Urethane sealant is much more durable and a stronger adhesive. SikaFlex 221 is a good example. I need it for covering the connection inside the junction box.
I strongly urge you to avoid using any adhesive for solar panels. Keep in mind that flexible solar panels don't last long. You will probably need to replace them every couple of years. That will be a challenge with them glued in place. For rigid panels, the best adhesive would be M6 bolts. These are rigid panels being mounted on aluminium brackets.
Thin-film solar panels (see page 296), in particular, need adhesives around the edges because they typically don't have frames to protect them. They need an additional moisture barrier called a side or edge seal. Many manufacturers use butyl, either in a liquid or tape form. Butyl-casting resins provide water vapor-tight sealing.
What is a solar adhesive?
An adhesive is a substance that unites or bonds surfaces together. In the solar industry, adhesives are used throughout the process of manufacturing and installation. Henkel's adhesive Loctite 3388P enables high-strength ingot bonding in solar applications.
What types of sealants can be used for solar panels?
Other types of adhesives and coatings, such as epoxy-based or UV-curable sealants, may also be used for specific sealing applications in solar panels, depending on the manufacturer's recommendations and the installation's specific requirements. Waterproofing is a critical aspect of sealing solar panels.
Silicone sealants are commonly used for solar panel sealing due to their moisture resistance, adhesion, flexibility, and UV resistance properties. Effective sealing techniques, such as edge sealing and junction box sealing, along with regular maintenance and inspection, contribute to solar panels' longevity and optimal performance.
To seal the gaps between solar panels, a suitable sealant, such as silicone sealant, can be applied along the edges and joints of the panels. It is important to ensure a complete and consistent sealant layer to prevent moisture ingress and protect the panels.