Helium Tank Material Research

We know that Helium gas can escape through pores just in the case of balloon. So I researched for what kind of material can hold Helium gas for a long time.

Then I stumbled upon this website http://blimpguys.com/helium.htm

A company that sells BLIMPS which is a big balloon that is usually used for advertisement.

photo courtesy: http://blimpguys.com/galleryPhoto.htm

Then I read up what kind of materials they use and TA-DA I found it!
POLYURETHANE VINYL. The website even explains its characteristics.

I find it very suitable for the helium tank for our bag.