It is flexible all the way down to 1C. The closer to freezing you get, the less flexible it becomes.
At around 60C it’s very flexible.
By and large it behaves much like rubber o-ring material, I find. i.e. if you make it thin like a tiny o-ring it will be very wobbly. But if you thicken it up, it has some inner strength and bounce-back.
I am not certain what the “glass transition” refers to. Perhaps contact Formlabs for some detail. Glass is technically a liquid. Perhaps above 27 degrees you can permanently deform it with only mild stresses. That’s what I would presume “glass transition” refers to.
If you have any not-too-technical questions I can likely answer. I’ve been printing with Flexible 80a for a few weeks now.
I find it’s a little difficult to smooth the support structure dimples off prints. The only thing I’ve tried that helps is freezing the material, then frantically sanding before it reaches room temperature. That’s the most annoying feature of Flexible 80a.