Polyamide (also known as nylon) is the first synthetic fiber to be industrially produced. Its molecular chains are connected through amide bonds, and it has outstanding advantages such as high strength, good wear resistance, excellent elasticity, and resistance to oil and solvents. Therefore, it is widely used in clothing (such as stockings and sportswear), outdoor equipment, automotive parts, and engineering plastics. The main drawback is that it has a strong moisture absorption property, and its size and performance will significantly deteriorate in a humid environment.