IEC 62788-5-1:2020

IEC 62788-5-1 ®
Edition 1.1 2022-01
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 5-1: Edge seals – Suggested test methods for use with edge seal materials

Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 5-1: Joints d’étanchéité périphériques – Méthodes d’essai suggérées
pour l’utilisation des matériaux de joints d'étanchéité périphériques

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 19 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un
en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour
comité d’études, …). Elle donne aussi des informations sur adapté à vos besoins.
les projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au
Restez informé sur les nouvelles publications IEC. Just
monde, avec plus de 22 300 articles terminologiques en
Published détaille les nouvelles publications parues.
anglais et en français, ainsi que les termes équivalents dans
Disponible en ligne et une fois par mois par email.
19 langues additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC 62788-5-1 ®
Edition 1.1 2022-01
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 5-1: Edge seals – Suggested test methods for use with edge seal materials
Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 5-1: Joints d’étanchéité périphériques – Méthodes d’essai suggérées
pour l’utilisation des matériaux de joints d'étanchéité périphériques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-5384-7

IEC 62788-5-1 ®
Edition 1.1 2022-01
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
Measurement procedures for materials used in photovoltaic modules –
Part 5-1: Edge seals – Suggested test methods for use with edge seal materials

Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 5-1: Joints d’étanchéité périphériques – Méthodes d’essai suggérées
pour l’utilisation des matériaux de joints d'étanchéité périphériques

– 2 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 7
3.2 Symbols . 7
4 Recommended tests . 7
4.1 General . 7
4.2 Moisture permeation properties . 7
4.2.1 Moisture breakthrough time . 7
4.2.2 Fickian materials . 8
4.2.3 Non-Fickian materials . 8
4.3 Electrical properties . 8
4.3.1 Dielectric strength of the film . 8
4.3.2 Volume resistivity . 9
4.3.3 Comparative tracking index . 9
4.4 Adhesion testing . 9
4.4.1 General . 9
4.4.2 Lap shear strength . 9
4.4.3 “T” peel test . 10
4.4.4 90° peel test . 11
4.4.6 180° peel test . 11
4.4.5 Butt joint test . 11
4.5 Durability of the materials . 12
4.5.1 Relative thermal endurance . 12
4.5.2 Dielectric strength degradation . 13
4.5.3 Accelerated stress testing . 13
4.6 Flame resistance . 15
4.7 Coefficient of thermal expansion . 15
4.8 Rheological properties . 15
4.8.1 Complex shear modulus . 15
4.8.2 Melt flow rate . 15
4.9 Other data . 16
5 Test report . 16
Bibliography . 17

Figure 1 – Lap shear test sample for proving cemented joint . 10
Figure 2 –Photograph (a)) and schematic (b)) of a z-tensile adhesion test specimen . 12
Figure 3 – Schematic of test structure for RTI or RTE dielectric durability testing . 13
Figure 4 – Test flow for cemented joint evaluation . 14

© IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –

Part 5-1: Edge seals –
Suggested test methods for use with edge seal materials

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 62788-5-1 edition 1.1 contains the first edition (2020-03) [documents 82/1658/FDIS
and 82/1689/RVD] and its amendment 1 (2022-01) [documents 82/1973/FDIS and
82/1991/RVD].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red
text. A separate Final version with all changes accepted is available in this publication.

– 4 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
International Standard IEC 62788-5-1 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62788 series, published under the general title Measurement
procedures for materials used in photovoltaic modules, can be found on the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under webstore.iec.ch
in the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

