Study On High Crystallinity Polypropene

High crystalline polypropylene (HCPP) is a kind of special PP material with very highthermal deformation temperature about140℃. HCPP has advantages such as highercrystallinity, crystallization temperature, crystallization rate and heat deformation temperature,gloss and surface abrasion, resulting in wide application and low cost of production. Therewere two methods to prepare HCPP. One is using highly active and high-performancecatalyst system to enhance crystalline of PP, the other is adding a certain amount of additivesto improve crystallization speed of PP resin polymer for changing the crystallization of PP. Inrecent years, with the development of automobile industry, high-speed trains, constructionindustry and electronic telecommunications, the production and demand of polypropylenewas increased significantly. PP has becomes the fastest growth plastic in past10years.Catalyst is very important in Propylene polymerization process. Internal electron donor isnecessary for the activity of catalyst. External electron donors and nucleating agent was usedto enhance the crystalline of PP.PC-1catalyst and six external electron donors was prepared. The external electrondonors were used to polymerization of PP. It is very difficult to prepare high melt index andhigh polyprolene through a single external electron donors system.The reason is that someelectron donors can well improve hydrogen sensitivity, and improve the structure bearingcapacity. If we can combine with the two electron donors system with complexing electrondonors system which has hydrogen sensitivity and structure bearing capacity, we can getexternal electron donor which has superior propertity. A crystallization which was namedSED2530was prepared thtough complexing electron donors (contains the component part Ⅰand Ⅱ, part Ⅰcan improve the structure bearing capacity, part Ⅱ can well improvehydrogen sensitivity). Second, crystallization of PP was improved through selecting ofsuitable nulceating agent. HPN-68L, NA-21, sodium benzoate and synthesized nucleatingagent were mixed with polypropylene respectively, granulated with a twin screw extruder andprepared testing samples in an injection molding machine. The crystal morphology of thesamples was observed with a polarizing microscope, and the thermal and mechanicalproperties of the samples were characterized by via of DSC and universal testing machine.Last, complexing electron donor and nucleating agent was comfirmed.The results show that: The process by preparing the catalyst PC-1, PP has a high activity,crystallinity and ability stereoregularity by complexing external electron donor technology.The nucleating agents added can significantly improve the crystallization temperature of PP,the flexural strength and modulus, increase tensile modulus slightly, decrease diameter of the crystallizatized PP ball and the breaking elongation, but there was no significant change intensile strength. The performance of synthesized nucleating agent is equivalent to that ofHPN-68L. HCPP (crystalline beyond65%)was obtained through complexing electron donorand selecting of suitable nucleating agent.