Polypropylene fibers, the scientific name is melting near the flame, flammable, slowly burning away from the fire and emitting black smoke. The flame is yellow at the top and blue at the bottom. It emits an oil smell. After burning, the ash is hard round, light yellow brown particles, and the hand twists are fragile. It is made from propylene by polymerization and melt spinning. Polypropylene fiber was formally industrialized in 1957, and it is a rising star in synthetic fibers. Because of the advantages of simple production process, low cost, high strength and light relative density, polypropylene fiber has developed rapidly. At present, polypropylene fiber is the fourth largest variety of synthetic fibers and the lightest fiber in common chemical fibers.