© IEC 2022
MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –

Part 5-1: Edge seals –
Suggested test methods for use with edge seal materials

1 Scope
This part of IEC 62788 provides procedures for standardized test methods for evaluating the
properties of materials designed to be used as edge seals. When modules are constructed with
impermeable (or extremely low permeability) front- and backsheets designed to protect
moisture-sensitive photovoltaic (PV) materials, there is still the possibility for moisture to get in
from the sides. This moisture ingress pathway can be restricted by using a low-diffusivity
material around the perimeter of a module between the impermeable front- and backsheets.
Alternatively, it can be desirable to use a low-diffusivity encapsulant, which may significantly
reduce moisture ingress over the lifetime of the module, and to evaluate it in a similar way to
an edge seal material.
In addition to restricting moisture ingress, edge seal materials also provide electrical insulation.
To perform these functions, edge seal materials are relied upon to adhere well.
The test methods described in this document are intended to be used to standardize the way
edge seals are evaluated. The use of tests in this document does not evaluate compatibility
with other materials or appropriateness for a given technology. Only some of these tests are
applied for IEC 61215 and IEC 61730, and that status depends on the specific design. It is not
required that all of these tests be performed, but that if these measurements are made that they
be performed as outlined here.
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.
IEC 60112, Method for the determination of the proof and the comparative tracking indices of
solid insulating materials
IEC 60243-1:2013, Electrical strength of insulating materials – Test methods – Part 1: Tests at
power frequencies
IEC 60243-2:2013, Electrical strength of insulating materials – Test methods – Part 2:
Additional requirements for tests using direct voltage
IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5:
Determination of relative thermal endurance index (RTE) of an insulating material
IEC 60664-1, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60695-11-10, Fire hazard testing – Part 11-10: Test flames – 50 W horizontal and vertical
flame test methods
– 6 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
IEC 61730-2:2016, Photovoltaic (PV) module safety qualification – Part 2: Requirements for
testing
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC 62788-1-2, Measurement procedures for materials used in photovoltaic modules –
Part 1-2: Encapsulants – Measurement of volume resistivity of photovoltaic encapsulants and
other polymeric materials
IEC TS 62788-2:2017, Measurement procedures for materials used in photovoltaic modules –
Part 2: Polymeric materials – Frontsheets and backsheets
IEC 62788-6-2, Measurement procedures for materials used in photovoltaic modules –
Part 6-2: General Tests – Moisture permeation testing with polymeric materials
ISO 62, Plastics – Determination of water absorption
ISO 1133-1, Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR)
of thermoplastics – Part 1: Standard method
ISO 4587, Adhesives – Determination of tensile lap-shear strength of rigid-to-rigid bonded
assemblies
ISO 6721-6, Plastics – Determination of dynamic mechanical properties – Part 6: Shear
vibration – Non-resonance method
ISO 11359-2, Plastics – Thermomechanical analysis (TMA) – Part 2: Determination of
coefficient of linear thermal expansion and glass transition temperature
ISO 11443, Plastics – Determination of the fluidity of plastics using capillary and slit-die
rheometers
ISO 15512, Plastics – Determination of water content
UL 746B, Polymeric materials – Long term property evaluations
UL 746C, Polymeric materials – Use in electrical equipment evaluations
ASTM D3835–08, Standard test methods determination of properties of polymeric materials by
means of a capillary rheometer
ASTM D6869–03, Standard test method for coulometric and volumetric determination of
moisture in plastics using the Karl Fischer reaction (the reaction of iodine with water)
ASTM D7191–10, Standard test method for determination of moisture in plastics by relative
humidity sensor
3 Terms, definitions and symbols
For the purposes of this document, the terms and definitions given in IEC TS 61836 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
© IEC 2022
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
edge seal
polymeric material designed to be placed between two impermeable (or with extremely low
permeability) frontsheet and backsheet materials to restrict moisture ingress from the sides
3.1.2
Fickian
material for which the diffusivity is constant, independent of the concentration of the permeant
within the experimental uncertainty
3.2 Symbols
t time required for an edge seal to reach 10 % of its equilibrium water vapour
10 %
transmission rate [h]
-0,5
K 10 % moisture ingress breakthrough proportionality constant [cm·h ]
10 %
-0,5
K Arrhenius prefactor for K [cm·h ]
o10 % 10 %
-0,5
Ea Arrhenius activation energy for K [cm·h ]
K10 % 10 %
X edge seal film thickness [mm]
D Fickian diffusivity at a given temperature [cm /s]
D Arrhenius prefactor for diffusivity [cm /s]
o
Ea Arrhenius activation energy for diffusivity [kJ/mol]
D
S maximum absorption of moisture in a material in equilibrium with liquid water [g/cm ]
S irreversible absorption capacity of moisture in a material [g/cm ]
IR
S Arrhenius prefactor for solubility [g/cm ]
o
Ea Arrhenius activation energy for solubility [kJ/mol]
S
-2 -1
P permeability [g·mm·m ·day ]
-2 -1
P Arrhenius prefactor for permeability [g·mm·m ·day ]
o
Ea Arrhenius activation energy for permeability [kJ/mol]
p
4 Recommended tests
4.1 General
This document is intended to be used as a guideline for presenting edge seal data. When the
properties outlined in this document are reported, they shall be reported as measured using the
outlined methods. A datasheet may include more data, or less data, than the list of tests
outlined. The tests outlined are recommendations only.
