zirconocene/MAO catalysts are about 10 to 100 times more active for ethene polymerisation than conventional Ziegler catalyst systems. Every Zr atom forms about 46 000 polymer chains per hour. Calculations show that one ethene unit is inserted every 3 x 10^-5 seconds, a very rapid rate of reaction indeed.

Chain termination occurs when a Zr-H bond forms before the addtion of another ethene molecule.