Standard Laboratory Moisture Regain Corrections for Raw Cotton and Cellulosic Fibres
Commercial moisture regain corrections adjust oven-dry cellulosic fibre mass using statutory allowances to prevent buyers paying pure water rates on dry matter.
Hygroscopic Hysteresis
Moisture Equilibrium
Fibres demonstrate a difference in their equilibrium moisture content depending on whether they are reaching a state from a wetter or a drier condition. This property, known as hygroscopic hysteresis, means that a fabric conditioned in a humid room will hold more water than the same fabric conditioned in a dry room. The lag between these states is a fundamental characteristic of natural polymers like wool and cotton.
Absorption Path
Standard laboratory conditions require samples to be pre-conditioned to a low moisture level before the final conditioning. This step minimizes the effect of hygroscopic hysteresis by ensuring all samples approach the target moisture level from the same direction. Without this control, test results for weight and strength show inconsistent values.
Production Consequence
The molecular structure of the fibre creates internal resistance to the movement of water molecules. During desorption, the water is held more tightly within the amorphous regions than it is during the initial absorption phase of hygroscopic hysteresis. This creates two distinct curves on a moisture graph that do not overlap.
Climate Control
In a mill environment, hygroscopic hysteresis influences how yarn behaves during spinning and how fabric takes up dye. Consistent climate control in the factory helps manage this effect to ensure uniform product quality.