ISO/TS 14778:2021
(Main)Paper and board — Measurement of water contact angle by optical methods
Paper and board — Measurement of water contact angle by optical methods
This document specifies the method for optical assessment of the contact angle between water and the surface of paper and board, where the process of droplet formation, application to planar substrates, or measurement of the droplet shape in contact with the solid is performed by automated equipment. The limits of measurement are determined by the capabilities of the instrumentation used. The instrumental capabilities defined by this document use a digital image capturing system operating at a minimum of 50 frames per second and needs the ability to perform the first measurement after no more than 20 ms to 40 ms contact between the droplet and substrate. The test method is applicable to most kinds of paper or board however it cannot be applicable to structured materials.
Papier et carton — Mesurage de l'angle de contact de l'eau par des méthodes optiques
General Information
Buy Standard
Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 14778
First edition
2021-01
Paper and board — Measurement of
water contact angle by optical methods
Papier et carton — Mesurage de l'angle de contact de l'eau par des
méthodes optiques
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and references . 1
4 Principle . 2
5 Reagents . 3
6 Apparatus . 3
7 Sampling . 5
8 Conditioning . 5
9 Preparation of test pieces . 5
10 Procedure. 6
10.1 General . 6
10.2 Mounting of the test piece . 6
10.3 Calibration and adjustment of apparatus . 6
10.4 Method of measurement . 7
11 Expression of results . 8
12 Test report . 8
Annex A (informative) Precision . 9
Bibliography .12
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee
SC 2, Test methods and quality specifications for paper and board.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
Introduction
The interaction between the liquid and the solid phases influences the contact angle. Contact angles
above 90° define a situation where the liquid is repelled by the solid; below 90° defines a situation of
attraction where the liquid wets the surface. The magnitude above or below 90° shows the relative
degree of repulsion or attraction between the two phases.
On many surfaces the contact angle varies with duration of contact through a combination of spreading,
penetration (in the case of porous substrates) and evaporation. Both manual and automated apparatus
are available for optical measurement of contact angle, but automated equipment is preferred for
precision and rapid measurement, and because it is often applicable to a wider combination of liquid
and paper or board samples.
Contact angle measurement is used to predict how liquids interact with paper surfaces. This document
describes the most common form of test, using water as probe liquid, and from the data a probable
interaction between the paper surface and another liquid with comparable surface tension and viscosity
characteristics is often inferred. The veracity of this inference should be tested wherever possible.
Notwithstanding the above, contact angle measurement is used widely as a predictive tool in several
industrial settings, for example:
a) for assessing writing, ruling or printing quality with water-based or solvent based inks (e.g. in
inkjet, gravure or flexographic printing);
b) for gluing applications;
c) for wet offset lithographic printing;
d) for hot-foil applications;
e) for barrier or release coatings;
f) for coating applications.
In some cases, measurements of contact angle are used to calculate two or three components of the
surface energy of the paper or board, which requires the use of two or three liquids of known surface
energy, respectively. In such cases, the values calculated for the components of surface energy will be
[1]
related to the liquids chosen for the analysis . This is not covered in this document.
The test method described in this document is sometimes known as ‘static’ or even ‘sessile drop’,
since on many surfaces the droplet remains static and in equilibrium with the paper surface and air.
Yet on paper and board surfaces the droplet often changes its dimensions with time, due to sorption
and wetting phenomena. This has led some instrument manufacturers and researchers to describe the
automated optical technique outlined in this document as measurement of the ‘dynamic’ contact angle.
This document does not use the term ‘dynamic’ because this nomenclature confuses a measurement
changing with respect to time with one that changes due to a plane of shear. For example, the Willhelmy
plate method of contact angle measurement, which measures the force required to push a solid material
[2]
into and then pull it out from a liquid reservoir, is a true ‘dynamic’ method .
Similarly, this document does not cover the situation where a droplet is placed on a horizontal surface
that is subsequently tilted so that gravity causes the droplet to assume an asymmetric shape, then to
commence movement.
