nonhygroscopic

Nonhygroscopic describes materials that do not absorb moisture from the surrounding air to any significant extent. In practice, a nonhygroscopic substance exhibits little or no weight gain, swelling, or alteration in properties when exposed to typical humidity levels.

Moisture uptake can occur by absorption into the bulk or by adsorption on surfaces. Nonhygroscopic materials tend to have low polarity, hydrophobic surfaces, or tightly crosslinked structures that hinder water diffusion. Measurement of nonhygroscopic behavior is usually done by exposing samples to controlled humidity and assessing changes in weight, dimensions, dielectric properties, or other relevant characteristics.

Commonly cited nonhygroscopic materials include fluoropolymers such as PTFE (Teflon), FEP, PFA, and PVDF, which are highly resistant to moisture uptake. Some paraffin-based hydrocarbons and waxes also show very low moisture absorption. Many metals and dense ceramics exhibit negligible bulk moisture uptake, though surface adsorption can occur under certain conditions.

Applications for nonhygroscopic materials span electronics, optics, packaging, seals, and precision instrumentation, where unwanted moisture can cause dimensional changes, swelling, corrosion, or changes in electrical properties. In such contexts, the low moisture affinity helps maintain performance and reliability under varying environmental humidity.

See also: hygroscopicity, moisture diffusion, hydrophobicity, moisture sensitivity level.