1、Designation: D 7340 07Standard Practice forThermal Conductivity of Leather1This standard is issued under the fixed designation D 7340; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthes
2、es indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is intended to determine the thermalconductivity of a sheet material. This practice is not limited toleather, but may be used for any poorl
3、y conductive materialsuch as rubber, textile and cork associated with the construc-tion of shoes.1.2 A constant heat source is sandwiched between twoidentical metal cylinders which are mounted with their axesvertical. A test specimen is placed on the top surface of theupper cylinder and a third iden
4、tical metal cylinder is placed ontop of the test specimen so that all the cylinders and the testspecimen are concentrically aligned (see Fig. 1). The heatsource is switched on and the temperatures of the three blocksallowed to reach equilibrium. The thermal conductivity of thetest specimen is then d
5、etermined from the steady-state tem-peratures of the three blocks, the exposed surface areas of theblocks and test specimen and the thickness of the test speci-men.1.3 This practice does not apply to wet blue.1.4 This standard does not purport to address all of thesafety concerns, if any, associated
6、 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:2D 1610 Practice for Conditioning Leather and LeatherProducts fo
7、r TestingD 1813 Test Method for Measuring Thickness of LeatherTest Specimens2.2 Other Standard:SATRA TM 146 Thermal Conductivity3. Terminology3.1 Definitions:3.2 thermal conductivitythe quantity of heat conductedper unit time through unit area of a slab of unit thicknesshaving unit temperature diffe
8、rence between its faces.4. Summary of Practice4.1 Aconditioned specimen of leather (see Practice D 1610)is placed between two plates at different temperatures. Theupper plate is at a constant temperature while the temperatureof the lower plate is slowly changing. The temperature differ-ence is measu
9、red by thermocouples. The rate of flow of heatthrough the specimen is proportional to the area and thetemperature difference of the faces of the specimen, andinversely proportional to the thickness. Assuming no heat loss,the amount of heat flowing through the specimen per unit timeis equal to the am
10、ount of heat received by the lower plate(copper block receiver) per unit time.5. Significance and Use5.1 Part of the function of a shoe is to assist the foot inmaintaining body temperature and to guard against large heatchanges. The insulating property of a material used in shoeconstruction is depen
11、dent on porosity or the amount of airspaces present. A good insulating material has a low thermalconductivity value, k. The thermal conductivity value increaseswith an increase in moisture content since the k value for wateris high, 14 by 104cal cm/s cm4 C (0.59 W/mK).6. Apparatus and Materials6.1 A
12、 “Lees disc” apparatus, see Fig. 1, consisting of:6.1.1 A metal, see 11.1.2, cylindrical block, which willsubsequently be referred to as block B1, with:6.1.1.1 A diameter of (D), in millimetres, which is known toan accuracy of 0.2 mm (see 11.1.1).6.1.1.2 Aheight of (H), in millimetres, which is know
13、n to anaccuracy of 0.2 mm (see 11.2).6.1.1.3 A small hole of diameter 2 6 1 mm drilled radiallyto its center.6.1.1.4 A type K thermocouple inserted into the hole untilits junction is at the bottom of the hole.6.1.1.5 The remaining volume of the hole filled with a highthermal conductivity compound wi
14、th a thermal conductivity ofbetter than 0.8 W/(mC), for example a metal oxide filled pasteof the type used between high power semiconductor electronicdevices and heat sinks.1This practice is under the jurisdiction ofASTM Committee D31 on Leather andis the direct responsibility of Subcommittee D31.03
15、 on Footwear.Current edition approved May 1, 2007. Published June 2007.2For 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 AST
