ASTM D2578-99a
(Test Method)Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films
Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films
SCOPE
1.1 This test method covers the measurement of the wetting tension of a polyethylene or polypropylene film surface in contact with drops of specific test solutions in the presence of air.
1.2 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. Specific hazards statements are given in Section 8.
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 2578 – 99a
Standard Test Method for
Wetting Tension of Polyethylene and Polypropylene Films
This standard is issued under the fixed designation D 2578; 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.
gGL cosu5gGS2gSL (1)
1. Scope *
1.1 This test method covers the measurement of the wetting
where:
tension of a polyethylene or polypropylene film surface in
u = angle of contact of the edge of the drop with the
contact with drops of specific test solutions in the presence of
solid surface,
air.
gGL = surface energy of the gas - liquid interface,
1.2 This standard does not purport to address all of the
gGS = surface energy of the gas - solid interface, and
safety concerns, if any, associated with its use. It is the gSL = surface energy of the solid - liquid interface.
responsibility of the user of this standard to establish appro-
4.1.1 The right side of the above equation (the difference
priate safety and health practices and determine the applica-
between the surface energies of the gas - solid and solid -
bility of regulatory limitations prior to use. Specific hazards
liquid interfaces) is defined as the wetting tension of the solid
statements are given in Section 8.
surface. It is not a fundamental property of the surface but
depends on interaction between the solid and a particular
NOTE 1—This test method is equivalent to ISO 8296.
environment.
2. Referenced Documents 4.1.2 When the gas is air saturated with vapors of the liquid,
gGL will be the surface tension of the liquid. If the angle of
2.1 ASTM Standards:
contact is 0° the liquid is said to just wet the surface of the
D 618 Practice for Conditioning Plastics for Testing
solid, and in this particular case (since cos u = 1) the wetting
2.2 ISO Standard:
tension of the solid will be equal to the surface tension of the
ISO 8296
liquid.
3. Summary of Test Method 4.2 The ability of polyethylene and polypropylene films to
retain inks, coatings, adhesives, etc., is primarily dependent
3.1 In this test method drops of a series of mixtures of
upon the character of their surfaces, and can be improved by
formamide and ethyl Cellosolve of gradually increasing sur-
one of several surface-treating techniques. These same treating
face tension are applied to the surface of the polyethylene or
techniques have been found to increase the wetting tension of
polypropylene film until a mixture is found that just wets the
a polyethylene or a polypropylene film surface in contact with
film surface. The wetting tension of the polyethylene or
mixtures of formamide and ethyl Cellosolve in the presence of
polypropylene film surface will be approximated by the surface
air. It is therefore possible to relate the wetting tension of a
tension of this particular mixture.
polyethylene or a polypropylene film surface to its ability to
4. Significance and Use
accept and retain inks, coatings, adhesives, etc. The measured
wetting tension of a specific film surface can only be related to
4.1 When a drop of liquid rests on the surface of a solid, and
acceptable ink, coating, or adhesive retention through experi-
a gas is in contact with both, the forces acting at the interfaces
ence. Wetting tension in itself is not a completely acceptable
must balance. These forces can be represented by surface
measure of ink, coating, or adhesive adhesion.
energies acting in the direction of the surfaces and it follows
that:
NOTE 2—A wetting tension of 35 dynes/cm or higher has been
generally found to reveal a degree of treatment normally regarded as
acceptable for tubular film made from Type 1 polyethylene and intended
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
for commercial flexographic printing. It is, however, possible that some
and is the direct responsibility of Subcommittee D20.19 on Film and Sheeting.
other level of wetting tension may be required to indicate the acceptability
Current edition approved July 10, 1999. Published August 1999. Originally
of polyethylene films made by other processes, or from other types of
published as D 2578 – 67. Last previous edition D 2578 – 99.
polyethylene, or intended for other uses.
Annual Book of ASTM Standards, Vol 08.01.
At the present date, insufficient experience has been gained to state a
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036. generally acceptable level of wetting tension for polypropylene films for
Registered trademark of Union Carbide Corp. for ethylene glycol monoethyl
commercial flexographic printing.
ether.
*A Summary of Changes section appears at the end of this standard.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 2578
5. Interferences 7.2 If desired, add to each of the formamide ethyl Cello-
solve mixtures a very small amount of dye of high tinctorial
5.1 Since the wetting tension of a polyethylene or polypro-
value. The dye used should be of such color as to make drops
pylene film in contact with a drop of liquid in the presence of
or thin films of the solutions clearly visible on the surface of
air is a function of the surface energies of both the air - film and
polyethylene or polypropylene film and must be of such
film - liquid interfaces, any trace of surface-active impurities in
chemical composition that it will not measurably affect the
the liquid reagents or on the film may affect the results. It is,
wetting tension of the solutions in the concentration used.
therefore, important that the portion of the film surface to be
tested not be touched or rubbed, that all equipment be
8. Hazards
scrupulously clean, and that reagent purity be carefully
8.1 Formamide may cause skin irritation and is particularly
guarded. Glass apparatus in particular is likely to be contami-
dangerous in direct contact with the eyes. Safety goggles
nated with detergents having very strong surface tension
should be worn when making up new test mixtures.
reducing ability unless specific precautions are taken to ensure
8.2 Ethyl Cellosolve is a highly flammable solvent.
their absence such as cleaning with chromic-sulfuric acid and
8.3 Both ethyl Cellosolve and formamide are toxic and
rinsing with distilled water.
should be handled with due precaution.
6. Apparatus 8.4 All tests should be performed with adequate ventilation.
6.1 Cotton-Tipped Wooden Applicators, approximately 150
9. Sampling
mm (6 in.) in length.
9.1 The minimum amount of film required for this test
6.2 Burets, two, 50-mL.
depends upon the skill of the operator. This usually amounts to
6.3 Bottles, 100-mL, with caps and labels.
one sample across the entire width of a roll in order to obtain
a representative value.
7. Reagents and Materials
9.2 Extreme care must be taken to prevent the surface of the
7.1 Prepare mixtures of reagent grade formamide
film sample from being touched or handled in the areas upon
(HCONH ) and reagent grade ethyl Cellosolve
which the test is to be made.
(CH CH OCH CH OH) in the proportions shown in Table 1
3 2 2 2
9.3 Usually it will be adequate to make one determination at
for the integral values of wetting tension in the range over
1 1 3
each location ⁄4, ⁄2, ⁄4of the way across the width of the film,
which measurements are to be made. For extremely precise
to arrive at an average value for the sample or to determine
work, mixtures for determining fractional values of wetting
when treatment is uneven.
tension may be made up by interpolating between the concen-
trations shown in Table 1.
10. Conditioning
NOTE 3—Although the mixtures of ethyl Cellosolve and formamide
10.1 Conditioning—Condition the test specimens at 23 6
used in this test method are relatively stable, exposure to extremes of
2°C (73.4 6 3.6°F) and 50 6 5 % relative humidity for not less
temperature or humidity should be avoided.
than 40 h prior to test in accordance with Procedure A of
Practice D 618, for those tests where conditioning is required.
TABLE 1 Concentration of Ethyl Cellosolve—Formamide
In cases of disagreement, the tolerances shall be 61°C
Mixtures Used in Measuring Wetting Tension of
(61.8°F) and 62 % relative humidity.
Polyethylene and Polypropylene Films
10.2 Test Conditions—Conduct tests in the standard labora-
A B
Formamide, Ethyl Cellosolve, Wetting Tension,
tory atmosphere of 23 6 2
...
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