4.2 Moisture permeation properties
4.2.1 Moisture breakthrough time
1/2
10 % moisture ingress breakthrough proportionality constant [K , (X = K · t )] at
10 % 10 % 10 %
(85 ± 2) °C as determined in IEC 62788-6-2. Include activation energy if available. For a Fickian
1/2
material, K = 3,89 · D .
10 %
– 8 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
4.2.2 Fickian materials
) if available.
Permeability (P) at (85 ± 2) °C steady state. Include activation energy (Ea
p
If the material is Fickian, report the diffusivity (D) at (85 ± 2) °C and activation energy for
diffusivity (Ea ) as determined from IEC 62788-6-2. Also indicate the temperature range over
D
which the diffusivity was measured.
If the material is Fickian, report the solubility (S) at (85 ± 2) °C and activation energy for
solubility as determined from IEC 62788-6-2. Also indicate the temperature range over which
the solubility was measured.
4.2.3 Non-Fickian materials
For non-Fickian materials, report the solubility (S) at (85 ± 2) °C using ISO 62, ASTM D7191-10,
ASTM D6869-03, or ISO 15512. Samples should be equilibrated at temperature while placed in
a sealed container with water, but not in contact with the water. The use of sufficient sample
equilibration time shall be verified by testing multiple samples at progressively longer times.
Samples should be tested immediately after removal from the container because of the potential
for the evaporation of moisture.
If applicable, also report the irreversible solubility (S ) by measuring the reversible absorption
IR
of a sample saturated at (85 ± 2) °C using ISO 15512, ASTM D7191-10 or ASTM D6869-03 and
subtracting that from S.
NOTE If the sample contains desiccant, ASTM D7191-10 and ASTM D6869-03 may not work because the water
may be irreversibly adsorbed. Furthermore, for molecular sieve-type desiccants, the time required to remove trace
amounts of water fully from the desiccant can severely limit the accuracy of these methods and the temperature
required to dry the samples can cause other volatile molecules to evaporate.
4.3 Electrical properties
4.3.1 Dielectric strength of the film
Perform a measurement of dielectric strength in accordance with IEC 60243-2 for a DC test.
This shall conform to IEC TS 62788-2:2017, 4.5.1 and IEC TS 62788-2:2017, Annex C. Use a
material thickness that is useable at a practical voltage, which is rarely greater than 100 kV DC,
for the testing equipment. The surfaces of the samples shall be free of volumetric defects (e.g.
bubbles, voids or foreign particles) and be made smooth, which may require curing according
to the manufacturer’s specifications.
Measure and report values before and after saturation with water to duplicate conditions after
the desiccant is spent. For the saturated samples, precondition at (85 ± 2) °C and (85 ± 5) %
relative humidity (RH) prior to testing. Allow materials to equilibrate at room temperature prior
to testing. Ensure that saturated samples do not dry out before testing, but one may remove
any water droplets from the surface. The amount of time needed for equilibration will be
determined by the manufacturer such that the mass of the sample does not increase over the
course of 24 h.
Materials shall be tested in a surrounding medium selected to prevent flashover as indicated in
IEC 60243-1 and IEC 60243-2. The short-time (rapid-rise) method (see IEC 60243-1:2013,
-1
10.1) shall be used with a voltage rise of 2 000 V·s unless breakdown occurs in less than
10 s. Equal diameter electrodes measuring (25 ± 1) mm shall be used as indicated in
IEC 60243-1:2013, 5.2.1.2.
NOTE In IEC 61730-1:2016, 5.6.4.3, requirements for the dielectric testing are described for that document. This
test method only applies if the edge seal material is part of "relied upon insulation". Because of the potential of
polyisobutylene (PIB) based desiccants to absorb or to dissolve in mineral oil, this test is performed as quickly as is
reasonable.
© IEC 2022
4.3.2 Volume resistivity
Volume resistivity in accordance with IEC 62788-1-2. Test before and after saturation with water
to evaluate the properties of the material with the spent desiccant. Condition at room
temperature in a sealed package to prevent moisture exposure for the "before exposure"
condition. Precondition at (85 ± 2) °C and (85 ± 5) % RH prior to testing. The manufacturer shall
determine the amount of time needed to fully saturate the desiccant (if applicable) and fill the
material with moisture such that the weight no longer increases over time.
NOTE In IEC 61730-1:2016, 5.6.4.2, if the edge seal functions as a cemented joint, then in the context of
6 6
IEC 61730-1 it has a volume resistivity greater than 50 × 10 Ω·cm when dry and greater than 10 × 10 Ω·cm when
wet. For most polymeric materials, these values would be expected to be exceeded by many orders of magnitude.
4.3.3 Comparative tracking index
Comparative tracking index (CTI) in accordance with IEC 60112 or UL 746C.
NOTE If the material is used as the relied upon insulation, then in the context of IEC 61730-1 the CTI determines
the material group that is then used to define the creepage distance. If the edge seal is considered a cemented joint
in the PV module, then IEC 61730-1 does not use creepage and clearance distances, but distances through cemented
joints.
4.4 Adhesion testing
4.4.1 General
Adhesion testing is designed to conform to the data necessary to consider the edge seal being
listed as a cemented joint in accordance with IEC 61730-2. As such, the strength is reported as
the average and standard deviation of 10 replicate measurements.
4.4.2 Lap shear strength
Lap shear strength at (23 ± 2) °C in accordance with ISO 4587 using a sample thickness of
(0,5 ± 0,1) mm, an overlap area of (25 ± 0,25) mm × (12,5 ± 0,25) mm, and a strain pull rate of
-1
(0,8 ± 0,01) mm·min (see Figure 1, taken from Figure 11 in IEC 61730-2:2016.) Typically, at
least one substrate in a PV module will be glass; therefore, testing is accomplished with
photovoltaic soda lime glass. If one of the substrate surfaces in the module application is not
glass and is a rigid substrate, then that substrate shall be tested.

