A Comparative Study of Calorimetric Methods to Determine theCrosslinking Degree of the Ethylene-Co-Vinyl Acetate Polymer Usedas a Photovoltaic Encapsulant

EVA copolymer foils are widely used as encapsulantsfor photovoltaic (PV) cells in PV modules. These foilsneed to be crosslinked during module manufacturing, toenhance their properties. Accurate and reliable methods for thedetermination of their crosslinking degree are thus very important.In this work, two semi-empirical calorimetric methods areconsidered and compared to a scientifically sound rheologicalmethod used as a reference. The main purpose of this work isto reveal the chemical and physical fundamentals on which thetwo calorimetric methods are based, to allow for a scientificunderstanding of their advantages, and limitations. For one ofthese calorimetric methods, the so-called “Melt-Freeze” method,we have sought for a deeper understanding of the underlyingcrystallization physics through the use of successive selfnucleationand annealing experiments, which give access tothe crystallite size distribution of EVA, and to the influence ofcrosslinking upon it.