Propylene polymerization was carried out with MCM-41 supported rac-Et(Ind)2ZrCl2 catalysts, in the presence and absence of beta-cyclodextrin. The resultant PP was studied by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Through comparison of the results, it was found that the channels of MCM-41 could act as a nanoreactor of propylene polymerization and the polypropylene (PP) contained in the channels had noncrystal structure. However, the PP could grow out of the channels and form some crystals after the active sites on the surface of MCM-41 were destroyed. This showed that the channels of MCM-41 had great confinement effects on propylene polymerization.
Summary: In this paper, the graft of poly(propylene) fiber with acrylic acid is investigated. The effects of grafting temperature, monomer concentration, and grafting time on the grafting degree of acrylic acid onto poly(propylene) fiber are discussed. In contrast to the conventional method of determining the grafting degree gravimetrically, the acid‐base titration method used in this paper was more efficient, even at low grafting degree. High‐performance liquid chromatography (HPLC) was used to estimate the averaged length of the grafted poly(acrylic acid) chains on each grafted site of poly(propylene) backbone. And also a mechanism for the grafting polymerization is proposed.Possible microstructures of two PP‐g‐AA samples at the same grafting degree.imagePossible microstructures of two PP‐g‐AA samples at the same grafting degree.
Two novel cycloalkoxy silane compounds (ED1 and ED2) were synthesized and used as the external electron donors (EEDs) in Ziegler-Natta catalysts with diethyl 2,3-diisopropylsuccinate as internal electron donor. The results indicated that the Ziegler-Natta catalysts using ED1 and ED2 as EEDs had high catalytic activities and good stereoselectivities. The melt flow rate (MFR) and gel permeation chromatography (GPC) results revealed that the obtained polypropylene has higher MFR and lower average molecular weights than the commercial EED cyclohexyl methyl dimethoxysilane. The differential scanning calorimetry (DSC) results indicated that new isospecific active centers formed after the introduction of new external donors. The work implied that the novel EEDs could improve the hydrogen sensitivities of the catalyst system and obtain polymers with high melt flow rate.
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