1、Designation: D 696 03Standard Test Method forCoefficient of Linear Thermal Expansion of PlasticsBetween 30C and 30C with a Vitreous Silica Dilatometer1This standard is issued under the fixed designation D 696; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of revision, 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 determination of the coefficientof linear thermal exp
3、ansion for plastic materials having coef-ficients of expansion greater than 1 3 1061C by use of avitreous silica dilatometer. At the test temperatures and underthe stresses imposed, the plastic materials shall have a negli-gible creep or elastic strain rate or both, insofar as theseproperties would
4、significantly affect the accuracy of the mea-surements.NOTE 1There is no similar or equivalent ISO standard.1.1.1 Test Method E 228 shall be used for temperaturesother than 30C to 30C.1.1.2 This test method shall not be used for measurementson materials having a very low coefficient of expansion (le
5、ssthan 1 3 1061C). For materials having very low coefficientof expansion, interferometer or capacitance techniques arerecommended.1.2 The thermal expansion of a plastic is composed of areversible component on which are superimposed changes inlength due to changes in moisture content, curing, loss of
6、plasticizer or solvents, release of stresses, phase changes andother factors. This test method is intended for determining thecoefficient of linear thermal expansion under the exclusion ofthese factors as far as possible. In general, it will not bepossible to exclude the effect of these factors comp
7、letely. Forthis reason, the test method can be expected to give only anapproximation to the true thermal expansion.1.3 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.4 This standard does not purport to address all of thesafety co
8、ncerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 618 Practice for Conditioning Plasti
9、cs for Testing2D 883 Terminology Relating to Plastics2D 4065 Practice for Determining and Reporting DynamicMechanical Properties of Plastics3E 228 Test Method for Linear Thermal Expansion of SolidMaterials with a Vitreous Silica Dilatometer4E 691 Practice for Conducting an Interlaboratory Study toDe
10、termine the Precision of a Test Method4E 831 Test Method for Linear Thermal Expansion of SolidMaterials by Thermomechanical Analysis43. Terminology3.1 DefinitionsDefinitions are in accordance with Termi-nology D 883 unless otherwise specified.4. Summary of Test Method4.1 This test method is intended
11、 to provide a means ofdetermining the coefficient of linear thermal expansion ofplastics which are not distorted or indented by the thrust of thedilatometer on the specimen. For materials that indent, see 8.4.The specimen is placed at the bottom of the outer dilatometertube with the inner one restin
12、g on it. The measuring devicewhich is firmly attached to the outer tube is in contact with thetop of the inner tube and indicates variations in the length ofthe specimen with changes in temperature. Temperaturechanges are brought about by immersing the outer tube in aliquid bath or other controlled
13、temperature environment main-tained at the desired temperature.5. Significance and Use5.1 The coefficient of linear thermal expansion, a, betweentemperatures T1and T2for a specimen whose length is L0atthe reference temperature, is given by the following equation:a5L22 L1!/L0T22T1!# 5DL/L0DT1This tes
14、t method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties(Section D20.30.07).Current edition approved April 10, 2003. Published June 2003. Originallyapproved in 1942. Last previous edition approved in 1998 as D 6
15、96 98.2Annual Book of ASTM Standards, Vol 08.01.3Annual Book of ASTM Standards, Vol 08.02.4Annual Book 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, U
16、nited States.where L1and L2are the specimen lengths at temperatures T1and T2, respectively. a is, therefore, obtained by dividing thelinear expansion per unit length by the change in temperature.5.2 The nature of most plastics and the construction of thedilatometer make 30 to +30C 22F to +54F a conv
17、enienttemperature range for linear thermal expansion measurementsof plastics. This range covers the temperatures in whichplastics are most commonly used. Where testing outside of thistemperature range or when linear thermal expansion character-istics of a particular plastic are not known through thi
18、stemperature range, particular attention shall be paid to thefactors mentioned in 1.2 and special preliminary investigationsby thermo-mechanical analysis, such as that prescribed inPractice D 4065 for the location of transition temperatures,may be required to avoid excessive error. Other ways ofloca
