ASTM standard\ASTM D1505-1998 (Part -1)

aliaslam

Designation: D 1505 – 98 An American National Standard
Standard Test Method for
Density of Plastics by the Density-Gradient Technique1
This standard is issued under the fixed designation D 1505; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 This test method covers the determination of the density
of solid plastics.
1.2 This test method is based on observing the level to
which a test specimen sinks in a liquid column exhibiting a
density gradient, in comparison with standards of known
density.
NOTE 1—The comparable ISO method is R1183-1987.
1.3 The values stated in SI units are to be regarded as the
standard.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate
safety and health practices and determine the applicability
of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D 941 Test Method for Density and Relative Density (Specific
Gravity) of Liquids by Lipkin Bicapillary Pycnometer2
D 1928 Practice for Preparation of Compression-Molded
Polyethylene Test Sheets and Test Specimens3
D 2839 Practice for Use of a Melt Index Strand for Determining
Density of Polyethylene4
E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method5
2.2 ISO Standard:
R 1183-1987 Methods for Determining the Density and
Relative Density of Noncellular Plastics6
3. Terminology
3.1 Definition:
3.1.1 density of plastics—the weight per unit volume of
material at 23°C, expressed as follows:
D23C, g/cm 3
(1)
NOTE 2—Density is to be distinguished from specific gravity, which is
the ratio of the weight of a given volume of the material to that of an equal
volume of water at a stated temperature.
4. Significance and Use
4.1 The density of a solid is a conveniently measurable
property which is frequently useful as a means of following
physical changes in a sample, as an indication of uniformity
among samples, and a means of identification.
4.2 This test method is designed to yield results accurate to
better than 0.05 %.
NOTE 3—Where accuracy of 0.05 % or better is desired, the gradient
tube shall be constructed so that vertical distances of 1 mm shall represent
density differences no greater than 0.0001 g/cm.3 The sensitivity of the
column is then 0.0001 g/cm3·mm. Where less accuracy is needed, the
gradient tube shall be constructed to any required sensitivity.
5. Apparatus
5.1 Density-Gradient Tube—A suitable graduate with
ground-glass stopper.7
5.2 Constant-Temperature Bath—A means of controlling
the temperature of the liquid in the tube at 23 6 0.1°C. A
thermostatted water jacket around the tube is a satisfactory and
convenient method of achieving this.
5.3 Glass Floats—A number of calibrated glass floats covering
the density range to be studied and approximately evenly
distributed throughout this range.
5.4 Pycnometer, for use in determining the densities of the
standard floats.
5.5 Liquids, suitable for the preparation of a density gradient
(Table 1).
NOTE 4—It is very important that none of the liquids used in the tube
exert a solvent or chemical effect upon the test specimens during the time
of specimen immersion.
5.6 Hydrometers—A set of suitable hydrometers covering
the range of densities to be measured. These hydrometers
should have 0.001 density graduations.
1 This test method is under the jurisdiction of ASTM Committee D-20 on Plastic
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods
(Section D20.70.01).
Current edition approved March 10, 1998. Published February 1999. Originally
published as D 1505 – 57 T. Last previous edition D 1505 – 96.
2 Discontinued; see 1992 Annual Book of ASTM Standards, Vol 05.01.
3 Annual Book of ASTM Standards, Vol 08.01.
4 Annual Book of ASTM Standards, Vol 08.02.
5 Annual Book of ASTM Standards, Vol 14.02.
6 Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036. 7 Tubes similar to those described in Refs (6) and (12) may also be used.
1
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
COPYRIGHT American Society for Testing and Materials
Licensed by Information Handling Services
5.7 Analytical Balance, with a sensitivity of 0.001 g.
5.8 Siphon or Pipet Arrangement, for filling the gradient
tube. This piece of equipment should be constructed so that the
rate of flow of liquid may be regulated to 10 6 5 mL/min.
6. Test Specimen
6.1 The test specimen shall consist of a piece of the material
under test. The piece may be cut to any shape convenient for
easy identification, but should have dimensions that permit the
most accurate position measurement of the center of volume of
the suspended specimen (Note 5). Care should be taken in
cutting specimens to avoid change in density resulting from
compressive stress.
NOTE 5—The equilibrium positions of film specimens in the thickness
range from 0.025 to 0.051 mm (0.001 to 0.002 in.) may be affected by
interfacial tension. If this affect is suspected, films not less than 0.127 mm
(0.005 in.) in thickness should be tested.
6.2 The specimen shall be free of foreign matter and voids
and shall have no cavities or surface characteristics that will
cause entrapment of bubbles.
7. Preparation of Density-Gradient Columns
7.1 Preparation of Standard Glass Floats8—Prepare glass
floats by any convenient method such that they are fully
annealed, approximately spherical, have a maximum diameter
less than one fourth the inside diameter of the column, and do
not interfere with the test specimens. Prepare a solution (400 to
600 mL) of the liquids to be used in the gradient tube such that
the density of the solution is approximately equal to the desired
lowest density. When the floats are at room temperature, drop
them gently into the solution. Save the floats that sink very
slowly, and discard those that sink very fast, or save them for
another tube. If necessary to obtain a suitable range of floats,
grind selected floats to the desired density by rubbing the head
part of the float on a glass plate on which is spread a thin slurry
of 400 or 500-mesh silicon carbide (Carborundum) or other
appropriate abrasive. Progress may be followed by dropping
the float in the test solution at intervals and noting its change
in rate of sinking.
7.2 Calibration of Standard Glass Floats (see Appendix
X1):
7.2.1 Place a tall cylinder in the constant-temperature bath
maintained at 23 6 0.1°C. Then fill the cylinder about two
thirds full with a solution of two suitable liquids, the density of
which can be varied over the desired range by the addition of
either liquid to the mixture. After the cylinder and solution
have attained temperature equilibrium, place the float in the
solution, and if it sinks, add the denser liquid by suitable means
with good stirring until the float reverses direction of movement.
If the float rises, add the less dense liquid by suitable
means with good stirring until the float reverses direction of
movement.
7.2.2 When reversal of movement has been observed, reduce
the amount of the liquid additions to that equivalent to
0.0001-g/cm3 density. When an addition equivalent to 0.0001-
g/cm3 density causes a reversal of movement, or when the float
remains completely stationary for at least 15 min, the float and
liquid are in satisfactory balance. The cylinder must be covered
whenever it is being observed for balance, and the liquid
surface must be below the surface of the liquid in the
constant-temperature bath. After vigorous stirring, the liquid
may continue to move for a considerable length of time; make
sure that the observed movement of the float is not due to liquid
motion by waiting at least 15 min after stirring has stopped
before observing the float.
7.2.3 When balance has been obtained, fill a freshly cleaned
and dried pycnometer with the solution and place it in the 23
6 0.1°C bath for sufficient time to allow temperature equilibrium
of the glass. Determine the density of the solution by
normal methods (Test Method D 941) and make “in vacuo”
corrections for all weighings. Record this as the density of the
float. Repeat the procedure for each float.
7.3 Gradient Tube Preparation (see appendix for details):
7.3.1 Method A—Stepwise addition.
7.3.2 Method B—Continuous filling (liquid entering gradient
tube becomes progressively less dense).
7.3.3 Method C—Continuous filling (liquid entering gradient
tube becomes progressively more dense).
8. Conditioning
8.1 Test specimens whose change in density on conditioning
may be greater than the accuracy required of the density
determination shall be conditioned before testing in accordance
with the method listed in the applicable ASTM material
specification.