TECHNICAL SPECIFICATION ISO/TS 14778:2021(E)
Paper and board — Measurement of water contact angle by
optical methods
1 Scope
This document specifies the method for optical assessment of the contact angle between water and the
surface of paper and board, where the process of droplet formation, application to planar substrates, or
measurement of the droplet shape in contact with the solid is performed by automated equipment.
The limits of measurement are determined by the capabilities of the instrumentation used. The
instrumental capabilities defined by this document use a digital image capturing system operating at
a minimum of 50 frames per second and needs the ability to perform the first measurement after no
more than 20 ms to 40 ms contact between the droplet and substrate.
The test method is applicable to most kinds of paper or board however it cannot be applicable to
structured materials.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for
monitoring the atmosphere and conditioning of samples
ISO 13530, Water quality – Guidance on analytical quality control for chemical and physicochemical water
analysis
3 Terms and references
For the purposes of this document, the following terms and definitions apply:
3.1
baseline
line of contact between the water droplet and paper or board surface, determined by optical means and
taken as the plane from which the contact angle is measured
Note 1 to entry: Precise measurement of contact angle requires precise assessment of the baseline. For the
optical system to achieve the best estimate of the baseline, it may be necessary to tilt the camera so that it views
the droplet slightly from above, at a shallow angle (typically 0-3° relative to the horizontal), rather than directly
from the side (0°). Experience shows this small change in viewing angle does not affect the measured contact
[3]
angle value but can enhance detection of the baseline .
3.2
contact angle
Θ
angle to a baseline (3.1), formed by means of a tangent on the droplet contour through one of the three-
phase points at the specified contact time
Note 1 to entry: The contact angle is expressed in degrees (°).
3.3
contact time
duration of contact(s) between the water droplet and the test piece surface, as measured automatically
from the instant at which the timing mechanism is triggered to the instant of measurement
3.4
droplet height
H
distance from the top of the droplet in contact with the test piece surface as measured from the baseline
(3.1) at the specified contact time (3.3)
Note 1 to entry: The droplet height is expressed in millimetres.
3.5
droplet base diameter
D
maximum width of the droplet base in contact with the test piece surface, as measured along the
baseline (3.1) at the specified contact time (3.3)
Note 1 to entry: The droplet base diameter is expressed in millimetres.
3.6
three-phase point
point of intersection of the liquid/solid, liquid/gaseous and solid/gaseous boundary lines
4 Principle
A water droplet is applied to the horizontal planar surface of paper or board, the angle of contact it
makes with the material is assessed by optical digital imaging.
Figure 1 — Principle of measurement
2 © ISO 2021 – All rig
...
TECHNICAL ISO/TS
SPECIFICATION 14778
First edition
2021-01
Paper and board — Measurement of
water contact angle by optical methods
Papier et carton — Mesurage de l'angle de contact de l'eau par des
méthodes optiques
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and references . 1
4 Principle . 2
5 Reagents . 3
6 Apparatus . 3
7 Sampling . 5
8 Conditioning . 5
9 Preparation of test pieces . 5
10 Procedure. 6
10.1 General . 6
10.2 Mounting of the test piece . 6
10.3 Calibration and adjustment of apparatus . 6
10.4 Method of measurement . 7
11 Expression of results . 8
12 Test report . 8
Annex A (informative) Precision . 9
Bibliography .12
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee
SC 2, Test methods and quality specifications for paper and board.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
Introduction
The interaction between the liquid and the solid phases influences the contact angle. Contact angles
above 90° define a situation where the liquid is repelled by the solid; below 90° defines a situation of
attraction where the liquid wets the surface. The magnitude above or below 90° shows the relative
degree of repulsion or attraction between the two phases.
On many surfaces the contact angle varies with duration of contact through a combination of spreading,
penetration (in the case of porous substrates) and evaporation. Both manual and automated apparatus
are available for optical measurement of contact angle, but automated equipment is preferred for
precision and rapid measurement, and because it is often applicable to a wider combination of liquid
and paper or board samples.
Contact angle measurement is used to predict how liquids interact with paper surfaces. This document
describes the most common form of test, using water as probe liquid, and from the data a probable
interaction between the paper surface and another liquid with comparable surface tension and viscosity
characteristics is often inferred. The veracity of this inference should be tested wherever possible.
