SIST EN 17408:2020
(Main)Determination of the flowability and application behaviour of viscoelastic adhesives using the oscillatory rheometry
Determination of the flowability and application behaviour of viscoelastic adhesives using the oscillatory rheometry
This document specifies a measuring method for the characterization of rheological properties of structural adhesives using oscillatory rheometry. The advantage of the method in comparison to rotational viscometry measurements lies in the separation of elastic and viscous material properties, thus allowing to define the viscoelastic properties. This enables more precise information concerning the flow behaviour of the materials, thereby resulting in a better understanding of their processing properties.
The method described is particularly suitable for filled and paste-like adhesives. These are frequently processed using automated pump and application systems in industrial applications and shall be set precisely considering their rheological properties. As the rheological behaviour of uncured adhesives is mostly independent of their properties in the cured state, the standard can also serve for the examination of non-structural adhesives.
Bestimmung des Fließ- und Applikationsverhaltens von viskoelastischen Klebstoffen mit Hilfe der Oszillationsrheometrie
Dieses Dokument legt ein Messverfahren zur Charakterisierung der rheologischen Eigenschaften von Strukturklebstoffen mit Hilfe der Oszillationsrheometrie fest. Außerdem kann das Prüfverfahren auch auf das reaktive Gemisch mehrerer Komponenten oder auf die Komponenten eines pastösen Reaktionsklebstoffes angewendet werden. Der Vorteil des Verfahrens gegenüber Rotationsviskosimetrie¬messungen liegt in der Auftrennung von elastischen und viskosen Materialeigenschaften, wodurch die Festlegung der viskoelastischen Eigenschaften ermöglicht wird. Dadurch sind genauere Informationen über das Fließverhalten der Stoffe zugänglich, die zu einem besseren Verständnis ihrer Verarbeitungs¬eigenschaften führen.
Das beschriebene Verfahren eignet sich insbesondere für gefüllte und pastöse Klebstoffe. Diese werden im industriellen Einsatz häufig unter Verwendung automatisierter Pump und Auftragssysteme verarbeitet, und werden unter Beachtung ihrer rheologischen Eigenschaften präzise eingestellt. Da das rheologische Verhalten ungehärteter Klebstoffe meist unabhängig von ihren Eigenschaften im ausgehärteten Zustand ist, kann das Dokument auch zur Untersuchung nicht struktureller Klebstoffe dienen.
Détermination de l'attitude du fluage et de l'application des adhésifs viscoélastiques avec la méthode de la rhéologie oscillométrique
Le présent document spécifie une méthode de mesure permettant la caractérisation des propriétés rhéologiques des adhésifs structuraux en recourant à la rhéologie oscillométrique. En outre, le mode opératoire d’essai peut être appliqué au mélange réactif de plusieurs composants ou aux composants d’un matériau en pâte se liant par réaction. L'avantage de cette méthode par rapport aux mesurages de la viscosimétrie rotative réside dans la séparation des propriétés élastiques et visqueuses du matériau, permettant ainsi de définir les propriétés viscoélastiques. Ceci permet d'obtenir des informations plus précises concernant le comportement à l'écoulement des matériaux, avec pour résultat une meilleure compréhension de leurs propriétés d'application.
La méthode décrite convient particulièrement aux adhésifs chargés et en pâte. Leur utilisation fait fréquemment intervenir des systèmes automatisés de pompage et d'application dans les applications industrielles ; leur dosage doit être précis et tenir compte de leurs propriétés rhéologiques. Étant donné que le comportement rhéologique des adhésifs non durcis est très largement indépendant de leurs propriétés à l'état durci, le présent document peut également servir à l'examen d'adhésifs non structuraux.
Ugotavljanje sipkosti in uporabnosti viskoelastičnih lepil z uporabo oscilacijske reometrije
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 17408:2020
01-november-2020
Ugotavljanje sipkosti in uporabnosti viskoelastičnih lepil z uporabo oscilacijske
reometrije
Determination of the flowability and application behaviour of viscoelastic adhesives using
the oscillatory rheometry
Bestimmung des Fließ- und Applikationsverhaltens von viskoelastischen Klebstoffen mit
Hilfe der Oszillationsrheometrie
Détermination de l'attitude du fluage et de l'application des adhésifs viscoélastiques avec
la méthode de la rhéologie oscillométrique
Ta slovenski standard je istoveten z: EN 17408:2020
ICS:
83.180 Lepila Adhesives
SIST EN 17408:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 17408:2020
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SIST EN 17408:2020
EN 17408
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2020
EUROPÄISCHE NORM
ICS 83.180
English Version
Determination of the flowability and application behaviour
of viscoelastic adhesives using the oscillatory rheometry
Détermination de l'aptitude à l'écoulement et à Bestimmung des Fließ- und Applikationsverhaltens
l'application des adhésifs viscoélastiques avec la von viskoelastischen Klebstoffen mit Hilfe der
méthode de la rhéologie oscillométrique Oszillationsrheometrie
This European Standard was approved by CEN on 3 August 2020.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17408:2020 E
worldwide for CEN national Members.
