Investigation of multilayered aluminium-coated polymer laminates by focused ion beam (FIB) etching

Multilayered aluminium-coated polymer laminates are the common barrier envelopes of vacuum insulation panels used as thermal insulations in building applications. These laminates are made of up to ten distinct layers including three barrier layers made by vacuum web coating. The thickness of each aluminium layer (30–100 nm) influences the overall thermal performance of the panels as well as the temperature at joints between adjacent panels. Two commercially available barrier envelopes have been investigated by means of focused ion beam etching for an adequate determination of the effective thickness of the aluminium layers. Additional information has been gained on interfacial failure between aluminium and its neighbouring polymeric film or adhesive layer as well as disruptions in the aluminium layer itself. These provide hints related to air and moisture permeation, the key properties of barrier envelopes in building applications where a lifetime of 20 to 50 years is required.