Equilibrium Isotherm
Thermodynamic equilibrium curves tracking the release of bound water from saturated cellulosic fibers represent the upper moisture path in sorption hysteresis loops. This upper moisture release profile, identified in fiber physics as the desorption branch, shows higher equilibrium moisture regain at any given relative humidity than the corresponding adsorption path. Flax fibers drying from a wet state hold more water within lumen structures and microfibrillar pores than dry fibers gaining moisture under identical atmospheric conditions.
Spinning mill laboratories reference these sorption curves to control moisture content during yarn conditioning and wet spinning preparation.
Hysteresis Mechanism
Structural hydrogen bonding between hydroxyl groups in flax cellulose delays the release of absorbed water molecules as ambient relative humidity decreases. Water trapped inside capillary pores requires higher vapor pressure differentials to evaporate than surface moisture demands. Measuring moisture content along this curve requires climate chambers capable of stepping humidity downward while monitoring sample weight until equilibrium is established.
The resulting values establish safe moisture limits for storing hackled flax bales to prevent fungal growth.
Processing Boundary
Sorption history effects vanish once fibers reach complete dryness or full water saturation. Ambient humidity fluctuations in warehouse storage cause non-equilibrium transitions between drying and wetting curves, rendering static isotherm models inaccurate for rapid moisture changes.
