1、Designation: D 2715 92 (Reapproved 2007)An American National StandardStandard Test Method forVolatilization Rates of Lubricants in Vacuum1This standard is issued under the fixed designation D 2715; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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. Scope1.1 This test method covers the determination of the rates ofvolatilization of lubricants in a
3、 thermal-vacuum environment atpressures and temperatures necessary to obtain a measurablerate of evaporation, or evidence of decomposition.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated w
4、ith 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:2E 296 Practice for Ionization Gage Application to SpaceSimulators
5、E 297 Methods for Calibrating Ionization Vacuum GageTubes33. Summary of Test Method3.1 A known quantity of specimen is placed in a thermalvacuum balance system and the evaporated material is con-densed on a cold plate. The weight of the specimen iscontinually recorded as a function of time for nomin
6、al constantsurface area.4. Significance and Use4.1 This test method provides data for comparison of theevaporation rate of lubricants used in unshielded bearings inthe space environment.5. Apparatus5.1 Recording Vacuum Microbalance, with capacity of 1 gor more, sensitivity of 0.01 mg or less, zero s
7、tability of 0.025mg or less for 8 h with ranges of weight change of 10 mg ormore, and 0.1 mg or less, capable of being pumped to 105Pa(107torr) or less.5.1.1 When Procedure B for the more volatile samples isused, the vacuum requirement shall be 102Pa (104torr) orless.5.2 Vacuum SystemA pumping syste
8、m capable of main-taining a starting pressure of 106to 105Pa (108to 107torr)(5.1.1). An optically dense baffle system should be used toensure freedom from back-streaming. A conventional bell jarsystem with an oil diffusion pump, a mechanical back-uppump, and an optically dense, liquid, nitrogen-cool
9、ed baffle hasbeen found satisfactory on the configuration as shown in Fig. 1.5.3 Furnace, with thermocouple indicator, capable of main-taining a constant sample temperature 63C. All parts of thisfurnace must be proved to be usable at the highest temperatureand vacuum contemplated.5.4 Recorder, capab
10、le of recording weight changes continu-ously with the balance used, to the performance specified in5.1.5.5 Specimen Container, made of 300 series stainless steelin the form of a straight cylinder with an aspect ratio of heightto diameter of approximately 1:14. Where chemical reactionsare experienced
11、 with the container, alternative materials maybe used.5.6 Contacting Thermocouple, touching solid or immersedin liquid specimens, with the leads brought out in such a wayas not to influence balance indication.5.7 Cold PlateA condensing shield cooled with liquidnitrogen to immobilize molecules evapor
12、ated from the lubri-cant which subtends, at least, a 160 arc from the center of thesample.5.8 Nude Ionization Gage, installed as described in PracticeE 296 and calibrated as described in Methods E 297.5.9 Optional Supplemental Equipment:5.9.1 Mass Spectrometer, to identify degassing products andevap
13、orating species.5.9.2 Infrared Optical Pyrometer System, for determiningthe specimen temperature. This must be calibrated against thethermocouple for each material used, due to emissivity effects.5.9.3 Copper Tab, on a cold plate facing the specimen, forX-ray analysis of the condensate.5.9.4 Noncont
14、act Specimen Thermocouple, calibratedagainst 5.5.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.11 on Engineering Sciences of High Performance Fluids and Solids.Current edition approved May 1,
15、2007. Published June 2007. Originallyapproved in 1968. Last previous edition approved in 2002 as D 2715 92 (2002).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 th
16、e standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.9.5 Pressure Recording Pen, added to the recorder.5.9.6 Time Derivative Computer, to report the rate directly.6. Reagen
17、ts and Materials6.1 Antiwetting AgentA low-surface tension material forcoating the specimen container and the thermocouple. Itsvolatility must be low enough to contribute less than 5 % to theevaporation rate of any sample to be tested.6.2 Calibration MaterialPure compound of suitablephysical propert
