Hemicellulose Bonding
Structural hemicellulose polymers that tether cellulose microfibrils together in the primary cell walls of flax plants determine the initial cohesion of the bast tissue. These molecular junctions, referred to as xyloglucan cross-links, must be partially degraded during the dew-retting process to allow for the efficient extraction of individual fibre bundles from the stem. Agronomists and mill laboratory technicians document the extent of retting in the fibre quality certificate to evaluate the extractability of the raw flax.
Retting Efficiency
If the xyloglucan cross-links are not sufficiently broken down during retting, the flax fibres remain tightly bound to the surrounding woody core and pectin layers. This incomplete breakdown results in heavy mechanical damage during scutching, which lowers the yield of long line fibres and increases the production of low-value tow. In contrast, over-retting breaks down the essential cellulose structures, which severely reduces the tensile strength of the harvested fibres.
Spinning Acceptance
Mill quality control teams test the softness and divisibility of incoming flax bundles to ensure that the molecular bonding has been optimized for the spinning process. The mill compares these retting-related properties against the buyer’s acceptance criteria to assign the raw material to the correct spinning grade. This analysis is recorded in the incoming fibre test log, which is used to adjust the parameters of the combing and drafting machines.
By ensuring the proper release of these molecular bonds, the mill can produce a yarn with consistent diameter and high tensile strength for the weaving department.
