Hygroscopic

Hygroscopic materials absorb moisture from the surrounding air, leading to changes in mass, dimensions and mechanical properties. For technical fabrics, polyamide (PA) is notably hygroscopic: water uptake softens the polymer, alters tensile behaviour and can shift aperture geometry, affecting cut‑off and tracking in belts. Hygroscopic powders change flowability and may agglomerate, altering cake structure and ∆p evolution. Engineering controls address both storage and operation: conditioned storage (sealed packaging, desiccants), pre‑drying or pre‑equilibration before critical measurements, and material selection that limits moisture uptake where dimensional stability is paramount (e.g., PET, PPS, PEEK or stainless wire). Specifications should state test humidity/temperature and permissible drift in permeability and dimensions so QA data remain comparable across seasons and sites.