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SIST EN 17408:2020
EN 17408:2020 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Symbols and units . 12
5 Test method . 12
5.1 General . 12
5.2 Principle of measurement . 12
5.3 Standard test . 13
5.4 Extended test . 13
6 Test equipment . 13
6.1 Oscillatory rheometer . 13
6.2 Measuring system . 14
6.3 Temperature controlling system . 15
6.4 Inerting . 15
7 Sampling and sample preparation . 15
8 Implementation . 15
8.1 General . 15
8.2 Setting parameters . 16
8.3 Standard test . 16
8.4 Extended test . 16
9 Interpretation . 16
10 Test report . 18
Bibliography . 19
2
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SIST EN 17408:2020
EN 17408:2020 (E)
European foreword
This document (EN 17408:2020) has been prepared by Technical Committee CEN/TC 193 “Adhesives”,
the secretariat of which is held by UNE.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2021, and conflicting national standards shall
be withdrawn at the latest by March 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
SAFETY WARNING — Persons using this document are expected to be familiar with normal laboratory
practice. This document cannot address all safety problems that could be associated with its
application. It is the responsibility of the user to define measures for health and safety at work and
ensure that these correspond with the European and national regulations.
ENVIRONMENTAL PROTECTION NOTE — The materials approved in this document can have negative
effects on the environment. As soon as technological progress leads to better alternatives to these
materials, they will be removed from the standard as far as possible. At the end of the test, the user is
expected to ensure a suitable disposal of the waste according to regional conditions.
3
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SIST EN 17408:2020
EN 17408:2020 (E)
1 Scope
This document specifies a measuring method for the characterization of rheological properties of
structural adhesives using oscillatory rheometry. Moreover, the testing procedure can be applied to the
reactive mixture of several components or the components of a reactive bonding paste material. The
advantage of the method in comparison to rotational viscometry measurements lies in the separation of
elastic and viscous material properties, thus allowing the defining of the viscoelastic properties. This
enables more precise information concerning the flow behaviour of the materials, thereby resulting in a
better understanding of their processing properties.
The method described is particularly suitable for filled and paste-like adhesives. These are frequently
processed using automated pump and application systems in industrial applications and will be set
precisely considering their rheological properties. As the rheological behaviour of uncured adhesives is
mostly independent of their properties in the cured state, the document can also serve for the
examination of non-structural adhesives.
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 923, Adhesives - Terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 923 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4
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SIST EN 17408:2020
EN 17408:2020 (E)
3.1
shear deformation
γ
relation of deflection s to the distance between the plates geometry or gap width H of a sample located
between two plates at linear deflection of the upper plate in accordance with the tangent of the angle of
deflection φ (see Figure 1)
γϕ= s / H = tan (1)
( )
Figure 1 — Deflection s and angle of deflection φ of the test portion in the shear gap H [1]
Note 1 to entry: For a circular deflection in the plate/plate measuring system of a rheometer, this relation only
applies for an infinitesimal surface element. The deflection here depends on the distance to the axis of rotation
and is hence not uniform within the shear gap. The deformation value is, therefore, usually related to the plate
edge (i.e. to r ), sometimes also to a mean distance to the axis of rotation (e.g. 2/3 r ). In this document, the
max max
plate edge is used as a reference value. The cone/plate configuration yields a constant deformation based on the
gap width H raise equivalent to the deflection s increasing outwards in the entire shear gap.
3.2
deformation function
γ (t)
mathematical representation of the sinusoidal change in the deformation during oscillatory tests with
controlled deformation
γγ tt= sin()ω (2)
( )
A
where
γ (t) is the deformation at the time point t;
γ is the maximum deformation (deformation amplitude);
A
ω is the angular frequency, in rad/s, with ω = 2 π f.
