| ?-Modified isotactic polypropylene(?-iPP)is one of the most important high performance iPP resins for its improved impact strength,excellent tensile properties and high distortion temperature.In this paper,a novel difunctional catalyst(DCTPA/Ti/Mg/BMMF)was designed and prepared by combining a ?-nucleating agent N,N'-dicyclohexyl-terephthalamide(DCTPA)and Ziegler-Natta catalyst.The ?-nucleator supported Ziegler-Natta catalyst system proved to be effective for both propylene isotactic polymerization and polymer ?-modification,and ?-crystalline-specified polypropylene(?-iPP)resins efficiently produced by the in-reactor polymerization was realized.The main content and results are as follows:(1)Designing of the functional DCTPA/Ti/Mg/BMMF catalyst: The chemical structure of the DCTPA/Ti/Mg/BMMF catalyst was investigated using FTIR,XPS and XRD.The results indicated that TiCl4 anchored to the DCTPA crystal particles via the Lewis acid-base interaction between Ti and O,and the TiCl4-anchoring provided spots for MgCl2 and subsequently 9,9-bis(methoxylmethyl)(BMMF)fluorine was successfully incorporated by reacting BMMF with DCTPA/Ti/Mg to give the final catalyst DCTPA/Ti/Mg/BMMF with MgCl2 and DCTPA as co-supports.The morphology and composition of the functional catalyst DCTPA/Ti/Mg/BMMF could be facilely controlled.(2)Propylene polymerization catalyzed by DCTPA/Ti/Mg/BMMF: Detailed study of propylene polymerization catalyzed by functional catalyst was carried out and compared with that of conventional CS-1 catalyst without any nucleating agent.It was found that the polymerization kinetics exhibited as slow-decay manner,and higher activity was achieved with catalysts containing relatively lower nucleating agent content.Elevating the polymerization temperature would first increase but then reduce the catalytic activity,while the influence of temperature on polypropylene isotacticity was little(isotacticity were between 97-99%,which was similar with that of CS-1).High hydrogen responsibility was realized with these novel catalysts,which facilitated the control of polymer molecular weight.The resulted iPP particles exhibited spherical morphology and ? crystal melting peaks were observed in the DSC curves,indicating ?-crystalline-specified function was realized by the functional catalysts.(3)Morphology,structure and properties of ?-crystalline-specified iPP: The in-situ dispersion of nucleating agent in the polymers was investigated by POM and TEM,and the broken-out section morphology was observed by SEM.The results showed that the novel catalyst improved the homogeneous dispersion of DCTPA fragment in iPP by catalyst-polymer morphology replication effect during propylene polymerization.With the polymerization proceeding,fine dispersion of DCTPA granules in iPP matrix with nanometer scale was realized and the ?-nucleating agent/iPP complex was obtained.The non-isothermal crystallization of the complex was studied in detail,and the results showed that the half-crystallization time decreased with the increasing of the DCTPA content and the cooling rate;moreover,the interaction between the nucleator and the polymer matrix was proved to be strong so that the nucleator dispesion size was stable in polymeric systems. |
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