– 10 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
Dimensions in millimetres
Key:
1 area held in grips
2 cemented joint
3 PV module front glass
4 PV module back glass
NOTE Schematic taken from IEC 61730-2:2016, Figure 11.
Figure 1 – Lap shear test sample for proving cemented joint
−1
NOTE ISO 4587 specifies that the test should take (65 ± 20) s or use a shear load rate of 8,3 MPa·min to
−1
9,8 MPa·min . Edge seals typically fail at between 200 % and 600 % strain at around 0,5 MPa. For a sample 0,5 mm
−1 −1 -1 -1
thick, the pull rate is between 1 mm·min and 3 mm·min 0,76 mm min and 4 mm min , but IEC 61730 specifies
−1
0,8 mm·min . If the shear load rate is used, edge seals would be expected to fail in around 3 s to 3,6 s.
4.4.3 “T” peel test
For applications with flexible substrates or superstrates test the adhesion strength as a peel
test. Samples shall be tested in a “T” peel configuration in accordance with IEC 61730-2:2016,
10.24 (MST 35). Always use the complete superstrate and substrate laminates in the test
sample because the mechanics of the adherend will affect the loading properties and the final
values. Use two sets of samples, one comprising only superstrates, and another comprising
only substrates. This serves to test adhesion to both surfaces and may make it easier to
−1
maintain angles of (90 ± 10)° as specified in MST 35. The pull rate shall be (50 ± 5) mm·min .
The sample width shall be (10 ± 1) mm. Condition the samples for at least 16 h at (23 ± 2) °C,
or according to the edge seal manufacturer’s recommendation, prior to testing.

