Since I am wearing a lot of sweaters lately and picking off all the little balls that accumulate, I decided to find out what pilling actually is and what process is used for anti-pilling fabrics.
Pilling is associated with spun yarn fabrics that contain synthetics and protein fiber materials such as silk and animal hair (wool, mohair, cashmere, etc). With natural fibers, friction while wearing breaks microfibers from the threads, moves to the surface and forms balls. Synthetics more readily move to the surface due to their smoothness and higher tensile.
Anti-pilling finish cements fibers within the yarn so that their dragging becomes more difficult. There is a patent for an anti-pilling treating method for protein fiber material (US Patent 7108724) "comprising the step of subjecting protein fiber to intermolecular cross-linking reaction under weak alkaline conditions in a treating bathcomprising a cross-linking agent containing a pyrimidine compound which is dichloropyrimidine or trichloropyrimidine." Whoa. Chemistry big time!