Metallocene and Ziegler-Natta Catalysts

Abstract

Fifty years ago, Karl Ziegler and Natta won the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds with aluminum-alkyls as co-catalysts. Polyolefins are constantly growing and are now one of the most important highconsumption polymers. New metallocene/methylaluminoxane (MAO) catalysts have made it possible to synthesize polymers with highly defined microstructure, tacticity and steroregularity, such as long chain branched or block copolymers with excellent properties. Melt spinning of the fibers of metallocene-catalyzed isotactic polypropylene (PP) and standard equivalent of Ziegler-Natta isotactic polypropylene and therefore the properties of PP and several thermal and mechanical properties of fiber have been investigated. Ziegler-Natta catalysts were prepared by a reaction method which employed Mg(OEt)2 as a precursor. Newly developed metallocene-catalyzed PP possesses higher isotacticity and crystallinity than commercial ones, so the mechanical properties of the final product are guaranteed.