From the horse's mouth:https://www.fender.com/articles/tech-ta ... f-finishes
Fender introduced polyurethane finishes (often shortened to “urethane”) on its instruments in the late 1960s; allowing a glossier, more even finish by replacing multiple layers of nitro clear coating with a mere two layers of aliphatic urethane.
Fender continues to use urethane finishes on many of its instruments (American Standard Series, various artist models), with variants including flatter satin urethane (necks on Deluxe, Standard, Highway One, American Deluxe and American Standard models) and thicker, shinier gloss urethane (American Specials, Ritchie Blackmore Stratocaster).
Polyester is just for mex models.
So please spare me with that kind of knowledge.
As for Gibbys, the modern finish on my ex Studio Shred or my current Studio has zero to do with traditional Gibson nitro. It is way harder and more durable than the traditional nitro (of which I have a couple next to this for comparison), not sticky and no fading/cracking either.
Many modern plasticizers are urethane-blends by the way. I suspect Gibson use either these (likely) or some PVC-based flavor (maybe), anyway it's not your grandpa's nitro.https://www.sciencedirect.com/science/a ... 1801001222
Polyurethane blends exhibit better structural properties compared to the other plasticizers.
edit - one more bit I found, seems like it's acrylic:
you can add up to 7% nitro back to acrylic and still get that yellowing/cracking "effect". which is what Gibson does currently, and they pay a monthly fee to do so because the EPA regs state that the current maximum allowed nitro component is only 5%