Sweaters generally have the problem of pilling, and then good sweaters worn for a long time in fact, there will be a certain amount of pilling problems, why sweaters of this material is easy to pilling? 1. raw material factors: the higher the quality of wool raw materials, the better the fineness, the denser the surface scales, curl degree is good, feel soft, but easy to tangle, pilling. 2. the fabric tissue structure is different (flat needle, Yuan Bao, double Yuan Bao, etc.), different density (loose, tight) will also produce different degrees of pilling phenomenon, the State Technical Supervision Bureau of pilling test is based on different pile specifications (count) woven into the specified specifications density, tissue structure of the sample in the specified time in the pilling box test, and then assess the level. 3. wearing with different objects (smooth, rough) contact, will also produce different degrees of pilling phenomenon, sleeves, pockets and other parts of the frequent friction is also easy to pilling. 4. from the process: if the twist is loose, the pile is more round and fat, the strip is fuller, but easier to pilling, the opposite is the twist is tight, it will lose the style of pile, like a rope.