Focused ion beam (FIB) etching to investigate aluminium-coated polymer laminates subjected to heat and moisture loads

Multilayered aluminium-coated polymer laminates are the common barrier envelopes of vacuum insulation panels used as high performance thermal insulation in building applications. These laminates are made of up to ten distinct layers including three aluminium barrier layers applied by vacuum web coating. During their expected lifetime, which is required to last longer than 20 years, they will be subjected to heat and moisture loads induced by internal and external climatic conditions. This paper investigates the deteriorations of the barrier function of two different laminates commonly used for the production of vacuum insulation panels. These were subjected to well defined exterior heat and moisture loads and investigated by means of focused ion beam etching. Delamination of the polyurethane adhesive layers and stress induced relaxation in them are made visible. Oxidised aluminium layers are also detected by this method.