1、Designation: D 5930 09Standard Test Method forThermal Conductivity of Plastics by Means of a TransientLine-Source Technique1This standard is issued under the fixed designation D 5930; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the 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. Scope*1.1 This test method covers the determination of the thermalconductivity of plastics over a temperature rang
3、e from 40 to400C. The thermal conductivity of materials in the range from0.08 to 2.0 W/m.K can be measured covering thermoplastics,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 safetycon
4、cerns, 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 Documents2.1 ASTM
5、 Standards:2C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC 1113 Test Method for Thermal Conductivity
6、of Refracto-ries by Hot Wire (Platinum Resistance Thermometer Tech-nique)D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 2717 Test Method for Thermal Conductivity of LiquidsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 1225 Te
7、st Method for Thermal Conductivity of Solids byMeans of the Guarded-Comparative-Longitudinal HeatFlow Technique3. Terminology3.1 DefinitionsTerminology used in this standard is inaccordance with Terminology D 883.3.2 Definitions of Terms Specific to This Standard:3.2.1 temperature transient, nthe te
8、mperature 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
9、 perpendicular 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, lapp.3.2.2.2 DiscussionThermal con
10、ductivity 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. Thermal conductivity may vary withdirection and orientation of the specimen since some materialsare not isotropic with respect to th
11、ermal conductivity. In thecase of thermoset polymers, thermal conductivity may varywith 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 capacity.3.3 Symbols:3.3.1 CProbe
12、constant.3.3.2 lThermal 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.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the di
13、rect responsibility of Subcommittee D20.30 on Thermal Properties.Current edition approved Aug. 15, 2009. Published September 2009. Originallyapproved in 1997. Last previous edition approved in 2001 as D 5930 - 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu
14、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohock
15、en, PA 19428-2959, United States.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 of the specimen being tested. Theapparatus is at a constant ini
16、tial 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. The temperature rise of the line-source varies line
17、arly with the logarithm of time (3). Thisrelationship can be used directly to calculate the thermalconductivity of the sample. The line-source of heat can beachieved in a number of ways. In this test method, it is in theform of a probe as described in 7.2.5. Significance and Use5.1 The relative simp
18、licity 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 study the effect of compositional changes suchas chemical r
19、eaction 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 test conditions. Because this test method does notcontain a
20、 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 probecan be established, thereby eliminating effects of thermalconta
21、ct resistance. These materials include viscous fluids andsoft solids.6.1.1 Thermal-Contact ResistanceIn the solid state, acontact resistance can develop due to the interface between thespecimen and the measuring device. Conventional methodsattempt to account for this by introducing a conductive past
22、ebetween the specimen and the sensor. This reduces, but maynot eliminate, the effect of contact resistance. In the line-sourcemethod, contact resistance manifests itself as a nonlinearity inthe initial portion of the transient (see Fig. 1). The techniquehas a method to account for this phenomenon. B
23、y extendingthe time of the measurement, it is possible to progress beyondthe region of thermal-contact resistance, achieving a statewhere the contact resistance does not contribute to the mea-sured transient (7). This state typically is achieved after about10 to 20 s in the measurement. The larger t
24、he contactresistance, the greater is this time. It is, therefore, important tomake a sufficiently long measurement to exclude the portion ofthe transient that shows the effect of the contact resistance. Theduration of measurement, however, cannot be too long, or elsethe heat wave can strike a sample
25、 boundary, thereby violatingthe theoretical conditions of the measurement.6.1.2 Shrinkage Upon SolidificationPlastics tend toshrink significantly upon solidification. This shrinkage isespecially so for the semi-crystalline materials, which experi-ence a significant change in specific volume upon cry
26、stalliza-tion. This crystallization can result in large gaps being devel-oped between the specimen and the sensing device. To accountfor shrinkage, a simple compression scheme described in 9.5can permit the line-source probe to move downward to take upthe slack. Steps also must be taken to minimize
27、specimenvolume so as to reduce the extent of shrinkage.6.2 Measurements on in viscid fluids are subject to thedevelopment of convection currents which can affect themeasurement. Because of the transient nature of the measure-ment, these effects are not as pronounced. They cannot beeliminated, howeve
