Flexible 80A thermal properties


I’m confused by the thermal properties listed in the datasheet for Flexible 80A resin, which says it has a glass transition temperature of 27 degrees C (80.6F). How can that be? What does that mean? Is it solid and not flexible below that temp? Surely it doesn’t start to deform above that temp?

I’m trying to understand how well this material holds up to heat in the real world – like inside a hot car for example? Any data on that and/or real world experience?


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.


That’s helpful, thanks. I know in the FDM world glass transition temp is a decent ballpark for how hot the plastic can get before warping in the sun, etc., but it must be different for flexible resin.

Do you think it would hold up reasonably well in the place of a small rubber piece on the outside of an old car?


Depends on how much friction it sees. If this material is hot and it’s being consistently exposed to a mild friction I imagine it would fall apart pretty quickly. But if it’s not exposed to friction it should be okay for a good while.

I do not know how well this resin handles prolonged UV exposure. Formlabs recommends only 10 minutes of cure time, which is a little unusual. So it’s possible it could decay to UV exposure, but again, I’m not certain. All my prints in Flexible are for indoor applications.