"Re Franco, I take it that polycryo is the proper spelling? For some reason I thought I had seen it as polycro, but I'm not sure where."

As far as I know it is a GossamerGear made up brand name to describe the type of window insulation material they use for groundsheets.
Two Greek words
Poly : much or multi
Cryo : frost /ice cold. Cryo is the Latin version of Kryo .

possibly the most misspelled brand name along with the Thermarest (Therm-a-rest) variants, like Thermorest.

BTW, not that the above is important or going to make Great Britain great ...