ASTM D5930-17 Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique.pdf

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1、Designation: D5930 17Standard Test Method forThermal Conductivity of Plastics by Means of a TransientLine-Source Technique1This standard is issued under the fixed designation D5930; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the thermalconductivity of plastics over a temperature range f

3、rom 40 to400C. It is possible to measure the thermal conductivity offilled and unfilled thermoplastics, thermosets, and rubbers inthe range from 0.08 to 2.0 W/m.K.1.2 The values stated in SI units shall be regarded asstandard.1.3 This standard does not purport to address the safetyconcerns, if any,

4、associated with its use. It is the responsibilityof the user of this standard to establish proper safety andhealth practices and determine the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this test method.1.4 This international standard was developed

5、in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents

6、2.1 ASTM Standards:2C177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC1113 Test Method for Thermal Conducti

7、vity of Refracto-ries by Hot Wire (Platinum Resistance ThermometerTechnique)D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD2717 Test Method for Thermal Conductivity of LiquidsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE1225 Test

8、 Method for Thermal Conductivity of SolidsUsing the Guarded-Comparative-Longitudinal Heat FlowTechnique3. Terminology3.1 DefinitionsTerminology used in this standard is inaccordance with Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 temperature transient, nthe temperature

9、 rise associ-ated with the perturbation of a system, initially at a uniformtemperature. The system does not attain thermal equilibriumduring the transient.3.2.2 thermal conductivity, nthe time rate of steady heatflow/unit area through unit thickness of a homogeneous mate-rial in a direction perpendi

10、cular to the surface induced by a unittemperature difference.3.2.2.1 DiscussionWhere other modes of heat transfer arepresent in addition to conduction, such as convection andradiation, this property often is referred to as the apparentthermal conductivity, app.3.2.2.2 DiscussionThermal conductivity

11、must be associ-ated with the conditions under which it is measured, such astemperature and pressure, as well as the compositional varia-tion of the material. It is possible that thermal conductivity willvary with direction and orientation of the specimen since somematerials are not isotropic with re

12、spect to thermal conductivity.In the case of thermoset polymers, it is possible that thermalconductivity will vary with the extent of cure.3.2.3 thermal diffusivitya heat-transport property given bythe thermal conductivity divided by the thermal mass, which isa product of the density and the heat ca

13、pacity.3.3 Symbols:3.3.1 CProbe constant.3.3.2 Thermal conductivity, W/m.K.3.3.3 QHeat output per unit length, W/m.3.3.4 T2The temperature (K) recorded at time t2.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on T

14、hermal Properties.Current edition approved Aug. 1, 2017. Published August 2017. Originallyapproved in 1997. Last previous edition approved in 2016 as D5930 - 16. DOI:10.1520/D5930-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.

15、org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

16、This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade

17、 (TBT) Committee.13.3.5 T1The temperature (K) recorded at time t1.3.4 Subscript:3.4.1 avaverage.3.4.2 appapparent.3.4.3 refreference.4. Summary of Test Method4.1 Line-Source TechniqueThis is a transient method fordetermining thermal conductivity (1, 2).3A line source of heatis located at the center

18、of the specimen being tested. Theapparatus is at a constant initial temperature. During the courseof the measurement, a known amount of heat produced by theline-source results in a heat wave propagating radially into thespecimen. The rate of heat propagation is related to the thermaldiffusivity of t

19、he polymer. The temperature rise of the line-source varies linearly with the logarithm of time (3).Itispossible to use this relationship to directly calculate the thermalconductivity of the sample. There are a number of ways toachieve the line source of heat. In this test method, it is in theform of

20、 a probe as described in 7.2.5. Significance and Use5.1 The relative simplicity of the test method makes itapplicable for a wide range of materials (4, 5). The techniqueis capable of fast measurements, making it possible to take databefore the materials suffer thermal degradation. Alternatively,it i

