SIST EN 62788-1-6:2017

SLOVENSKI STANDARD
SIST EN 62788-1-6:2017
01-julij-2017
0HULOQLSRVWRSNL]DPDWHULDOHXSRUDEOMHQHYIRWRQDSHWRVWQLKPRGXOLKGHO
(QNDSVXODQWL3UHVNXVQHPHWRGH]DGRORþDQMHVWRSQMHVWUMHYDQMDYHWLOHQYLQLOQLK
DFHWDWQLKHQNDSVXODQWLK
Measurement procedures for materials used in photovoltaic modules - Part 1-6:
Encapsulants - Test methods for determining the degree of cure in Ethylene-Vinyl
Acetate
Werkstoffe, die in photovoltaischen Modulen verwendet werden – Messverfahren - Teil 1
-6: Verkapselungsstoffe – Prüfverfahren zur Bestimmung des Aushärtungsgrads der
Ethylen-Vinyl-Acetat-Verkapselung
Procédures de mesure des matériaux utilisés dans les modules photovoltaïques - Partie
1-6: Encapsulants - Méthodes d'essai pour déterminer le degré de durcissement dans
l'éthylène-acétate de vinyle
Ta slovenski standard je istoveten z: EN 62788-1-6:2017
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
SIST EN 62788-1-6:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 62788-1-6:2017

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SIST EN 62788-1-6:2017


EUROPEAN STANDARD EN 62788-1-6

NORME EUROPÉENNE

EUROPÄISCHE NORM
May 2017
ICS 27.160

English Version
Measurement procedures for materials used in photovoltaic
modules - Part 1-6: Encapsulants - Test methods for determining
the degree of cure in Ethylene-Vinyl Acetate
(IEC 62788-1-6:2017)
Procédures de mesure des matériaux utilisés dans les Werkstoffe, die in photovoltaischen Modulen verwendet
modules photovoltaïques - Partie 1-6: Encapsulants - werden - Messverfahren - Teil 1-6: Verkapselungsstoffe -
Méthodes d'essai pour déterminer le degré de Prüfverfahren zur Bestimmung des Aushärtungsgrads der
durcissement dans l'éthylène-acétate de vinyle Ethylen-Vinyl-Acetat-Verkapselung
(IEC 62788-1-6:2017) (IEC 62788-1-6:2017)
This European Standard was approved by CENELEC on 2017-03-03. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.



European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 62788-1-6:2017 E

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SIST EN 62788-1-6:2017
EN 62788-1-6:2017
European foreword
The text of document 82/1197/FDIS, future edition 1 of IEC 62788-1-6, prepared by IEC/TC 82 “Solar
photovoltaic energy systems" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN 62788-1-6:2017.

The following dates are fixed:
(dop) 2017-12-03
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2020-03-03
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.

Endorsement notice
The text of the International Standard IEC 62788-1-6:2017 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 61215 (series) NOTE Harmonized as EN 61215 (series).
ISO 11357-2 NOTE Harmonized as EN ISO 11357-2.
ISO 11357-3 NOTE Harmonized as EN ISO 11357-3.

2

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SIST EN 62788-1-6:2017
EN 62788-1-6:2017

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61215-1 -  Terrestrial photovoltaic (PV) modules - EN 61215-1 -
Design qualification and type approval -
Part 1: Test requirements
ISO 291 2008 Plastics - Standard atmospheres for EN ISO 291 2008
conditioning and testing
ISO 6427 2013 Plastics - Determination of matter EN ISO 6427 2014
extractable by organic solvents
(conventional methods)
ISO 10147 -  Pipes and fittings made of crosslinked EN ISO 10147 2012
polyethylene (PE-X) - Estimation of the
degree of crosslinking by determination of
the gel content
ISO 11357-1 2009 Plastics - Differential scanning calorimetry - -
(DSC) - Part 1: General principles
ISO/IEC 17025 2005 General requirements for the competence EN ISO/IEC 17025 2005
of testing and calibration laboratories
ASTM D2765-11 -  Standard Test Methods for Determination - -
of Gel Content and Swell Ratio of
Crosslinked Ethylene Plastics

