Spinning globe

Polymerization Catalyst

Copyright, American Chemical Society, 1996

Polyethylene chemical and physical versatility of polyethylene has made it an extremely valuable commodity in the world market. With such a fast growing demand, both the product and the production technology continues to expand. Some attributes of polyethylene include it's flexibility (without the use of plasticizers), its physical properties are not very dependent on temperature, it is chemically inert to most chemicals and it is extremely hydrophobic and hence resistant to water. These properties make polyethylene an extremely useful product with a wide variety of applications.

Currently, the most promising catalysts are the metallocene catalysts developed from transition metals such as Zirconium, Titanium and Hafnium. In the past, Ziegler-Natta catalysts catapulted the production of LDPE and HDPE. Although based on transition metals such as titanium and zirconium, the metallocenes differ in that they have well-defined single catalytic sites and well-understood molecular structures. Stereoselective catalytic sites can polymerize almost any monomers beyond the tradition ethylene to octene olefins.

Current research proposes that the reaction mechanisms to produce polymers follow similar patterns as the Ziegler-Natta catalysts. Experimental data indicates that active part of the catalyst in the polymerization process is the cationic alkyl-metallocene complex. The stereo specificity of the desired polymerization of LLDPE is thereby achieved due to the constrained transition metal site.

Start Over

Go Back