaturesofrapid moduli changearenor-mally referred t
9、o as transition temperatures.4.Significance4.1Theelastic component,G,andnonelas-tic component,G,ofthe complexshearmod-ulus,G*.are twoofthe fundamental constantsofanyviscoelastic material.These two con-stants largely determine the dynamic mechan-ical performanceofthe material inshearpro-videdthatthem
10、aximumstrain is relatively low.They are defined by the equation:G*=G+iG.G*is referred to as the complex shearmodulus,Gtheelastic shear modulus,andGthe loss modulusofa material.TheratioG/Gisa measureofthe capacityofa viscoelasticmaterial todampmechanical vibrations.4.2 Plotting the dynamic elasticand
11、none-lastic moduliofa material versus temperatureprovides a graphic representationofrigidityIThis methodisunderthe jurisdictionofASTM Com-mittee D-20 on Plasticsandis the direct responsibilityofSubcommIttee D 20,10onMechanical Properties.Currentedition approvedJune26,1981.Published Oc-tober1981.Ongm
12、allypublished as D 2236-64T.Last pre-viosedition D 2236-70(1976).3Annual BookofASTMStandards.Parts22,35.and39,Annual BookofASTMStandards,Part 35.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest inform
13、ation.andenergy absorption as a functionoftemper-ature.4.3This method can be used to locate thetransition temperaturesofa plastic,thatis,occur in the mobilityofa polymer.These tem-peratures at which significant changes transi-tions are manifested by a decrease inGwithincreasing temperatureormore pre
14、cisely bymaximums in the logarithmic decrement.4.4 This testcanbe used to measure theeffectsofreinforcement,orfiller typeorbothandconcentration,processing conditionsandthe like on the rigidityofa polymer compositeespecially in relationship to temperature.Itisalso a useful tool for determining the de
15、greeofpolymer crystallinity based on established re-lationships.5.Apparatus5.1Thepurposeofthe apparatusisto holda plastic specimen,either rectangularorcircu-lar in cross section,so that the specimen acts asthe elastic element in a torsional pendulum.5.2 The apparatusshall consistofthe follow-ing(see
16、 Fig.I):5.2.1FixedClamp-Upperclamp(see 5.4),rigidly fixed,with space below to accommodatespecimens anywhere from25to150mm(I to6 in.)long between clamps.5.2.2 Inertia MemberClamp-Lowerclampmounted rigidly to the inertia member.5.2.3 InertiaMember-Maybe appropri-ately eithera diskora rod.Theinertia membershall be equipped so that oscillations can becounted to determine the frequencyofthe pen-dulum.Theinertia member shall be suitablyequipped to measure the amplitudeofthe os-cillations.The momentofi