ASTM D5930-2001 Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique《用瞬变线源技术对塑料热导性的标准试验方法》.pdf

《ASTM D5930-2001 Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique《用瞬变线源技术对塑料热导性的标准试验方法》.pdf》由会员分享，可在线阅读，更多相关《ASTM D5930-2001 Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique《用瞬变线源技术对塑料热导性的标准试验方法》.pdf（5页珍藏版）》请在麦多课文档分享上搜索。

1、Designation: D 5930 01Standard 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 (e) 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 ran

3、ge 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 are to be regarded asstandard.1.3 This standard does not purport to address the safetyc

4、oncerns, 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 current ISO document that duplicates this testmethod.2. Referenced Doc

5、uments2.1 ASTM Standards:C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate Apparatus2C 518 Test Method for Steady-State Heat Flux and ThermalTransmission Properties by Means of the Heat Flow MeterApparatus2C 1113 Test Meth

6、od for Thermal Conductivity of Refracto-ries by Hot Wire (Platinum Resistance Thermometer Tech-nique)3D 618 Practice for Conditioning Plastics for Testing4D 883 Terminology Relating to Plastics4D 2717 Test Method for Thermal Conductivity of Liquids5E 177 Practice for Use of the Terms Precision and B

7、ias inASTM Test Methods6E 1225 Test Method for Thermal Conductivity of Solids byMeans of the Guarded-Comparative-Longitudinal HeatFlow Technique63. Terminology3.1 DefinitionsTerminology used in this standard is inaccordance with Terminology D 883.3.2 Definitions of Terms Specific to This Standard:3.

8、2.1 temperature transient, nthe temperature 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 ho

9、mogeneous mate-rial in a direction 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,

10、lapp.3.2.2.2 DiscussionThermal conductivity 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 materialsar

11、e not isotropic with respect to thermal conductivity.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 constant.3.3.2 lThermal conductivity, W/m.K.3.3.3 QHea

12、t 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:1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties.Curre

13、nt edition approved March 10, 2001. Published May 2001. Originallypublished as D 593097. Last previous edition D 593097.2Annual Book of ASTM Standards, Vol 04.06.3Annual Book of ASTM Standards, Vol 15.01.4Annual Book of ASTM Standards, Vol 08.01.5Annual Book of ASTM Standards, Vol 05.02.6Annual Book

14、 of ASTM Standards, Vol 14.02.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.4.1 avaverage.3.4.2 appapparent.3.4.3 refreference.4. Summary of Test Method4.1 Line-So

15、urce TechniqueThis is a transient method fordetermining thermal conductivity (1, 2).7A line source of heatis located at the center 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 r

16、esults 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 linearly with the logarithm of time (3). Thisrelationship can be used directly to calculate the thermalconduct

17、ivity 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 simplicity of the test method makes itapplicable for a wide range of materials (4, 5). The techniqueis capable

18、 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 reaction or aging (6). Short measurement timespermit generation of large amounts of data with little effort

19、.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 numerical precision and bias statement, it shall not beused as a referee test method in case of dispute.6

20、. Interferences6.1 The line-source method produces results of highestprecision with materials where intimate contact with the probecan be established, thereby eliminating effects of thermalcontact resistance. These materials include viscous fluids andsoft solids.6.1.1 Thermal-Contact ResistanceIn th

21、e 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 pastebetween the specimen and the sensor. This reduces, but maynot eliminate, the effect of contact resistance

22、. 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. By extendingthe time of the measurement, it is possible to progress beyondthe region of thermal-contact res

23、istance, 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 the contactresistance, the greater is this time. It is, therefore, important tomake a sufficiently long mea

24、surement 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 boundary, thereby violatingthe theoretical conditions of the measurement.6.1.2 Shrinkage Upon Solidificat

25、ionPlastics tend toshrink significantly upon solidification. This shrinkage isespecially so for the semi-crystalline materials, which experi-ence a significant change in specific volume upon crystalliza-tion. This crystallization can result in large gaps being devel-oped between the specimen and the

