Modern days party balloons are mostly made of rubber and filled with air or helium. When rubber balloons are filled with air, their shapes can last for weeks. When rubber balloons are filled with helium, they seldom can hold their shape for more than a few hours. The helium gas molecules are too small to be contained by the stretched rubber membrane. The molecules slowly escape through the gaps among the polymer molecules.
In the last decade, some more expensive helium balloons are made of thin unstretchable impermeable myler films. The myler balloons have attractive shiny reflective surfaces and are printable with color pictures and patterns. The most important attributes are its light weight and its ability to keep the helium gas from escaping for two to three weeks. It became the material of choice for helium balloons.
Large helium balloons are used as high flying vessels to carry scientific instruments (as in weather balloons) or even human passengers.
See also: [Hot air balloon]?
![[Home]](wikipedia.png)