Mechanisms and chemistry of anti-pilling finishes
Fig 1 Pill curves for fabrics with normal and modified polyester fibers
For all kinds of finishes, special product groups are known and listed in catalogues. There is, however, no group of anti-pilling products in the International Textile Auxiliaries Buyers¡¯ Guide. The reason is not that this finish is not important enough. This astonishing fact may be explained by:
The large variety of parameters that influence the pilling behaviour ,
The corresponding variety of approaches to anti-pilling finishes,
The circumstance that textile auxiliary products mostly recommend products that are primarily used for other purposes for anti-pilling finishes,
There are only a few general recipes for anti-pilling finishes,
The need for specific solutions for every type of article, including all other finishing components.
Several chemical finishing approaches have been taken to prevent pills from accumulating on fabric surfaces. The first approach is to prevent loose fibers from forming the initial ¡®fuzz¡¯ by applying polymeric coatings that bind the fibers into the fabric surface. These finishes typically include friction reducing lubricants to minimize abrasion damage. The most useful polymers are acrylic copolymers since they can be easily modified to yield tough, flexible films with good adhesion to fiber surfaces.
The second chemical finish approach to reduce pilling is to cause the pills to fall off the fabric as soon as they are formed. This can be accomplished by reducing fiber strength. For synthetic fibers, changes in the polymer structure can be made prior to extrusion. Figure 1 gives pill curves for two identical fabrics made from different polyester yarns. One yarn was made with normal polyester staple fibers, the second was made with polyester fibers that had been modified to have lower strength. The fabric made from the lower strength fibers had significantly less pilling, illustrating the positive effect of weaker fibers on pilling. The use of these lower strength polyester fibers in polyester /cotton blend fabrics will greatly reduce pilling. Modified fibers are called pilling-poor if the pills are scrubbed off within two hours in the random tumble pilling test and if the maximum of the pill curve is lower than rating 6 of the ¡®Reutlinger Pillgrad¡¯ as shown by the horizontal broken line in Fig. 1. With 100% cotton fabrics, treatment with durable press agents will, in addition to providing durable press properties, reduce the fiber strength sufficiently to improve pilling performance.
A third approach to reducing pilling tendency is applicable to 100% cotton fabrics. As described in Chapter 17 on enzymatic finishes the use of cellulose enzymes during wet processing can remove enough of the loose fibers in the yarns so that pilling is greatly reduced.