The introduction of medium-density polyethylene in plastic bottles, medium-density polyethylene, is achieved through the copolymerization of alpha olefins during the synthesis process to control density. In the United States in 1970, it was produced by the slurry method, and its production and synthesis process adopted the LLDPE method. Alpha olefins commonly used propylene, 1-butene, 1-hexene, l-octene, etc., the amount of its impact on the size of the density, in general. The amount of olefin is about 5% (mass). MDPE molecular backbones introduce an average of 20 methyl branches per 1,000 carbon atoms, or 13 ethyl branches, and their performance varies depending on how much and how long the branches are.
Copolymerization can increase the number of connecting chains between the small lamellae of the crystals. MDPE is characterized by its long-term resistance to environmental stress cracking and strength. MDPE has a relative density of 0.926-0.953, a crystallinity of 70%-80%, an average molecular weight of 200,000, a tensile strength of 8-24 MPa, an elongation at break of 50%-60%, melting The temperature is 126-135°C, the melt flow rate is 0.1-35 g/10 min, and the heat distortion temperature (0.46 MPa) is 49-74°C. MDPE can be used extrusion, injection, blow molding, rotational molding, rotation, powder molding processing methods, production process parameters and HDPE and LDPF similar, commonly used in pipes, films, hollow containers.