Due to its abundant raw materials, low prices, easy processing and molding, and excellent comprehensive performance, it is a type of polymer material with the largest output and widely used. Among them, polyethylene and polypropylene are the most important. The main varieties include polyethylene and some ethylene based copolymers, such as ethylene vinyl acetate copolymers, ethylene acrylic acid or acrylate copolymers, as well as polypropylene and some propylene copolymers, poly 1-butene, poly 4-methyl-1-pentene, and cyclic olefin polymers. There are also higher olefin polymers with smaller yields, such as poly (1-butene) and polymers of 1-butene, mainly prepared by gas-phase polymerization. They can undergo crystal transformation when placed at room temperature and can be processed into pipes, plates, films, and fibers through processes such as extrusion, blow molding, and injection. Due to their outstanding creep resistance and stress cracking resistance, they are often used as pipeline materials at temperatures ranging from -25 to 100 ℃; Poly (4-methyl-1-pentene), a polymer of 4-methyl-1-pentene, prepared by directional polymerization, is the lightest polymer with high transparency, good insulation and corrosion resistance, and high gas permeability (11 times that of polyethylene). However, it has poor resistance to impact, stress cracking, and photooxidative aging. Injection and extrusion methods can be used for manufacturing optical instruments, chemical and medical devices, electronic devices and insulation materials, gas separation membranes and packaging materials, fibers, etc