© IEC 2022
4.4.4 90° peel test
For applications with flexible to rigid substrates, IEC 61730-2:2016, 10.24 (MST 35) specifies
a 90° peel test. Because the substrate choice can dramatically affect the adhesion strength,
results from the “T” peel test may not be sufficient to give confidence that the set of materials
will pass the cement joint evaluation in a 90° configuration. Use the same combination of rigid
−1
and flexible substrates as is intended for the application. Pull at (50 ± 5) mm·min . Use a long
enough shaft or use a sliding sample holder such that the angle is always (90 ± 5) °. For these
samples, the test area width shall be (10 ± 1) mm wide for the flexible substrate, but the rigid
substrate can be of any dimension practical (e.g. laminate the flexible substrate to the rigid one
and cut test strips to the correct width).
4.4.6 180° peel test
The peel test may also be performed with a 180° pull test as recommended by the backsheet
standard IEC TS 62788-2:2017, Clause B.1.
4.4.5 Butt joint test
This test is conducted by preferably sampling from a production PV module, but can also be
accomplished using a module mock-up or mini-module. Rectangular Test specimens are cut
from the edge seal-covered perimeter. The total sample area shall be between 0,5 cm and
1,5 cm , and the maximum aspect ratio of the largest and smallest dimension shall be less than
1,5. This means that rectangular or even circular samples may be used. But in coring a sample,
caution shall be used to ensure the samples are not damaged by torque. If cut from a production
module, it is recommended that one side of the test specimen shall have a length equal to the
width of the edge seal (typically 1 cm to 1,5 cm) and the other should be of a similar length
within ±25 %. Test specimens may be cut out using any method that is convenient so long as it
produces a clean cut and does not significantly deform the samples. For glass test specimens,
it is recommended that cutting be accomplished using a wet saw or a water jet saw. Flexible
substrates may be cut out using shears, a saw, or any other appropriate means. One may also
use engineered coupons with pre-cut superstrate and substrate material. If this is done the
thermal treatment and material thickness shall be taken.
To test the specimens, they shall be mounted to a handle. This is accomplished by adhering
bolts to each side of the test specimen, creating a mounted test sample for pulling the joint
apart. Elevator bolts have a large flat surface suitable for adhesion. However, any bolt type may
be used so long as it is large enough to cover the entire surface of the test specimens. Epoxy-
based adhesives have been demonstrated to work well enough to carry out the adhesion test,
but it may require some trial and error effort to find the best one for each material. The bolts
shall be adhered such that the bolt axis goes through the center of the samples and such that
the two bolts are parallel. Mounted test samples may be assembled by securing the bottom
bolt's flat side upright and adhering the test specimen making sure it is centered and that the
surfaces are parallel. Once the adhesive is sufficiently cured, the top bolt is adhered to the test
specimen and positioned to be parallel and centered with respect to the other bolt.
For tempered glass samples, all glass fragments shall remain adhered to the bolt's surface after
testing. Similarly, for flexible substrates, all the surface test area shall remain adhered to the
bolt surfaces. For flexible substrates, there can be concerns with the adhesive used to attach
to the bolt, squeezing out of the sides of the samples and directly adhering the bolts together.
Because of this, thin substrates may be glued to the bolts before being cut out of the module
and then subsequently cut out along the perimeter of the bolt. Another method would be to cut
the test specimen to the exact size of the bolt, then, upon assembly, excess adhesive would be
scraped off from the sides.
Using a load frame with grips attached to the specimen bolts (Figure 2a)), pull the samples
−1
apart using a load frame displacement rate of 1 mm·min while recording the applied force.
The stress at failure, σ , is the ratio of the maximum applied force, F , to the sample area
max max
A,
– 12 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
F
max
σ =
(1)
max
A
If a sufficiently accurate strain gauge can be attached to the samples, the strain at break, γ ,
max
may be determined as the ratio of the displacement at the point of maximum force, x , in a
max
force-displacement curve to the sample thickness, t.
x
max
γ = (2)
max
t
The load frame displacement cannot be used for this purpose.
Measure 10 samples and report the average and standard deviation.

