A spool's opening date is a poor substitute for its exposure history. A reviewed 2022 experiment exposed one commercial 1.75 mm nylon to 40 °C and 80% RH for 0, 24, 48, and 72 hours, then compared extrudate, thin walls, and tensile specimens.[1]
Under that specific humid condition, moisture reached about 5.5 wt.% after 72 hours without an observed saturation plateau. Evaporating water bubbles expanded and burst after extrusion; higher moisture also reduced melt viscosity and promoted void formation or foaming.[1]
A single roughness value did not reflect all visible surface irregularity. The tensile comparison was also bounded: only 0.9% and 5.5% moisture groups, four specimens per group. The 72-hour group showed 8% maximum strain and lower yield and ultimate tensile strength.[1] These numbers are experimental conditions, not universal acceptance limits for every PA grade or composite.
Record the exact material and lot, ambient temperature and RH, time outside controlled storage, feed method during printing, drying history, and repeatable extrudate or coupon observations. Use the material manufacturer's current data sheet for drying temperature and duration. The paper's 40 °C value was a humid exposure temperature, not a drying prescription.
This process record is EyeContact's practical application of the study. Final acceptance still depends on the production material, machine, geometry, and required part tests.
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