ISO 15989:2004

INTERNATIONAL ISO
STANDARD 15989
First edition
2004-12-01
Plastics — Film and sheeting —
Measurement of water-contact angle of
corona-treated films
Plastiques — Film et feuille — Détermination de l'angle de contact avec
l'eau des feuils traités par effluve

Reference number
ISO 15989:2004(E)
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ISO 15989:2004(E)
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ISO 15989:2004(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test liquid . 4
7 Test specimens . 4
8 Conditioning . 4
9 Test conditions . 4
10 Procedure . 4
11 Calculation and interpretation of results . 6
12 Precision . 8
13 Test report . 8
Annex A (informative) Significance and use of contact-angle measurements . 9
Annex B (informative) Interference effects in the measurement of the contact angle . 11
Annex C (informative) Surface tension and contact angle . 12
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ISO 15989:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15989 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 11, Products.
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INTERNATIONAL STANDARD ISO 15989:2004(E)
Plastics — Film and sheeting — Measurement of water-contact
angle of corona-treated films
1Scope
This International Standard specifies a method of measuring the contact angle of water droplets on corona-
treated polymer film surfaces and subsequently determining the wetting tension of the film.
The method is applicable to practically any polymer film. It is not applicable, however, if the surface of the film
exhibits a chemical affinity for water.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ASTM E 691:1999, Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a
Test Method (Equivalent to ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and
results — Part2: Basic method for the determination of repeatability and reproducibility of a standard
measurement method)
ASTM D 724, Standard Test Method for Surface Wettability of Paper (Angle-of-Contact Method)
ASTM D 5946, Standard Test Method for Corona-Treated Polymer Films Using Water Contact Angle
Measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
surface energy
energy associated with the intermolecular forces at the interface between two surfaces, measured as free
energy per unit area
NOTE It is expressed in mN/m.
3.2
wetting tension
γ
c
tension taken to be equal to the surface tension of the liquid which just exhibits a zero contact angle with the
surface of a polymer film
NOTE This is used to give an estimate of the film's surface energy in mN/m. The unit dyne/cm is also used in industry for
surface energy and wetting tension (1 dyne/cm= 1 mN/m).
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ISO 15989:2004(E)
3.3
polarity
value which quantifies the concentration of polar functional groups on a polymer film surface
NOTE It is expressed as the polar component of the surface energy over the total surface energy.
3.4
static contact angle
θ
angle between a plane solid surface and the tangent drawn in the vertical plane at the interface between the
plane solid surface and the surface of a droplet of liquid resting on the surface
4Principle
Droplets of water are placed on a specimen of film and the contact angle measured. The wetting tension of the
film is then determined from a conversion chart.
See Annex A for the significance and use of contact-angle measurements and Annex B for interference effects
in the measurement of the contact angle.
5 Apparatus
5.1 Contact-angle meter (goniometer)
A commercially available contact-angle meter, including a light source, optical system, specimen stage and
liquid delivery system, may be used.
The light source can be a halogen, incandescent or fibre-optic type of lamp, as long as neither the specimen nor
the liquid is affected by the heat from the light source.
The viewing optics can be video, CCD camera, ocular lens or projection optics and shall be configured such that
magnifications from ×6 to ×30 can be used.
The specimen stage shall be such that the specimen can be positioned with the test surface flat and horizontal.
When the specimen is moved to view a new area, it shall be possible to avoid the previously wetted area.
The liquid-delivery system shall be a pump-driven or manual microsyringe. For the greatest droplet-formation
accuracy, a small-capacity, i.e. 100µl to 250µl, microsyringe shall be used.
In order to be able to test liquids requiring different droplet sizes, it shall be possible to accommodate flat-tipped
needles of various gauges from 24 gauge to 32 gauge. Stainless-steel needles are preferred, but other types,
such as needles coated with polytetrafluoroethylene, may also be used.
5.2 Droplet image projection apparatus
Alternatively, a droplet-projection contact-angle meter (see Figure 1) may be used. It shall be capable of
projecting the image of a droplet of liquid on the surface of the substrate onto a screen so that the angle of the
tangent to the droplet at the substrate surface can be measured. The apparatus shall consist of the following
elements:
5.2.1 Angle-measuring instrument, such as a protractor or similar device, for measurement of the contact
angle.
