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Compressive‐shear adhesion characterization of polyvinyl‐butyral and ethylene‐vinyl acetate at different curing times before and after exposure to damp‐heat conditions
Author(s) -
Chapuis Valentin,
Pélisset Ségolène,
RaeisBarnéoud Marylène,
Li HengYu,
Ballif Christophe,
PerretAebi LaureEmmanuelle
Publication year - 2014
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.2270
Subject(s) - materials science , ethylene vinyl acetate , composite material , polyvinyl butyral , polyvinyl acetate , adhesive , adhesion , polymer , vinyl acetate , layer (electronics) , copolymer
Photovoltaic (PV) module efficiency and reliability are two factors that have an important impact on the final cost of the PV electricity production. It is widely accepted that a good adhesion between the encapsulant and the different substrates of a PV module is needed to ensure long‐term reliability. Several testing procedures exist that use a metric derived from the force at interface failure to characterize the adhesion. It has, however, not been demonstrated that those metrics relate directly to the interfacial adhesion (defined as the surface energy density needed to break interfacial bonds), and the obtained results usually relate to an apparent adhesion strength. In this work, we describe a new design for compressive‐shear testing of polymer layers bonded to rigid substrates. We use it to characterize real interfacial adhesion of ethylene‐vinyl acetate (EVA) and polyvinyl‐butyral (PVB) to a glass substrate before and after degradation in damp‐heat. Our results show that a peak‐force based metric is unable to capture the evolution of adhesion through degradation, and a new metric based on the elastic strain energy of the encapsulant is proposed. Moreover, we show that PVB adhesion to glass is much more affected by damp‐heat exposure where polymer saturation takes place, in comparison with the adhesion of EVA to glass. The presented characterization protocol is a powerful tool that can help in assessing the reliability of an encapsulant facing specific degradation conditions. Copyright © 2012 John Wiley & Sons, Ltd.

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