Curing of EVA
The most widely used encapsulant is EVA (ethylene vinyl acetate copolymer), due not only to its high Resistività elettricaElectrical resistivity or electrical resistance is a fundamental material property that quantifies how strongly a given material opposes the flow of electric current.electrical resistivity, low fusion and polymerization temperature, and low water absorption ratio, but also to appropriate optical transmission properties.
As the polymerization reaction is irreversible, the thermal treatment of the PV cell encapsulation is crucial.
The quality and lifetime of the PV modules/arrays depend on the caliber of this production process.
In this example, Dielectric Analysis of an EVA sample was carried out in the lab furnace of the DEA. The DEA system is optimally designed for materials with standard to long curing times (> 3 min).
Time and temperature ramps can be easily programmed at heating rates of up to 40 K/min. In addition, all disposable comb sensors can be used in the furnace to ensure a broad application range of the system setup.
The multi-frequency measurement (with frequencies between 1 Hz and 10000 Hz) was carried out, and the ion viscosity (Ω.cm) was monitored. Presented here is the behavior of the ion viscosity at 1 Hz.
The cross-linking reaction by using peroxide was observed under isothermal conditions at 150°C.
The increase in the ion viscosity correlates with the increase in the degree of cure. After 60 min, the ion viscosity remains nearly constant, which indicates that the cross-linking reaction has essentially finished.