3

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SIST EN 62788-1-6:2017




IEC 62788-1-6

®


Edition 1.0 2017-01




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Measurement procedures for materials used in photovoltaic modules –

Part 1-6: Encapsulants – Test methods for determining the degree of cure in

Ethylene-Vinyl Acetate




Procédures de mesure des matériaux utilisés dans les modules

photovoltaïques –


Partie 1-6: Encapsulants – Méthodes d'essai pour déterminer le degré de

durcissement dans l'éthylène-acétate de vinyle












INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 27.160 ISBN 978-2-8322-3857-8



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
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SIST EN 62788-1-6:2017
– 2 – IEC 62788-1-6:2017 © IEC 2017
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Principle . 7
5 DSC secondary method . 8
5.1 Instrument and equipment for the secondary method . 8
5.1.1 General . 8
5.1.2 Electronic balance . 8
5.1.3 Differential scanning calorimeter . 8
5.1.4 Instrument calibration . 8
5.2 Specimen preparation for the secondary method. 9
5.2.1 Sampling and storage . 9
5.2.2 Preparation procedures . 9
5.3 Test requirements for the secondary method . 9
5.3.1 Environment requirements . 9
5.3.2 Parameter settings (residual enthalpy method) . 10
5.3.3 Parameter settings (melt/freeze method) . 10
5.3.4 Parameter settings (combined enthalpy and melt/freeze method) . 10
5.4 Test procedure for the secondary method . 11
5.5 Calculation and expression of the results for the secondary method . 11
5.5.1 Enthalpy method . 11
5.5.2 Melt/freeze method . 12
5.6 Uncertainty of measurements for the secondary method . 16
6 The primary method . 16
6.1 Principle for the primary method . 16
6.2 Instrument and equipment for the primary method . 17
6.2.1 Electronic balance . 17
6.2.2 Soxhlet extractor . 17
6.2.3 Thimble . 17
6.2.4 Heating apparatus . 17
6.2.5 Handling apparatus. 18
6.2.6 Solvent . 18
6.3 Specimen preparation for the primary method . 18
6.3.1 Sampling and storage . 18
6.3.2 Preparation procedures . 18
6.4 Test requirements for the primary method – Environment requirements . 19
6.5 Test procedure for the primary method . 19
6.6 Calculation and expression of the results for the primary method . 19
7 Test report . 19
Annex A (informative) Limitations of the primary and secondary measurement methods
. 21
Bibliography . 23

Figure 1 – Example result for the DSC residual enthalpy method . 12

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IEC 62788-1-6:2017 © IEC 2017 – 3 –
Figure 2 – Location of temperatures and temperature ranges used in the melt/freeze DSC
method . 13
Figure 3 – Example of the temperature bounds applied for an automated software
integration algorithm . 14
Figure 4 – Representation of the measurement profile for an EVA test specimen . 16

Table 1 – Summary of the results for the example measurements shown in Figure 2 . 14

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SIST EN 62788-1-6:2017
– 4 – IEC 62788-1-6:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

MEASUREMENT PROCEDURES FOR MATERIALS USED
IN PHOTOVOLTAIC MODULES –

Part 1-6: Encapsulants – Test methods for determining
the degree of cure in Ethylene-Vinyl Acetate

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.
International Standard IEC 62788-1-6 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this standard is based on the following documents:
FDIS Report on voting
82/1197/FDIS 82/1231/RVD

Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
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.

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SIST EN 62788-1-6:2017
IEC 62788-1-6:2017 © IEC 2017 – 5 –
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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.

