ISO 16260:2025

International
Standard
ISO 16260
Second edition
Paper and board — Determination
2025-12
of internal bond strength
Papier et carton — Détermination de la force de cohésion interne
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus and technical data . 2
5.1 Apparatus .2
5.2 Technical data .5
5.2.1 Instrument/pendulum ranges .5
5.2.2 Aluminium platen/anvil .5
5.2.3 Pendulum .5
5.2.4 Adhesive tape .6
5.2.5 Test piece .7
6 Sampling . 7
7 Conditioning . 7
8 Preparation of test assemblies . 7
8.1 Preparation of strips .7
8.2 Load of preparation station .7
8.3 Operation of preparation station .7
8.4 Separation of the test pieces .8
9 Calibration . 8
10 Procedure . 8
10.1 Atmospheric conditions.8
10.2 Selection of instrument range .8
10.3 Horizontal position of the pendulum.8
10.4 First test assembly .8
10.5 Release of the pendulum .8
10.6 Examination of the test piece .8
10.7 Notation of the test value .8
10.8 Repetition .9
10.9 Use of test pieces of high internal bond strength .9
11 Expression of results . 9
11.1 Mean value .9
11.2 Standard deviation .9
12 Comparison of results . 9
13 Test report . 9
Annex A (normative) Maintenance and calibration .11
Annex B (normative) Verification of device .13
Annex C (informative) Precision .15
Bibliography . 17

iii
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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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.
This second edition cancels and replaces the first edition (ISO 16260:2016), which has been technically
revised.
The main changes are as follows:
— addition of a reference to possible different results, depending on the type of tester in the introduction;
— update of 5.1.6 regarding “Analog ply bond devices” and “Digital ply bond devices” and addition of
Figure 3;
— update of Table 1, regarding the contact force (former mass);
— update of 5.2.2 “Aluminium platen/anvil”;
— addition of 5.2.3.1 “Reduced pendulum length";
— revision of Clause 8 “Preparation of test assemblies” and Clause 9 “Calibration”;
— update of 10.2 “Selection of instrument range”;
— addition of new Clause 12 “Comparison of results”;
— revision of Clause 13 “test report”;
— renumbered former Annex B to Annex C, with addition of the used tester type;
— addition of “Verification of device” as new Annex B;
— editorial changes.
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
Introduction
Paper and board sheets can, during printing, conversion or specific product applications, be subjected to
impulses, impacts or shock loads of sufficient magnitude to cause structural failure. Commonly observed in-
plane structural failures include surface picking, blistering and interior delimitation.
This document describes one method for determining the internal bond strength of a product of pulp, paper
or board by measuring the energy needed to delaminate a paper or board sample in the "Z" (thickness)
[4][8]
direction. There are other published methods for determining “Z” or thickness direction tensile
strength, but in this method, the delaminating force is applied at a rate significantly higher than in other
methods. This method can, therefore, be preferred for predicting sheet performance under printing or
converting conditions.
Different types of testers (mechanical and electronic) are in use for this method. The results obtained with
the two types of testers may not be not comparable (see Clause 12).

v
International Standard ISO 16260:2025(en)
Paper and board — Determination of internal bond strength
1 Scope
This document specifies a method to measure the energy required to rapidly delaminate a test piece of
paper or board. Rupture of the test piece in the “Z” or thickness direction is initiated by a pendulum having a
defined mass, moving at a defined velocity.
The procedure is suitable for both single- and multi-ply papers and boards, including coated sheets and
those that are laminated with synthetic polymer films. It is particularly suitable for papers and boards that
[4][8]
can be subjected to z-direction rapid impacts, impulses or shock loads during printing or conversion.
The test procedure entails the adherence of double-sided adhesive tape to both sides of the test piece under
pressure. For this reason, the method is unsuitable for materials that can be structurally damaged by
compression or are porous enough to permit migration of the tape adhesive into or through the test piece.
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.
EN 755-2:2013, Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 2: Mechanical
properties
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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
internal bond strength
average potential energy, expressed as J/m of surface, required to delaminate a test piece under the
conditions of the test
Note 1 to entry: The result is the difference of the potential energy before and the remaining energy after delaminating
the test piece.
3.2
test assembly
test piece, laminated between two pieces of double-sided adhesive tape, with the bottom side of the lower tape
adhered to a rigid metal anvil and the upper side of the upper tape adhered to an “L”-shaped aluminium platen

