Preparation of ultra high molecular weight polyethylene with MgCl2/TiCl4 catalyst: effect of internal and external donor on molecular weight and molecular weight distribution
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Ultra high molecular weight polyethylene (UHMWPE) was prepared by using MgCl2-supported TiCl4 catalyst in conjunction with triethylaluminium (TEA) cocatalyst. The effects of internal and external donor on polydispersity index (PDI) of UHMWPE were investigated. The catalyst activity with various kinds of internal donor decreased in the following order: none > succinate > phthalate > diether, while the catalyst activity was less influenced by the structure of external donor. The PDI of UHMWPE was examined by using gel permeation chromatography (GPC) analysis and/or rheometry measurements. The PDI obtained by rheometer was matched with the results obtained by GPC within an error of max. 20%. The highest molecular weight and PDI of UHMWPE were obtained by the catalyst of succinate as internal donor. It was also observed that the molecular weight and PDI of UHMWPE were less affected by the introduction of external donor.
KeywordsUHMWPE Internal donor External donor Molecular weight distribution