ABSTRACT
The year 1954 saw a major breakthrough in the plastics industry with the invention of stereospecific catalysts by Carl Ziegler and Giulo Natta [1]. These Ziegler-Natta catalysts, initially commercialized by Phillips Petroleum Co., made it possible to produce linear polyethylene-medium density polyethylene (MDPE) and high density polyethylene (HDPE)—via the use of much lower pressures (less than 500 psi) than those required for the low density polyethylene (LDPE) produced by the Imperial Chemical Industries Ltd. (ICI-LDPE) process (40,000 psi). The invention of the Ziegler-Natta catalysts also spurred the development of polypropylene (PP), currently the second most popular plastics material. Polypropylene cannot be produced by the free radical process that produces LDPE.
