IEC 62788-6-2:2020

Measurement procedures for materials used in photovoltaic modules - Part 6-2: General tests - Moisture permeation testing of polymeric materials

IEC 62788-6-2:2020 provides methods for measuring the steady-state water vapour transmission rate (WVTR), water vapour permeability (P), diffusivity (D), solubility (S), and moisture breakthrough time (Ƭ10) (defined as the time to reach 10 % of the steady state WVTR) for polymeric materials such as encapsulants, edge seals, frontsheets and backsheets. These measurements can be made at selected temperatures and humidity levels as deemed appropriate for evaluation of their performance in PV modules. Measurement is accomplished by inspection of the transient WVTR curve and by fitting it to a theoretical Fickian model. This document is best applied to monolithic films. If multilayer films are used, the D and S values are only apparent values, but the steady-state values can still be measured.

Procédures de mesure des matériaux utilisés dans les modules photovoltaïques - Partie 6-2: Essais génériques - Essais de perméation à l’humidité des matériaux polymères

l’IEC 62788-6-2:2020 fournit des méthodes de mesure du coefficient de transmission de la vapeur d’eau (WVTR – water vapour transmission rate) en régime établi, de la perméabilité de la vapeur d'eau (P), de la diffusivité (D), de la solubilité (S) et du temps d’infiltration de l’humidité (Ƭ10) (défini comme étant le temps permettant d’atteindre 10 % du WVTR en régime établi) pour les matériaux polymères tels que les encapsulants, les joints d’étanchéité périphériques et les couches avant et arrière. Ces mesurages peuvent être effectués à des températures et niveaux d’humidité choisis jugés appropriés pour l’évaluation de leurs performances dans les modules PV. Le mesurage est effectué par l’examen de la courbe du WVTR transitoire et par l’ajustement de cette courbe au modèle fickien théorique. Le présent document présente la meilleure application aux films monolithiques. Si des films multicouches sont utilisés, les valeurs de D et S sont uniquement des valeurs apparentes, mais les valeurs en régime établi peuvent tout de même être mesurées.

General Information

• Status: Published
• Publication Date: 18-Mar-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 2 - TC 82/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 20-Mar-2020
• Completion Date: 19-Mar-2020

Standards Content (Sample)

IEC 62788-6-2 ®
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 6-2: General tests – Moisture permeation testing of polymeric materials

Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 6-2: Essais génériques – Essais de perméation à l’humidité des matériaux
polymères
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IEC 62788-6-2 ®
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –

Part 6-2: General tests – Moisture permeation testing of polymeric materials

Procédures de mesure des matériaux utilisés dans les modules

photovoltaïques –
Partie 6-2: Essais génériques – Essais de perméation à l’humidité des matériaux

polymères
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-7921-2

– 2 – IEC 62788-6-2:2020 © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 7
3.1 Terms and definitions . 7
3.2 Symbols . 7
4 Apparatus . 8
5 Test specimens . 8
6 Procedure . 9
7 Calculations . 10
7.1 Determination of diffusivity and solubility of moisture . 10
7.2 Determination of breakthrough constant . 11
7.3 Variable temperature measurement . 12
7.4 Variable relative humidity measurement . 13
8 Test report . 13
Annex A (informative) Example data . 15
A.1 Example of Fickian diffusion . 15
A.2 Example of failed measurement of Fickian diffusion . 16
A.3 Example of non-Fickian diffusion . 17
Bibliography . 19

Figure 1 – Diagram of a diffusion cell . 9
Figure A.1 – Example of Fickian diffusion in EVA at 85 °C and 100 % RH with a 2,84
mm thick film . 16
Figure A.2 – Example of a failed data set for Fickian diffusion in polyethylene
terepthalate at 22 °C and 100 % RH . 17
Figure A.3 – Example of non–Fickian diffusion in a desiccant filled polyisobutylene
material used as an edge seal . 18

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

Part 6-2: General tests –
Moisture permeation testing of polymeric materials

FOREWORD
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International Standard IEC 62788-6-2 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1659/FDIS 82/1690/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.

– 4 – IEC 62788-6-2:2020 © IEC 2020
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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INTRODUCTION
This part of IEC 62788 describes methods to measure the permeation properties of polymeric
materials. The degr
...