1、Designation: D5930 16Standard 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 ofmaterials in the range from 0.08 to 2.0 W/m.K coveringthermoplastics, thermosets, and rubbers, filled and reinforced.1.2 The values stated in SI units shall be regarded asstandard.1.3 This standard does not purport to address the sa
4、fetyconcerns, if any, 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.2. Referenced Documents2
5、.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 Conductiv
6、ity 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
7、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
8、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 perpendic
9、ular 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 m
10、ust 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 res
11、pect 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 cap
12、acity.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 t2.3.3.5 T1The temperature (K) recorded at time t1.3.4 Subscript:3.4.1 avaverage.3.4.2 appapparent.3.4.3 refreference.1This test method is un
13、der the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties.Current edition approved Sept. 1, 2016. Published September 2016. Originallyapproved in 1997. Last previous edition approved in 2009 as D5930 - 09. DOI:10.1520/D5930-16
14、.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.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 sta
15、ndardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. 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 of the specime
16、n 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 the polymer. Th
17、e 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 a probe as de
18、scribed 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 is possible to
19、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 widerange of
20、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 the probehas
21、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 measuring device
22、.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 initial portion of t
23、he 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 transient (7). Thi
24、s 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. The duration o
25、f measurement, however,must not be too long, or else the heat wave striking a sampleboundary exists, thereby violating the theoretical conditions ofthe measurement.6.1.2 Shrinkage Upon SolidificationPlastics tend to shrinksignificantly upon solidification. This shrinkage is especially sofor the semi
26、-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, and possibly permit theline-source pr
27、obe 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 on in viscid fluids are subject to thedevelopment of convection currents, w
28、hich have been knownto affect the measurement. Because of the transient nature ofthe measurement, these effects are not as pronounced. Theycannot be eliminated, however.6.3 Although the technique is not limited by temperature, atmeasurements above 500C, a significant amount of heattransfer occurs du
29、e to radiation so that only a appis possibleto be measured.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 of heat. The resulting temperature t
30、ransient 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-to-diameter ratio of the probe must b
31、e greater than 20. Theresistance of the line-source heater must be known to within60.1 %. The probe also contains a temperature sensor tomeasure the temperature transient. A typical sensor for theline-source probe is a high-sensitivity J-type thermocouple3The boldface numbers in parentheses refer to
32、 the list of references at the end ofthis standard.FIG. 1 Line-Source TransientD5930 162used 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 itis subject to during measurements
33、.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 is recorded for the duration of the
34、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 must be at least once every second.7.5
35、 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 transient, thereby affecting thetest
36、result. The environment shall be free from excessivevibration.7.5.1 AmbientFor measurements close to ambient, astirred water bath is one method to be used to maintain the testtemperature. Alternatively, the specimen, adequately shieldedto protect it from convection, placing in air is a possiblealter
37、native.7.5.2 Cryogenic TemperaturesPlacing an adequatelyshielded from convection specimen in a controlled cryogenicbath or chamber is acceptable.7.5.3 Elevated TemperaturesAt temperatures aboveambient, a special heated cell is required. This consists of avertical cylindrical heated chamber, fitted w
38、ith 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 properties. Moisturecauses molten polymer sampl
39、es 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 specimen prepared from samples in the form ofpl
40、astic pellets, liquids, foams, or soft solids are acceptable. Thespecimen-preparation method depends on the type of materialbeing tested. If the material is believed to be anisotropic, atleast three specimens must be tested. Specimens must belonger than the line-source probe and large enough in radi
41、us tohave at least 4 mm of material surrounding the probe, so thatthe expanding heat wave will not strike a boundary during themeasurement.9.2 Viscous LiquidsThese include pastes and semisolids.Pour or extrude the specimen into a test tube or similarcylindrical container. The container must be fille
42、d 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. The specimen of any size or shape as long as it islarger than the minimum specified in 9.1 i
43、s acceptable. In thecase where 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 temperature of the thermoplas
44、tic.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, is oftenneeded to fill the sample cell. When the specimen is wellm
45、olten, 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 sample in the sameman
46、ner 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 contact as the plastic shrin
47、ks areacceptable and recommended. These loads optimally willapply a pressure of 1 to 7 MPa on the specimen.9.6 Thermosets and RubberPreheat the sample cell to aloading temperature, above the glass transition, where thespecimen is fluid enough to be molded but will not undergoFIG. 2 Adaptation for Me
48、asurements at Elevated TemperaturesD5930 163significant 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 specimen from bonding to thecell. Charge or pour the uncured specimen in the same manneras
49、 in 9.4. For best results, do not coat the probe with releaseagents since this might affect the test results.10. Calibration10.1 The actual probe and sample cell differ in many waysfrom the theoretical situation, which assumes an infinitely longprobe in an infinite specimen. Judicious design of the probeand sample cell will often minimize some of the non-idealities.Practical limitations in probe construction, however, are suchthat a calibration is necessary to account for such effects as thethermal mass of the probe and the fact that the preci
