Determination of stabilisers in polymeric materials used as encapsulants in photovoltaic modules

Synthetic polymers are used as encapsulants or front and back sheets in photovoltaic modules. Since the concentrations of (intact) stabilisers are crucial for the durability of the polymeric material, the current study provides methods for the determination of stabilisers in commercially relevant encapsulants for photovoltaic modules: ethylene vinyl acetate (EVA), polyvinyl butyral (PVB) and thermoplastic silicone elastomer (TPSE). For identification of the stabilisers present in EVA, direct analysis in real time coupled with mass spectrometry (DART-MS) is employed as a rapid method applicable to the polymeric film without sample preparation. For qualitative analysis of PVB and TPSE, but also for the subsequent quantification of the identified stabilisers in all investigated encapsulants, gas chromatography (GC) coupled with MS as well as high performance liquid chromatography (HPLC) coupled with UV and MS detectors are applied. Optimised protocols for the preparation of stabiliser extracts needed for these methods are presented for all three materials.