Here's a reference chart from Johnsonite:
It comes down to this:
Thermoplastic can be recycled into more thermoplastic.
Thermoset material can be recycled, but only into other things.
from rlhudson.com:
"…a thermoset material will not remelt or otherwise regain the processibility it had before being cured. … Thermoset polymers outperform other materials (such as thermoplastics, see below) in a number of areas… thermoset parts tend to make more effective seals.
A thermoplastic material softens (becomes pliable and plastic) when heated, but it does not cure or set. …. A thermoplastic material can therefore be reprocessed many times, though continual recycling will eventually degrade the polymer."
So, from a sustainability point of view, it may be more responsible to specify a product that has more flexible opportunities for being recycled at the end of it's life (Thermoplastic). On the other hand, if products made with thermoset material are in demand, does it matter? The jury is still out.
Of course if you take the post-consumer use out of the equation, this brings up all the usual questions about whether it's better to use rapidly-renewable or recycled materials for production. And then you're into embodied energy questions, Life-cycle costing, etc. Complicated. It just depends.
Until I have a chance to dig deeper, I'm going to specify thermoplastic material, on the assumption that as long I and others are specifying it, there will be demand for it to be reprocessed into more.
