Crosslinking Behavior of Ethylene‐Vinyl Acetate Copolymer Encapsulants in Dependence of the Additive Composition

ABSTRACT The three‐dimensional crosslinking of encapsulants in photovoltaic (PV) modules significantly defines their thermomechanical properties and is usually initiated using peroxides and crosslinking accelerators. However, it has been shown that excess peroxides lead to undesirable side reactions such as browning, which is directly linked to the PV module power losses. Therefore, the encapsulant formulation should be adjusted accordingly, on the one hand, keeping the peroxide concentration possibly low and, on the other hand, enabling a sufficiently high gel content (GC). This work investigates the basic interaction of the crosslinking peroxide Luperox TBEC and the crosslinking accelerator Perkalink 301 (TAIC) with differential scanning calorimetry (DSC), to address this issue. In addition, their reaction potential with the antioxidant butylhydroxytoluene (BHT) is investigated. It is shown that stabilizing additives can have an influence on the peroxide crosslinking process, which can affect the resulting crosslinking state and require optimization of the lamination conditions. The additive content of commercial PV encapsulants is quantified using pyrolysis gas‐chromatography mass spectrometry (PY‐GCMS). Subsequently, a number of films with different TBEC and TAIC contents are produced, and their GC is analyzed as a function of the additive concentrations and lamination conditions. A range of formulations leading to a GC > 75% was identified which can be used as a guidance for encapsulant manufacturers.