26、 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 specimenvolume so as to reduce the extent of shrinkage.6.2 Measurements on inviscid fluids are subject to

27、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, however.6.3 Although the technique is not limited by temperature, atmeasurements above 500C, a significant amount

28、 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-temperature environ-ment. During the measurement, the line-source probe producesa precise amount of heat. The resulti

29、ng temperature transient isrecorded, preferably, on a computer data-acquisition system, asspecified in 7.4. This transient is analysed 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

30、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 typical sensor for theline-source probe is a high-sensitivity J-type thermocoupleused because of its large See

31、beck coefficient. The housingsheath of the probe must be robust enough to ensure that the7The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Line-Source TransientD5930012probe does not bend or deform under the adverse conditions itis subject to duri

32、ng 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 is recorded for the d

33、uration 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 and10 C over the duration of the measurement. The frequency ofdata acquisition must be at least once

34、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 within6 0.1C. Failure to attain this criterion can compromise thelinearity of the transient, thereby affecting the t

35、est result. Theenvironment should 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, the specimen, adequately shielded to protect itfrom convection, may be placed in air.7.5.2 Cryogenic Temp

36、eraturesThe 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 heated cell is required. This consists of avertical cylindrical heated chamber, fitted with a removablep

37、lug 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 need to be dried becausemoisture can affect the properties. Moisture causes moltenpolymer samples to foam, which will

38、affect the measuredthermal conductivity. If conditioning is necessary, see theapplicable material specification or Practice D 618.9. Preparation 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

39、-preparation method depends on the typeof material being tested. If the material is believed to beanisotropic, at least three specimens must 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 exp

40、anding heat wave will not strike a boundaryduring the measurement.9.2 Viscous LiquidsThese include pastes and semisolids.Pour or extrude the specimen into a test tube or similarcylindrical container. The container must be filled with suffi-cient quantity of fluid such that the probe is immersedcompl

41、etely.9.3 Soft SolidsInsert the line-source probe directly intothe specimen, taking care to see that it does not bend duringinsertion. The specimen 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 d

42、estroyed, itis permissible to drill a pilot hole that is smaller than the probediameter to aid in insertion.9.4 Thermoplastics in the MeltPreheat the sample cell tothe lowest processing temperature of the thermoplastic. Load-ing specimens at a low temperature is desirable to ensure anair-free specim

43、en. Pour a charge of the specimen, typically inpellet or powder form, into the cell and compress into ahomogeneous specimen. Several charges, 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

44、 systems may be employed to contain thespecimen. For thermally unstable materials, follow materialmanufacturers recommendations on temperature exposurelimits.9.5 Solid ThermoplasticsLoad the sample in the samemanner as in 9.4. The following precautionary steps are neededto account for shrinkage of t

45、he specimen as it solidifies. Theprobe shall be fitted with a dynamic sealing system permittingit to move with the shrinking specimen. Static 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.

46、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 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 a

47、ssilicone oil to prevent the cured specimen from bonding to thecell. Charge or pour the uncured specimen in the same manneras 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 man

48、y waysfrom the theoretical situation, which assumes an infinitely longFIG. 2 Adaptation for Measurements at Elevated TemperaturesD5930013probe in an infinite specimen. Some of the non-idealities can beminimized by judicious design of the probe and sample cell.Practical limitations in probe construct

49、ion, however, are suchthat a calibration is needed to account for such effects as thethermal mass of the probe and the fact that the precise lengthof the line-source cannot be determined. A probe constant isobtained by calibrating the probe against a material of knownthermal conductivity. The constant depends on the probecharacteristics and has no significant temperature sensitivity.The ideal value of the probe constant is 1.0. Typical valuesrange from 0.8 to 0.9.10.2 Reference MaterialAn ideal reference material is awell-characterized, viscous li