Preparation of ultra-high molecular weight polyprolene

Ultra-high molecular weight polypropylene (UHWMPP) is a kind of thermoplastic engineering plastics which has viscosity-averaged molecular weight of more than 1 million, along with incredible strength, high wear resistance, strong antioxidant abilities, and thus it can be used to prepare the polypropylene products with high strength and modulus, as well as high resistance to corrosion, impact and stress crack. The main purpose of the study is to produce the polypropylene with molecular weight over 2 million, which can be used as a 3D printing material to avoid the problems of high melt viscosity and low fluidity caused by long molecular chain. Based on the traditional Ziegler-Natta catalyst, the main catalyst was loaded with metal ions and organics. The molecular weight of the polypropylene was controlled by controlling the chain transfer of propylene and hydrogen (active hydrogen-containing substance) was not added during the polymerization to prevent the termination of the reaction. The effects of the polymerization action temperature, polymerization action time, promoters and external electron donors on the molecular weight of polypropylene were investigated. The molecular weight of the prepared polypropylene was characterized by viscometry and temperature rising elution fractionation method. Finally, the ultra-high molecular weight polypropylene with molecular weight of more than 2.04 million was successfully prepared at polymerization reaction temperature of 70℃, polymerization time of 60min, with triisobutylaluminum as the promoters and P Donor as the external donor. © 2018, Chemical Industry Press. All right reserved.