Moisture Regain and Sorption Behaviour
topic
Polyester has very low moisture regain: 0.4% at 65% RH, 20°C (cf. cotton 8.5%, wool 14%). Moisture absorption occurs only in amorphous regions. Low moisture causes electrostatic charge buildup (surface resistivity >10¹² Ω), poor comfort perception (clammy feel), and slow drying. Modified polyester: hygroscopic finishing (PEG coating, wicking finishes), hollow fibre (increased surface area for moisture transport), or hydrophilic copolymers (PEG units in chain) achieve 1.5–4% regain.
Role
Moisture regain is a fundamental limitation of polyester in apparel comfort. Understanding the thermodynamic basis of low sorption, its consequences for comfort and static, and engineering solutions is essential for moisture management textile design.