Standard Moisture Regain Determination in Scutched Flax Fibre
Standard moisture regain in scutched flax fibre is set at 12.0% of bone-dry mass using ISO 6741-1 forced-convection oven drying at 105 degrees Celsius.
Hysteresis Variance
Sorption Discrepancy
A physical phenomenon describes the difference in moisture content that occurs depending on whether a fiber is undergoing absorption or desorption. In the valuation of flax shipments, hysteresis variance explains why two samples in the same environment can display different moisture regain percentages depending on their previous moisture history. This behavior arises because the crystalline structure of cellulose accommodates water molecules differently during wetting than during drying.
Structural Cause
The cellulose chains in flax contain hydroxyl groups that form hydrogen bonds with water molecules. During desorption from a wet state, some of these bonding sites remain occupied longer than they would during the absorption process from a dry state. This creates a lag in the moisture equilibrium curves, resulting in higher moisture content at a given relative humidity during drying.
The size of this lag depends on the crystallinity of the fiber and the temperature of the surrounding air. It represents a fundamental property of natural cellulosic fibers that cannot be eliminated by processing.
Commercial Impact
Invoices and quality certs must account for this discrepancy to avoid disputes over the net weight of flax consignments. Laboratories pre-condition samples in a standard atmosphere before testing to eliminate the influence of prior exposure. This step ensures that all measurements are comparable.