A successful integration of suspended plastic films into insulating glass units basically depends on the surface properties of the film. Perfect adhesion to the primary sealant is required in order to ensure mechanical stability as well as moisture vapour and gas impermeability and not to compromise the performance of the product during its service life.

Film adhesion to the sealant is in a first step investigated with different sealant materials and adhesion enhancing additives. The results are evaluated by comparison with films commonly used for this application. Single-component films show poor adhesion strength independently of the sealing material used and fail the test, whereas composite films perform very well as expected and are selected for further investigations.

In a second step preliminary accelerated tests on small insulating units (350 x 500 mm) are carried out to meet the long term test requirements for moisture penetration and gas concentration tolerances, according to EN 1279-2 and -3 [8, 9]. Moisture absorption is measured after 3 weeks ageing in a climate chamber at a constant high temperature (58°C) and high humidity (RH >95%) regime. All investigated samples reports results, which are in agreement with the specified normative value. Gas permeability rate is measured after 3, 6 and 12 weeks ageing under the same conditions. Gas losses are still higher than the required 10%, which is supposed to depend on the suboptimal adhesion of the microstructured surface to the sealant, strong enough to ensure mechanical stability, but not efficient enough to guarantee gas tightness. The low reproducibility of the measurements indicates a high sensitivity to the manufacturing process, which still has to be improved.