How does EVA compare to PVB as encapsulation material?
EVA film in solar packaging
EVA film was introduced in the 1980s. It is a hot melt adhesive film, at room temperature it is non-tacky and with good mechanical properties. These properties make it a suitable material for the solar cell encapsulation and outdoor use.
PVB (Poly vinyl butyral: polyvinyl butyral) in solar packaging
Polyvinyl butyral is a resin which is used typically in different applications that require strong binding properties, transparency, adhesion to different surfaces, flexibility and toughness.
US scientists have invented PVB after improvising ways to sandwich polymer material layers between two layers of ordinary glass.
Difference between EVA and PVB
EVA used for crystalline silicon cell packaging. Also EVA film can be used to essentially protect the cell and the PV cell cover glass plate and for adhesion between layers.
PVB is used mainly in the thin-film cells, double glazing assembly building integrated PV modules (BIPV) and other fields, the PVB material is produced by different companies. Currently Dupont, Kuraray are some other companies also producing PVB products.
- The lamination process for EVA and PVB
Both EVA and PVB have different temperature requirements as each material needs a specific range. EVA has good thermoplastic properties and the material requires normal temperature range. PVB has high temperature requirements (about 155 ℃), which for laminating machine is considered relatively high.
- Other differences
There are many other differences between PVB and EVA which include that PVB is a building material, so its gas barrier performance is very good, and has very good adhesive properties, and much better weather resistance. The main disadvantage for PVB is that it has poor water vapor barrier properties, which in solar cells causes many problems. It is not advisable to use common interlayers of PVB when the laminate will have prolonged exposure to moisture or water as delamination can occur over time.
PVB mechanical properties are less than that of EVA and manufacturing process is more difficult. Another factor is the cost of both materials. PVB is more economic than EVA, as the price of EVA is more than three times.