16、M website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.2 A circular electrical heater element which:6.1.2.1 Has a diameter of (D) 6 0.5 mm.6.1.2.2 Is capable of dissipating a minimum power densityof 400 W/m2from each of its ci
17、rcular faces. See 11.1.1.6.1.2.3 Has a cylindrical metal block, see 11.1.3, withthermocouple as block B1 (6.1.1), of diameter (D) 6 0.5 mmand of height (H) 6 0.2 mm bonded to its top and bottom faceswith a high thermal conductivity adhesive compound. Thesetwo blocks will subsequently be referred to
18、as B2 and B3.(WarningDo not attempt to separate these blocks from theheater element.)6.1.3 A fourth metal cylindrical block fitted with a thermo-couple as (6.1.1) of diameter (D) 6 0.5 mm and of thickness 86 2 mm. This is for measuring the ambient temperature of thesurrounding atmosphere and will su
19、bsequently be referred to asblock B4.6.1.4 A power supply unit connected to the heater element(6.1.2). The unit should be capable of supplying sufficientpower to enable the heater element (6.1.2) to dissipate a powerdensity of 400 W/m2from each of its circular faces.6.1.5 A means of measuring the po
20、wer being supplied to theheater element (6.1.3) to an accuracy of 64 mW. See 11.1.2.6.1.6 A method of mounting the heater and block assembly(6.1.2) so that air can circulate freely around all the outsideedges of the assembly.6.1.7 A device capable of measuring and displaying thetemperatures of the t
21、hermocouples in the four brass cylindricalblocks to an accuracy of 60.2C.36.2 A circular press knife of diameter (D) 6 0.5 mm.6.3 Adial thickness gauge which applies a pressure of 13.866 0.35 oz (393 6 10 g) on the test specimen and is capable ofmeasuring to an accuracy of 0.01 mm. This is identical
22、 to thegauge used in Test Method D 1813.7. Preparation of Test Specimens7.1 Place the uncut sheet material in a standard controlledenvironment of 20 6 2C/65 6 2% relative humidity or 23 62C/50 6 2% relative humidity or for a minimum of 48 h.Include details of the conditions used in the test report.7
23、.2 Use the press knife (6.2) to cut two circular testspecimens of diameter (D) 6 0.5 mm.8. Procedure8.1 Use the thickness gauge (6.3) to measure the thickness(S) at the center of each test specimen and record these twovalues in millimetres to the nearest 0.05 mm.8.2 Ensure that the heater assembly (
24、6.1.2) is mountedvertically so that block B2 is above block B3 (see Fig. 1). Itshould also be situated in a temperature-controlled environ-ment of 20 6 2C and mounted in such a way that air cancirculate freely about the assembly.8.3 Place one of the test specimens onto the upper surface ofblock B2 a
25、nd carefully rest the block B1 on top of the testspecimen. In the case of test specimens used for footwear, thesurface of the specimen which would usually be nearest thefoot should be placed against block B2 so that it is closest tothe heater element.Adjust the positions of the block B1 and thetest
26、specimen until they are both concentrically aligned withthe heater assembly (6.1.2).8.4 Switch on the power supply unit (6.1.4) and adjust ituntil it is delivering sufficient power to heat the brass cylin-drical blocks B2 and B3 to a steady-state temperature of 35 65C.At an ambient temperature of 20
27、C a power density of 300W/m2from each of the circular faces of the heater should besufficient. See 11.1.2.3Suitable apparatus is available from SATRA; www.satra.co.uk.FIG. 1 SATRA Lees Disc Thermal Conductivity ApparatusD73400728.5 At regular intervals of approximately 30 min record thetemperature o
28、f the four blocks B1, B2, B3 and B4 as TE1,TE2, TE3 and TE4 respectively in C to the nearest 0.2C.When three sets of successive readings taken over a total timeperiod of not less than 60 min are found to be within 60.2Cfor each block then record these last three sets of readings in Cto the nearest 0
29、.2C.8.6 Remove the test specimen and block B1 from the heaterassembly (6.1.2) and repeat the procedure in 8.3 to 8.5 for theother test specimen.9. Calculation9.1 Convert all length and thickness values from mm to mby dividing them by 1000.9.2 Calculate for the apparatus. See 11.1.1.9.2.1 1 Exposed a
