Raman and Infrared microscopical analysis of multilayer backsheets
Sprache des Titels:
Englisch
Original Buchtitel:
EU PVSEC Proceedings
Original Kurzfassung:
For backsheets and frontsheets of PV modules currently a variety of polymeric materials is used. Fluoropolymers which exhibit good chemical and physical properties are still dominating. However, this material is cost intensive. Therefore, alternative materials have been developed and introduced into the market. Besides, TPT backsheets based on PVF (T) and Polyester (P) many other backsheet types, also without fluoropolymers, are now commercially available. The main objective of this work is to investigate commercially relevant backsheets as to their layer structure and material composition. Various multilayer backsheet laminates were selected and categorized. Raman and Infrared microscopical techniques were implemented and applied to analyse the layer structure and materials used. The results showed that multilayer backsheets are mainly three layer assemblies with an average total thickness of about 350 m. The predominant core component is PET with a layer thickness of about 220 m. Backsheets with high performance fluoropolymers exhibit often a symmetric structure. In contrast, fluoropolymer-free backsheets based on engineering thermoplastics, such as polyester (PET) or polyamide (PA) show also an asymmetric build-up, also with thermoplastic ethylene vinylacetate (EVA) as an inner layer material. The most important inorganic modifier is the white pigment Titanium dioxide (TiO2) used in the outer layers. In only two backsheets TiO2 was identified in the middle layer. Raman microscopy is suitable for the simultaneous identification of inorganic crystalline modifiers and organic polymeric components. Infrared microscopy is only capable to detect organic compounds. So the combination of these two techniques provides a powerful tool for backsheet analysis and classification. Due to the small thickness of the adhesive layers in further work special focus is given on high resolution Raman microscopical techniques.
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