Weather-resistant PV Backsheets
Come Wind, Come Weather
Highly productive manufacturing processes and new concepts for saving materials and energy are vital to the future viability of the solar industry. Development of innovative adhesives and sealants plays an important part in meeting the challenges facing the market, .
Liofol two-component PUR systems offer good weathering properties (Image: Henkel)
The main components of solar modules with photovoltaic cells of crystalline silicon are the glass lens, two EVA sheets in which both the silicon solar cells and the electrical contacts are embedded, and then a final layer in the form of a protective, backsheet, usually comprised of a multi-film laminate. During the 20 to 25 years of its service lifetime, the backsheet is expected to continuously withstand all the tough weathering conditions to which it is exposed in outdoor areas. In particular, the adhesives used in the backsheet have to resist hydrolysis. Two-component PUR systems developed under the Liofol brand offer good resistance to hydrolytic attack. They are also reported to resist UV degradation and to withstand temperatures of up to 150°C such as may be encountered during module manufacturing for periods of 25 to 35 min. Composite sheets laminated with this brand of adhesives are subjected to rigorous industrial testing, e.g. thermal resistance tests at 200 °C, and weathering at 85 °C and 85 % relative humidity for 1000, 2000, or 3000 h, depending on customer demands.