Preparation of Ultra-High Molecular Weight Polypropylene Using Ziegler-Natta Catalyst via Combining Internal Electron Donor and Cocatalyst Loading

Due to the development of the new energy industry,polypropylene with ultra-high molecular weight plays a crucial role for battery isolation membrane.This work investigated the effect of internal electron donor of Ziegler-Natta catalyst system on the molecular weight of the obtained polypropylene.The scanning electron microscope （SEM） and Canon camera were used to characterize the surface morphologies of catalyst particles and polymer particles,respectively.Compared with the polypropylene particles featuring a spherical shape,these study results confirmed that the morphology duplication theory from the catalyst particle to the morphology of polymer particle was exhibited.The gel permeation chromatography （GPC） results revealed that the obtained polypropylene has a much higher average molecular weight than those prepared by conventional method.The Fourier transform infrared spectrometry （FT-IR） and X-ray photoelectron spectroscopy （XPS） revealed that the carbonyl oxygen atom on ester group was preferentially bound to Mg and Ti,as compared to the ether oxygen atom.The XPS results showed that the ratio of Ti 3+ /Ti 4+ could be changed by internal electron donors.When Ti 3+ content was nearly 99% in the Ziegler-Natta catalyst system,isotactic polypropylene with an ultra-high molecular weight of up to 1.42×10~6 g/mol was obtained by Cat.3.This result implied that internal electron donor ID3 could reduce theβ-hydride elimination reaction to further increase the molecular weight of the obtained polymer.