Polypropylene (PP) is one of the five general-purpose plastics, which is widely used in daily life. Polypropylene is the lightest plastic material. Its appearance is colorless and translucent. As a food grade plastic, it is widely used in food packaging, such as foam plastic boxes, PP plastic cups and so on. Polypropylene can be divided into five categories according to the main use: PP injection molding, PP drawing, PP fiber, PP film, PP pipe.