30、rea of block B1 = A1 = exposed area ofblock B3 = A3, where:A1 5 A3 5px D! x 0.25 x D 1 H !9.2.2 Exposed area of block B2, A2, where:A2 5 H x p x D9.3 For each test specimen calculate:9.3.1 Exposed area of test specimen, As, where:As 5 S x p x D9.3.2 Power supplied to heater, P, where:P! 5 V x ISee 1
31、1.1.2.9.4 For each set of readings calculate:9.4.1 The temperatures of blocks B1, B2 and B3 aboveambient as:T1 5 TE1TE4T2 5 TE2TE4T3 5 TE3TE49.4.2 The average temperature of test specimen Ts where:Ts 5 0.5 x T1 1 T2 !9.4.3 The thermal conductivity of the test specimen, K inwatts per metre per degree
32、 centigrade W/mC. See 11.1.where:K 5 P x S x As x Ts 1 2x A1 x T1 ! 4 A1xT11AsxTs1A2xT2 1 A3xT3!x0.5xpxD2xT22T1!9.5 Calculate the arithmetic mean of the six values ofthermal conductivity, Ka to three significant figures.9.6 Calculate the average thermal resistance of the testspecimens, R in metres s
33、quared, degree centigrade per watt(m2 C/W) to three significant figures from the arithmetic meanor the thermal conductivities using the formula:R 5SaKawhere Sa is the arithmetic mean thickness of the twospecimens, and Ka is the arithmetic mean thermal conduc-tivity.10. Test Report10.1 Include in the
34、 test report:10.1.1 Reference to this practice; ASTM D 7340,10.1.2 A full description of the material,10.1.3 The arithmetic mean thermal conductivity as calcu-lated in 9.5,10.1.4 The arithmetic mean thermal resistance as calculatedin 9.6,10.1.5 The pressure on the test specimen, see 11.2, and10.1.6
35、Any deviations from this practice.11. Additional Notes11.1 The “Lees Disc” Apparatus:11.1.1 Dimensions of cylindrical blocks B1, B2 and B3.11.1.1.1 The blocks used have diameter 76.2 mm and height23.1 mm. Hence:A1 5 exposed area of block B1 5 A35 exposed area of block B3 5 0.0101 m2A2 5 exposed are
36、of block B2 5 0.0055 m211.1.1.2 Pressure on test specimen = 1.93 kPa, see 11.211.1.2 Heater Power:11.1.2.1 Power input to an electrical heater element in watts,can be measured by multiplying the voltage across the heaterV in volts, by the current through the heater I, in amperes.11.1.2.2 The power i
37、nput to the heater of the SATRAequipment necessary in an ambient environment of 20 6 2Cto heat blocks B2 and B3 to a steady state temperature of 35 65C, in approximately four h, is 2.52 W; this is normallyachieved by a current of 0.14 A at a voltage of 18 V.11.1.3 Metal Used for Blocks:11.1.3.1 A me
38、tal with a high thermal conductivity is recom-mended, such as one containing a high percentage of copper.Brass: 70/30 copper/zinc is suitable and is used in the SATRAapparatus.11.2 Pressure on the Test Specimen:11.2.1 Air is a poor conductor of heat, and the insulatingproperties of materials which e
39、nclose air are highly dependenton the amount of air trapped inside them. As a material iscompressed the air enclosed in the material is squeezed out andthe thermal conductivity of the material increases. It is there-fore critical that the thermal conductivity of a material whichnormally contains air
40、 in its structure is always measured underthe same pressure. In the vertically orientated Lees apparatusas used by SATRA the pressure on the test specimen isdetermined by the weight and base surface area of block B1.11.2.2 The pressure exerted by a cylindrical block is givenby the product of the blo
41、ck height, density, and the accelerationdue to gravity. When using brass of density 8.5 g/cm3(see11.1.3), a block height of 23.2 6 0.2 mm is required to give apressure on the test specimen of 2.0 6 0.2 kPa (see 6.3).12. Keywords12.1 conductivity; insulating; leather; thermalD7340073ASTM Internationa
42、l takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their o
43、wn responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be a
44、ddressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards,
45、at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D7340074