5
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SIST EN 17408:2020
EN 17408:2020 (E)
3.3
shear stress function
τ (t)
the deformation as phase-shifted sinusoidal function of the shear stress related to the response of the
sample located in the gap (see Figure 2)
τ ttτ sin ωδ + (3)
( ) ( )
A
where
τ (t) is the shear stress at the time point t;
τ is the maximum shear stress (shear stress amplitude);
A
ω is the angular frequency, in rad/s, with ω = 2 π f;
δ is the angle phase shift (loss angle).
Note 1 to entry: In the case of ideal-elastic behaviour (according to Hooke), the loss angle δ is 0°, i.e.
deformation and shear stress are always in the same phase. Maximum shear stress is measured at maximum
deformation. In the case of ideal-viscous behaviour (according to Newton), the loss angle δ = is 90°, i.e. the shear
stress curve is ahead of the deformation curve by 90°. The maximum shear stress at deformation zero results
here, i.e. at highest angular velocity of the test specimen.
Figure 2 — Deformation and shear stress function during oscillation test [3]
6
=
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SIST EN 17408:2020
EN 17408:2020 (E)
3.4
storage modulus
G'
calculated from the energy stored during deformation, completely available for recovering after the end
of the deformation process
τ
A
G′ = cos δ (4)
( )
γ
A
where
τ is the maximum shear stress (shear stress amplitude);
A
γ is the maximum deformation (deformation amplitude);
A
δ is the angle phase shift (loss angle).
Note 1 to entry: The storage modulus represent the elastic portion of the applied energy and describes a typical
solid property (solid like).
3.5
loss modulus
G''
calculated from the energy irreversibly consumed during the deformation, dissipated as heat
τ
A
G′′ = sin()δ (5)
γ
A
where
τ is the maximum shear stress (shear stress amplitude);
A
γ is the maximum deformation (deformation amplitude);
A
δ is the angle phase shift (loss angle).
Note 1 to entry: The loss modulus represents the viscous (liquid like) portion of the applied energy dissipated
as heat or work.
7
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SIST EN 17408:2020
EN 17408:2020 (E)
3.6
complex shear modulus
G*
vector sum of storage modulus G' and loss modulus G''
*
G τγ t / t G′′ + iG · ′ (6)
( ) ( )
* ' 2 '' 2
G GG+ (7)
where
τ (t) is the shear stress at the time point t;
γ (t) is the deformation at the time point t;
G' is the storage modulus;
G'' is the loss modulus;
i is the imaginary part.
Note 1 to entry: When performing oscillatory tests on ideally elastic materials, i.e. completely inflexible, stiff
and rigid solids, Hooke's Law applies, as indicated in Formula (6).
Note 2 to entry: All kinds of materials have a viscoelastic behaviour, this consists of a viscous and an elastic
portion. Their sum is the complex shear modulus G*, represented in the ‘complex plane’ (see Figure 3).
Figure 3 — Vector diagram showing G’, G'' and the resulting vector G*
Note 3 to entry: This plane is spread out using the ‘real axis’ (x-axis) and the ‘imaginary axis’ (y-axis) and the
imaginary unit i −1 is the ‘negative root’ that characterizes the complex number.
8
=
=
==
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SIST EN 17408:2020
EN 17408:2020 (E)
3.7
loss factor
tan (δ)
calculated as the quotient of loss modulus and storage modulus
tan δ = G"/ G' (8)
( )
where
G' is the storage modulus;
G'' is the loss modulus.
Note 1 to entry: The loss factor corresponds to the ratio between dissipated and reversibly stored deformation
energy.
3.8
complex viscosity
η*
ratio between the time-dependent values of the stress and deformation of shear rate
ητ* = tt/ γ
(9)
( ) ( )
where
τ (t) is the shear stress at the time point t;
is the deformation or shear rate at the time point t.
γ
(t)
Note 1 to entry: The complex viscosity is linked to the amount of the complex shear modulus via a simple
relation as shown in Formula 10.
|η*| Gf* / ω (with ωπ2 )
(10)
Note 2 to entry: Similar to the complex shear modulus, the complex viscosity also comprises an elastic and a
viscous component or better it is a sum of the real part η' and imaginary part η”.
9
==
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SIST EN 17408:2020
EN 17408:2020 (E)
3.9
linear-viscoelastic range
LVE range
range of low deformations, in which the amplitudes τ and γ are proportional to one another
A A
Note 1 to entry: The quiescent structure of the substance is extensively retained in this range, and the
deformations are reversible. The functions of G*, G' and G'' (and likewise the viscosity variables linked to this) are
constant and form a plateau value (see Figure 4). For many of the adhesives considered here, this is the case with
deformation values less than or equal to 0,1 %. Besides the material situations, the LVE range also depends on the
temperature and measuring frequency. Strictly speaking, the rheological relations indicated above only apply
exactly in this range. However, the LVE range shall be occasionally departed from to describe the practical
behaviour of adhesives.