19、ting phase changes or transition temperatures using thedilatometer itself may be employed to cover the range oftemperatures in question by using smaller steps than 30C54F or by observing the rate of expansion during a steadyrise in temperature of the specimen. Once such a transitionpoint has been lo
20、cated, a separate coefficient of expansion fora temperature range below and above the transition point shallbe determined. For specification and comparison purposes, therange from 30C to +30C 22F to +86F (provided it isknown that no transition exists in this range) shall be used.6. Apparatus6.1 Fuse
21、d-Quartz-Tube Dilatometer suitable for this testmethod is illustrated in Fig. 1. A clearance of approximately 1mm is allowed between the inner and outer tubes.6.2 Device for measuring the changes in length (dial gage,LVDT, or the equivalent) is fixed on the mounting fixture sothat its position may b
22、e adjusted to accommodate specimens ofvarying length (see 8.2). The accuracy shall be such that theerror of indication will not exceed 61.0 m 4 3 105in. forany length change. The weight of the inner silica tube plus themeasuring device reaction shall not exert a stress of more than70 kPa 10 psi on t
23、he specimen so that the specimen is notdistorted or appreciably indented.6.3 Scale or Caliper capable of measuring the initial lengthof the specimen with an accuracy of 60.5 %.6.4 Controlled Temperature Environment to control thetemperature of the specimen. Arrange the bath so a uniformtemperature i
24、s assured over the length of the specimen. MeansFIG. 1 Quartz-Tube DilatometerD696032shall be provided for stirring the bath and for controlling itstemperature within 60.2C 60.4F at the time of thetemperature and measuring device readings.NOTE 2If a fluid bath is used, it is preferable and not diffi
25、cult to avoidcontact between the bath liquid and the test specimen. If such contact isunavoidable, take care to select a fluid that will not affect the physicalproperties of the material under test.6.5 Thermometer or ThermocoupleThe bath temperatureshall be measured by a thermometer or thermocouple
26、capableof an accuracy of 60.1C 60.2F.7. Sampling7.1 Sampling shall be conducted in accordance with thematerial specification for the material in question.8. Test Specimen8.1 The test specimens shall be prepared under conditionsthat give a minimum of strain or anisotropy, such as machining,molding, o
27、r casting operations.8.2 The specimen length shall be between 50 mm and 125mm.NOTE 3If specimens shorter than 50 mm are used, a loss in sensitivityresults. If specimens greatly longer than 125 mm are used, the temperaturegradient along the specimen may become difficult to control within theprescribe
28、d limits. The length used will be governed by the sensitivity andrange of the measuring device, the extension expected and the accuracydesired. Generally speaking, the longer the specimen and the moresensitive the measuring device, the more accurate will be the determina-tion if the temperature is w
29、ell controlled.8.3 The cross section of the test specimen may be round,square, or rectangular and shall fit easily into the measurementsystem of the dilatometer without excessive play on the onehand or friction on the other. The cross section of the specimenshall be large enough so that no bending o
30、r twisting of thespecimen occurs. Convenient specimen cross sections are: 12.5by 6.3 mm 12 in. by14 in., 12.5 by 3 mm 12 by18 in., 12.5mm 12 in. in diameter or 6.3 mm 14 in. in diameter. Ifexcessive play is found with some of the thinner specimen,guide sections shall be cemented or otherwise attache
31、d to thesides of the specimen to fill out the space.8.4 Cut the ends of the specimens flat and perpendicular tothe length axis of the specimen. If a specimen indents from theuse of the dilatometer, then flat, thin steel or aluminum platesshall be cemented or otherwise firmly attached to the specimen
32、to aid in positioning it in the dilatometer. These plates shall be0.3 to 0.5 mm 0.012 to 0.020 in. in thickness.9. Conditioning9.1 Conditioning Condition the test specimens at23 6 2C 73.4 6 3.6F and 50 6 5 % relative humidity fornot less than 40 h prior to test in accordance with Procedure Aof Pract
33、ice D 618 unless otherwise specified by the contract orrelevant material specification. In cases of disagreement, thetolerances shall be 61C 61.8F and 62 % relative humid-ity.9.2 Test Conditions Conduct tests in the Standard Labo-ratory Atmosphere of 23 6 2C 73.4 6 3.6F and 50 6 5%relative humidity,
34、 unless otherwise specified by the contract orrelevant material specification. In cases of disagreement, thetolerances shall be 61C 61.8F and 62 % relative humid-ity.10. Procedure10.1 Measure the length of two conditioned specimens atroom temperature to the nearest 25 m 0.001 in. with thescale or ca