18、ies to simulate the lubricant under investiga-tion. (N-heptadecane and bis m-(m-phenoxyphenoxy) phenylether have been found satisfactory. Tin provides a low evapo-ration rate material, the performance of which can be checkedby the Langmuir equation.)46.3 Liquid Nitrogen, commercial grade.6.4 Helium,
19、 ACS purified grade.7. Specimen Preparation7.1 Remove dissolved gases from the bulk lot prior to testusing a separate vacuum chamber. Break the vacuum in thechamber with helium. A large enough sample of materialshould be degassed in this pretreatment so that it will suffice forall anticipated test r
20、uns. A mass spectrometer can be used toverify complete degassing.7.2 If required as evidenced by creepage of lubricant in firstrun, coat the container and the thermocouple with the anti-wetting agent (6.1). Silicones are especially likely to requirethis precaution.7.3 Add to the container the requir
21、ed amount of sample, 756 5 mg/cm2of area exposed for evaporation. Press solids andsemisolids into the container with sufficient pressure to assure4Freundlich, M. M., “Microbalance for Measuring Evaporation Rates inVacuum,” Vacuum, Vol 14, 1963, pp. 293297.FIG. 1 Apparatus for Measuring Evaporation R
22、ates in VacuumD 2715 92 (2007)2the apparent surface area approximates the real surface area. Ifa coherent surface cannot be achieved, note this fact in thereport.8. System Calibration8.1 Calibrate the system in the vacuum, using one of thecalibration materials, over the temperature range to be used,
23、following the procedure shown in 9.1-9.8.8.2 The rates obtained are compared with those predicted bythe Langmuir equation:5G 5 7.77p=M/T (1)where:G = evaporation rate, g/cm2s,p = vapor pressure, Pa,M = molecular weight, andT = temperature, K.8.2.1 If the measured rates differ by more than 620 % from
24、those calculated, take all possible corrective steps to locate thesource of the discrepancy. Use of a calibration factor is notencouraged, but may be tolerated in some cases if so reported.A factor greater than 2 or less than 0.5 casts such doubt on theresults as to practically invalidate them and r
25、equire correctiveaction.9. Procedure A9.1 Immerse the thermocouple in the sample, and bring thefurnace to approximate operating temperature.9.2 Suspend the sample and the container in position overthe furnace, and tare to near the upper limit of the range.9.3 Assemble the vacuum apparatus and pump t
26、he system togive a chamber pressure of 106to 105Pa (108to 107torr).9.4 Start the liquid nitrogen flowing and cool the cold plateto 143 K (200F) or lower. Stabilize the furnace temperature.9.5 Measure the pressure near the furnace position with thenude ionization gage.9.6 Move the furnace into operat
27、ing position surroundingthe specimen. Start the recorder, and mark the recorder chartstart of heat.9.7 Hold the temperature constant at the required level forsufficient length of time to measure the rate of weight changeand determine constancy of this rate.NOTE 1A time derivative computer may be use
28、d to report rate ofweight change directly.9.8 Monitor pressure changes manually or by the secondpen on the recorder when available. When the test temperatureis reached, and a steady weight loss condition attained,establish the sample weight and measure the evaporation ratefor this percentage point o
29、f the original weight. If the materialhas uniform molecular weight throughout, the rate will notchange with progressing evaporation. If the rate changes,continue measurement until the time for a single rate determi-nation exceeds 3 h.9.9 Determine rates for several temperatures, using a freshsample
30、for each determination. Temperature intervals of 25 K,which approximate a ten-fold increase in rate, are usuallysuitable.NOTE 2If the sample is known to be an essentially pure compound,repetitive measurements are permissible. If such purity is merely sus-pected, judgment may be made on the basis tha
31、t a sample is not to bereused after a determination in the course of which the rate has changedmore than 25 % at a single temperature. However, if the supply is limited,it is possible to obtain some meaningful data on a spot basis, as indicatedbelow.9.10 After primary data have been obtained at incr
32、easingtemperature levels on a sample which meets the above criterionof less than 25 % change during any single measurement, makespot measurements at decreasing temperature levels to detectany changes in the specimen.10. Procedure B10.1 Immerse the thermocouple, suspend the sample, andposition the fu
