Production method - HDPE
The manufacture of polythene using Ziegler-Natta catalysts takes place
under very different conditions to LDPE, and results in a more rigid
Chain length and branching
Depending on production methods, the lengths of the chains produced can vary enormously, giving rise to polymer molecules with widely different molecular weights, and different properties.
Low molecular weight HDPE (less than 80,000) is very brittle. Commercial HDPE is usually in the range 80,000 to 1,200,000, representing carbon chains between 5,000 and 1 million atoms in length.
A higher degree of branching gives a softer and more elastic polymer.
For further information on this mechanism, see the Catalysis site.