a) b)
Figure 2 –Photograph (a)) and schematic (b)) of a z-tensile adhesion test specimen
NOTE The current qualification tests, IEC 61215 (all parts) and IEC 61730 (all parts), do not use this test, but it is
being considered as a replacement for future versions of IEC 61215 and IEC 61730 because it can be used with
either tempered glass or flexible substrates.
4.5 Durability of the materials
4.5.1 Relative thermal endurance
Edge seal materials shall have a relative thermal endurance determined in accordance with
IEC 60216-5 or UL 746B. Evaluate the electrical properties for RTI/RTE using the dielectric
strength (see Figure 3). Evaluate the mechanical properties for RTI/RTE using the lap shear
test (4.4.2) or peel tests (4.4.3 or 4.4.4) depending on the application.
NOTE IEC 61730-1 specifies that materials used as insulation must have a minimum index equal to or greater than
the maximum normalized operating temperature (MST 21), or a minimum of 90 °C, whichever is higher.

© IEC 2022
4.5.2 Dielectric strength degradation
For insulating material where the module depends on the edge seal for electrical insulation
(IEC 60664-1), carry out a dielectric strength degradation test on a substrate coupon as shown
−1
in Figure 3 to better mimic the end use. Use a ramp rate of 500 V·s DC. Thickness does not
matter because only changes in this property are being looked for, but effort should be made
to use relevant thicknesses. The thickness should be uniform throughout the sample. There
should be no air gaps in the edge sealant.
RTI/RTE dielectric sample requirements:
Fifty (50) samples (10 for as received, 20 for aging, 10 for UV and 10 for water immersion).
Void.
Dielectric samples for RTI, UV exposure or water immersion testing

Front profile Side profile
Source: Underwriters Laboratories

Figure 3 – Schematic of test structure for RTI or RTE dielectric durability testing
4.5.3 Accelerated stress testing
4.5.3.1 General
This procedure is intended to demonstrate conformity to the cemented joint criteria of
IEC 61730-2:2016, 10.25 (MST 36). This sequence consists of: 200 h damp heat MST 53,
−2 −2
60 kWh·m UV MST 54, 10 humidity freeze cycles MST 52, another 60 kWh·m UV MST 54,
and another 10 humidity freeze cycles MST 52; see Figure 4.

– 14 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
4.5.3.2 Cemented joint evaluation
A total of 20 adhesion test samples shall be constructed as in 4.4 utilizing either a peel test, lap
shear tess, or butt joint test. Ten samples shall be set aside and not exposed and 10 shall be
put through the sequence of 4.5.3.1 and the other 10 shall not be exposed. The unexposed and
exposed samples shall be evaluated to determine if 50 % of the adhesion strength is maintained
after exposure.
The module safety tests (MSTs) are described in IEC 61730-2.
Figure 4 – Test flow for cemented joint evaluation
NOTE The lap shear and peel tests are used to define a material as providing a "cemented joint" in IEC 61730-2,
MST 36 and MST 35. They require 50 % retention of lap shear strength after this specified set of exposures. This
result is used to define a material as a cemented joint for purposes of specifying the distance through the cemented
joints.
4.5.3.3 Dielectric strength degradation after UV exposure
Perform a dielectric strength degradation coupon test (4.5.2) after the weathering exposure
described in 4.5.3.1, using 10 replicate samples. Report percent retention relative to unexposed
samples. This is similar to the cemented joint test except that dielectric stress testing is
performed instead of adhesion testing.