Notwithstanding the above, contact angle measurement is used widely as a predictive tool in several
industrial settings, for example:
a) for assessing writing, ruling or printing quality with water-based or solvent based inks (e.g. in
inkjet, gravure or flexographic printing);
b) for gluing applications;
c) for wet offset lithographic printing;
d) for hot-foil applications;
e) for barrier or release coatings;
f) for coating applications.
In some cases, measurements of contact angle are used to calculate two or three components of the
surface energy of the paper or board, which requires the use of two or three liquids of known surface
energy, respectively. In such cases, the values calculated for the components of surface energy will be
[1]
related to the liquids chosen for the analysis . This is not covered in this document.
The test method described in this document is sometimes known as ‘static’ or even ‘sessile drop’,
since on many surfaces the droplet remains static and in equilibrium with the paper surface and air.
Yet on paper and board surfaces the droplet often changes its dimensions with time, due to sorption
and wetting phenomena. This has led some instrument manufacturers and researchers to describe the
automated optical technique outlined in this document as measurement of the ‘dynamic’ contact angle.
This document does not use the term ‘dynamic’ because this nomenclature confuses a measurement
changing with respect to time with one that changes due to a plane of shear. For example, the Willhelmy
plate method of contact angle measurement, which measures the force required to push a solid material
[2]
into and then pull it out from a liquid reservoir, is a true ‘dynamic’ method .
Similarly, this document does not cover the situation where a droplet is placed on a horizontal surface
that is subsequently tilted so that gravity causes the droplet to assume an asymmetric shape, then to
commence movement.
TECHNICAL SPECIFICATION ISO/TS 14778:2021(E)
Paper and board — Measurement of water contact angle by
optical methods
1 Scope
This document specifies the method for optical assessment of the contact angle between water and the
surface of paper and board, where the process of droplet formation, application to planar substrates, or
measurement of the droplet shape in contact with the solid is performed by automated equipment.
The limits of measurement are determined by the capabilities of the instrumentation used. The
instrumental capabilities defined by this document use a digital image capturing system operating at
a minimum of 50 frames per second and needs the ability to perform the first measurement after no
more than 20 ms to 40 ms contact between the droplet and substrate.
The test method is applicable to most kinds of paper or board however it cannot be applicable to
structured materials.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for
monitoring the atmosphere and conditioning of samples
ISO 13530, Water quality – Guidance on analytical quality control for chemical and physicochemical water
analysis
3 Terms and references
For the purposes of this document, the following terms and definitions apply:
3.1
baseline
line of contact between the water droplet and paper or board surface, determined by optical means and
taken as the plane from which the contact angle is measured
Note 1 to entry: Precise measurement of contact angle requires precise assessment of the baseline. For the
optical system to achieve the best estimate of the baseline, it may be necessary to tilt the camera so that it views
the droplet slightly from above, at a shallow angle (typically 0-3° relative to the horizontal), rather than directly
from the side (0°). Experience shows this small change in viewing angle does not affect the measured contact
[3]
angle value but can enhance detection of the baseline .
3.2
contact angle
Θ
angle to a baseline (3.1), formed by means of a tangent on the droplet contour through one of the three-
phase points at the specified contact time
Note 1 to entry: The contact angle is expressed in degrees (°).
3.3
contact time
duration of contact(s) between the water droplet and the test piece surface, as measured automatically
from the instant at which the timing mechanism is triggered to the instant of measurement
3.4
droplet height
H
distance from the top of the droplet in contact with the test piece surface as measured from the baseline
(3.1) at the specified contact time (3.3)
Note 1 to entry: The droplet height is expressed in millimetres.
3.5
droplet base diameter
D
maximum width of the droplet base in contact with the test piece surface, as measured along the
baseline (3.1) at the specified contact time (3.3)
Note 1 to entry: The droplet base diameter is expressed in millimetres.
3.6
three-phase point
point of intersection of the liquid/solid, liquid/gaseous and solid/gaseous boundary lines
4 Principle
A water droplet is applied to the horizontal planar surface of paper or board, the angle of contact it
makes with the material is assessed by optical digital imaging.
Figure 1 — Principle of measurement
2 © ISO 2021 – All rig
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.