Figure 4 — G' and G'' as function of the deformation with the critical value γ
L
of the linear-viscoelastic range [1]
3.10
stability
structural strength
deformation stability of an adhesive bead in respect to gravity or other external forces
Note 1 to entry: This property also referred to as structural strength is crucially determined by the elastic
material character, which impedes the substance from flowing due to its restoring forces. Contrariwise, viscous
properties play a secondary role, as high viscosity slows, but does not prevent, flow. Permanent stability is only
observed at sufficiently high storage modulus or when G' > G''.
EXAMPLE An adhesive with G' = 100 kPa and G'' = 10 kPa has greater deformation stability than a product
with G' = 10 kPa and G'' = 100 kPa. However, both exhibit the same amount of |G*| and also yield (at identical
deformation and frequency) the same |η*| and τ values.
3.11
yield point
τ
y
stress measured at the end of the linear-viscoelastic range (see Figure 5)
Note 1 to entry: The yield point τ can be regarded as minimum shear stress at which the structure of a
y
substance is initially weakened (en: “yield point”). This value is also frequently used for characterization of the
stability. As the LVE range does not end in a sharp point, its limit shall be extrapolated by approximation, e.g. via
tangent method. Many rheometers allow an automatic curve evaluation and the determination of τ using
y
software.
10
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SIST EN 17408:2020
EN 17408:2020 (E)
3.12
flow point or flow stress
τ
f
stress at the intersection of the curves of G' and G'' (see Figure 5)
Note 1 to entry: The flow point τ is approximate for the stress through which a substance is able to flow. This
f
value can serve for estimating the effort or the pressure that a pump has to apply in order to move material in a
pipe line (“pumping”).
...
SLOVENSKI STANDARD
oSIST prEN 17408:2019
01-september-2019
Ugotavljanje sipkosti in uporabnosti viskoelastičnih lepil z uporabo oscilacijske
reometrije
Determination of the flowability and application behaviour of viscoelastic adhesives using
the oscillatory rheometry
Bestimmung des Fließ- und Applikationsverhaltens von viskoelastischen Klebstoffen mit
Hilfe der Oszillationsrheometrie
Détermination de l'attitude du fluage et de l'application des adhésifs viscoélastiques avec
la méthode de la rhéologie oscillométrique
Ta slovenski standard je istoveten z: prEN 17408
ICS:
83.180 Lepila Adhesives
oSIST prEN 17408:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 17408:2019
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oSIST prEN 17408:2019
DRAFT
EUROPEAN STANDARD
prEN 17408
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2019
ICS 83.180
English Version
Determination of the flowability and application behaviour
of viscoelastic adhesives using the oscillatory rheometry
Détermination de l'attitude du fluage et de l'application Bestimmung des Fließ- und Applikationsverhaltens
des adhésifs viscoélastiques avec la méthode de la von viskoelastischen Klebstoffen mit Hilfe der
rhéologie oscillométrique Oszillationsrheometrie
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 193.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17408:2019 E
worldwide for CEN national Members.
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oSIST prEN 17408:2019
prEN 17408:2019 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Symbols and units . 10
5 Test method . 11
5.1 General . 11
5.2 Principle of measurement . 11
5.3 Standard test . 11
5.4 Extended test . 12
6 Test equipment . 12
6.1 Oscillatory rheometer . 12
6.2 Measuring system . 12
6.3 Temperature controlling system . 13
6.4 Inerting . 13
7 Sampling and sample preparation . 14
8 Implementation . 14
8.1 General . 14
8.2 Setting parameters . 14
8.3 Standard test . 14
8.4 Extended test . 15
9 Interpretation . 15
10 Test report . 16
Bibliography . 17
2
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oSIST prEN 17408:2019
prEN 17408:2019 (E)
European foreword
This document (prEN 17408:2019) has been prepared by Technical Committee CEN/TC 193
“Adhesives”, the secretariat of which is held by UNE.
This document is currently submitted to the CEN Enquiry.
SAFETY WARNING — Persons using this document shall be familiar with normal laboratory practice.
The standard cannot address all safety problems that may be associated with its application. It is the
responsibility of the user to define measures for health and safety at work and ensure that these
correspond with the European and national regulations.
