engleski

Permeation of hydrogen and other types of buoyant gases through foils for balloons and their tensile properties

The application of novel materials for buoyant, rotating, cylinder shaped balloons filled with hydrogen or small (buoyant) gases requires an analysis of optimal solution considering permeation and mechanical properties. In order to make a materials selection for this wind power system easier, it is desirable to have more information on potential envelope materials. In this work different monolayered and multilayered foils for such balloons are considered, all of them purchased by respective producer. The foils tested are Polyester-polyurethane of 100 μm thickness, Heptax of 25 μm thickness, Octax of 25.3 μm thickness, EVAL of 60 μm thickness, Epurex of 80 μm thickness, Aerofabrix of 50 μm thickness, and Aerofabrix blue of 70 μm thickness. All the foils are thermally bondable and all the tests are performed both on thermally seamed and seamless foils. Permeation tests are performed by means of the time-lag method, with hydrogen, helium and nitrogen. Mechanical properties are tested under long time and short time tensile stresses, by means of a standard tensile machine and an impact tensile apparatus (Charpy), respectively. Since machining influences molecular orientation, leading to a potential anisotropy, both mechanical tests are performed on the machining direction and on the direction perpendicular to the machining. First tests on dynamic mechanical behavior of the thin foils on a large temperature range from -190 °C up to 140 °C are performed as well giving information on complex modulus, mechanical damping and energy losses depending on temperature. These dynamic tests under tensile tests are performed by means of Dynamic Mechanical Analysis (DMA). There is not any generally superior foil. The final choice has to be made considering conditions under which the foil will be used.

gas permeation; mechanical tests; hydrogen; buoyant gases; foils; balloons

Istraživanje je provedeno u sklopu FP7/HAWE (High Altitude Wind Energy) projekta.