Optimization of Soxhlet Extraction Parameters for Gel Content Determination of Co-Extruded EPE

With the transition to TOPCon technology raising several challenges regarding reliability and long-term stability of PV modules, tailored encapsulant solutions like EPE (EVA+POE+EVA) are more commonly used in PV module production due to their advantageous properties. The optimization and adaptation of precise quality control is hereby most important. While the measurement of Gel Content (GC) with DMA, DSC and FTIR are relative methods, Soxhlet offers a more accurate and reliable quantitative alternative. This study focuses on optimizing Soxhlet extraction parameters for GC measurements of co-extruded EPE encapsulants. The influence of various extraction cycle times as well as number of cycles and resting time in cooling solvent on GC values is investigated. Furthermore a sweep of extraction time from 8-24 h is performed for two different EPE and POE encapsulants to identify the point at which the change in GC saturates. At this point any further increase in extraction time will not lead to significant changes in GC values. With EPE this point of saturation was found at 22-24 h while POE exhibits this saturation behavior at 20-26 h minimum extraction time highly depending on the specific material.