PIB edge sealant: application, advantages and disadvantages
PIB (Polyisobutene ) is a polymer which is used as an edge sealant in solar PV modules.
Edge sealant in Solar PV
Edge sealants are used in Solar PV industries for thin film and crystalline silicon PV modules.Furthermore, they help in delaying moisture ingress, which protects cells, connections, and conductive oxide coatings from corrosion and degradation. Also, they strengthen the electrical isolation for PV modules. The many advances in sealing systems help PV manufacturers in finding ways to reduce costs and improve the protections of cells.
Edge sealants are required to provide the following for solar modules:
- Very low MVTR (moisture vapor transmission rate)
- Reliable bonding throughout a range of temperatures and conditions
- Easy manufacturing process
- UV temperature degradation resistance
- Good adhesion properties.
PIB as an edge sealant
PIB – Polyisobutene or polyisobutylene- is a class of organic polymers which is prepared by polymerization of isobutene. The form of PIB is typically as gummy colorless solids.
PIB is used in many applications but is most popular as commercial adhesives. In Solar PV industries PIB is used as an edge sealant for thin film and crystalline silicon PV modules.
Advantages and disadvantages of using PIB as an edge sealant
The main advantage of PIB edge sealant is structurally bonding the glass panes or outer layer together with the PV components while providing a high level of gas diffusion and moisture vapor resistance. This helps in reducing water vapor and gas permeability in the area around the glass edge. PIB edge sealant also helps minimize the loss of energy saving inert gases from the unit.
Yet, the strength of thermoplastic PIB can decrease rapidly with temperature increases, so a PIB seal alone for the PV module cannot guarantee the structural integrity; this is why a secondary sealant can be required. This secondary sealant is applied around the perimeter of the glass. The secondary sealant functions as an adhesive for uniting the outer layers while preventing excessive movement under various environmental conditions. Typically used secondary sealants include PU (Polyurethane), SI (silicone) and PS (polysulphide)
The typical thickness of a primary PIB edge sealant is around 0.2 to 0.6 mm, while the secondary seal width is around 4 mm. A PIB seal’s adhesion is not resistant to continuous exposure of water like in rainy conditions.