Naslov
The role of acetic acid in degradation of polymers for photovoltaic modules.

Autori
Mihaljević, Antonija

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, diplomski rad, diplomski

Fakultet
Fakultet kemijskog inženjerstva i tehnologije

Mjesto
Zagreb

Datum
25.09

Godina
2015

Stranica
68

Mentor
Govorčin Bajsić, Emi

Neposredni voditelj
Oreški , Gernot

Ključne riječi
PV modules; polymers; EVA; acetic acid; permeation; degradation

Sažetak
The main aim of this thesis was to measure the acetic acid permeation rates of various backsheet films at different temperature levels.At the moment, the dominating encapsulation material for PV modules is chemically cross-linked ethylene vinyl acetate copolymer (EVA). Besides the time and energy consuming module lamination process, the major drawback of EVA is the formation of corrosive degradation products like acetic acid. Acetic acid, which is formed during oxidation of ethylene vinyl acetate (EVA), leads to corrosion of the metal parts in a PV module, PID effect and to loss of adhesion and subsequent delamination of the PV module components. Furthermore, the formed acetic acid accelerates the oxidation process of EVA. Additionally, the degradation of the cell and the cell interconnections can be accelerated by degradation co-products of the encapsulant or by molecules and substances which diffused through the encapsulant. In this thesis the influence of temperature was investigated and permeation rates were measured by gravimetry. The samples were cut to size in order to fit in an open screw cup. Vials were filled with acetic acid and closed with the previously prepared screw cup containing the sample, which now functions as a membrane. The weight loss over 30 days was followed gravimetrically at 25°C, 65°C and 85°C. Gravimetric analysis showed significant differences in the permeation behavior. The lowest permeation rates were found for laminates containing a polyester (PET) core layer and fluorpolymers. Co-extruded backsheets based on polyamides and polyolefines exhibited values which were up to 110 times higher than for laminates containing PET. According to the Arrhenius equation, an increase in temperature resulted in higher permeation rates. Higher concentration of acetic acid was found in minimodules with backsheets with lower AATR due to autocatalytic effect of retained acetic acid on the interface EVA/backsheet. Degradation of EVA due to acetic acid was investigated via spectroscopic methods (UV/Vis/NIR and Raman spectroscopy). Results showed that lower degradation was observed in minimodules combined with backsheets with high AATR.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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