Unilever headquarters in Hafen City Hamburg | photo © formTL. BEHNISCH AND PARTNERS. Ethylene tetrafluoroethylene (ETFE) is an extremely resilient plastic foil, low in weight but high in light permeability. It ages very slowly, and its service life is about 25 years. The overall structure generates low surface tension meaning that dirt is hardly able to settle firmly on the foil and instead gets washed away by the rain.