Cotton and other natural and man-made cellulosic fibers develop pills or protruding fibers during spinning, weaving and wet processing operations, due to abrasions. These pills make the appearance of the yarn or fabric to be dull and hazy. In order to improve the appearance it is necessary to either remove the protruding fibers or to cement it to the surface properly by the application of some over coating.
What is Biopolishing (bio-polishing)?
Cotton and other natural and man-made cellulosic fibers can be improved by an enzymatic treatment called Bio-Polishing or Biofinishing. The main advantage of Bio-Polishing is the prevention of pilling.
Enzyme cellulases hydrolyze the micro fibrils (hairs or fuzz or pills) protruding from the surface of yarn because they are most susceptible to enzymatic attack. This weakens the micro fibrils, which tend to break off from the main body of the fiber and leave a smoother yarn surface.
After Bio-Polishing, the fabric shows a much lower pilling tendency. Other benefits of removing fuzz are a softer, smoother feel and superior brightness of the dyed shade or white. Unlike conventional softeners, which tend to be washed out and often result in a greasy feel, the softness-enhancing effects of Bio-Polishing are wash proof and non-greasy.
For cotton fabrics, the use of Bio-Polishing is optional for upgrading the fabric. However, Bio-Polishing is almost essential for the new polynosic fiber lyocell. Lyocell is made from wood pulp and is characterized by a tendency to fibrillate easily when wet. In simple terms, fibrils on the surface of the fiber peel up. If they are not removed, finished garments made with lyocell will end up covered in pills. This is the reason why lyocell fabric is treated with cellulases during finishing. Cellulases also enhance the attractive, silky appearance of lyocell.
Bio-Polishing of wool:
Wool is made of protein and so this treatment features a protease that modifies the wool fibers. 'Facing up' is the trade term for the ruffling up of the surface of wool garments by abrasive action during dyeing. Enzymatic treatment reduces facing up, which significantly improves the pilling performance of garments and increases softness.
Biopolishing of Silk:
Proteases are also used to treat silk. Threads of raw silk must be degummed to remove sericin, a proteinaceous substance that covers the silk fiber. Traditionally, degumming is performed in an alkaline solution containing soap. This is a harsh treatment because the fiber itself, the fibrin, is also attacked. However, the use of proteolytic enzymes is a better method because they remove the sericin without attacking the fibrin. Tests with high concentrations of enzymes show that there is no fiber damage and the silk threads are stronger than with traditional treatments.
Anti-pilling finish (Synthetics and blends):
Pilling is an unpleasant phenomenon usually associated with spun yarn fabrics, especially when they contain polyester. Fibers are released from the yam by bending and abrasion, and they combine together at the surface of the material to form knots known as pills.
Resin finishing reduces the Pilling tendency. However, following treatment also can impart anti-pilling to the fabric.
Anionic polyacrylate - 20-50 g/l
Silicic acid product 20-60 g/l
Nonionic softner 2-4 g/l
Pad and dry in the stenter.