21、s possible to study the effect of compositional changes suchas chemical reaction or aging (6). Short measurement timespermit generation of large amounts of data with little effort.The line-source probe and the accompanying test specimen aresmall in size, making it possible to subject the sample to a

22、 widerange of test conditions. Because this test method does notcontain a numerical precision and bias statement, it shall not beused as a referee test method in case of dispute.6. Interferences6.1 The line-source method produces results of highestprecision with materials where intimate contact with

23、 the probehas been established, thereby eliminating effects of thermalcontact resistance. These materials include viscous fluids andsoft solids.6.1.1 Thermal-Contact ResistanceIn the solid state, it ispossible that a contact resistance is developed due to theinterface between the specimen and the me

24、asuring device.Conventional methods attempt to account for this by introduc-ing a conductive paste between the specimen and the sensor.This reduces, but some effect of contact resistance is stillpossible. In the line-source method, contact resistance mani-fests itself as a nonlinearity in the initia

25、l portion of the transient(see Fig. 1). The technique has a method to account for thisphenomenon. By extending the time of the measurement, it ispossible to progress beyond the region of thermal-contactresistance, achieving a state where the contact resistance doesnot contribute to the measured tran

26、sient (7). This state typicallyis achieved after about 10 to 20 s in the measurement. Thelarger the contact resistance, the greater is this time. It is,therefore, important to make a sufficiently long measurementto exclude the portion of the transient that shows the effect ofthe contact resistance.

27、The duration of measurement, however,must not be too long, because the possibility of the heat wavestriking a sample boundary exists, thereby violating the theo-retical requirements of the measurement.6.1.2 Shrinkage Upon SolidificationPlastics tend to shrinksignificantly upon solidification. This s

28、hrinkage is especially sofor the semi-crystalline materials, which experience a signifi-cant change in specific volume upon crystallization. Theprobability exists that this crystallization will result in largegaps being developed between the specimen and the sensingdevice. To account for shrinkage,

29、and possibly permit theline-source probe to move downward to take up the slack asimple compression scheme as described in 9.5 has been usedsuccessfully. Steps also must be taken to minimize specimenvolume so as to reduce the extent of shrinkage.6.2 Measurements in viscid fluids are subject to the de

30、vel-opment of convection currents, which have been known toaffect the measurement. Because of the transient nature of themeasurement, these effects are not as pronounced. They cannotbe eliminated, however.6.3 Although the technique is not limited by temperature, atmeasurements above 500C, a signific

31、ant amount of heattransfer occurs due to radiation so that it is possible to measureonly a app.7. Apparatus7.1 The apparatus consists of a line-source probe imbeddedin a specimen contained in a constant-temperature environ-ment. During the measurement, the line-source probe producesa precise amount

32、of heat. The resulting temperature transient isrecorded, preferably, on a computer data-acquisition system, asspecified in 7.4. This transient is analyzed to obtain the thermalconductivity.7.2 Line-Source ProbeThe line-source probe contains aheater that runs the length of the probe (3). The length-t

33、o-diameter ratio of the probe must be greater than 20. The3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Line-Source TransientD5930 172resistance of the line-source heater must be known to within60.1 %. The probe also contains a temperature sen

34、sor tomeasure the temperature transient. A typical sensor for theline-source probe is a high-sensitivity J-type thermocoupleused because of its large Seebeck coefficient. The housingsheath of the probe must be robust enough to ensure that theprobe does not bend or deform under the adverse conditions

35、 itis subject to during measurements.7.3 Heater Power SourceThe power input to the line-source heater comes from a DC voltage source. The precisionof the voltage source must be within 60.25 % over the entireduration of the test.7.4 Recording DeviceThe temperature transient from theline-source probe

36、is recorded for the duration of the test. Atemperature measurement device with a resolution of 0.1C isrequired. Data are acquired for 30 to 120 s depending on thetype of material. Typical temperature rises are between 2 and10C over the duration of the measurement. The frequency ofdata acquisition mu

