ETFE

Ethylene tetrafluoroethylene, ETFE,

a kind of plastic, was designed to have high corrosion resistance and strength over a wide temperature range.ETFE has a very high melting temperature, excellent chemical, electrical and high energy radiation resistance properties. When burned ETFE releases hydrofluoric acid.

ETFE is effectively the high strength version of the other three in this group, often featuring slightly diminished capacities in other fields by comparison.

Combustion of ETFE occurs in the same way as a number of other fluoropolymers, in terms of releasing hydrofluoric acid (HF). HF is extremely corrosive, and so appropriate caution must be exercised.

Compared to glass, ETFE film is 1% the weight, transmits more light and costs 24% to 70% less to install. It's also resilient (able to bear 400 times its own weight, self-cleaning (due to its nonstick surface) and recyclable. On the other hand it is prone to punctures by sharp edges, therefore it is mostly used for roofs. In sheet form as commonly employed for architecture, it is able to stretch to three times its length without loss of elasticity. Employing heat welding, tears can be repaired with a patch or multiple sheets assembled into larger panels.

http://en.wikipedia.org/wiki/ETFE