Don't know about the plastic ones, but an old friend has sanded the
resin ones down for years to use as filler in some of the kits that he
makes. And yes, he's recycled the resin powder into some new pieces.
He did a set of 1:24 Volkswagen engines some years ago, I put one into
a scratchbuilt model of a homebuit aircraft that came out looking nice.
Well, I take them and melt them down in a bottle of liquid glue. I have then
made a mold out of silicon and made a part with it.
Just use the brush ion the bottle to "paint" it in the mold as thick as you
want, then let it dry.
I also use it to build up areas where I put parts together as on custom cars.
It's more time consuming than putty, but better in