ASTM D2715-92(2002)

An American National Standard
Designation: D 2715 – 92 (Reapproved 2002)
Standard Test Method for
Volatilization Rates of Lubricants in Vacuum
This standard is issued under the fixed designation D 2715; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope mg or less for 8 h with ranges of weight change of 10 mg or
−5
more, and 0.1 mg or less, capable of being pumped to 10 Pa
1.1 This test method covers the determination of the rates of
−7
(10 torr) or less.
volatilization of lubricants in a thermal-vacuum environment at
5.1.1 When Procedure B for the more volatile samples is
pressures and temperatures necessary to obtain a measurable
−2 −4
used, the vacuum requirement shall be 10 Pa (10 torr) or
rate of evaporation, or evidence of decomposition.
less.
1.2 The values stated in SI units are to be regarded as the
5.2 Vacuum System—A pumping system capable of main-
standard.
−6 −5 −8 −7
taining a starting pressure of 10 to 10 Pa (10 to 10 torr)
1.3 This standard does not purport to address all of the
(5.1.1). An optically dense baffle system should be used to
safety concerns, if any, associated with its use. It is the
ensure freedom from back-streaming. A conventional bell jar
responsibility of the user of this standard to establish appro-
system with an oil diffusion pump, a mechanical back-up
priate safety and health practices and determine the applica-
pump, and an optically dense, liquid, nitrogen-cooled baffle has
bility of regulatory limitations prior to use.
been found satisfactory on the configuration as shown in Fig. 1.
2. Referenced Documents
5.3 Furnace, with thermocouple indicator, capable of main-
taining a constant sample temperature 63°C. All parts of this
2.1 ASTM Standards:
furnace must be proved to be usable at the highest temperature
E 296 Practice for Ionization Gage Application to Space
and vacuum contemplated.
Simulators
5.4 Recorder, capable of recording weight changes continu-
E 297 Methods for Calibrating Ionization Vacuum Gage
ously with the balance used, to the performance specified in
Tubes
5.1.
3. Summary of Test Method
5.5 Specimen Container, made of 300 series stainless steel
in the form of a straight cylinder with an aspect ratio of height
3.1 A known quantity of specimen is placed in a thermal
to diameter of approximately 1:14. Where chemical reactions
vacuum balance system and the evaporated material is con-
are experienced with the container, alternative materials may
densed on a cold plate. The weight of the specimen is
be used.
continually recorded as a function of time for nominal constant
5.6 Contacting Thermocouple, touching solid or immersed
surface area.
in liquid specimens, with the leads brought out in such a way
4. Significance and Use
as not to influence balance indication.
5.7 Cold Plate—A condensing shield cooled with liquid
4.1 This test method provides data for comparison of the
nitrogen to immobilize molecules evaporated from the lubri-
evaporation rate of lubricants used in unshielded bearings in
cant which subtends, at least, a 160° arc from the center of the
the space environment.
sample.
5. Apparatus
5.8 Nude Ionization Gage, installed as described in Practice
E 296 and calibrated as described in Methods E 297.
5.1 Recording Vacuum Microbalance, with capacity of 1 g
5.9 Optional Supplemental Equipment:
or more, sensitivity of 0.01 mg or less, zero stability of 0.025
5.9.1 Mass Spectrometer, to identify degassing products and
evaporating species.
This test method is under the jurisdiction of ASTM Committee D02 on
5.9.2 Infrared Optical Pyrometer System, for determining
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
the specimen temperature. This must be calibrated against the
D02.11 on Engineering Sciences of High Performance Fluids and Solids.
thermocouple for each material used, due to emissivity effects.
Current edition approved Oct. 15, 1992. Published December 1992. Originally
published as D 2715 – 68. Last previous edition D 2715 – 86.
5.9.3 Copper Tab, on a cold plate facing the specimen, for
Annual Book of ASTM Standards, Vol 15.03.
X-ray analysis of the condensate.
Discontinued; see 1985 Annual Book of ASTM Standards, Vol 15.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 2715 – 92 (2002)
FIG. 1 Apparatus for Measuring Evaporation Rates in Vacuum
5.9.4 Noncontact Specimen Thermocouple, calibrated 6.3 Liquid Nitrogen, commercial grade.
against 5.5.
6.4 Helium, ACS purified grade.
5.9.5 Pressure Recording Pen, added to the recorder.
5.9.6 Time Derivative Computer, to report the rate directly.
7. Specimen Preparation
6. Reagents and Materials
7.1 Remove dissolved gases from the bulk lot prior to test
using a separate vacuum chamber. Break the vacuum in the
6.1 Antiwetting Agent—A low-surface tension material for
chamber with helium. A large enough sample of material
coating the specimen container and the thermocouple. Its
volatility must be low enough to contribute less than 5 % to the should be degassed in this pretreatment so that it will suffice for
evaporation rate of any sample to be tested. all anticipated test runs. A mass spectrometer can be used to
6.2 Calibration Material—Pure compound of suitable verify complete degassing.
physical properties to simulate the lubricant under investiga-
7.2 If required as evidenced by creepage of lubricant in first
tion. (N-heptadecane and bis m-(m-phenoxyphenoxy) phenyl
run, coat the container and the thermocouple with the anti-
ether have been found satisfactory. Tin provides a low evapo-
wetting agent (6.1). Silicones are especially likely to require
ration rate material, the performance of which can be checked
this precaution.
by the Langmuir equation.)
7.3 Add to the container the required amount of sample, 75
6 5 mg/cm of area exposed for evaporation. Press solids and
Freundlich, M. M., “Microbalance for Measuring Evaporation Rates in semisolids into the container with sufficient pressure to assure
Vacuum,” Vacuum, Vol 14, 1963, pp. 293–297.
D 2715 – 92 (2002)
the apparent surface area approximates the real surface area. If 9.9 Determine rates for several temperatures, using a fresh
a coherent surface cannot be achieved, note this fact in the sample for each determination. Temperature intervals of 25 K,
report. which approximate a ten-fold increase in rate, are usually
suitable.
8. System Calibration
NOTE 2—If the sample is known to be an essentially pure compound,
8.1 Calibrate the system in the vacuum, using one of the
repetitive measurements are permissible. If such purity is merely sus-
calibration materials, over the temperature range to be used, pected, judgment may be made on the basis that a sample is not to be
reused after a determination in the course of which the rate has changed
following the procedure shown in 9.1-9.8.
more than 25 % at a single temperature. However, if the supply is limited,
8.2 The rates obtained are compared with those predicted by
it is possible to obtain some meaningful data on a spot basis, as indicated
the Langmuir equation:
below.
G 5 7.77p M/T (1)
=
9.10 After primary data have been obtained at increasing
temperature levels on a sample which meets the above criterion
where:
...