Most of the polymers in use in firearms are blends of nylon. The Remington Nylon 66 was put on the market in 1959, HK produced the VP70 pistol and had polymer furniture for the G3 by the early 1970s, fuel tanks for cars came out in 1974, Gerber started making knife handles in the late 70's, and it's what Glocks and Pmags use, too. Formulas and additives make it what we see today.
The Nylon 66 was popular in Alaska, plastic fuel tanks are in cars used there and in Canada, Magpul doesn't limit use of their mags to warm weather only. If anything, there has been more development to make it heat resistant for automotive use. That's been a bigger area of concern. Cars have had polymer manifolds for a decade or more. No big deal parking them in Minnesota and worrying they will explode if it backfires on a cold frosty morning.
Salomon uses Zytel in their ski boot bindings - this stuff gets used in a lot of things we don't even pay attention to, and it's already been in use by consumers for decades.
Plastic stocks don't sponge up moisture to soak the frame underneath for weeks at a time, and plastic sheaths don't have tanning chemicals in them to bleed onto the blade and ruin it. Nylon knife handles don't swell up, dry out, and loosen like wood or leather, and plastic mags don't set up electrolysis with brass casings when stored for months in a humid trunk the way steel or aluminum does. It's precisely the reason we did move to composites in combat weapons - they do a much better job in rough environments.
Don't stress over it being plastic, it's exactly why guns are still affordable. If anything, the stuff is extending the service life of weapons far beyond previous expectations because it's not decaying or contributing to it. What obsoletes a lot of weapons these days is progress in dynamic designs, not the plastic. Wood and steel were bad enough.
