Is Nylon 6 Cast and Extruded waterproof?

Both forms of Nylon 6 (cast and extruded) are not fully waterproof, they are hygroscopic, meaning they naturally absorb moisture from the environment. Whilst they don't dissolve or degrade in water, the absorbed moisture can affect their performance and dimensions, especially in precision applications. Nylon 6 can absorb 2-3% by weight at typical room humidity or as much as 8-9% by weight at full saturation.