I don't know a lot about polymer, but I watched a few YouTube videos on polymer80 builds and Glocks. In more than one video, the person speaking says to wet sand the polymer frames, and they explain that polymer frames incorporate H2O into their material structure. They then go on to say that wet sanding is therefore important in keeping the frame hydrated. I'm assuming that was said as far as keeping it looking aesthetically pleasing rather than being imperative for functionality, because the wet sanding comments were mentioned when they were talking about how dry sanding makes the material look scratchy. I started to look up more info on this, and found articles unrelated to polymer firearm frames specifically, but rather about certain types of polymers being water absorbent, which brings me to believe that there is truth about these frames incorporating water into their structure. I know that there are many different types of polymers, and I'm assuming that these 80% polymer Glock-like receiver brands, as well as Glock frames, have their own unique proprietary polymer materials. However, despite proprietary differences, I assume the materials chosen by different manufacturers are very closely related, and if what was said in a few videos I've seen about polymer frames having H2O as part of the physical material structure, it got me to questioning the effects of below freezing temperatures on these frames. When H2O freezes, intramolecular forces, hydrogen bonding forces, a lowering density, etc., all happens, and causes the water to expand. This creates enough force to crack concrete in the winter when temperatures freeze. My question is, wouldn't freezing temperatures cause permanent damage to these frames just the same? Obviously there isn't a ton of water incorporated into the material, so it wouldn't cause noticeable damage if out in the cold once, but I'd think that even with a little bit of H2O absorbed into the material, with repeated freezing and warming, that overtime it could severely weaken/damage the frame.