37、st be at least once every second.7.5 Specimen EnvironmentA constant-temperature envi-ronment must be maintained through the duration of the test soas to provide a temperature stability in the specimen of within60.1C. Failure to attain this criterion will on occasionscompromise the linearity of the t

38、ransient, thereby affecting thetest result. The environment shall be free from excessivevibration.7.5.1 AmbientFor measurements close to ambienttemperature, use of a stirred water bath is one method to beused to maintain the test temperature.Alternatively, placing thespecimen, adequately shielded to

39、 protect it from convection, isa possible alternative.7.5.2 Cryogenic TemperaturesPlacing a specimen ad-equately shielded from convection in a controlled cryogenicbath or chamber is acceptable.7.5.3 Elevated TemperaturesAt temperatures aboveambient, a special heated cell is required. This consists o

40、f avertical cylindrical heated chamber, fitted with a removableplug at the bottom. The specimen is loaded from the top and isdischarged through the bottom, once the test is complete (seeFig. 2).8. Conditioning8.1 Many thermoplastic materials must be dried becausemoisture has been shown to affect the

41、 properties. Moisturecauses molten polymer samples to foam, which will affect themeasured thermal conductivity. Conditioning is generally not arequirement of this test; if conditioning is necessary, see theapplicable material specification or Practice D618.9. Preparation of Test Specimen9.1 The test

42、 specimen prepared from plastic pellets, liquids,foams, or soft solids is acceptable. The specimen-preparationmethod depends on the type of material being tested. If thematerial is believed to be anisotropic, at least three specimensmust be tested. Specimens must be longer than the line-sourceprobe

43、and large enough in radius to have at least 4 mm ofmaterial surrounding the probe, so that the expanding heatwave will not strike a boundary during the measurement.9.2 Viscous LiquidsThese include pastes and semisolids.Pour or extrude the specimen into a test tube or similarcylindrical container. Th

44、e container must be filled with suffi-cient quantity of fluid such that the probe is immersedcompletely.9.3 Soft SolidsInsert the line-source probe directly into thespecimen, taking care to see that it does not bend duringinsertion.Aspecimen of any size or shape as long as it is largerthan the minim

45、um specified in 9.1 is acceptable. In the casewhere the specimen cannot be penetrated without beingdestroyed, it is permissible to drill a pilot hole that is smallerthan the probe diameter to aid in insertion.9.4 Thermoplastics in the MeltPreheat the sample cell tothe lowest melt processing temperat

46、ure of the thermoplastic.Loading specimens at a low temperature is desirable to ensurean air-free specimen. Pour a charge of the specimen, typicallyin pellet or powder form, into the cell and compress into ahomogeneous mass. Several charges, tamped well, are oftenneeded to fill the sample cell. When

47、 the specimen is wellmolten, insert the probe so as to be near the axial center of thespecimen. Sealing systems are sometimes employed to containthe specimen. For thermally unstable materials, follow materialmanufacturers recommendations on temperature exposurelimits.9.5 Solid ThermoplasticsLoad the

48、 sample in the samemanner as in 9.4. The following precautionary steps are neededto account for shrinkage of the specimen as it solidifies. Theprobe shall be fitted with a dynamic sealing system permittingit to move with the shrinking specimen. Static loads placed onthe probe to help maintain contac

49、t as the plastic shrinks areacceptable and recommended. These loads optimally willapply a pressure of 1 to 7 MPa on the specimen.FIG. 2 Adaptation for Measurements at Elevated TemperaturesD5930 1739.6 Thermosets and RubberPreheat the sample cell to aloading temperature, above the glass transition, where thespecimen is fluid enough to be molded but will not undergosignificant reaction (6). If the sample cell is to be reused, wipethe walls of the cell with a thin layer of a release agent such assilicone oil to prevent the cured sp