33、rnace as described in 9.1-9.3.10.2 Assemble the vacuum apparatus and pump the systemto give a chamber pressure of 103to 102Pa (105to 104torr).10.3 Conduct the rest of the test as described in 9.4-9.10.11. Calculations11.1 When the evaporation rate proves to be constant withinthe limit of a 25 % decr
34、ease during a determination, or 25 %/hif the determination takes less than 1 h, the evaporation rate foreach temperature is as follows:R 5 w02 w1!/t12 t0! (2)where:R = evaporation rate, g/s,w1= weight of sample at the end of the test, g,w0= initial weight of the sample, g,t1= time at the end of the
35、test, s, andt0= initial time of the test, s.11.2 If the sample has a changing rate, this rate is calculatedfor each of the standard degrees of evaporation required in 12.2as follows:11.2.1 The weight required at each evaporation level is:wr5 100w02 Ew0!/100 (3)where:wr= weight at specified evaporati
36、on loss, g,w0= initial weight of sample, g, andE = evaporation loss, %.11.2.2 Draw a line tangent to the curve on the recorder chartat each weight corresponding to the evaporation loss from11.2.1 and calculate the evaporation rate as follows:R 5 wa2 wb!/tb2 ta! (4)where:R = evaporation rate, g/s,wa=
37、 weight at one point on the tangent line, g,wb= weight at a second point on the tangent line, g,ta= time at a point on the tangent line corresponding towa,s,and5Buckley, D. H., and Johnson, R. L., “Evaporation Rates for Various Organicand Solid Lubricants in Vacuum to 108Millimetres of Mercury at 55
38、 to 1100F,”National Aeronautics and Space Administration Technical Note D-2081, 1963.D 2715 92 (2007)3tb= time at a point on the tangent line corresponding towb,s,11.3 The evaporation rate per unit area is:E 5 R/A!C (5)where:E = evaporation rate per unit area, g/cm2s,R = evaporation rate from 11.1 o
39、r 11.2, g/s,A = surface area of sample exposed for evaporation, cm2,andC = calibration factor from 8.2, if applicable.11.4 If the molecular weight of the sample is known, therates may be converted to vapor pressures by the equationgiven in 8.2.As the molecular weight enters as square root, theallowa
40、ble error is twice that for the vapor pressure.12. Report12.1 For specimens of constant rate according to 11.1, thereport shall consist of the evaporation rate per unit area foreach temperature, plus a statement of any deviations incoherence of surface as in 7.3, or variation in chamber pressurebeyo
41、nd the limits in 9.3, or decomposition found in 9.10.12.2 For specimens of variable rate according to 11.2, thereport shall consist of the evaporation rate per unit area foreach temperature at intervals of 5 % (based on the sampleweight in 7.3) from the first obtainable one as far as the data gobut
42、not to exceed a running time of 3 h unless this isspecifically required. Any deviations (see 12.1) are to bereported.12.3 For specimens of variable rate, and such limited supplyas to require reuse at another temperature, the report willcontain the data which could be obtained. For example, such arep
43、ort might indicate:5 %, 10 % measured at 473 K,15 %, 20 % measured at 498 K,25 %, 30 %, 35 % measured at 523 K,40 %, 45 %, 50 % remeasured at 498 K.13. Precision and Bias13.1 The data shown in Fig. 3 of the paper5were used toprepare the following statement on Procedure A. Cooperativetesting to prepa
44、re a statement on Procedure B is being planned.13.1.1 RepeatabilityDuplicate results by the same opera-tor should be considered suspect if they differ by more than45 % of their mean value (95 % confidence level).13.1.2 ReproducibilityThere is no immediate plan to de-termine the data necessary to dev
45、elop the reproducibilitystatement.13.2 BiasNo general statement is made on bias for thisstandard since the data used to determine the correlation cannotbe compared with accepted reference material.14. Keywords14.1 lubricants; volatilization; volatilization ratesASTM International takes no position r
46、especting 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 own responsibility.Thi
47、s 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 addressed to ASTM Inte
48、rnational 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, at the address shown
49、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).D 2715 92 (2007)4
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