ENVIRONMENTAL PROTECTION NOTE — The materials approved in this standard can have negative
effects on the environment. As soon as technological progress leads to better alternatives to these
materials, they shall be removed from the standard as far as possible. At the end of the test, the user
shall ensure a suitable disposal of the waste corresponding to the regional conditions.
3
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oSIST prEN 17408:2019
prEN 17408:2019 (E)
1 Scope
This document specifies a measuring method for the characterization of rheological properties of
structural adhesives using oscillatory rheometry. The advantage of the method in comparison to
rotational viscometry measurements lies in the separation of elastic and viscous material properties,
thus allowing to define the viscoelastic properties. This enables more precise information concerning
the flow behaviour of the materials, thereby resulting in a better understanding of their processing
properties.
The method described is particularly suitable for filled and paste-like adhesives. These are frequently
processed using automated pump and application systems in industrial applications and will be set
precisely considering their rheological properties. As the rheological behaviour of uncured adhesives is
mostly independent of their properties in the cured state, the standard can also serve for the
examination of non-structural adhesives.
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 923, Adhesives — Terms and definitions
DIN 53019-1, Viscometry — Measurement of viscosities and flow curves by means of rotational
viscometers — Part 1: Principles and measuring geometry
DIN 53019-2, Viscosimetry — Determination of viscosity and flow curves with rotational viscosimeters —
Part 2: Viscosimeter calibration and determination of the uncertainty of measurement
DIN 1342-1, Viscosity — Part 1: Rheological concepts
3 Terms and definitions
For the purposes of this document, the terms and definitions given in DIN 53019-1, DIN 53019-2,
EN 923 and DIN 1342-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
shear deformation
γ
relation of deflection s to the distance between the plats geometry or gap width H of a sample located
between two plates at linear deflection of the upper plate in accordance with the tangent of the angle of
deflection φ (see Figure 1)
γϕ= sH/ = tan (1)
( )
4
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oSIST prEN 17408:2019
prEN 17408:2019 (E)
Figure 1 — Deflection s and angle of deflection φ of the test portion in the shear gap H [7]
Note 1 to entry: For a circular deflection in the plate/plate measuring system of a rheometer, this relation only
applies for an infinitesimal surface element. The deflection here depends on the distance to the axis of rotation
and is hence not uniform within the shear gap. The deformation value is, therefore, usually related to the plate
edge (i.e. to r ), sometimes also to a mean distance to the axis of rotation (e.g. 2/3 r ). In this document, the
max max
plate edge is used as a reference value (as recommended in DIN 53019-1). The cone/plate configuration yields a
constant deformation based on the gap width H raise equivalent to the deflection s increasing outwards in the
entire shear gap.
3.2
deformation function
γ (t)
mathematical representation of the sinusoidal change in the deformation during oscillatory tests with
controlled deformation
γγ tt= sin()ω (2)
( )
A
where
γ (t) is the deformation at the time point t;
γ is the maximum deformation (deformation amplitude);
A
f is the frequency, in Hz;
ω is the angular frequency, in rad/s, with ω = 2 π f.
5
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oSIST prEN 17408:2019
prEN 17408:2019 (E)
3.3
shear stress function
(t)
deformation as phase-shifted sinusoidal function of the shear stress related the response of the sample
located in the gap (see Figure 2)
τ ttτ sin ωδ + (3)
( ) ( )
A
where
τ (t) is the shear stress at the time point t;
τ is the maximum shear stress (shear stress amplitude);
A
f is the frequency, in Hz;
ω is the angular frequency, in rad/s, with ω = 2 π f.
δ is the angle phase shift (loss angle).
Note 1 to entry: In the case of ideal-elastic behaviour (according to Hooke), the loss angle δ is 0°, i.e.
deformation and shear stress are always in the same phase. Maximum shear stress is measured at maximum
deformation. In the case of ideal-viscous behaviour (according to Newton), the loss angle δ = is 90°, i.e. the shear
stress curve is ahead of the deformation curve by 90°. The maximum shear stress at deformation zero results
here, i.e. at highest angular velocity of the test specimen.
Figure 2 — Deformation and shear stress function during oscillation test [7]
3.4
storage modulus
G'
calculated from the energy stored during deformation, completely available for recovering after the end
of the deformation process
τ
A
G′ = cos δ (4)
( )
γ
A
where
τ is the maximum shear stress (shear stress amplitude);
A
γ is the maximum deformation (deformation amplitude);
A
δ is the angle phase shift (loss angle).
