No.
Bakelite off the top of my head was the first true, non natural polymer.
It had to be set with heat and pressure and what you got was what you got.
Like other early natural based and synthetic based products, it was good to replace more scare natural materials.
It would have been used in some components in WWI.
In WWII there were plenty of synthetic rubber, Bakelite, and other polymers used. But they were not really ready to replace most metal components in firearms, and would not have been cost effective compared to wood stocks, etc.
Later on, there were still issues with developing brittleness, runny ness, UV exposure, chemical exposure, etc.
Do any of you own cars from the 60s and early 70s?
Did you own them in when they were ten, twenty years old?
Let alone now.
Stuff gets brittle and cracks. Stuff gets soft, mushy, and sticky.
There were some developments that came about by the 80s and 90s that simply were not there