When the nylon webbing in the state is slowly cooled, spherulites are rapidly formed at 235~245℃. Spherulites are not only included in the crystalline part, but also in the amorphous part, and the crystallinity is 20% to 40%.

The spherulites include positive spherulites preferentially oriented in the radial direction and negative spherulites preferentially oriented in the tangential direction. Nylon-66 spherulites are usually positive spherulites, but negative spherulites can be formed when heated to melt and crystallize at 250~265 °C. The formation rate of spherulites and the size of spherulites are not only significantly affected by the cooling temperature, but also by the melting temperature, molecular weight and other factors.
Polyamide fiber is a general term for a class of fibers with C9-NH groups on the macromolecular chain. The commonly used aliphatic polyester amines are mainly polyamide 6 and 'polyamide 66. The trade names in my country are nylon 6 and nylon 66. Nylon fibers are mainly filaments, and a small amount of short fibers are mainly used for blending with cotton, wool or other chemical fibers. Nylon filaments are widely used for texturing to manufacture elastic yarns as raw materials for weaving or knitting. Nylon fibers are generally spun by the melt method. According to the determination, the wear resistance of nylon fiber is 20 times that of cotton fiber, 20 times that of wool, and 50 times that of viscose.