I used to design and build scientific equipment for the South Pole. We had to do all our own materials testing because manufacturers would only specify their products to the bottom of the MILSPEC temperature range and the South Pole goes below that.
I remember one spool of cabling in particular - it was beautiful stuff, highly flexible, high current carrying, just what we needed. It stayed awesome right to the bottom of the milspec temperature range, at which point the exterior sheathing went through some kind of phase transition and froze solid, followed by the interior insulation having a different coefficient of thermal expansion than the exterior sheathing resulting in the whole thing shattering itself into pieces just a few degrees below military operating temperatures.