Chemical Whiteness
Spinning output subjected to chemical whitening processes constitutes a distinct category of textile material designed for high-brightness linen fabrics. This category typically includes bleached flax yarn, which has undergone treatment with hydrogen peroxide or sodium hypochlorite to remove natural lignins and hemicelluloses. Removing these non-cellulosic impurities increases the yarn brightness but reduces its original weight and tensile strength.
Mills verify the whiteness level using spectrophotometer readings against standard barium sulfate plates.
Tensile Loss
Alkalis and oxidizing agents used during wet processing degrade the chain length of flax cellulose. Consequently, bleached flax yarn exhibits a lower degree of polymerization and reduced single-end breaking force compared to grey yarn. Wet spinning mills must carefully manage the exposure time and bath temperature to prevent excessive chemical damage to the long flax fibres.
Independent laboratories determine the damage factor by measuring the fluidity of the dissolved cellulose in cupriethylenediamine hydroxide. Keeping this fluidity index within specified limits ensures that the yarn retains sufficient strength for high-speed weaving looms. Spun lots that fail these strength thresholds are re-routed to domestic knitting applications where warp stress is absent.
Absorbency Level
Purified cellulose resulting from the bleaching treatment shows an immediate increase in moisture absorption capacity. Woven linen produced from bleached flax yarn requires fewer pre-treatments before dyeing or printing, saving processing water and chemical inputs. The removal of natural waxes ensures rapid moisture uptake across the fabric surface.
