The effect of moisture regain on the structural and thermal properties of down

This study investigates the impact of moisture regain on the density, volume, compression, and thermal conductivity of down. The moisture regain of dry down is presumed to be almost 0.00%. Under relative humidity conditions of 40%, 65%, and 95%, with corresponding values of 5.29%, 8.80%, and 11.03%, respectively. The results show that as relative humidity increases, down absorbs moisture more rapidly. The density of down increases from 1.29 g·cm−3 to 1.36 g·cm−3, and volume expansion rate rises from 1.28% to 5.13% as moisture regain increases. The compression modulus dropped from 280 Pa to 117 Pa. The compression recovery rate decreases significantly, from 41.43% to 27.29% in the first cycle, with similar reductions observed in subsequent cycles. Thermal conductivity increases from 0.032 W·m−1·°C−1 to 0.048 W·m−1·°C−1, indicating a negative impact on thermal insulation. The investigation provides foundational data on the effects of moisture regain on the structural properties and thermal performance of down, contributing valuable insights for its application in various humidity conditions.