A Short History of Polyethylene
Low density polyethylene (LDPE) was discovered by accident in the 1930’s at the Imperial Chemical Industries (ICI) works in England. The reaction required extremely high pressure.
High density polyethylene (HDPE) was developed initially in the 1950’s by Phillips in the USA when they discovered a catalyst that would allow polymerisation under mild temperatures and pressures.
Then in 1963, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of a catalyst that would allow ethylene and propylene to polymerise under even milder conditions.
The Ziegler-Natta catalyst, based on titanium compounds and aluminium alkyls, was one of the most important scientific discoveries of the 20th Century.
The conventional Ziegler-Natta catalyst remains the most widely used catalyst in HDPE and LLDPE production today.
Metallocene is a catalyst used in the production of linear low density polyethylene (LLDPE).
Like all catalysts, metallocene is not consumed in the reaction. Its role is to encourage the ethylene molecules to come together.
Metallocene is special because each catalyst molecule has only one active site, identical to the next catalyst molecule. This is in contrast to conventional LLDPE catalysts.
The discovery of these “single-site” metallocene catalysts has provided a breakthrough in controlling the crystalline structure or “architecture” of polyethylene.