Boring fact but I commissioned the foam making part of Tempur plant in Tennessee. I used to have the formulations and chemical lists for their foams and some serious NDA’s as well!
Local hotel that Tempur used for guests and that I pretty much lived in had Tempur mattresses flown in from Europe. Hated the mattresses at first but got used to it. As above-very warm, and difficult to turn over on once you’ve sunk into it.
We have a memory foam topper on a pocket sprung decent mattress and its the best of both worlds.
If you’re buying one then Tempur are still the best ones, Vita Foam, Recticels and Carpenters visco foams are very close, anything else is crap.