© IEC 2022
4.5.3.4 Water immersion testing
Water immersion for outdoor exposure rating shall immerse samples in 70 °C water for 7 days.
Samples shall be dried and cooled to room temperature prior to additional testing. Testing after
water immersion is designed to evaluate the properties after the desiccant is spent.
Void.
4.5.3.5 Adhesion after water immersion
Perform the adhesion test, using the construction as appropriate from 4.4 and 10 replicates,
after water immersion exposure. Report percent retention relative to unexposed samples.
Void.
4.5.3.6 Dielectric strength after water immersion
Perform a film dielectric strength degradation coupon test (4.5.2) after water immersion
exposure in accordance with 4.5.3.4. Report percent retention relative to unexposed samples
for 10 replicate samples.
Void.
4.6 Flame resistance
Horizontal and/or vertical burn classifications in accordance with IEC 60695-11-10.
4.7 Coefficient of thermal expansion
Measure in accordance with ISO 11359-2. Report value from −40 °C to 150 °C.
NOTE Because edge seal materials are typically composed primarily of uncrosslinked, or sparsely crosslinked
polyisobutylene based materials, it might not be possible to measure the thermal expansion coefficient with this
method.
Void.
4.8 Rheological properties
4.8.1 Complex shear modulus
−1
Complex shear modulus G* measured at 150 °C and 1 rad·s in accordance with the RH
described in ISO 6721-6. Additionally, data may be reported from a temperature sweep from
−40 °C to 180 °C. The strain should be adjusted such that it is within the linear region, for
example 0,5 % strain. For temperature sweep data, report temperature ramp rate or thermal
equilibrium conditions. For linear elastic materials, the Young’s modulus (E) can be estimated
as
EG=21⋅ +ν (3)
( )
where ν is Poisson’s ratio.
4.8.2 Melt flow rate
The flow rate from a hot melt pump can be of practical interest. For constant shear rate
measurements, as applied by a hot melt pump, use ISO 11443 or ASTM D3835-08 on a capillary
−1 −1
rheometer to measure at least 4 points from 0,3 s to 20 s . For constant shear stress
measurements, use the melt mass flow rate (MFR) or melt volume rate in ISO 1133-1. Report

– 16 – IEC 62788-5-1:2020+AMD1:2022 CSV
© IEC 2022
die size, temperature, and shear stress. The conditions selected should be appropriate for the
application of the material. A full profile of temperature versus shear rate is the most useful.
4.9 Other data
The PV module manufacturer should have compatibility testing performed on all materials and
adhesives in and around the module.
Void.
5 Test report
A report of the tests, with measured performance characteristics, shall be prepared by the test
agency laboratory. For specific tests, report in accordance with the referenced documents or
as indicated in the body of this document for those tests selected. Each test report shall include
at least the following information:
a) a title;
b) name and address of the test laboratory and location where the tests were carried out;
c) unique identification of the report and of each page;
d) name and address of client, where appropriate;
e) description of the sample construction and identification of the item tested for each test
method, including specimen dimensions;
f) characterization and condition of the test item, including the method and details of specimen
preparation (including curing, lamination, or similar processing, if applicable), measurement
temperature, preconditioning temperature and RH;
g) date of receipt of the test item and date(s) of test, where appropriate;
h) reference to sampling procedure, where relevant;
i) measurements, examinations and deri
...