35、liper (see 6.3).10.2 Cement or otherwise attach the steel plates to the endsof the specimen to prevent indentation (see 8.4). Measure thenew lengths of the specimens.10.3 Mount each specimen in a dilatometer. Carefullyinstall the dilatometer in the 30C 22F controlled envi-ronment. If liquid bath is
36、used, make sure the top of thespecimen is at least 50 mm 2 in. below the liquid level of thebath. Maintain the temperature of the bath in the range from32C to 28C 26 to 18F 6 0.2C 0.4F until thetemperature of the specimen along the length is constant asdenoted by no further movement indicated by the
37、 measuringdevice over a period of 5 to 10 min. Record the actualtemperature and the measuring device reading.10.4 Without disturbing or jarring the dilatometer, change tothe +30C +86F bath, so that the top of the specimen is atleast 50 mm 2 in. below the liquid level of the bath. Maintainthe tempera
38、ture of the bath in the range from +28 to 32C +82to 90F 6 0.2C 60.4F until the temperature of thespecimen reaches that of the bath as denoted by no furtherchanges in the measuring device reading over a period of 5 to10 min. Record the actual temperature and the measuringdevice reading.10.5 Without d
39、isturbing or jarring the dilatometer, change to30C 22F and repeat the procedure in 10.3.NOTE 4It is convenient to use alternately two baths at the propertemperatures. Great care should be taken not to disturb the apparatusduring the transfer of baths. Tall Thermos bottles have been successfullyused.
40、 The use of two baths is preferred because this will reduce the timerequired to bring the specimen to the desired temperature. The test shouldbe conducted in as short a time as possible to avoid changes in physicalproperties during long exposures to high and low temperatures that mightpossibly take
41、place.10.6 Measure the final length of the specimen at roomtemperature.10.7 If the change in length per degree of temperaturedifference due to heating does not agree with the change inlength per degree due to cooling within 10 % of their average,investigate the cause of the discrepancy and, if possi
42、ble,eliminate. Repeat the test until agreement is reached.11. Calculation11.1 Calculate the coefficient of linear thermal expansionover the temperature range used as follows:a5DL/L0DTa = average coefficient of linear thermal expansion perdegree Celsius,DL = change in length of test specimen due to h
43、eating or tocooling,D696033L0= length of test specimen at room temperature (DL andL0being measured in the same units), andDT = temperature differences, C, over which the change inthe length of the specimen is measured.The values of a for heating and for cooling shall be averagedto give the value to
44、be reported.NOTE 5Correction for thermal expansion of silica is 4.3 3 1071C.If requested, this value should be added to the calculated value tocompensate for the expansion of the apparatus equivalent to the length ofthe specimen. If thick metal plates are used, appropriate correction mayalso be desi
45、rable for their thermal expansions.12. Report12.1 The report shall include the following:12.1.1 Designation of material, including name of manufac-turer and information on composition when known.12.1.2 Method of preparation of test specimen,12.1.3 Form and dimensions of test specimen,12.1.4 Type of
46、apparatus used,12.1.5 Temperatures between which the coefficient of linearthermal expansion has been determined,12.1.6 Average coefficient of linear thermal expansion perdegree Celsius, for the two specimens tested.12.1.7 Location of phase change or transition point tem-peratures, if this is in the
47、range of temperatures used,12.1.8 Complete description of any unusual behavior of thespecimen, for example, differences of more than 10 % inmeasured values of expansion and contraction.13. Precision and Bias13.1 Table 1 is based on a round robin conducted in 1989 inaccordance with Practice E 691 inv
48、olving nine materials andfive laboratories. For each material, all samples are prepared atone source, but the individual specimens are prepared at thelaboratory that tested them. Each test result is the average oftwo individual determinations. Each laboratory obtained onetest result for each materia
49、l. WarningThe explanations of“r” and “R” (13.2-13.2.3) only are intended to present ameaningful way of considering the approximate precision ofthis test method. The data presented in Table 1 should not beapplied to the acceptance or rejection of materials, as these dataapply only to the materials tested in the round robin and areunlikely to be rigorously representative of other lots, formula-tions, conditions, materials, or laboratories. In particular,