Note 1 to entry: The storage modulus represent the elastic portion of the applied energy and describes a typical
solid property (solid like).
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3.5
loss modulus
G”
calculated from the energy irreversibly consumed during the deformation, dissipated as heat
τ
A
G′′ = sin(δ ) (5)
γ
A
where
τ is the maximum shear stress (shear stress amplitude);
A
γ is the maximum deformation (deformation amplitude);
A
δ is the angle phase shift (loss angle).
Note 1 to entry: The loss modulus represent the viscous (liquid like) portion of the applied energy dissipated as
heat or work.
3.6
Complex shear modulus
G*
vector sum of storage modulus G' and loss modulus G”
*
G τγ t / t G′ + i · G′′ (6)
( ) ( )
* ' 2 '' 2
G GG+ (7)
where
τ (t) is the shear stress at the time point t;
γ (t) is the deformation at the time point t;
G' is the storage modulus;
G” is the loss modulus.
Note 1 to entry: When performing oscillatory tests on ideally elastic materials, i.e. completely inflexible, stiff
and rigid solids, Hooke's Law applies, as indicated in Formula (6).
3.7
loss factor
tan (δ)
calculated as the quotient of loss modulus and storage modulus
(8)
tan δ = G"/ G'
( )
where
G' is the storage modulus;
G” is the loss modulus.
Note 1 to entry: The loss factor corresponds to the ratio between dissipated and reversibly stored deformation
energy.
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3.8
complex viscosity
η*
ratio between the time – dependent values of the stress and deformation of shear rate
ητ* = t/ γ t (9)
( ) ( )
where
τ (t) is the shear stress at the time point t;
γ (t) is the deformation or shear rate at the time point t.
Note 1 to entry: The complex viscosity is linked to the amount of the complex shear modulus via a simple
relation:
| η* | Gf* / ω (with ωπ2 ) (10)
Note 2 to entry: Similar to the complex shear modulus, the complex viscosity also comprises an elastic and a
viscous component or better it is a sum of the real part η' and imaginary part η”.
3.9
linear-viscoelastic range
LVE range
range of low deformations, in which the amplitudes τ and γ are proportional to one another
A A
Note 1 to entry: The quiescent structure of the substance is extensively retained in this range, and the
deformations are reversible. The functions of G*, G' and G” (and likewise the viscosity variables linked to this) are
constant and form a plateau value (see Figure 3). For many of the adhesives considered here, this is the case with
deformation values less than or equal to 0,1 %. Besides the material situations, the LVE range also depends on the
temperature and measuring frequency. Strictly speaking, the rheological relations indicated above only apply
exactly in this range. However, the LVE range shall be occasionally departed from to describe the practical
behaviour of adhesives.
Figure 3 — G' and G” as function of the deformation with the critical value γ
L
of the linear-viscoelastic range [7]
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3.10
stability
structural strength
deformation stability of an adhesive bead in respect to gravity or other external forces
Note 1 to entry: This property also referred to as structural strength is crucially determined by the elastic
material character, which impedes the substance from flowing due to its restoring forces. Contrariwise, viscous
properties play a secondary role, as high viscosity slows, but does not prevent, flow. Permanent stability is only
observed at sufficiently high storage modulus or when G' > G”.
EXAMPLE An adhesive with G' = 100 kPa and G” = 10 kPa has greater deformation stability than a product
with G' = 10 kPa and G” = 100 kPa. However, both exhibit the same amount of |G*| and also yield (at identical
deformation and frequency) the same |η*| and τ values.
3.11
yield point
τ
y
stress measured at the end of the linear-viscoelastic range (see Figure 4)
Note 1 to entry: The yield point τ can be regarded as minimum shear stress at which the structure of a
y
substance is initially weakened (en: “yield point”). This value is also frequently used for characterization of the
stability. As the LVE range does not end in a sharp point, its limit shall be extrapolated by approximation, e.g. via
tangent method. Many rheometers allow an automatic curve evaluation and the determination of τ using
y
software.
3.12
flow point or flow stress
τ
f
stress at the intersection of the curves of G' and G” (see Figure 4)
Note 1 to entry: The flow point τ is approximate for the stress through which a substance is able to flow. This
f
value can serve for estimating the effort or the pressure that a pump has to apply in order to move material in a
pipe line (“pumping”).
Figure 4 — G' and G” as function of the shear stress, measured in the amplitude test [7].
The yield strengths τ and τ are highlighted
y f
Note 2 to entry: The LVE range ends at the value τ (corresponding point γ in Figure 3).
y L
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