塑料测试方法.docx

1、塑料测试方法Tensile Properties - ASTM D638Tensile testing is performed by elongating a specimen and measuring the load carried by the specimen. From a knowledge of the specimen dimensions, the load and deflection data can be translated into a stress-strain curve. A variety of tensile properties can be ext

2、racted from the stress-strain curve. Tensile TestPropertyDefinitionTensile Elongation at Break Tensile elongation corresponding to the point of rupture.Tensile Elongation at YieldTensile elongation corresponding to the yield (an increase in strain does not result in an increase in stress).Tensile St

3、rength at BreakTensile stress corresponding to the point of rupture.Tensile Strength at YieldTensile stress corresponding to the yield point (an increase in strain does not result in an increase in stress).Tensile StrengthTensile stress at a specified elongation.Tensile Strength, UltimateThe highest

4、 tensile stress a material can support before failing.Tensile ModulusThe ratio of tensile stress to tensile strain of a material in the elastic region of a stress-strain curve. A Tangent tensile modulus value is the slope of the elastic region of the stress-strain curve and is also known as Youngs M

5、odulus, or the Modulus of Elasticity. A Secant tensile modulus value is the slope of a line connecting the point of zero strain to a point on the stress-strain curve at a specified strain. This is used for materials that exhibit little or no linear behavior.Illustration of Tangent and Secant Tensile

6、 ModuliTest Specimen SummarySpecimenRigidity CaseNoteThicknessType IRigidPreferred specimen.7 mm (0.28 in)Type IIRigidUse when Type I specimen does not break in the narrow section.7 mm (0.28 in) 14 mm (0.55 in)Type IVRigid/NonrigidShould be used for comparison between materials in different rigidity

7、 cases. Essentially the same as Die C specimen from ASTM D412.4 mm (0.16 in)Type VRigidUsed when limited material is available or laboratory space is a concern (for environmental testing)4 mm (0.16 in)Type I, II, III, and V SpecimenType IV SpecimenFlexural Properties - ASTM D790A test specimen is he

8、ld as a simply supported beam and is subjected to three-point bending. The specimen is deflected until it either breaks or the outer fiber strain reaches 5%.Two procedures are used for flexural testing. ProcedureDescriptionStrain RateAFor materials that break at relatively small deflections.0.01 mm/

9、mm/minBFor materials that undergo large deflections during testing.0.10 mm/mm/minFlexural Test ConfigurationLocation of Maximum Fiber Stress/StrainTermDefinitionFlexural ModulusThe ratio of outer fiber stress to outer fiber strain.Flexural Stress at YieldThe outer fiber stress corresponding to test

10、specimen yield.Flexural Stress at BreakThe outer fiber stress corresponding to test specimen failure.Flexural StrengthThe maximum outer fiber stress sustained by a specimen during testing.Izod Impact Strength - ASTM D256Energy per unit thickness required to break a test specimen under flexural impac

11、t. Test specimen is held as a vertical cantilevered beam and is impacted by a swinging pendulum. The energy lost by the pendulum is equated with the energy absorbed by the test specimen.Notes: Charpy Impact Strength is no longer covered under this test method, but is included because Charpy values a

12、re still reported under this method. Unnotched Izod Impact Strength, covered by ASTM D4812, is included here because it is often cited as being tested by ASTM D256. Optional units of energy per unit area are supported by the standard. These are the ISO style units.Notched Izod SpecimenMethodNameTest

13、 DescriptionDiagramANotched Izod Impact StrengthSpecimen is held as a vertical cantilevered beam and is broken by a pendulum. Impact occurs on the notched side of the specimen.BCharpy Impact StrengthSpecimen is held as a simply supported beam and is impacted on the side opposite the notch. This meth

14、od is no longer covered under ASTM D256 but is still reported as such.CEstimated Net Izod Impact StrengthThis method is the same as Method A except that the energy required to toss the broken portion of the specimen is included in the energy calculation. Preferred over Method A for materials with im

15、pact strength below 27 J/m (0.5 ft-lb/in)DNotch Radius Sensitivity TestProvides an indication of notch sensitivity. Notch sensitivity is calculated using: b = (E2 - E1) / (R2 - R1) where b is the notch sensitivity, E1 and E2 are the energy required to break a small and large radius notched specimen,

16、 and R1 and R2 are the radii of the small and large radius notches. Units are J/m/mm of notch radius.EReversed Notched Izod Impact StrengthSame test as Method A except the specimen is impacted on the side opposite the notch.Unnotched Izod Impact StrengthUnnotched specimen is held as a vertical canti

