Organo silanes, used as external donors to modify Ziegler Natta (ZN) catalysts in propylene polymerization have been shown to bring in extra benefits to the polypropylene (PP) produced in terms of enhanced isotacticity and other physical characteristics. Since ethylene is a symmetrical molecule unlike propylene and there is no need to control tacticity in polyethylene (PE) as in case of PP, use of donors in ethylene polymerization is rarely done. With a view to explore similar benefits, a series of organo silanes including tetraalkoxy silanes, substituted trialkoxy silanes, substituted dialkoxy silanes etc. were studied as external donors in ethylene polymerization. A significant shifting of molecular weight distribution towards higher molecular weight fraction was observed for high density polyethylene (HDPE) with the use of organo silane donors as judged by size exclusion chromatography. The organo silane donor modified ZN catalysts were also observed to significantly enhance the molecular weight during ethylene polymerization (up to 15 million g/mole on ASTM scale) compared to PE, obtained without using any donor. The donors were further found to narrow down the particle size distribution (PSD) and lower the average particle size (APS) of resulting PE. It was found that the characteristics of resulting PE strongly depend on geometry and the electronic environment of the donors used during polymerization.

Effect of organo silane donors in ethylene polymerization

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.