5.2.2 Filter, used to reduce the heat falling on the specimen and the droplet.
5.2.3 Ventilated lamp house, containing a light source.
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ISO 15989:2004(E)
Key
1 250 W projection lamp
2tube
3lens
4 hypodermic syringe
5specimen
6 microscope
7water cell
8 horizontal specimen stage
9 frosted-glass screen
Figure 1 — User-constructed droplet-projection contact-angle meter
5.2.4 Microscope draw tube, suitable for projecting the image of the droplet onto a screen with an
enlargement of ×25.
5.2.5 Frosted-glass screen, onto which the droplet image is projected.
5.2.6 Horizontal specimen stage, capable of accommodating the test specimen, and with a means of
adjusting the stage vertically.
5.2.7 Tube, containing a lens to concentrate the beam of light.
5.2.8 Hypodermic syringe, capacity 1ml, fitted with a flat-tipped 27 gauge stainless-steel needle and
capable of providing 150 to 200 droplets.
5.3 Computer-based systems
PC-based systems with automatic image analysis capabilities are available for contact-angle measurements.
These systems provide a greater degree of accuracy in comparison to the droplet-projection system.
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ISO 15989:2004(E)
6 Test liquid
Use distilled water or ultra-pure water (as used for HPLC). Keep the water in a clean container.
NOTE 1 Reagent-grade deionized water may also be used, but the results will not be as accurate.
NOTE 2 Any contamination introduced into the water will affect the results.
7 Test specimens
7.1 The minimum amount of film required for this test is a strip approximately 25 mm wide and 300 mm long.
If the specimen is taken from a roll, the direction of the specimen relative to the machine direction of the web
shall be noted.
7.2 Extreme care shall be taken to prevent the surface of the specimen from being touched or handled in the
areas in which the test is to be made.
7.3 The number of measurements per specimen shall be determined using published tables for sampling
plans. The recommended number of readings per specimen is ten.
NOTE Complete tables can be found in most books on quality control. See e.g. J.A. Duncan, Quality Control and Industrial
Statistics, 3rd ed., Irwin, Homewood, IL, USA, 1965.
7.4 For the purpose of determining the wetting-tension profile across the width of the roll, contact-angle
measurements can be made at intervals of one specimen length (i.e. approximately 300 mm) across the width
of the roll.
8 Conditioning
8.1 Conditioning is not generally required for routine quality assurance or process control measurements as it
will affect the measured value which will no longer be representative of the actual conditions.
8.2 Conditioning is required for interlaboratory measurements intended to compare results. In such cases,
◦ ◦
condition the specimens at C± 2 C and (50± 5) % relative humidity for not less than 40 h prior to testing.
23
◦
In cases of disagreement, the tolerances shall be ± 1 C and ±2% relative humidity. Whenever possible,
conduct testing under the same conditions as used for conditioning.
9 Test conditions
Special test conditions are not generally required for routine quality assurance.
10 Procedure
10.1 Place a specimen on the specimen holder of the instrument. Make sure the specimen is lying flat without
wrinkles and distortions.
10.2 Suspend a 1µl2 to µl droplet of water (see Clause 6) at the end of the syringe needle. Bring the surface
of the mounted specimen into contact with the pendant droplet. Then move the surface of the specimen away to
complete droplet transfer (see Figure 2). Do not drop or squirt droplets on to the specimen surface.
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ISO 15989:2004(E)
NOTE Larger, 5µl8 to µl, droplets may be used. However, larger droplets may lose their spherical shape, resulting in some
degree of error.
a) Droplet on syringe b) Droplet transfer c) Droplet on surface
Key
1 syringe needle
2 water
3 specimen surface
Figure 2 — Water droplet transfer technique
10.3 Use one of measurement techniques a), b) and c) described below to determine the contact-angle value.
Follow the instrument manufacturer's instructions concerning the maximum time between transferring the water
droplet and measurement, if specified. If not specified, make the measurement within 1 min± 10 s of droplet
transfer.
a) Measure the contact angle directly with a protractor, aligning the protractor cursor line with the tangent to
the droplet at the specimen surface.
b) Measure the angle between the specimen surface and the line from the three-phase point to the apex of the
droplet. Multiply the number obtained by 2 to give the contact angle.
NOTE This technique is the subject o
...