Polypropylene is a polymer formed by free radical polymerization of propylene monomer. It has a non-toxic, odorless, tasteless milky white and highly crystalline shape. It is a crystalline material. At present, there are many kinds of polypropylene resins produced in China, such as flat wire grade polypropylene, biaxially oriented polypropylene special resin (BOPP special material), injection molding grade polypropylene and ethylene propylene copolymer polypropylene.