Balloons should hang in the air for two days. What can best be used for this? With helium, the balloon loses pressure after just a few hours and shrivels.
Answer
Rubber balloons filled with helium leak quickly. Rubber is a cross-linked molecule with large holes, and helium is a single atom molecule. So a bad combination.
Better combinations are:
– cover the skin of the balloon with a metal film, e.g. a thin vapor-deposited sheet of aluminium. While not perfect, it is much less permeable than rubber.
– use a gas with larger molecules that is lighter than air, eg H2 (hydrogen) or CH4 (natural gas).
Answered by
Engineer Bart Dierickx
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