28、r.6.3 Although the technique is not limited by temperature, atmeasurements above 500C, a significant amount of heattransfer occurs due to radiation so that only a lappcan bemeasured.7. Apparatus7.1 The apparatus consists of a line-source probe imbeddedin a specimen contained in a constant-temperatur
29、e environ-ment. During the measurement, the line-source probe producesa precise amount 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
30、 line-source probe contains aheater that runs the length of the probe (3). The length-to-diameter ratio of the probe must be 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 typ
31、ical 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 the3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 L
32、ine-Source TransientD5930092probe does not bend or deform under the adverse conditions 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 entireduratio
33、n of the test.7.4 Recording DeviceThe temperature transient from theline-source probe 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 betw
34、een 2 and10C over the duration of the measurement. The frequency ofdata acquisition must 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 within60.1
35、C. Failure to attain this criterion can compromise thelinearity of the transient, thereby affecting the test result. Theenvironment shall be free from excessive vibration.7.5.1 AmbientFor measurements close to ambient, astirred water bath may be used to maintain the test temperature.Alternatively, t
36、he specimen, adequately shielded to protect itfrom convection, may be placed in air.7.5.2 Cryogenic TemperaturesThe specimen, adequatelyshielded to protect it from convection, may be placed in acontrolled cryogenic bath or chamber.7.5.3 Elevated TemperaturesAt temperatures above am-bient, a special
37、heated cell is required. This consists of avertical cylindrical heated chamber, fitted with a removableplug at the bottom. The specimen is loaded from the top andcan be discharged through the bottom, once the test is complete(see Fig. 2).8. Conditioning8.1 Many thermoplastic materials must be dried
38、becausemoisture can affect the properties. Moisture causes moltenpolymer samples to foam, which will affect the measuredthermal conductivity. Conditioning is generally not a require-ment of this test; if conditioning is necessary, see the applicablematerial specification or Practice D 618.9. Prepara
39、tion of Test Specimen9.1 The test specimen may be prepared from samples, whichcan be in the form of plastic pellets, liquids, foams, or softsolids. The specimen-preparation method depends on the typeof material being tested. If the material is believed to beanisotropic, at least three specimens must
40、 be tested. Specimensmust be longer than the line-source probe and large enough inradius to have at least 4 mm of material surrounding the probe,so that the expanding heat wave will not strike a boundaryduring the measurement.9.2 Viscous LiquidsThese include pastes and semisolids.Pour or extrude the
41、 specimen into a test tube or similarcylindrical container. The 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 intothe specimen, taking care to see that it does not bend duringinsertion. The s
42、pecimen can be of any size or shape as long asit is larger than the minimum specified in 9.1. In the case wherethe specimen cannot be penetrated without being destroyed, itis permissible to drill a pilot hole that is smaller than the probediameter to aid in insertion.9.4 Thermoplastics in the MeltPr
43、eheat the sample cell tothe lowest melt processing temperature 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,
44、 tamped well, may beneeded to fill the sample cell. When the specimen is wellmolten, insert the probe so as to be near the axial center of thespecimen. Sealing systems may be employed to contain thespecimen. For thermally unstable materials, follow materialmanufacturers recommendations on temperatur
45、e exposurelimits.9.5 Solid ThermoplasticsLoad the 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
46、 loads can thenbe placed on the probe to help maintain contact as the plasticshrinks. These loads optimally will apply a pressure of 1 to 7MPa 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
47、 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 specimen from bonding to thecell. Charge or pour the uncured specimen in the same manneras in 9.4. For bes
48、t results, do not coat the probe with releaseagents since this might affect the test results.FIG. 2 Adaptation for Measurements at Elevated TemperaturesD593009310. Calibration10.1 The actual probe and sample cell differ in many waysfrom the theoretical situation, which assumes an infinitely longprob
49、e in an infinite specimen. Some of the non-idealities can beminimized by judicious design of the probe and sample cell.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 precise lengthof the line-source cannot be determined.Aprobe constant mustbe obtained by calibrating the probe against a material ofknown thermal conductivity. The constant depends on theprobe characteristics and has no significant temperature sensi-tivity.