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SIST EN 62788-1-6:2017
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MEASUREMENT PROCEDURES FOR MATERIALS USED
IN PHOTOVOLTAIC MODULES –

Part 1-6: Encapsulants – Test methods for determining
the degree of cure in Ethylene-Vinyl Acetate



1 Scope
This part of IEC 62788 defines the terminology, test equipment, test environment, specimen
preparation, test procedures, and test report for measuring the degree of cure of Ethylene-Vinyl
Acetate (EVA) encapsulation sheet used in photovoltaic (PV) modules. The differential scanning
calorimetry (both residual enthalpy and melt/freeze protocols) and gel content methods are
included herein. This procedure can be used by material- or module-manufacturers to verify that
the cross-linking additive is present and is active. The procedure can also be used to verify the
module manufacturing (lamination) process for the purposes of quality- and process-control.
The procedure can also be used to assess the uniformity of the EVA formulation within a roll as
well as to compare variation of the EVA formulation from roll to roll. This procedure can be
applied to uncured or recently cured EVA sheet as well as uncured or recently cured EVA from
PV modules.
This test procedure can also be applied to cross-linking ethylenic co-polymers other than EVA.
The temperatures identified for the calorimetry measurements in this procedure have been
optimized for EVA. Therefore, if the test procedure is applied to other encapsulation materials,
the range of the test temperatures can have to be adjusted based on the active temperature of
the curing agent and/or the melt/freeze temperature of the base material.
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 61215-1, Terrestrial photovoltaic (PV) modules – Design qualification and type approval –
Part 1: Test requirements
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration
laboratories
ISO 291:2008, Plastics – Standard atmospheres for conditioning and testing
ISO 6427:2013, Plastics – Determination of matter extractable by organic solvents
(conventional methods)
ISO 11357-1:2009, Plastics – Differential scanning calorimetry (DSC) – Part 1: General
principles
ISO 10147:2011, Pipes and fittings made of crosslinked polyethylene (PE-X) – Estimation of the
degree of cross-linking by determination of the gel content
ASTM D2765-11, Standard test methods for determination of gel content and swell ratio of
crosslinked ethylene plastics

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IEC 62788-1-6:2017 © IEC 2017 – 7 –
3 Terms and definitions
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 Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Calculations related to these definitions are given in 5.5.
3.1
degree of cure
G
unitless parameter that characterizes the extent of cross-linking within EVA
Note 1 to entry: Unlike the cross-link density, which is a physical quantity defined by the theory of rubber elasticity,
the degree of cure in a polymer may be assessed by any experimental method that distinguishes partially cured
specimens with respect to one another or with respect to a reference material. The degree of cure can be correlated
to the gel content, which is the mass percentage of insoluble material (assumed to be cross-linked) within the
specimen.
3.2
heat flow
Q
thermal flux across a specified area in the direction of a temperature gradient, W
–1
Note 1 to entry: The specific heat flow, q, is defined as the thermal flux per unit mass of the specimen, W g .
3.3
differential scanning calorimetry
DSC
thermoanalytical technique described in ISO 11357-1, in which the difference in the amount of
heat flow required to change the temperature of a material specimen and a reference is
measured as a function of temperature or time
Note 1 to entry: Both the specimen and reference are maintained at nearly the same temperature during DSC
characterization. DSC may be applied to quantify the amount of heat generated or absorbed during the processing
(curing) of EVA. The effects of cross-linking, which occur from changes in the molecular structure of the EVA, may also
be examined using DSC at the phase transitions (glass transition, melting point, and crystallization temperature). The
determination of the phase transition temperatures is described in ISO 11357-2 and ISO 11357-3.
3.4
differential scanning calorimeter
instrument used to measure the heat flow difference between the test crucible (containing the
specimen) and reference (typically empty) crucible
3.5
gel content
percentage of mass content of polymer insoluble in a specified solvent after extraction according
to the specified test conditions
Note 1 to entry: The gel is typically composed of insoluble cross-linked material.
4 Principle
The degree of cure of EVA may be quickly inferred using a "secondary method", such as
differential scanning calorimetry (DSC, ISO 11357-1), described in Clause 5. Established
alternative secondary methods, as identified in Annex A, or specialized equipment may also be
used directly for the purpose of manufacturing and quality control. When the results of the