17、levered beam and is broken by a pendulum. This method is covered under ASTM D4812 but is commonly reported under ASTM D256.Instrumented Dart Impact - ASTM D3763The energy required to puncture a material by impact with a falling dart under specified test conditions. This test measures the multiaxial

18、impact behavior of a material and can be used as a measure of the rate sensitivity of a material.Impactor HeadA 12.7 mm (0.5 in) diameter hemispherical head dart is dropped from a height sufficient to produce a specified impact velocity. The dart is equipped with load and displacement transducers so

19、 that a load/displacement plot of the test can be produced. Energy is the area beneath the load/displacement plot. Energy reported is either energy to peak load or total energy.Energy TypesVicat Softening Temperature - ASTM D1525The temperature at which a 1mm2 flat-ended needle will penetrate 1mm in

20、to a material under a specified load and heating rate. The vicat softening temperature can be used to compare the heat-softening characteristics of different materials.Two different heating rates and two different loads may be used for testing.Heating Rate A: 50C/hr Heating Rate B: 120C/hrLoading 1:

21、 10 N (1 kg) Loading 2: 50 N (5 kg)Deflection Temperature Under Load (DTUL) - ASTM D648The temperature at which a test specimen deflects 0.25 mm when loaded in 3-point bending at a specified maximum outer fiber stress. Deflection temperature is used to determine short-term heat resistance.A test spe

22、cimen is loaded in 3-point bending in the edgewise direction. Outer fiber stresses used for testing are 0.455 MPa (66 psi) and 1.82 MPa (264 psi). The temperature is increased at 2C/min until the specimen deflects 0.25 mm (0.010 in).Coefficient of Linear Thermal Expansion (CLTE) - ASTM E831The chang

23、e in length per unit length of a material per degree of temperature change.CLTE is measured using a thermomechanical analyzer. The specimen is held in an enclosure and is contacted by a probe leading to a displacement sensor. A small force of 1 to 100 mN is applied to the specimen to keep the probe

24、in contact with the specimen.Thermomechanical Analyzer SetupThe enclosure is brought to a starting temperature. The temperature within the enclosure is increased at a rate of 5C/min. The expansion of the specimen is measured by the displacement sensor over the temperature range of interest. ASTM E83

25、1 covers temperatures between -120 and 600C.CLTE () is calculated using the formula: = L / (Lo * T) where L is the change in length of the specimen, Lo is the original length of the specimen, and T is the temperature change during the test.Water Absorption - ASTM D570The percent increase in weight o

26、f a material after exposure to water under specified conditions. Water absorption can influence mechanical and electrical properties. Factors such as the type of material, additives, temperature, and length of exposure can affect the amount of water absorbed.For testing, the specimens are dried and

27、cooled. Three testing procedures are commonly employed. Only data from the same testing procedures are readily comparable.ProcedureTest DescriptionWater Absorption 24 hrsTest specimens are immersed in distilled water at a specified temperature for 24 hours. Testing is most commonly done at 23C (73.4

28、F)Water Absorption SaturationTest specimens are immersed in distilled water at a specified temperature until the water absorption essentially ceases.Water Absorption Equilibrium.Test specimens are exposed to a humid environment at a specified temperature for 24 hours. Testing is most commonly perfor

29、med at 50% relative humidity (RH) and 23C (73.4F).Melt Mass-Flow and Melt Volume-Flow Rate - ASTM D1238Extrusion rate of a resin through an orifice of defined dimensions at a specified temperature and load. Flow rates can be used to differentiate grades or provide a measure of degradation of a mater

30、ial as a result of molding.Melt Flow Rate ProceduresProcedureDescriptionAManual OperationBAutomatically Timed Flow Rate MeasurementCAutomatically Timed Flow Rate Measurement for High Flow Rate Polyolefins Using Half-Height, Half Diameter DieThe testing conditions are most commonly reported as temper

31、ature/load (i.e. 190C/2.16 kg). In the past several test conditions were given alphabetical designations, these designations are described below.Historical Melt Flow Rate ConditionsConditionTemperature (C)Load (kg)A1250.325B1252.16C1502.16D1900.325E1902.16F19021.6G2005H2301.2I2303.8J26512.5K2750.325L2302.16M1901.05N19010O3001.2P1905Q2351R2352.16S2355T2502.16U31012.5V3102.16W2852.16X3155