The Impact of the Lamination Process on the Adhesion Properties at the Glass-Encapsulant Interface and Damp Heat Stability of PV Modules

This paper presents an extensive study of the influences of the lamination process on the adhesion properties of the glass-encapsulant interface of different laminates. The investigations were conducted on small-scale laminates which were laminated with different material combinations at peak lamination temperatures from 140°C to 180°C. As a measure of the long-term durability, the laminates were exposed to damp heat (DH) up to 3000 hours. We investigated the development of the adhesion between encapsulant and glass by peel tests, the measurement of the gel content and the colour change of the backsheet by measurements of the yellowness index. The peel test results show that the relative maintained peel force (RMPF) varies in the range from 15.7-73.0% depending on the material and the lamination process. It is obtained that the EVA laminates showed less degradation in peel force after DH than POE samples and a higher lamination temperature was beneficial in peel force and gel content before and after ageing for cross-linking encapsulants such as EVA and POE. For the used TPO the peel force did not change for different lamination temperatures. We showed that with lamination temperatures up to 180 °C EVA, POE and TPO modules can be manufactured and withstand DH ageing but they may show a slightly increased yellowing of the rear side.