4 Principle
A square test piece is adhered to a flat metal anvil by means of double-sided adhesive tape. An “L”-shaped
aluminium platen with the same surface area as the test piece is then adhered to the upper surface of the
test piece, again, using double-sided adhesive tape. The test assembly is shown in Figure 1. The test assembly
is secured in position and a pendulum allowed to impact the upper inside surface of the platen, causing it to
rotate about its outside corner, splitting the test piece in the “Z” or thickness direction (see Figure 2). The
energy absorbed in rupturing the test piece is calculated from the measurement of the subsequent over-
swing of the pendulum and the known masses and dimensions of the system components.
Key
1 test piece
2 double-sided adhesive tape
3 aluminium platen
4 metal anvil
Figure 1 — Components of a test assembly
Key
1 pendulum strike point and direction
Figure 2 — Pendulum to aluminium platen strike point
Precision data are provided in Annex C.
Verification of the measuring instrument compliance using an impact device is described in Annex B.
5 Apparatus and technical data
5.1 Apparatus
5.1.1 Test assembly preparation device, with the dimensions 25,4 mm ± 0,2 mm × 25,4 mm ± 0,2 mm for
testing by pressing the components of the test assembly (see 5.1.4) together at a controlled pressure for a

controlled time. During the pressure cycle, the aluminium platen (see 5.2.2) should be securely clamped in
position to prevent flexing.
NOTE Most commercially available preparation stations are capable of simultaneously preparing five test
assemblies.
Ensure that the test instrument is levelled in the front–back and left–right directions and the pendulum is
horizontal when in the latched position.
5.1.2 Pendulum, mounted on a pedestal by means of a horizontal spindle supported on low-friction
bearings. The pendulum shall be free to rotate from a horizontal position through at least 180°. At its
free end, the pendulum carries a metal striker ball which contacts the inside face of the aluminium platen
on the test assembly when the pendulum reaches the vertical position. To minimize energy losses due to
vibration, the centre of percussion of the pendulum should be at the point of impact of the striker ball with
the aluminium platen. There should be no looseness in the construction of pendulums that have augmented
weight assemblies.
5.1.3 Apparatus for securing the pendulum in a horizontal position, with provision for a rapid,
vibration-free release.
5.1.4 Test assembly, is formed from a stationary anvil (base) and a separable aluminium platen (5.2.2)
that is a right angle in cross section together with the test piece (5.2.5) and adhesive tape (5.2.4) (see
Figure 1).
Anvils intended for use in multiple test piece preparation stations should be indelibly marked to ensure that
they are always placed in the same position in the preparation station. The test assembly is securely held
in position so that the pendulum strikes the centre of percussion of the aluminium platen when the axis of
rotation is at the outside corner of the right angle of the platen (see Figure 2).
5.1.5 Apparatus for registering the peak angular swing of the pendulum after impact with the test
assembly.
5.1.6 Apparatus to convert the peak angular swing of the pendulum to an internal bond strength
value. Commonly employed methods include optical encoder computer and mechanical scale/friction
pointer. Examples are given in the list below:
a) Analog ply bond devices: For analogue ply bond devices, it is necessary to compensate the angle used
(see Figure 3). The scales of the analogue devices contain a compensation that takes account of the
original alloy of the platen. If the alloy is changed, the compensation used may not be appropriate and
this would lead to erroneous values being obtained. This correction factor is not applicable for digital
devices.
b) Digital ply bond devices: To improve comparability of the values, both the compensated and the
uncompensated ones shall be shown on the display. This shall be documented in the test report
(Clause 13).
a) Angular resistance not included in result
b) Angular resistance included in result
Key
1 pendulum
2 pendulum movement
3 pendulum swing with aluminium platen
4 pendulum swing without aluminium platen
5 difference is the resistance of aluminium platen
6 aluminium plate
Figure 3 — Different scales of analogue ply bond devices
5.1.7 Optional means to extend the range of the ply bond device. This can be achieved by fitting
pendulums of different masses, or by adding augmenting weights to the pendulum, or reducing the surface
area of the test piece by an amount not exceeding 50 %. The user of this document should consult the
manufacturer of the test instrument regarding the installation and verification of such options. Any such
modifications to the instrument shall be included in the test report.
5.1.8 Device suitable for cutting strips of the test material 25,4 mm ± 0,2 mm wide (see 5.2.5) and of
sufficient length to mount in the test assembly preparation device.
5.1.9 Knife or multi-blade cutting device, for separating test assemblies prepared in a multi-station test
assembly preparation device or station.
5.1.10 Double-sided adhesive paper tape, with a creped release liner (see 5.1.4 and 5.2.4).

5.1.11 Solvent, suitable for removing adhesive residue from the anvils and aluminium platens.
5.2 Technical data
5.2.1 Instrument/pendulum ranges
Table 1 — Instrument and pendu
...