Effects of Manufacturing-Induced Initial Material State and Lamination Duration on Thermomechanical Properties of Photovoltaic Encapsulants

Abstract

Encapsulants are vital for the structural integrity and protection of photovoltaic (PV) modules, yet the impact of processing history and crosslinking on their thermomechanical behaviour is often oversimplified in numerical simulations. This study experimentally investigates how lamination conditions affect six encapsulant types, including crosslinking (EVA, POE), noncrosslinking (TPO), and coextruded (EPE) materials. The crosslinking behaviour was characterized using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), while thermomechanical properties were assessed via digital image correlation. Results indicate that conventional DSC-based methods for the calculations of degree of crosslinking, while standard for EVA, have significant limitations when applied to multilayer encapsulants. Fourier transform infrared spectroscopy in attenuated total reflection mode combined with principal component analysis proved to be an effective, rapid method for qualitative clustering of crosslinked encapsulants. The findings reveal that manufacturing history strongly influences prelamination behaviour, even for the materials labelled under the same commercial nomenclature. Increased lamination duration drives encapsulants toward more isotropic coefficients of thermal expansion (CTE), with noncrosslinking materials reaching final CTE values faster. The presented dataset may support future investigations of stress development, thermomechanical interactions, and material selection in conventional and emerging PV module architectures.