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secondary method are to be compared between different institutions, they shall be calibrated
using a slower, more universal "primary" method, the gel content test as described in Clause 6,
similar to the procedures described in ISO 6427, ISO 10147 and ASTM D2765. The primary
method may also be applied for research and development when the results of the secondary
method are to be compared between formulations of EVA. A test procedure for the primary
method is described in Clause 6. The results of the primary or secondary methods may be
correlated to the module qualification tests (IEC 61215 series) or additional field durability data
to identify the minimum degree of cure necessary. Examples correlating between the secondary
and primary methods may be found in the bibliography of Annex A.
The DSC measurements for EVA may be interpreted based on the enthalpy of the cross-linking
reaction or the characteristics of the melt/freeze transition as described in 5.5. Because the
melt/freeze transition does not depend on the concentration of residual peroxide, the DSC
melt/freeze method may be applied to specimens obtained from fielded modules. Limitations of
the primary and secondary methods are discussed in Annex A.
5 DSC secondary method
5.1 Instrument and equipment for the secondary method
5.1.1 General
References for the application of the DSC method are provided in Annex A.
5.1.2 Electronic balance
The micro balance should have a measurement resolution of at least 0,01 mg, and a maximum
range of at least 20 mg.
5.1.3 Differential scanning calorimeter
5.1.3.1 The calorimeter should have a temperature accuracy of at least ±0,1 °C, temperature
precision of at least 0,01 °C, calorimetric accuracy of at least ±0,5 % (or 0,2 mW), calorimetric
sensitivity of at least 2 µW, and calorimetric repeatability of at least ±0,5 %.
–1
5.1.3.2 The oven heating/cooling rate should be adjustable between 5 °C min and
–1 –1
30 °C min measured with a thermometric accuracy of at least ±0,1 °C min .
5.1.3.3 The baseline drift (absolute value of signal change between the two integration limit,
for an empty cell) should be less than 50 µW, for the temperature range from –50 °C to 250 °C.
5.1.3.4 The baseline curvature (the biggest deviation from the integration baseline) should
be less than 50 µW, for the temperature range from –50 °C to 250 °C.
5.1.4 Instrument calibration
The instrument should be calibrated routinely according to the instrument manufacturer’s
specification, using the instrument supplier’s recommended calibration methods. Accuracy
calibration should be performed using standard substances, for example, indium or tin, as the
temperature and heat-flow verification material. Sapphire may be used to quantify the baseline
(curvature) of the instrument drift. The instrument should specifically be recalibrated if the test
rate, type of pan, or test atmosphere has been changed before DSC measurements.
NOTE The importance, performance, and considerations related to DSC instrument calibration are described further
in D. Chen, A. Green, D. Dollimore, "DSC: the Importance of Baseline Calibration", Thermochimica Acta, 284 (2), 1996,
429–433.

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5.2 Specimen preparation for the secondary method
5.2.1 Sampling and storage
5.2.1.1 Because the results for the secondary method may depend on the make of EVA, test
results may only be directly compared for the same formulation of EVA. Therefore, test
specimens should come from the same manufacturer and fabrication batch.
5.2.1.2 Additional experimentation shall be performed using uncured EVA to establish a
baseline for the uncured state (for both the DSC residual enthalpy and melt/freeze methods) and
a previously cured ("maximum cured") EVA used to establish a baseline for the final cured state
(for the melt/freeze method).
If the experiment is intended to monitor a production process, the "maximum cured" samples
should be taken from a laminated module or test sample subjected to the thermal history used in
lamination. If the experiment is intended to monitor the complete consumption of peroxide
(which often does not occur during the lamination of a PV module), additional processing (time
or temperature) may be required.
5.2.1.3 Operators should wear clean gloves when preparing and handling samples.
5.2.1.4 When storage is required, the EVA should be packaged in a marked, sealed bag for
later use.
5.2.1.5 Specimens should be kept dry (stored at below 50 % relative humidity), maintained
at ambient temperature, and not exposed to light.
It is recommended to verify that the results of the secondary method do not change with storage
time.
5.2.2 Preparation procedures
5.2.2.1 Weigh the empty specimen crucible and empty reference crucibles.
The use of aluminium crucibles is recommended for use with EVA.
5.2.2.2 Prepare EVA specimens 5 mg to 9 mg in size (or of a size recommended by the DSC
instrument manufacturer), obtained from a single sheet of material. The accuracy of the
measurement of the specimen mass should be at least 1 %.
5.2.2.3 A minimum of 2 samples shall be used fr
...